Severe Weather Potential April 17th 2013

Start off with the outlook itself which is posted above . We think the greatest threat for severe weather is going to be from OK then Northeast Into Missouri and East into Ark. This outlook is based on the NAM and the SREF with a blend of the ECM. 

First the culprit responsible for this severe weather event will be a low pressure developing over the OK /TX border and then moving NE from that location with a cold front extending to its south... brief diagram showing this..

As the low pressure moves NE the cold front will press south and off towards the east. As is generally the case the greatest chance of severe is to the North of the area of low pressure and we see this being no different .

There will also be a stationary front draped across the region as well which turns to a cold front once across the  east which was responsible for some of the severe weather which occurred on the 16th.
Once again we think that those located in TX will be spared the greatest severe due to two reasons. 
Reason # 1 is the timing of the cold front which is going to be between 6 Z and 12 Z or 1 AM and 7 AM CDT. 
Reason #2 is that the region is pretty well CAPPED up thru about 30 hrs... This is shown here with the CINH

Which this graph breaks down what those #s mean

CINH

0 - 50	Weak Cap
51 - 199	Moderate Cap
200+	Strong Cap

Also as the enhanced water vapor shows the greatest moisture is actually breaking out over Eastern TX and the eastern GOM..

The image below the satellite is the NAM which shows moisture from hrs 27 to 30 or 10 PM to 1 AM CDT and the moisture is North of the TX /OK border. 

So we strongly believe that the greatest severe weather will be north of that region and this is also based on the parameters as well..

First off its going to be a hot day across the region with temperatures in the 80-90 degree range with dewpoints in the 60s..

Behind the front we will be looking at temperatures cooling into the 50s 

When you have a temperature drop such as shown it generally brings about a severe weather event and this will be no different. 

The red zone is based on the EHI and where there is no CINH to hinder the severe ..

In this same general location the Helicity is quite steep as well..

There is plenty of Lift in the atmosphere ..

And ample enough shear to create the potential for Tornadic activity within the red zone on the map.

This shows as much as 100 knots of shear coming into the region. This is probably over doing it but this is about as extreme as one can get when it comes to wind shear.  CAPE which is like the fuel to add to the fire is also at 1000 or above ..

So we have all severe weather ingredients in place for severe weather to take place across the region. 
Further to the east in locations like KY and TN the risk for severe is much lower due to low parameters in place. However the stationary boundary could act as a trigger for some severe storms where the main threats would be wind and or hail with some heavy rains.

For those in KY and TN your timing looks to be overnight thursday night between 2 AM and 8 AM for the front to cross and garden variety type storms with heavy rains.