May 30th Severe Weather Outlook

Discussion and Weather Parameters. Let me start this off with saying yesterday in the Northeast was a rather active day. And despite the active day in the Northeast, our city where Down To Earth Forecasting is out of did not experience any severe weather in the center part of town. The last time a true severe storm occurred was July 2010. Today the 30th focus will shift to the south central part of the USA. We will start off looking at the parameters and then we will talk about what is going on at the surface. So TEMPERATURES are as follows: 70 to as high as 100 degrees. http://www.twisterdata.com/data/models/nam/221/maps/2012/05/30/00/NAM_221_2012053000_F24_TMPF_2_M_ABOVE_GROUND.pngDEW POINTS will be in the 60-70 degree range so some places will continue to feel that tropical like atmosphere.. http://www.twisterdata.com/data/models/nam/221/maps/2012/05/30/00/NAM_221_2012053000_F24_DPTF_2_M_ABOVE_GROUND.pngCAPE or INSTABILITY will once again be in the range of 500-3500..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/30/00/NAM_221_2012053000_F24_CAPE_SURFACE.png ..LIFT INDEX will be 0 to negative 10 depending on where you are located in the severe zone.. http://www.twisterdata.com/data/models/nam/221/maps/2012/05/30/00/NAM_221_2012053000_F24_PLI_30_0_MB_ABOVE_GROUND.png... Definitely no lack of SHEAR with 30-50 knots of SHEAR in place ..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/30/00/NAM_221_2012053000_F24_SHRM_500_MB.png .. ENERGY HELICITY INDEX is around 1 or above in OK and Southern Kansas and this would represent where Super Cells would be possible. http://www.twisterdata.com/data/models/nam/221/maps/2012/05/30/00/NAM_221_2012053000_F24_EHI_1000_M.png ...HELICITY is 200 or under...This generally is not something you like to see if you are the type that likes Tornado's . http://www.twisterdata.com/data/models/nam/221/maps/2012/05/30/00/NAM_221_2012053000_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png ... GFS shows very steep lapse rates across the region.. http://raleighwx.americanwx.com/models/gfs/00zgfslapse024.gif ..LAPSE RATES are as high as 7.5 to 8.0 which indicates that large Hail would be a potential today.. At the surface http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif You see a stationary front with an area of low pressure that was located over Western Oklahoma. By 6 Z http://www.hpc.ncep.noaa.gov/basicwx/91fwbgus.gif this map shows well where the stationary front should be located as well as the Dry line and the area of low pressure. This stationary front looks to turn into a cold front but will stay in relatively the same location ..making it quasi stationary and will be the trigger for severe storms to initiate along. While this is happening an Upper Level trough will also be making its way towards the east. Severe threats today will be mainly Hail and Winds with an area of tornado's at 2 % across the region mentioned above. To the north of the red line across OK/KS for example we would place winds/Hail at 30% ... Other wise ..if your specific area is not mentioned then you are in a lower risk of severe which means Hail and or Wind is possible...

Severe Outlook for May 27th 2012

Temperatures will be in the mid 70s to near 100 degrees.. http://www.twisterdata.com/data/models/nam/221/maps/2012/05/27/00/NAM_221_2012052700_F24_TMPF_2_M_ABOVE_GROUND.png...DEWPOINTS in the 60s to 70 range .. http://www.twisterdata.com/data/models/nam/221/maps/2012/05/27/00/NAM_221_2012052700_F24_DPTF_2_M_ABOVE_GROUND.png ... CAPE 500- 3500 http://www.twisterdata.com/data/models/nam/221/maps/2012/05/27/00/NAM_221_2012052700_F24_CAPE_SURFACE.png... LIFT INDEX is 0 to -10 depending on where you are located.. http://www.twisterdata.com/data/models/nam/221/maps/2012/05/27/00/NAM_221_2012052700_F24_PLI_30_0_MB_ABOVE_GROUND.png... ENERGY HELICITY INDEX around 1.0 to 2.0 http://www.twisterdata.com/data/models/nam/221/maps/2012/05/27/00/NAM_221_2012052700_F24_EHI_1000_M.png ..We are going to agree with what Storm Prediction Center Shows as the tornado threat area based on the EHI but we are going to extend it over all of Wisconsin.. Greatest HELICITY is across the Canadian border and not aligned up with the EHI ..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/27/00/NAM_221_2012052700_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png ..SHEAR is 40 -60 knots which is sufficient for severe weather.. http://www.twisterdata.com/data/models/nam/221/maps/2012/05/27/00/NAM_221_2012052700_F24_SHRM_500_MB.png ..So lets look at what we are actually looking at now..http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif Stationary front along the middle of the country northern tier stretching from east to west . Low pressure is over the Rockies region. This front will stay stationary and serve as a focal axis for severe weather potential. Also a cold front will develop from the low pressure moving out of the Rocky Mountain region and that will move off to the east. In the afternoon evening time the stationary front should begin to lift north as a warm front. With High EHI yesterday and not much in the way of severe weather and really no tornados at all reported and lower EHI today we would place the Tornado chance at 2%. At the present time we see nothing to support the moderate risk from what we are looking at on the guidance!

