Widespread Outbreak Wed, Another Thursday ..Could Friday as well?

Low pressure over Oklahoma with a cold front trailing northwards to a low pressure that is located over the Dakotas. This is the scenario expected to be at 8 AM in the morning.  This cold front is having a tough time making its way eastward but is doing so slowly each day. The reason for the hard time is because of the ridge that has built in over the east producing the very warm to hot weather with temperatures in the lower 90s.  You can see this ridge indicated by the high pressure off the east coast. So the system is forced more or less to move to the NE trying to take the path of least resistance. 
While the day is not over yet we once again have had widespread reports of severe weather all facets of severe were involved..

210 total reports on the day so far with the day still not over and this would qualify as the second day of the outbreak of severe weather. First being wed..second being thursday and now we head into friday and the question is due we have a third day that would qualify as an outbreak?

We think the answer continues to be yes it will be another widespread severe active day..

Firstly, temperatures once again are going to be in the 70s to 90s depending on where you are located..

Dew Points once again are going to be in the 60s and 70s indicating that the atmosphere will have moisture needed for severe weather. These storms will produce very heavy rains in addition to large hail and damaging winds. 

Wind shear is probably a bit more impressive today with the wind shear from 30 knots to as much as 60 knots across the region.

Convective Available potential energy or CAPE which is needed ingredient to feed fuel into any storms will range from 1000 to as much as 4000 down into the OK area.

Lift index will also be in place with lift index as low as negative 10 or greater.

EHI is highest once again from OK into Ark into Missouri and above 1 in further north locations as well . This is an indication of where the greatest chance for tornadic activity can be .

Helicity is also supportive of supercells in the aforementioned areas. And finally the SWEAT index which will be posted next is allocated with in these same general areas...

SWEAT INDEX

So with the warm to hot air in place, a trigger marching east to Northeast across the country ..severe parameters in place ..we once again expect today to be a very active day and could be just as widespread as the past two days have been. 

We remind you that if you are in the path of a tornado warned storm to seek shelter immediately until the storm has passed. If you are outside the areas that were mentioned above as tornadic activity possible then your main threats are winds and hail along with heavy rains.

Once again be safe and keep your eye to the sky when out and about! 

Outbreak Occurred On Wednesday -What about Thursday?

An outbreak occurred on Wednesday and not just some small limited area as some professional agencies were originally talking about. This is why we do not give forecasts until 24 hrs or less before the event because this certainly proved to NOT be a small limited area. 

So will Thursday be like wednesday or will it tone down some? This is going to depend on where you live and reside. 

Lets look at what should be current conditions for the afternoon and the evening ..

A cold front is going to be marching east across the central part of the Nation with a low pressure over the Dakotas region and a low back near the OK panhandle region where it turns into a warm front. All the action today is going to be out ahead of this cold front and slowly pressing to the east where a ridge has kind of set up shop and will be providing temperatures near if not in the 90s

So lets take a look at the parameters that will be in place for today. We think compared to yesterday today will be toned down with the exception of maybe in Central and Eastern OK. This is where we feel will have the best chance for Tornado's 

Though if you look at the EHI you will see above 1 going north and Northeast from OK which means supercells are possible and with the EHI tornadic activity could occur anywhere in that green area. 

CAPE is very widespread with 1000+ up depending on where you reside...

There is also plenty of lift across the region as well...

Highest SWEAT index is in OK to Kansas... 

Helicity is also elevated in pretty much the same areas as we mentioned above with the EHI..

Its going to be a muggy day out there with the dewpoints in the 60s and 70s across the region.

Wind shear will be at least 30 to as much as 50 knots which is sufficient for severe weather.

Looking at the ECM you can essentially see why there is such a broad area for severe weather but once again we think the worst will be across OK and KS as far as tornado potential is concerned. If you are outside these regions the main threats will be strong gusty winds and Large Hail...

We will be here to follow this situation all day today ..however we do not see this day being as bad as yesterday was with as many over all reports. 

Wednesday Perhaps The Most Severe Potential

We are going to start off by looking at what we think current conditions should be like at 18Z tomorrow afternoon. Now keep in mind we have been talking about this since the 25th of the month when we posted the map on our facebook page. 
We have one low pressure over Southeast Colorado from there extends a cold front that goes back to the west south west and another front that spreads to the north to a low pressure system over the Dakota region. From there we have a warm front that spreads east northeast into the great Lakes region and swings back south into the Northeast region. We also have a dry line south from the low over SE CO that goes directly due south.. It will be these low pressure areas , the associated fronts and the dry line that will be responsible for what could be an active day across the region.
One thing we will continue to have in place is extremely warm air across the region with temperatures in the 80s..

Dewpoints are going to continue to be also quite high across the region with 60s and 70s making it feel even warmer then it actually is and adding moisture into the atmosphere.

Now to the actual severe weather Parameters and we are going to be taking a look at the CAPE, SWEAT, Lift Index, EHI, Helicity and the Wind Shear.. We are going to start off with the shear first..

Shear will be 30-50 knots which is sufficient enough for severe weather to occur,  

Lift Index is as negative as negative 8 ..So there will be plenty of lift in the atmosphere.
Now on to the more important indexes that have to be taken into consideration, That would be the CAPE, SWEAT, EHI and Helicity..

