NWS BMX LATEST AFD
THURSDAY.
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 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
THURSDAY.
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 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