Main Threat

Southwest Nebraska, West-Central Kansas, Central Oklahoma, and Central Texas

Newer model guidance has came in and is showing a slight shift and some new things but the overall threat for strong tornadoes will exist in the areas above.  Earlier blog I wrote about this threat highlighted Southwest Nebraska, but as of right now it appears they will not be the main area as it has shifted further south into KS.  

The main trigger for the thunderstorm develoment will be along the dry line that will set up from Nebraska down thru Texas.  This dry line will meet up with an area of low pressure in Eastern Colorado.  A warm front will also be present and a main feature to watch to see where the instability gradient sets up to the north and how much moisture makes it into Nebraska.  The movement of the warm front will be key to see how far north the threat will exist for surface based storms capable of large tornadoes.  Right now it looks like this front is hanging right along the NE/KS border.  A cold front that will be attached to the low pressure will create a triple point that will become the main focus for tornadic activity.  This will increase the tornadic potential in KS into NE.  

High Tornadic threat area (Kansas and Nebraska)

The reason for this tornadic threat will be a combination of the triple point leading to increased shear, and the thermodynamics.  The most notable feature is the Easterly component to the low level and sfc winds.  The winds veer to the south aloft creating favorable directional shear.  Mid level jet streak will increase winds to 70kts at 500mb.  The effects of the upper level ridge will be felt if the WRF is correct showing the strongest winds at 250mb remaining behind the activity.  The threat will be greatly enhanced if the strong upper level winds shift eastward.  The 0-6km vertical shear around 50kts with strong directional shear will support rotating updrafts and a threat for long lived tornadoes.  0-3km helicity values will range from 300-500m2s2 which is very high and supportive of torandic activity.  Thermodynamics will also be supportive with MLCAPE values ranging from 1500-2500j/kg with a few areas around 3000j/kg.  Low LFC heights under 2000m AGL will allow for low level CAPE values to approach 100j/kg.  LCL heights under 1000m AGL combined with forecasted 3km VGP values between .4-.5m2s2 highlight the tornadic potential. 

Oklahoma and Texas

The instability will be higher in this area with MLCAPE values ranging from 2500-3500j/kg.  Wind fields will be weaker aloft and this will lead to a decreased threat in tornadic activity, but the threat will exist given the directional shear.  Strong jet diffluence aloft combined with 0-6km shear values around 40kts will support super cells.  Strong convective intstability with dry air in the mid levels will support a damaging wind threat.  Mid level thermal ridge over this area will not support much of a hail threat. 

Things to watch for......

Several things could shift things a little bit.

1) CAP-  The CAP needs to hold back activity into the early afternoon and needs to erode.  It looks good it will with sufficient day time heating and moisture and thermal advection along with sfc and low level convergence.

2)  Winds aloft-  If winds shift eastward we could see an enhanced risk for strong tornadoes and a much more organized tornadic threat further southward across OK/TX. 

3) Warm front-  Track the warm front because the area to the south of it (just to the south of it) should be the greatest threat area.