Severe Weather Outlook May 26th 2012

Severe Weather Outlook May 26th 2012
Temperatures in the 70s to 90s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/26/00/NAM_221_2012052600_F24_TMPF_2_M_ABOVE_GROUND.png
DEW POINTS in the 60s to 70 range
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/26/00/NAM_221_2012052600_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE or INSTABILITY 500-4000 depending on where you are located..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/26/00/NAM_221_2012052600_F24_CAPE_SURFACE.png
LIFT INDEX is 0 to negative 14 depending on where you are located..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/26/00/NAM_221_2012052600_F24_PLI_30_0_MB_ABOVE_GROUND.png
EHI is as high as 3.0 or above
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/26/00/NAM_221_2012052600_F24_EHI_1000_M.png
HELICITY from about 200 to as high as 450-500
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/26/00/NAM_221_2012052600_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
SHEAR is as much as 40 to 60 knots...
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/26/00/NAM_221_2012052600_F24_SHRM_500_MB.png
At the surface
http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif
Stationary front is draped across the middle of the country which turns to a cold front in the Northeast region.. This front will be the focus of severe weather potential.
Tornado potential will be where the EHI is above 1 this will be Kansas, Nebraska,Eastern and Southern South Dakota, Southern Minnesota, Iowa , Northern Illinois, Southwestern Wisconsin, Northern Missouri.. With the EHI that high we are going to issue a 10% chance of tornadic activity in that region..
Outside of the above mentioned area will be the potential for Damaging Winds and Hail..

Severe Weather Outlook For May 25th 2012

Severe Weather Outlook For May 25th 2012
We are going to start this off with looking at the current surface map..
http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif
You can see there is a cold front that goes from western Upper Michigan and then South and southwest wards. Behind this cold front is yet another cold front .. This cold front should become stationary..
http://www.hpc.ncep.noaa.gov/basicwx/92fwbgus.gif
Then begin to lift north as a warm front..
http://www.hpc.ncep.noaa.gov/basicwx/93fwbgus.gif
Now to be quite honest we are not that enthused with any severe weather happening to much during the day time because what is happening is that as the warm front lifts north this is bringing ridging over top of the region where the air mass has become moist and unstable. However..we have a lower level jet that will be strengthening as the evening goes on and we anticipate that coverage should increase. We have never been a proponent of severe weather from a warm front..so over all we are not expecting an extremely active day and as well there really is no impulse or piece of energy to add any fuel to this. This will all essentially be driven by low level warm air advection..
So lets look at the parameters that are in place on tonight's guidance..
TEMPERATURES
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/25/00/NAM_221_2012052500_F24_TMPF_2_M_ABOVE_GROUND.png
They will be from 70 to as high as near 100 depending on where you are located..
DEWPOINTS
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/25/00/NAM_221_2012052500_F24_DPTF_2_M_ABOVE_GROUND.png
50s and 60s with some smaller isolated 70 degree dew point readings.
CAPE
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/25/00/NAM_221_2012052500_F24_CAPE_SURFACE.png
Depending on where you are we range from 500-4000
LIFT INDEX
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/25/00/NAM_221_2012052500_F24_PLI_30_0_MB_ABOVE_GROUND.png
Lift index is from 0 to about negative 13 depending where you are located.
ENERGY HELICITY INDEX
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/25/00/NAM_221_2012052500_F24_EHI_1000_M.png
NOW..IF there is to be any tornado's today it would be in the following locations:
Southern part of Iowa into Southern Part Of Nebraska
Northern Missouri
All of Kansas
Oklahoma (all but the area not in the severe zone)
These areas would be at greatest risk for a tornado to occur because of the EHI being at 1 or above which could create super cells. One problem that will be fighting this however is the CAPPING that is coming in over top..
Greatest HELICITY is in NEBRASKA
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/25/00/NAM_221_2012052500_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
This is also where the most moisture "should be" so this increases the potential for tornadic activity to occur ..which we feel should be at about 5% in that area..Again, not a terribly high risk but the risk is there..
And last but not the least is the SHEAR in place..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/25/00/NAM_221_2012052500_F24_SHRM_500_MB.png
30-60 knots should be in place across the region..
GFS also suggests that lapse rates should be 6.0 or above which suggests that large hail is also going to be a possibility.
Overall the main threats will be winds and Large hail but the areas highlighted above should not be surprised to see the possibility of a tornado especially as the lower level jet increases. It is all going to be dependent on how much moisture return we can get with the ridging building in!

May 24th Severe Weather Outlook

Temperatures are in the 50s to 80s depending on where you are located...http://www.twisterdata.com/data/models/nam/221/maps/2012/05/24/00/NAM_221_2012052400_F24_TMPF_2_M_ABOVE_GROUND.png...DEWPOINTS.. are in the 50s to 60s depending on where you are located: http://www.twisterdata.com/data/models/nam/221/maps/2012/05/24/00/NAM_221_2012052400_F24_DPTF_2_M_ABOVE_GROUND.png...CAPE or INSTABILITY 500-3500 depending where you are located..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/24/00/NAM_221_2012052400_F24_CAPE_SURFACE.png ...EHI is above 1 into parts of Wisconsin..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/24/00/NAM_221_2012052400_F24_EHI_1000_M.png ...LIFT INDEX is 0 to about -8 ..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/24/00/NAM_221_2012052400_F24_PLI_30_0_MB_ABOVE_GROUND.png... HELICITY is about 200-250 ..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/24/00/NAM_221_2012052400_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png ...SHEAR is the most impressive with up to 80 knots of shear in some parts of the region..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/24/00/NAM_221_2012052400_F24_SHRM_500_MB.png ...At the surface..http://www.hpc.ncep.noaa.gov/basicwx/91fwbgus.gif ..a cold front will be slowly lifting eastwards ..also a piece of energy will be lifting NE thru Iowa and towards southern Canada. ..With the EHI above 1 super cells are possible and also with the Helicity around 200-250 in the same location as the EHI we are going to put a 5% tornado chance into the Wisconsin area.. Other wise the main threats will be winds and large hail along with heavy rain!

Severe Weather Outlook for the 23rd of May..

