Twin States Weather Blog

Early Afternoon Analysis

* I will be posting a few discussions this afternoon and evening regarding severe weather potential across our area. This one is from the 12z model guidance...

* A strong shortwave trough is ejecting out of the Rockies and into the Great Plains ahead of a strong embedded jet max pivoting through the longwave trough. The main energy moves northward through the central MS valley towards the Great Lakes, but another piece of energy extendeds southward and will lead to differential positive vorticity advection in our area (PVA). PVA is one type of uplift we look for in determining thunderstorm potential.

* We have fairly good confidence that a squall line will form across Kansas, Missouri, Arkansas, and portions of Louisiana that will work its way into Mississippi overnight. Within this squall line we expect embedded supercells due in part to the extremelly high value of wind shear (or changing of wind speed and direction with height). Damaging wind and isolated tornadoes are possible within this squall line, especially in portions of northern Mississippi.

* The challenge is determining how much instability will form ahead of the approaching squall line/frontal system. If enough instability forms ahead of the squall line, discrete supercell thunderstorms with the capability to produce tornadoes could form, and we think at least one or two discrete storms will form. If storms do fire, there is a high likelihood that they will rotate into supercells with a threat of tornadoes. Also, 0-3km CAPE is sufficient. 0-3km CAPE is a measurement of instability in the lowest level of the atmosphere. This is important because instability near the surface allows a greater likelihood of a storm to be both surface based and ingest the shear into the storm (one of the processes of supercell and tornadogenesis).

* Regardless, the threat is certainly present and will require a lot of analysis and nowcasting as a few uncertainties are present. Keep checking this blog frequently for more updates to our forecast!

posted by Renny Vandewege @ 1:18 PM