April 30th Severe Weather outlook

Severe Weather Outlook For April 30th 2012
First things first lets look at the surface map and as you can see the front that was stationary has indeed lifted north as we mentioned that it would..http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif
Once again this front has become quasi stationary...
And as you can see there is waves of low pressure along the front as well..
Low pressure will be located over western Illinois in about another hour.. This low will move east while pushing a warm front into the NE. This warm front will serve as a focal point for convective rains and the potential for severe weather into the PA and Ohio region and the stationary front will once again serve as a focal point for severe across the rest of the region..
http://www.ssd.noaa.gov/goes/comp/ceus/wv-l.jpg
As you can see by water vapor we do not have as much dry air in place as what we had previously ...
http://www.ssd.noaa.gov/goes/comp/ceus/flash-wv.html
Putting this in motion you can see how the atmosphere is becoming more moist by looking at the enhanced water vapor image and the orange colors. For those in TX notice that most of this is occurring to the north..
Since we base these forecasts on the parameters we like to look at the time period around when the heat of the day is at its best so when we do that we are looking at the CAPE here for 24 hrs. from 7 PM (Sunday evening)
http://www.twisterdata.com/data/models/nam/221/maps/2012/04/30/00/NAM_221_2012043000_F24_CAPE_SURFACE.png
CAPE ranges anywhere from about 500 to about 3000 depending where you are..
http://www.twisterdata.com/data/models/nam/221/maps/2012/04/30/00/NAM_221_2012043000_F24_PLI_30_0_MB_ABOVE_GROUND.png
Lift index goes to about - 8 again depending on where you are located...
http://www.twisterdata.com/data/models/nam/221/maps/2012/04/30/00/NAM_221_2012043000_F24_SHRM_500_MB.png
Shear is about 30 knots to as much as 60 knots..
HELICITY
http://www.twisterdata.com/data/models/nam/221/maps/2012/04/30/00/NAM_221_2012043000_F24_HLCY_1000_M_ABOVE_GROUND_0_M_ABOVE_GROUND.png
About 50-250 and under....
Remember with Helicity this information:
*150-300 Possible Super cell
*300 to 400 Super cell Severe Favorable
*400+ Tornadic Thunderstorms Favorable
So essentially the Helicity is suggesting that some locations in PA could have super cells.
EHI
http://www.twisterdata.com/data/models/nam/221/maps/2012/04/30/00/NAM_221_2012043000_F24_EHI_1000_M.png
You can see that most areas for EHI are below the threshold of 1 with the exception of SW PA .. and in NW TX...
Keep this in mind for EHI
*Interpretation of values:
*Greater than 1: Super cells likely
*1 to 5: Possibility of F2, F3 tornadoes
*5+: Possibility of F4, F5 tornadoes
So this suggests that SW PA could see super cell severe thunderstorms. It also suggests where the EHI is 2.25 that their could be some tornado's which is in NW TX to the south of the OK/TX panhandle..
Dew points are in the 60s
http://www.twisterdata.com/data/models/nam/221/maps/2012/04/30/00/NAM_221_2012043000_F24_DPTF_2_M_ABOVE_GROUND.png
Temperatures 70- 90 +
http://www.twisterdata.com/data/models/nam/221/maps/2012/04/30/00/NAM_221_2012043000_F24_TMPF_2_M_ABOVE_GROUND.png
The main threats outside of the areas mentioned above will be Large hail and wind..
It is indeed possible that locations such as TX outside of the area mentioned above stay on the southern side of any activity. Looking at water vapor
http://www.ssd.noaa.gov/goes/comp/ceus/flash-wv.html
Again does show the dry air trying to come back into the atmosphere.. Essentially we are not expecting any thing more then isolated tornado chances in the area mentioned around the 2.25 region for EHI ...and because we are essentially dealing with more in the way of a warm front and a stationary front...