Severe Weather Outlook for the 23rd of May..
Temperatures are in the 80s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/23/00/NAM_221_2012052300_F24_TMPF_2_M_ABOVE_GROUND.png
DEWPOINTS are in the 60s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/23/00/NAM_221_2012052300_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE 500-3000 depending where you are located:
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/23/00/NAM_221_2012052300_F24_CAPE_SURFACE.png
LIFT INDEX is 0 to -8 depending where you are located..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/23/00/NAM_221_2012052300_F24_PLI_30_0_MB_ABOVE_GROUND.png
ENERGY HELICITY INDEX is above 1 in locations of Iowa into Nebraska
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/23/00/NAM_221_2012052300_F24_EHI_1000_M.png
This indicates that super cells are possible in that region. HELICITY is low in those general areas at 00z
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/23/00/NAM_221_2012052300_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
However..it increases in the same areas as the EHI above indicates and gets to around 300. This means that there will be a 5% tornado risk in the areas mentioned above..
SHEAR is 40 to 60 knots...
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/23/00/NAM_221_2012052300_F24_SHRM_500_MB.png
So the parameters that are in place do in fact present a severe weather day across the regions that are highlighted with Nebraska into Iowa being on the receiving end of potential for tornadic activity.
The trigger in place will be a cold front which will be moving to the south south east ... As of 6 Z tonight this should be its position..
http://www.hpc.ncep.noaa.gov/basicwx/91fwbgus.gif

May 22nd 2012 Severe Weather Outlook.

Alright tonight we have started to do things a bit differently here with the severe weather forecasts. I have quite a few people that I personally know that are down in TX..so we are going to be using a TX zoomed in county map for the severe weather in TX which means that TX will not be highlighted on the main USA map..
So lets look at the Severe Weather Parameters that will be in place for May 22nd 2012 Severe Weather Outlook... There is no doubt about the temperatures it is going to be a scorcher with temperatures in the 80 to 90 + range...http://www.twisterdata.com/data/models/nam/221/maps/2012/05/22/06/NAM_221_2012052206_F18_TMPF_2_M_ABOVE_GROUND.png ...DEWPOINTS will be in the 50s on the western side of TX to the 60-70 range pretty much elsewhere..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/22/06/NAM_221_2012052206_F18_DPTF_2_M_ABOVE_GROUND.png ..CAPE VALUES are 500-4000 depending where you are located in the highlighted zones..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/22/06/NAM_221_2012052206_F18_CAPE_SURFACE.png ...LIFT INDEX from 0 to as low as negative 10 ..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/22/06/NAM_221_2012052206_F18_PLI_30_0_MB_ABOVE_GROUND.png ... ENERGY HELICITY VALUES are above 1 in North Dakota and South Dakota ..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/22/06/NAM_221_2012052206_F18_EHI_1000_M.png ..This means ND and SD will be our target zone for tornado potential...HELICITY is generally 200 or less in those areas ..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/22/06/NAM_221_2012052206_F18_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png ..this means that tornado potential will be in place but on the low side of 2% . No doubt that SHEAR will be in place with 30 knots to the south over TX to as high as 60 knots further N into the Dakota region..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/22/06/NAM_221_2012052206_F18_SHRM_500_MB.png ...Weather Synopsis .. A strong upper level trough ..You can see the disturbance moving across the Northern Rockies when looking at the satellite http://weather.unisys.com/satellite/sat_vis.php?image=ir&inv=0&t=l12&region=us ..So this trough in the upper levels will advance eastwards while a low pressure will be moving across the northern Rockies northeastwards into Southern Canada... A stationary front is pretty much expected to be draped across the region http://www.hpc.ncep.noaa.gov/basicwx/92fwbgus.gif and it will be this front that helps to trigger off the severe weather potential along with the upper level trough producing height falls out ahead of it and the disturbance moving towards the Dakotas into Southern Canada.. Main severe threats will consist of hail and winds with heavy rains with the worst of the severe to the north over the Dakotas where the strongest shear along with the EHI will be where they can expect Winds, Hail and Isolated tornado's! Sorry this is so late today but we were working on some other things that took longer to get accomplished then originally intended!

Discussion for Severe Weather Outlook for the 20th of May

Discussion for Severe Weather Outlook for the 20th of May 2012..http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif.. Current weather analysis as of 03 Z shows a cold front stretching north to south from the Canadian border to a low pressure system located over TX. This cold front is expected to move east and then stall across TX from about Wichita Falls to a Abilene TX line from NW to SE.. but will then cross the eastern parts of the severe zone ( TN/KY ) between 00z and 12 Z Sunday evening into Monday morning. Parameters for the region.. TEMPERATURES generally in the 80s ahead of the front...http://www.twisterdata.com/data/models/nam/221/maps/2012/05/20/00/NAM_221_2012052000_F24_TMPF_2_M_ABOVE_GROUND.png..DEWPOINTS 60-70 http://www.twisterdata.com/data/models/nam/221/maps/2012/05/20/00/NAM_221_2012052000_F24_DPTF_2_M_ABOVE_GROUND.png...CAPE 500 to about 3500 http://www.twisterdata.com/data/models/nam/221/maps/2012/05/20/00/NAM_221_2012052000_F24_CAPE_SURFACE.png ..LIFT INDEX to negative 8 http://www.twisterdata.com/data/models/nam/221/maps/2012/05/20/00/NAM_221_2012052000_F24_PLI_30_0_MB_ABOVE_GROUND.png.. EHI is essentially non existent..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/20/00/NAM_221_2012052000_F24_EHI_1000_M.png ...HELICITY essentially non existent http://www.twisterdata.com/data/models/nam/221/maps/2012/05/20/00/NAM_221_2012052000_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png ..SHEAR 30 knots and upwards..http://www.twisterdata.com/data/models/nam/221/maps/2012/05/20/00/NAM_221_2012052000_F24_SHRM_500_MB.png ..All and all with no EHI and no Helicity present we put the tornado chances at less then 2 % anywhere... Main threats will be damaging winds and hail and heavy rain..

