Alabama Skies Bulletin: Confidence increasing in likelihood of severe weather; Severe thunderstorm or tornado watch expected soon

Published 9:38 pm Sunday, June 18, 2023

The likelihood of severe weather in western Alabama is increasing. The Storm Prediction Center is expected to place parts of western Alabama under a watch soon as tornado supercells move into the state from Mississippi.

From the SPC:

Probability of Watch Issuance…80 percent

SUMMARY…A risk for all hazards of severe weather appears to be increasing across western AL. WW issuance is likely within the next hour depending on ongoing convective trends.

DISCUSSION…Multiple supercells have developed across central MS and are moving eastward through WW335. The 19/00z JAN sounding featured an uncapped boundary layer with nearly 4000 J/kg of MLCAPE, effective shear around 45 kts, and significant veering low-level shear contributing to 455 J/kg of ESRH (along with 235 J/kg in the lowest 1 km AGL). Despite generally weak synoptic forcing, these supercells acquired mid- and low-level mesocyclones rather quickly in this environment. At least one radar-indicated tornado has been observed, and all severe hazards remain possible as the storms  approach the MS/AL border.

Convective evolution in the highlighted area remains somewhat uncertain due to overturned air from convection earlier today.

Temperatures and dewpoints in western AL are generally a few degrees cooler than the environment in which the storms are currently located. This is contributing to substantially increasing MLCIN with eastward extent through the delineated area. This could contribute to rapidly weakening storms deeper into AL and decreasing severe hazards later tonight. However, modest low-level advection is anticipated which could lessen inhibition. The degree to which this may occur in a narrow zone ahead of the ongoing supercells remains uncertain. Should this occur, the threat for all severe hazards with these supercells — as well as any additional storms that develop in northern MS — could persist for the next few hours across western AL. Due to this scenario, downstream WW issuance appears likely during the next couple of hours.