April 29th Severe Weather Outlook

Just made some adjustments to the map that was made last night. The culprit responsible for the severe weather probabilities is essentially the same stationary front that is across the region..
http://www.hpc.ncep.noaa.gov/basicwx/91fwbgus.gif
Severe weather parameters
CAPE 500-2000 depending where you reside...
EHI is virtually non existent on the NAM
Helicity is also virtually non existent on the NAM
Lift index to about negative 7 depending where you reside..
Shear once again is 35 knots +
Temperatures in the 80s and 90s
Dew points in the 60s and 70s
If you go to this link ( time sensitive) http://www.ssd.noaa.gov/goes/comp/ceus/wv-l.jpg
You will see how the moisture blew up over N C TX and the reason for the storms that occurred west of there..but you can also see when you put this into motion that drier air is also filtering back into the region..
http://www.ssd.noaa.gov/goes/comp/ceus/flash-wv.html
Dry air is noted by the brown color on the enhanced water vapor..
This front is really not going to move to much thru out the day, It may lift slightly north as a warm front but then essentially settle slightly south by evening..
So in TX there could be some isolated severe but the main thing we expect in that region is rainfall. Most of the region still has a dry RH 700 mb level ...and as Water vapor shows dry air is filtering in behind left over convection from yesterday.
With NO EHI essentially and no Helicity we are not really seeing a Tornado threat anywhere..Of course you always risk the threat of one with a severe storm but if any were to occur we expect them to be more isolated...

April 28th Severe Weather Outlook

Severe Parameters
500 to about 3500 depending where you are..
EHI is essentially below 1 in all locations
Lift Index 0 to about - 8
Mid Level Lapse Rates 6.0 to 7.0
Across N KY around 300 this would indicate tornadic possibility but with EHI low thinking would be isolated..
Shear is not an issue with 30 + knots
At the surface..
Low pressure over NW Missouri will be moving towards the southeast. Trailing to the southwest is a cold front moisture starved on the southern end thru TX due to mentioned reasons above and to the east of this low is a warm front.. Southern part of this front will become stationary and it is the warm front off to the east that will bring about the chances for severe weather along with rainfall across the highlighted zone...

April 27th Severe Weather Outlook

Severe Weather Parameters
CAPE is 500-2000 depending on where you are located
EHI is +1 or higher in East Central KS
Helicity is at or about 300 in the same general region
This suggests that in this region there is the potential for tornado activity...
Lift Index is 0 to about -6 depending where you reside..
No lack of shear with 35-50 knots depending where you are located..
At the surface
http://www.hpc.ncep.noaa.gov/sfc/90fwbg.gif
There is a front draped across the region and this front will become stationary and become the focal point for severe weather.
In addition to this an area of low pressure will be moving across Kansas!

April 25th Severe Weather Potential

Severe Parameters
We are looking at CAPE values on the guidance from 500-4000.
Lift index actually as low as -10 on the NAM..
Temperatures are going to be from the 70s to as high as 100 perhaps + that if the NAM is correct in locations such as TX...
Speaking of TX we have them in the region of severe but all in all that region should be capped as the 700 mb level is dry as a bone. As a refresher this is what we use to look at to see if moisture can make it down to the ground...And in this case all the moisture should stay North of that region despite the high parameters that are in place..
Shear will be ample with 35-60 knots in place across the region..
Across the rest of the region there will also be a CAP in place with Westerly flow over the region. This will likely cause any severe weather to be caused by Warm Air Advection.
Mid Level lapse rates will be 6.0 + so we think that the greatest severe threat that will be in place would be Hail..However...with the severe being dependent on Warm Air Advection and the westerly flow this could cause more of isolated severe hail. Overall we are not seeing this as a major severe weather threat day!
At the surface low pressure and associated trough will be dropping Southeast out of Minnesota with its attending Warm front which will provide the Warm Air Advection push across the region. By Wednesday evening this low pressure should be located over NE Iowa with the warm front draping SSE ..
Again...not really impressed about severe weather chances ..leaning more towards isolated severe then anything else

Weekend Early Week Storm System

It would appear as if all models are in relative agreement as of the 00z runs with a frontal system coming thru but slowing up and a wave of low pressure riding up along the eastern Seaboard bringing with it heavy rains and gusty winds of which could gust as high as 60 mph.

This will all get underway Saturday with the cold front advancing slowly towards the east.

It appears as though something that has not happened all winter long will happen with this storm and that is we will have the northern stream energy phase up with the southern stream energy to produce a Late Season Nor'easter…

Heavy..Flash flooding rains will be the issue along with gusty winds which could bring or cause power outages in the locations that have them.

As we said all guidance agrees on this..

Even the ECM ensembles which are the last two images agree on this scenario..though the low is not as far west inland as the operational was.

Now we did not show it on the map above but keep in mind that there is a decent chance for rain to change over to snow in Western Pa.

Stay tuned for more information later this evening on this developing storm system!

April 21st Severe Weather Potential

Frontal system that looks to be crossing the region on Saturday looks as though as it could bring some severe weather across PA and into the south east! This is a day 2 map at this point so we are not really going to go into any details at the present time..Parameters however are favorable across this highlighted zone and there is also a trigger in the form of a cold front..Something to keep a watch on in addition to whether or not the coastal effects the area or not..