Severe Potential May 19th 2012

At the surface low pressure will be located over NW Kansas. Another area of low pressure will be over the Dakotas with an associated cold front. There is still yet another low pressure moving across the southern tier of Canada with a warm front extending towards the east from that low pressure area. These lows along with the cold front are generally going to move towards the east allowing the cold front to move towards the ESE.
A dry line will extend from the Ok/TX panhandle and run South/Southwest to SW TX. We do not have any part of TX in the severe zone because the 700 mb RH is relatively dry but ..there could be some isolated severe in the SW side of TX up towards Amarillo and Lubbock area...For the most part however we think that area should remain severe free..
Severe Parameters in Place for the Severe Zone are as follows:
Temperatures 70s to 90s depending on where you reside..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/19/00/NAM_221_2012051900_F24_TMPF_2_M_ABOVE_GROUND.png
Dew Points in the 60-70 range
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/19/00/NAM_221_2012051900_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE 500 to about 3500 depending where you are
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/19/00/NAM_221_2012051900_F24_CAPE_SURFACE.png
Lift Index 0 to - 9 depending on where you reside...
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/19/00/NAM_221_2012051900_F24_PLI_30_0_MB_ABOVE_GROUND.png
EHI is generally low
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/19/00/NAM_221_2012051900_F24_EHI_1000_M.png
However.. EHI does increase but not until later in the evening and this would be across Western Ok and North Central Wisconsin.
Helicity highest is over Canada and then also over Minnesota but this does not coincide with any areas of highest EHI...
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/19/00/NAM_221_2012051900_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
Shear from OK northwards 30 knots plus
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/19/00/NAM_221_2012051900_F24_SHRM_500_MB.png
So we do have parameters in place for severe weather to occur across the highlighted zone. Main threats will be hail and wind... with the tornado chance being 2% in the mentioned above areas where the EHI increases later in the evening...

Severe Weather Outlook May 16th 2012

Severe Weather Outlook May 16th 2012
Temperatures in the 70s-80's
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/16/00/NAM_221_2012051600_F24_TMPF_2_M_ABOVE_GROUND.png
DEW POINTS in the 60s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/16/00/NAM_221_2012051600_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE 500-2500 Depending where you reside in the severe zone..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/16/00/NAM_221_2012051600_F24_CAPE_SURFACE.png
An interesting aspect to the severe zone is the area of Western CT and western MA...EHI is actually favorable for the potential of a tornado..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/16/00/NAM_221_2012051600_F24_EHI_1000_M.png
LIFT Index is to about - 5 depending where you are..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/16/00/NAM_221_2012051600_F24_PLI_30_0_MB_ABOVE_GROUND.png
HELICITY to about 200
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/16/00/NAM_221_2012051600_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
SHEAR is 35 knots +
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/16/00/NAM_221_2012051600_F24_SHRM_500_MB.png
Trigger will be a cold front moving across the Northeast with a weaker front crossing the Southeast region.
Once the cold front moves off the coast the threat for severe will diminish. The main threats will be damaging winds with some hail possible ..However..keep in mind there could be an isolated tornado with the EHI being above 1 in the areas mentioned above..

Severe Weather Outlook For May 15th 2012

Severe Weather Outlook For May 15th 2012

Lets look at Parameters to start off with ...
Temperatures will be in the 60s to 80s depending on where you live..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/15/00/NAM_221_2012051500_F24_TMPF_2_M_ABOVE_GROUND.png
Dew Points will be in the 60-70 range again depending on where you live!
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/15/00/NAM_221_2012051500_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE is 500 to about 2500 Depending on where you reside..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/15/00/NAM_221_2012051500_F24_CAPE_SURFACE.png
LIFT INDEX to about negative 7 depending on where you are..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/15/00/NAM_221_2012051500_F24_PLI_30_0_MB_ABOVE_GROUND.png

EHI is essentially non existent ..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/15/00/NAM_221_2012051500_F24_EHI_1000_M.png
HELICITY is not very impressive either across any of the region..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/15/00/NAM_221_2012051500_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
Small portion of MI would be the greatest risk for a Isolated tornado...We do not see a big tornado chance because the EHI and Helicity is just really not pointing towards anything significant..
The other problem really is a lack of any significant SHEAR
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/15/00/NAM_221_2012051500_F24_SHRM_500_MB.png

LAPSE RATES
http://raleighwx.americanwx.com/models/gfs/00zgfslapse024.gif

We will turn to the GFS for these and they are pretty decent at 6.0 +

At the surface for a trigger we have a cold front that will be dropping from the SE thru the lakes region..

Along the eastern seaboard any severe will be related to the broad area of low pressure that will be moving thru the region along the stationary front.  Over all we are not impressed with the severe aspect...any storms that could manage to go severe would be more along the wind/hail threat and over all we think its a lower risk ..
http://weather.unisys.com/satellite/sat_ir_us.gif
The above is a look at current satellite and you can see there is alot of cloud cover in place across the region. If we can get the cloud cover to break and get some sunshine involved then we could be looking at a greater chance of severe.....locations to the south of say the PA /MD region have the greatest chance at this to occur...

Heavy Rains to move in after Midnight tonight!

