Yep, some potent shear/instability in place. Upscale growth from the storms to our northwest on Wednesday will push into AL for Thursday. But shear vectors don't support fully linear with the complex.I think we need a thread for this Thursday in Alabama...not your typical late-June upper air pattern
A consistent synoptic signal has existed the past few days with regards to an amplifying shortwave moving across the Great Plains southeastward into the mid-Mississippi River Valley overnight Wednesday. Positioning of favorable mid-level flow around the base of the trough suggests 40-50 kts of westerly winds at 500 mb across our area on Thursday as mid-level lapse rates steepen (~6.5-7.5 C/km) from the Southern Plains. With pre-existing low-level moisture in place, afternoon heating is expected to destabilize the troposphere such that 2,500-3,500 J/kg SBCAPE is possible with ~40-45 kts effective bulk shear. Severe weather is possible as a result of these shear/instability values, as well as height falls & cooling temperatures aloft associated with the shortwave trough.
Forecast hodographs suggest quasi-unidirectional flow with mean winds out of the west, with storm motions south of east. Enough ingestion of storm-relative helicity in the 0-3 km layer suggests discrete updrafts capable of developing mesocyclones, especially if surface wind vectors can back more southwesterly. This factor, as well as 500 mb temperatures approaching -10 C, suggests severe
hail would be a threat as well as damaging wind gusts. Forecast uncertainty of antecedent convective evolution and positioning of mesoscale features (such as surface boundaries) limits any
predictability for specific areas under greater probability for severe weather. (For example, an uncontaminated atmosphere will have better chances of severe weather coverage that afternoon versus ongoing convection during the morning limiting available instability over particular areas.) Thus, for now, a mention of severe weather will be added to the HWO with large hail and damaging winds the primary threats across all of Central Alabama until further forecast refinements are made. At this time, a tornado threat cannot be ruled out as there are varying scenarios for how this system will evolve.