11PM Day 1 Convective Outlook for Saturday, February 21. THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS EASTERN GULF STATES TO THE SOUTH ATLANTIC COAST
SUMMARY
Strong to locally severe thunderstorms are possible across parts of the eastern Gulf and south Atlantic coast states. Damaging gusts, large hail, and perhaps a brief tornado are the expected hazards.
Gulf States/South Atlantic Coast
Strong short-wave trough is ejecting east across KS/northern OK late this evening as a secondary 500mb speed max digs southeast toward the central High Plains. As the secondary short wave digs southeast, the northern/southern stream will become more phased over the MS Valley by late afternoon. Net result will be to suppress the primary corridor of strong west-southwesterly midlevel flow across the southern Plains/Gulf states into the middle Atlantic. As heights fall across the Midwest into the northern Gulf states, pressures will rise over the interior CONUS and the synoptic front should begin to surge southeast across the lower MS Valley.
Late this evening, scattered thunderstorms have developed over northern MS/AL, just north of the boundary within a zone of low-level warm advection. This activity should spread east and should be ongoing at the start of the period along the cool side of the boundary. While much of day1 convection will be elevated north of the wind shift, some boundary-layer heating is expected across the warm sector, and modest SBCAPE is expected where surface dew points will range from the upper 60s to near 70F. Forecast soundings suggest more than adequate deep-layer shear for sustaining organized rotating updrafts. Low-level shear is not expected to be particularly noteworthy so damaging gusts and hail are the primary concerns, though a brief tornado can not be ruled out. Convection will develop/spread east along the frontal zone and the greatest risk for robust convection will be during the afternoon/evening hours.