CAPE 

CAPE ranges from 1000 to about 3000 which is more then sufficient for severe weather. 

EHI you can see is quite high from locations In Southern TX to North Central Tx thru western OK and West Central Kansas into Central Nebraska ..

Allocating with these same regions is the Helicity 

We also have the SWEAT index lining right up with these same regions...

So we think that the best chances for tornados are going to be in the areas that we mentioned above. Outside these areas the main threats will be winds and hail. 
We are not going to go with a slight risk or severe zone in the Northeast as the guidance we are using suggests that there is no CAPE into these regions..especially the ECM so anything there would be Garden Variety and just local severe isolated..
Remember if you are in a path of a Tornado on the ground to take cover and shelter immediately and pay attention to your NWS outlets! 

May 28th Severe Weather Potential

Temperatures once again are going to be on the warm to hot side with temperatures in the 70s to 90s depending on where you live. Taking a look at what we expect current conditions to be like in the morning ...

We have an area of low pressure over Kansas attached to a cold front,, A low pressure back over Western Iowa where the front turns more stationary. A dry line from the Ok /TX panhandle southwest to south into West TX. Once again storms could fire along this dryline . We expect all modes of severe weather possible today from strong winds to Large Hail and Tornado potential but we will show you where we think tornado potential will be..

Looking at the severe weather parameters that will be in place ..

Convective Available Potential Energy will be from 1000-4000 depending on where you are located.

Plenty of lift in the atmosphere with the index as low as negative 12...

Wind shear will be 40-50 knots across the region which is sufficient enough for severe weather to occur.

Dewpoints once again will be in the 60s and 70s across the vast majority of the region..

Now looking at the tornado parameters we see that the EHI is kind of on the high side across NE OK , All of Kansas  into SE Nebraska east over into Missouri and central Illinois. We also see that the SWEAT Index is generally high in these same areas

And the Helicity index is at 250 or above across this general area as well..

So with that said we expect the tornado potential to be located in the areas we mention above ..if outside those areas then the main threat would be winds and hail.
In reference to TX we have included the area due to parameters ..however..with the exception of west TX..the rest of TX seems to be under a CAP..

So with all the parameters out of the way this is the outlook we have put together on where you can expect the severe weather to occur..

Severe Weather Potential May 27th 2013

Low pressure is going to be over eastern Colorado and extending southward across the TX Panhandle will be the dryline. A line of storms could fire along this dry line. The stationary front further to the north will be the focus for severe weather as well..

Lets look at the severe parameters first...starting with the temperatures which will be warm to hot from north to south with 70's to 90's

There will be no lack of convective available potential energy with CAPE as high as 4000.

There will also be ample lift in the atmosphere.. with the lift at around negative 10.

Wind Shear will be sufficient with 40 knots or slightly greater..

A New index yet we have not used this severe season so far is SWEAT .. To explain what SWEAT is..

What is SW?

SW (SWEAT= Severe Weather Threat Index) uses several variables to determine the likeliness of severe weather and tornadoes. 

2. How is SW determined?

SWEAT= 12(850Td) + 20(TT - 49) + 2(V850) + (V500) + 125(sin(dd500 - dd850) + 0.2)

*If TT less than 49, then that term of the equation is set to zero 

*If any term is negative then that term is set to zero

*Winds must be veering with height or that term is set to zero

850Td = 850 mb dewpoint temperature

TT = Total Totals Index

V850 = 850 mb wind speed

V500 = 500 mb wind speed

dd500 - dd850 = Directional veering of wind with height

The sounding below gives a SWEAT value of 148. Here is how that value was found:

850Td = 9 C

TT = 44

V850 = 15 knots

V500 = 10 knots

dd500 - dd850 = SSW (200 degrees) - SW (220 degrees) = sin(-20) = term set to zero since wind is not veering

Since TT is less than 49, that term is set to zero

SWEAT = 12(9) + 2(15) + 10 = 148

Although the sounding has good low level moisture and a deep layer of instability, it currently lacks significant speed and directional wind shear. This significantly reduces the tornado potential.

3. Operational significance of KI:

The SWEAT index assess low level moisture, convective environment (via TT), and changes in wind speed and direction with height (low level and middle level jet, horizontal vorticity). When all these factors occur together, the severe weather threat and tornado threat is enhanced. 

4. Pitfalls:

a. Always use index along with examining the actual sounding and forecast soundings. The sounding environment can change rapidly over time. 

SWEAT INDEX CHART

150-300 =Slight Severe

300-400 = Severe Possible

+400 =Tornadic Possible 

Now according to the SWEAT index chart anything over 400 means tornadic is possible..

So you can see that places like Western OK ..Most of KS and then isolated locations further NE into Dakota region and Western Nebraska have a chance at tornado potential.

This pretty much goes along with the EHI index as well..

Also the Helicity is in the same general area...

Now what may be the saving factor in these places not seeing the tornado's despite the parameters is that the GOM return flow is basically shut off but as you can see the parameters are in place. 

One final piece of information is the dew points which are in the 60s and 70s..

So with all that explained above we have put together this outlook ..

The main threats should be winds and hail but if we can get some return flow from the GOM going then the places mentioned above would have a shot at tornados. At this point the locations furthest north has the greatest shot for the tornado potential as there will be more moisture available...