Taking a look at what is going to transpire over the next 72 hours..
http://www.hpc.ncep.noaa.gov/basicwx/92fwbgus_init_2012051300.gif
By 12 Z there will be a cold front across western PA with a low pressure area that will be developing over the Southeast states.. the cold front will make its way eastwards and is expected to stall and become stationary across East Central PA. This will allow the low pressure developing in the southeast to track up and along the stalled out stationary front.
By Monday evening this low pressure should be located over SW Virginia.
For Mothers Day for the most part it should be a partly sunny day at least in the PA region..one exception could be across western PA ..In eastern PA the rainfall should wait to move in until after midnight and the heaviest rains look to occur on Monday evening and overnight.
A widespread 1 - 3 inches of rain is anticipated and this will cause ponding on roadways and also flash flooding ..and perhaps some small creeks to over flow their banks.
Not much instability to work with as far as thunderstorm activity is concerned but there could be some garden variety type thunderstorms as well.
It is possible that we could have training areas of rainfall which essentially means that the heaviest rains may keep training over the same region. If this occurs along with any thunderstorms we could be looking at some locations picking up over three inches of rain. Best chance of this would be from SE PA into NYC area.
Another cold front will pass thru on Wednesday but by this time the heaviest precipitation should be pushed off to the east with nothing but some lingering showers possible!

Heavy Rains the next 72 hrs.?

3-4 inches of rain according to HPC...We will look into this later this evening (overnight ) and have a complete update on this situation..
At the present time the moisture return via radar is not all that impressive..

May 11th Severe Weather Outlook!

May 11th Severe Weather Outlook
Temperatures across the region mainly in the 70s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/18/NAM_221_2012051018_F30_TMPF_2_M_ABOVE_GROUND.png
Dew points are in the 60s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/18/NAM_221_2012051018_F30_DPTF_2_M_ABOVE_GROUND.png
CAPE 500 to about 2000 depending on where you are located..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/18/NAM_221_2012051018_F30_CAPE_SURFACE.png
LIFT INDEX 0 to about -4
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/18/NAM_221_2012051018_F30_PLI_30_0_MB_ABOVE_GROUND.png
EHI is non existent across the severe zone
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/18/NAM_221_2012051018_F30_EHI_1000_M.png
HELICITY is also non existent across the severe zone
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/18/NAM_221_2012051018_F30_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
SHEAR is 35 knots +
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/18/NAM_221_2012051018_F30_SHRM_500_MB.png
If you are in TX and you are not in the severe zone this does not mean that you will be precipitation free but you will experience heavy rainfall and perhaps even garden variety thunderstorms but the greater emphasis will be on heavy rain..
The weather system responsible for the severe weather potential and the heavy rain is an Upper Level Low that you can see spinning on satellite..
http://www.ssd.noaa.gov/goes/comp/ceus/flash-vis.html
Time sensitive above as the sun is going down. With the EHI and Helicity practically non existent the severe threats will be mainly wind, hail and heavy rains!

Severe Weather Outlook May 10th 2012

Severe Weather Outlook May 10th 2012
Lets begin with looking at the severe parameters in place:
Temperatures will be in the 70s and 80s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/00/NAM_221_2012051000_F24_TMPF_2_M_ABOVE_GROUND.png
Dew points will be in the 50s and 60s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/00/NAM_221_2012051000_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE not overly impressive with 500 to about 2000
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/00/NAM_221_2012051000_F24_CAPE_SURFACE.png
Lift index is 0 to -7 depending where you are located
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/00/NAM_221_2012051000_F24_PLI_30_0_MB_ABOVE_GROUND.png
EHI is less then 1 all over until AFTER midnight a isolated location in southern TX reaches 1 around 1 AM to 7 AM time frame
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/00/NAM_221_2012051000_F24_EHI_1000_M.png
HELICITY is also not impressive ..but again it does become impressive more or less after midnight across the north where we have the small severe zone..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/00/NAM_221_2012051000_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
SHEAR is probably the most impressive ingredient with the severe parameters today with the range of 35 knots to as much as 80 knots to the north. It is because of this INCOMING shear that we have introduced a severe zone with a impulse that will be moving across the region. Again though this may not actually occur in the north till after midnight..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/10/00/NAM_221_2012051000_F24_SHRM_500_MB.png
Over all we are not that impressed with the severe chances as the parameters are essentially all very marginal with the exception of the shear to the north that is coming in with a little impulse of energy.
An upper level low will be responsible for the severe weather potential across southern TX. Again..with marginal parameters ...little EHI and Helicity..the greatest threats for severe weather will be Hail and or Winds. It is possible that an isolated tornado may occur but that should be more the exception then the norm...

May 7th Severe Weather outlook!

May 7th Severe Weather Outlook...
Current Surface map
http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif
Current Surface map at 00z or 7 PM shows low pressure over SW TX with a cold front extending to another low over the Ok Border and then the front continues to extend NE to another low over SE Iowa. From that low drapes a warm front which then turns into a cold front across the Southeast.
This whole frontal system and two areas of low pressure are basically going to be pushing off to the east northeast and cause a warm front to move towards the Northeast region.
The cold front will be the focus of the severe weather over the southeast region...
Temperatures will be in the 70-90 range across the region in discussion
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_TMPF_2_M_ABOVE_GROUND.png
Dew Points will be in the 60-70 range
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE approximately 500-3000 across the region depending on where you are located..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_CAPE_SURFACE.png
LIFT Index from 0 to negative 8 depending on where you are located..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_PLI_30_0_MB_ABOVE_GROUND.png
HELICITY
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
The greatest area is actually over Central PA but this region is not anticipating any severe weather ...due to lack of other parameters ..
SHEAR
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_SHRM_500_MB.png
The greatest is over Western TX and then the Northeast region and the upper Midwest. Else where the shear is lacking..
EHI
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_EHI_1000_M.png
As you can see EHI is lacking across the area. The lack of Helicity and the lack of EHI suggests that tornadoes will be less likely.
So we should be mainly dealing with severe weather in the form of winds and hail but as always ..you can never rule out an isolated tornado!

