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Severe Potential: MS/AR 10-17-12


The Storm Prediction Center in Norman, Oklahoma has issued a Slight Risk of severe thunderstorms across portions of the Mid south an Deep south with the biggest concern being across portions of eastern Arkansas and the Mississippi Delta region.  I will show this in a more graphical sense before we dig into the parameters.


The graphic above shows the tornado potential for this afternoon.  The 7am update indicates an expanded area from the MO/AR border southward into sections of Northeast Louisiana and into the Jackson, MS metro area.  The black “hatched” area that you see across the southern portion of the risk indicates the potential for significant tornadoes.  This is the area where the greatest parameters look to come together this afternoon and into the evening hours. 


A 100+ knot upper level jet will increase and move toward the region this evening.  The left exit region of the jet is shown digging into the after late this evening which will increase divergence and lift across the region.  The mid level trough axis will also be plowing into the region and provide abundant frontal forcing for organized severe weather.  Development of supercells later this afternoon will be potentially conditional and based on the amount of atmospheric instability that develops to overcome the minor inversion that will be in place.


As you can see above, the instability axis looks to develop over portions of Arkansas.  This axis really looks to narrow across the area as the front progresses eastward.  The biggest limiting factor that seems to be cutting down instability is low level moisture.  The low level jet is currently oriented WSW/SW across Arkansas and this isn’t advecting in the rich Gulf moisture needed to fuel severe storms.  Moisture will eventually increase with dewpoints reaching the lower to mid 60’s in a narrow axis this afternoon in response to the deep synoptic setup, but a widespread warm sector is quite unlikely.  Thus, a widespread tornado outbreak isn’t expected.  However, given that this is a fall setup we will have the potential for QLCS (linear convective segments) that can produce tornadic activity from comma head echos or embedded supercells.

We will monitor the development throughout the day since we won’t directly be chasing, but members of our team may venture out into the Delta region.  We will keep you posted…

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