May 7th Severe Weather outlook!

May 7th Severe Weather Outlook...
Current Surface map
http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif
Current Surface map at 00z or 7 PM shows low pressure over SW TX with a cold front extending to another low over the Ok Border and then the front continues to extend NE to another low over SE Iowa. From that low drapes a warm front which then turns into a cold front across the Southeast.
This whole frontal system and two areas of low pressure are basically going to be pushing off to the east northeast and cause a warm front to move towards the Northeast region.
The cold front will be the focus of the severe weather over the southeast region...
Temperatures will be in the 70-90 range across the region in discussion
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_TMPF_2_M_ABOVE_GROUND.png
Dew Points will be in the 60-70 range
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE approximately 500-3000 across the region depending on where you are located..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_CAPE_SURFACE.png
LIFT Index from 0 to negative 8 depending on where you are located..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_PLI_30_0_MB_ABOVE_GROUND.png
HELICITY
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
The greatest area is actually over Central PA but this region is not anticipating any severe weather ...due to lack of other parameters ..
SHEAR
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_SHRM_500_MB.png
The greatest is over Western TX and then the Northeast region and the upper Midwest. Else where the shear is lacking..
EHI
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/07/00/NAM_221_2012050700_F24_EHI_1000_M.png
As you can see EHI is lacking across the area. The lack of Helicity and the lack of EHI suggests that tornadoes will be less likely.
So we should be mainly dealing with severe weather in the form of winds and hail but as always ..you can never rule out an isolated tornado!

May 6th Severe Weather outlook

Severe Weather Outlook for May 6th
Lets begin by looking at the severe parameters in place ...
Temperatures will be in the 70s to 90s across the region..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/06/00/NAM_221_2012050600_F24_TMPF_2_M_ABOVE_GROUND.png
Dew Points are going to be in the 60s and 70s across the region..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/06/00/NAM_221_2012050600_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE will be from 500 to as much as 4500 across the region
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/06/00/NAM_221_2012050600_F24_CAPE_SURFACE.png
LIFT index from 0 to as low as negative 12 across the region
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/06/00/NAM_221_2012050600_F24_PLI_30_0_MB_ABOVE_GROUND.png
EHI Isolated locations that are 1 or higher...
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/06/00/NAM_221_2012050600_F24_EHI_1000_M.png
HELICITY greatest area is further north over the lakes region but this does not allocate well with the greatest EHI or other severe parameters ..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/06/00/NAM_221_2012050600_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
SHEAR
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/06/00/NAM_221_2012050600_F21_SHRM_500_MB.png
SHEAR is the biggest question as the greatest shear is over the NE region and the other area of greatest shear is behind the severe weather zone.
http://www.hpc.ncep.noaa.gov/basicwx/92fwbgus.gif
At the surface we see a low pressure over SW MN with a cold front to another area of low pressure over SW Kansas with the cold front then trailing to the south west and with the dry line running from the north to the south in TX. A Semi Stationary front also extends SE and then across the SE from the low pressure in SW MN. It is possible that there could be some severe weather along that front across the SE but we did not include that area in the outlook because that should be isolated and more in the way of heavier rain fall.
In TX the cold front will over take the dry line but for the most part of the day the TX region should be dry until later in the afternoon towards evening when moisture starts to increase. With no EHI and no Helicity to be concerned with the severe potential there would be for mainly winds and Hail and this is also called into question because of really a lack of shear. Essentially you can have the greatest parameters in place but if shear is really weak you really can not get anything strong enough to be sustained so again this should be a mainly isolated region for severe weather!
The greatest area of concern we have highlighted is in red and this is because of the EHI and we think this is the area that will have the greatest chance for a couple tornado's.

May 5th Severe Weather outlook

Generally we like to get this out before SPC gets their outlook out but unfortunately it did not work that way tonight. We originally were not going to do an outlook for today ..not because there was not going to be severe weather but just because of the time factor of not getting it out before them..

We busted on yesterdays outlook in TX..The CAP did break and severe reports did occur there..However..kind of a tit for tat type thing as the slight risk issued by SPC busted in E PA..

We have never claimed to be perfect and you can not get it all ..all the time..

So with that said we took a look at the parameters tonight and we were quite impressed with the area that we have labeled in red.. 
EHI across this area goes from a 1 to about a 3-4
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/05/00/NAM_221_2012050500_F24_EHI_1000_M.png
HELICITY is also impressive in the same area with 300 +
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/05/00/NAM_221_2012050500_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
SHEAR 40-60 knots
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/05/00/NAM_221_2012050500_F24_SHRM_500_MB.png
LIFT index to about -14 (starting at 0) depending where you are located...
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/05/00/NAM_221_2012050500_F24_PLI_30_0_MB_ABOVE_GROUND.png
CAPE from 500-5000
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/05/00/NAM_221_2012050500_F24_CAPE_SURFACE.png
Temperatures are 70-100's
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/05/00/NAM_221_2012050500_F24_TMPF_2_M_ABOVE_GROUND.png
DEW POINTS in the 60s-70s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/05/00/NAM_221_2012050500_F24_DPTF_2_M_ABOVE_GROUND.png
So these parameters above with the EHI and HELICITY and CAPE point to a strong case for tornadoes located in the region in red.

Further to the south into TX.. We have a dry line that will be the focus of some severe weather potential in the form of Hail with lapse rates being around 8.0 . We have to say we were debating about whether or not to include this area with the Water Vapor showing mainly dry air into that region..
http://www.ssd.noaa.gov/goes/comp/ceus/wv-l.jpg

Majority of your guidance such as the NAM/GFS show that this area should be mainly precipitation free which leans more towards what we are seeing with the water vapor image ..they suggest anything that develops would develop south of the FALLS region and that would not be until 7 PM till  1 AM time frame and it kills it off pretty quickly on both those models.

At the surface ... there is ridging across the central part of the USA but a trough and a strong impulse will be moving across the Rocky mountain region towards the Canadian border with a quasi stationary front across the region as well.  Also in addition to this will be a cold front that will be moving across the most active zone and this will provide added fuel to what is already a pretty potent parameter atmosphere.

We suggest if you are in that area that you stay tuned to the NWS or your favorite weather source for the latest information.
If a tornado warning should occur ..Make sure you have a plan in place and seek your place of shelter...
If you are outside that area then the risk for severe weather in those zones will be Hail and or Wind unless other wise specified above..

May 4th Severe Weather Outlook

We have switched maps again ..the last map though we liked the look of it ..created a lot of difficulty when it came to filling in the zones.
Taking a look at the water vapor image this evening..
http://www.ssd.noaa.gov/goes/comp/ceus/wv-l.jpg
You can see besides the SW TX region the air once again in TX is on the dry side... the moisture should increase a little bit this evening with any severe staying to the west of Wichita Falls TX area and perhaps some shower activity around the falls area. There after once again it looks as if dry air will be moving back into the region and this is the reason that we have not really included a southern extent despite the dry line being in place.
So lets look at the latest surface map to get a perspective on what is happening and should happen then for tomorrow..
http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif
You can see the stationary front and this stationary front has been what is causing severe weather along it ..along with the day time heating and parameters that are in place..
This stationary front is suppose to lift thru as a warm front into Southern New England and this warm front will bring a chance of severe winds and hail into the NE States..
The trigger needed for this severe weather chance will be a cold front that is on the move Southeast from the Great Lakes region. This front will clash into warm air that should be in place and with the parameters in place create the "spark needed" for the severe!
It will also be this same cold front that will bring the chance for severe weather into the rest of the zone..
So lets now look at the severe Parameters that will be in place in order to determine what type of severe weather we will be dealing with outside of the NE states!
TEMPERATURES in the 70s to the 100's (talk about HOT)
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/18/NAM_221_2012050318_F24_TMPF_2_M_ABOVE_GROUND.png
DEW POINTS in the 60s to 70s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/18/NAM_221_2012050318_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE 500-4500 depending on where you are located...
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/18/NAM_221_2012050318_F24_CAPE_SURFACE.png
LIFT INDEX to as low as negative 12
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/18/NAM_221_2012050318_F24_PLI_30_0_MB_ABOVE_GROUND.png
EHI is pretty significant in the OK region
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/18/NAM_221_2012050318_F24_EHI_1000_M.png
However..the HELICITY ..is not the greatest allocated with the EHI ..In other words the HELICITY is on the lower side..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/18/NAM_221_2012050318_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
In addition to this the air at 700 mb Relative Humidity level is rather dry..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/18/NAM_221_2012050318_F24_RH_700_MB.png
And in addition to that the shear is also lacking in that particular region. (elsewhere about 35+ knots)
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/18/NAM_221_2012050318_F24_SHRM_500_MB.png
Now if the CAP can be broken and we will have to keep an eye on the later models runs places like OK could end up seeing the potential for tornadoes! However..at the present time we think that the greatest threats in any of the zone will be straight line winds and hail.
Potential depending on future model runs for more of OK to be added into the coverage zone but will for now hold off on it!
Stay tuned

May 3rd Severe Weather outlook

May 3 Severe Weather Outlook
They often say a picture speaks 1000 words ..well in this case this picture speaks one word for the South central area....
http://www.ssd.noaa.gov/goes/comp/ceus/wv-l.jpg
That word is "Dry"...
Lets get right into it...It is going to be a warm day with temperatures in the 70s to 90s depending on where you are located...
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/00/NAM_221_2012050300_F24_TMPF_2_M_ABOVE_GROUND.png
As mentioned above with the water vapor the dry air and you can see this in the 700 mb RH depiction as well...
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/00/NAM_221_2012050300_F24_RH_700_MB.png
CAPE once again is 500-4500 depending on where you are located...
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/00/NAM_221_2012050300_F24_CAPE_SURFACE.png
Lift index is as low as -12
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/00/NAM_221_2012050300_F24_PLI_30_0_MB_ABOVE_GROUND.png
Shear as high as 70 knots over the North land west of the lakes
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/00/NAM_221_2012050300_F24_SHRM_500_MB.png
Helicity is actually most impressive over the Great lakes themselves versus actual land region..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/00/NAM_221_2012050300_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
EHI is above 1 in some isolated locations but the Helicity is not favorable in those locations so this just gives the indication that where those EHI values are could be the potential for some Tornadoes.

http://www.twisterdata.com/data/models/nam/221/maps/2012/05/03/00/NAM_221_2012050300_F24_EHI_1000_M.png
All and all it will be this cold front shown here as of 6 Z this morning...
http://www.hpc.ncep.noaa.gov/basicwx/91fwbgus.gif
That will be dropping towards the South and east that will bring the chance of severe weather once again to the areas depicted.
In eastern PA we think it will be more isolated as any storms will probably have a hard time making it over the mountains.
There will also once again be return moisture coming from the GOM and in this region you could see some severe as well..
Main threats are winds and hail... we put the tornado potential in the area reference with the EHI at 5% all other areas less then 2 %..
We will be tracking with statements and meso discussions from 12 noon thru 7 AM

May 2nd Severe Weather Outlook

Severe Outlook For May 2nd 2012
http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif
http://www.ssd.noaa.gov/goes/comp/ceus/wv-l.jpg
We are going to begin by looking at the water vapor image above along with the latest surface map from HPC.. Once again you can see the area that will end up being covered by dry air .
Essentially a stationary front is across the US from west to east with ripples or waves of low pressure or if you prefer impulses moving along that front. This front will once again be a focus of severe weather potential..
Now..there is some question as to whether or not the ongoing convective precipitation in the Ohio Valley area will have an effect on that regions severe weather.
http://weather.unisys.com/satellite/sat_ir_us.gif
Satellite shows there is clearing behind this batch of moisture.. so this moisture may help to make the atmosphere a bit more stable and hinder severe potential.
So lets look into the heart of matters with the severe parameters..
Temperatures 70s to 90s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/02/00/NAM_221_2012050200_F24_TMPF_2_M_ABOVE_GROUND.png
Dew points 60s and 70s
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/02/00/NAM_221_2012050200_F24_DPTF_2_M_ABOVE_GROUND.png
CAPE Values 500-4500 depending on where you are located
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/02/00/NAM_221_2012050200_F24_CAPE_SURFACE.png
Lift index to as low as negative 11 to 12
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/02/00/NAM_221_2012050200_F24_PLI_30_0_MB_ABOVE_GROUND.png
Based on EHI we would place the greatest threat for tornadoes over the Iowa region and perhaps Eastern Nebraska ..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/02/00/NAM_221_2012050200_F24_EHI_1000_M.png
In the overnight hours the EHI actually increases....
The highest Helicity is actually over E PA
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/02/00/NAM_221_2012050200_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
However we are not anticipating any severe weather making it into eastern PA. So over all the EHI suggests some tornado's are possible but the Helicity negates this factor somewhat. Suggesting super cells could occur with the potential for tornadoes mainly in the area mentioned above..
SHEAR is 35-60 knots across the region depending where you are..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/02/00/NAM_221_2012050200_F24_SHRM_500_MB.png
The stationary front shown in the surface analysis map will continue to lift northwards as a warm front . This is due to ridging pressing from the south towards the north...
With any storms that do form we will be looking at the potential for very heavy rains. We would break down the percentages like this..
Tornadoes in the area that we mentioned 5% risk with all other areas outside that region at less then 2 %
Winds in excess of 60 MPH 15%
Large Hail 15%

May 1 Severe Weather Outlook

Severe Weather Outlook For May 1st 2012
Taking a look at the water vapor image in motion you can virtually see that the moisture is lifting towards the NNE ..
http://www.ssd.noaa.gov/goes/comp/ceus/flash-wv.html
On the backside you can see dry air that is pushing into the TX region..to go along with this is the 700 mb which is for by 7 PM ..
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/01/00/NAM_221_2012050100_F24_RH_700_MB.png
You can see the RH level at 700 mb is dry for the majority of the region..So this has factored into the equation as that area is going to be CAPPED....

Now lets get to the heart of things for today..

Temperatures are going to be in the 70s to 90s
Dew points 60s and 70s

CAPE levels are 500-4000 depending where you are
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/01/00/NAM_221_2012050100_F24_CAPE_SURFACE.png
Levels of CAPE by definition:
*Interpretation of values:
*1 to 1,500 Positive CAPE
*1,500 to 2,500 Large
*2,500+ Extreme

Lift Index
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/01/00/NAM_221_2012050100_F24_PLI_30_0_MB_ABOVE_GROUND.png
As low as -8-9 depending on where you are.....

EHI
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/01/00/NAM_221_2012050100_F24_EHI_1000_M.png

You can see pretty much a large section has EHI that is at 1 or above ..

*Interpretation of values:
*Greater than 1:    Super cells likely
*1 to 5:     Possibility of F2, F3 tornadoes
*5+:     Possibility of F4, F5 tornadoes

Helicity 300 or less
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/01/00/NAM_221_2012050100_F21_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png

Interpretation of values:
*150-300 Possible Super cell
*300 to 400 Super cell Severe Favorable
*400+ Tornadic Thunderstorms Favorable

Mid Level Lapse rates 6.0 or above
http://raleighwx.americanwx.com/models/gfs/00zgfslapse024.gif
Surface Bulk shear 35 knots +
http://www.twisterdata.com/data/models/nam/221/maps/2012/05/01/00/NAM_221_2012050100_F24_SHRM_500_MB.png

At the surface a low pressure area is over western S Dakota with a dry line stretching to the south all the way into western TX.. Low pressure will be moving out of Montana to the east with a cold front attached to it. By 18 Z this low will then be located over the Dakotas border . From that low pressure area extends a stationary (quasi) front to a low pressure that will be over NYC..The western half of this front will lift into the Great Lakes region as a warm front ..
It is this low pressure area that will be moving out of Montana towards the lakes that will be responsible for the severe weather with also some severe possible along the quasi stationary front...

Due to the EHI more so then the Helicity we have added a large red zone. This red zone means that there is the potential in this highlighted area for all three aspects of severe weather from winds of 65 MPH or greater to Large hail to Tornado potential.

If you are in this area please stay tuned to your local weather radio and keep tuned into Down To Earth Forecasting as we will be providing coverage of watches and warnings from about 1 PM EST on till 6:30 AM..