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Short Term Discussion

By: NWS
By: NWS

THROUGH WEDNESDAY NIGHT). IT LOOKS LIKE WE ARE SEEING SOME MODEL CONSENSUS DEVELOP WITH THIS APPROACHING SYSTEM...WHICH CONSIDERING WE ARE ONLY 24 HOURS OUT...IS A GOOD THING. THERE ARE STILL SUBTLE DIFFERENCES THAT ARE PRESENT...BUT IT LOOKS LIKE THE OVERALL SYNOPTIC EVOLUTION OF THIS SYSTEM IS RELATIVELY CLEAR. FOR THE FORECAST GENERALLY STAYED CLOSE TO THE SOLUTION OFFERED BY THE GFS...BUT CONFIDENCE IN THE FORECAST IS SOME WHAT BOLSTERED BY THE SIMILARITY IN THE MASS FIELDS BETWEEN THE NAM AND GFS. AS THE UPPER TROF TAKES ON A NEGATIVE TILT AND MOVES INTO THE OZARKS...EXPECT THIS TO SIGNAL AN INCREASE IN ACTIVITY ACROSS OUR REGION TUESDAY MORNING. AS THIS IS OCCURRING ALOFT...STRENGTHENING THE DEEP LAYER SHEAR...THE SURFACE WARM FRONTAL BOUNDARY WILL BE LIFTING NORTHWARD. 295K-300K ISENTROPIC ASCENT WILL LIKELY RESULT IN A WIDESPREAD AREA OF SHOWER ACTIVITY NORTH OF THE BOUNDARY IN THE MORNING HOURS...MAINLY ALONG AND EAST OF THE APALACHICOLA RIVER. IN FACT...THE AREA OF MAXIMUM POSITIVE PRESSURE ADVECTION IS LOCATED ACROSS THE PANHANDLE AROUND 12Z...THEN MOVING NORTH OF THE REGION BY 18Z AS THE WARM FRONT LIFTS NORTHWARD AS THE SURFACE LOW TRACKS INTO SOUTHWESTERN ALABAMA. AS HAS BEEN ADVERTISED ALL ALONG WITH THIS SYSTEM...THE DYNAMICS ARE NOT THE PROBLEM FOR SEVERE WEATHER. 0-6KM DEEP LAYER SHEAR APPROACHES 50 TO 55 KNOTS ACROSS THE NORTHWESTERN THIRD OF OUR FORECAST AREA TUESDAY AFTERNOON. 0-1KM LOW LAYER SHEAR IS ALSO VERY FAVORABLE FOR ROTATING STORMS. IN FACT...THE LOWER LAYER SHEAR IS MORE IMPORTANT GIVEN THE RELATIVELY UNIMPRESSIVE LAPSE RATES...AS CONVECTION WILL LIKELY BE LOW TOPPED. INSTABILITY HAS AND CONTINUES TO BE THE QUESTION WITH THIS SYSTEM. WITH DEWPOINTS TODAY ALREADY RECOVERING INTO THE LOWER 60S...AND THE LIKELIHOOD THEY WILL INCREASE AS THE WARM FRONT MOVES INTO AND THROUGH THE REGION TUESDAY MORNING...THE SBCAPES INDICATED IN THE GFS AND NOW THE NAM...LOOK TO BE TILTING THE SCALE TOWARD A CHANCE OF ISOLATED SEVERE WEATHER. THERE IS A DELICATE BALANCE ACROSS THE REGION THOUGH BETWEEN SHEAR AND INSTABILITY. THE INCREASED SHEAR IS FAVORED IN A ZONE ACROSS THE NORTHWESTERN HALF OF THE REGION WHILE THE INSTABILITY IS MAXIMIZED FROM I-10 SOUTHWARD. THESE TWO AREAS OVERLAP IN ROUGHLY AN AREA BOUNDED BY US-84 AND THE FLORIDA GULF COAST. THUS...FEEL THAT AS THE WARM FRONT COMES THROUGH IN THE MORNING...THE POTENTIAL FOR SEVERE WEATHER...SPECIFICALLY ROTATING CELLS...WILL BE INCREASED IN THE PANHANDLE THEN SPREAD INLAND THROUGHOUT THE DAY. MODEL SOUNDINGS SHOW THE FLOW IN FLORIDA BECOMING MORE UNIDIRECTIONAL BY AFTERNOON...SO THE POTENTIAL FOR ISOLATED DAMAGING WINDS WILL ALSO EXIST WELL SOUTH OF THE WARM FRONT IF CONVECTION CAN BECOME FORCED ALONG THE COLD FRONTAL ZONE LATE IN THE DAY. WITH THE FAVORABLE ISENTROPIC ASCENT IN THE MORNING AND ADDITIONAL DYNAMICAL FORCING IN THE AFTERNOON...PRECIP LOOKS ASSURED ACROSS MUCH OF THE REGION. SO...I SEE NO REASON TO DEVIATE FROM THE 100 PERCENT POPS OFFERED FOR TOMORROW IN THE MAV GUIDANCE. OVERALL POTENTIAL FOR HEAVY RAIN LOOKS TO BE ON THE LOW SIDE. MAXIMUM STORM TOTAL QPF LOOKS TO BE NEAR 2-3 INCHES ACROSS SOUTHEAST ALABAMA AND THE FLORIDA PANHANDLE WITH 1-2 INCH VALUES ELSEWHERE. THE MODELS NOW AGREE THAT THE FRONTAL SYSTEM WILL STALL...SOMEWHERE EAST OF TALLAHASSEE ON TUESDAY NIGHT/WEDNESDAY MORNING AND GRADUALLY REMAIN THERE UNTIL LIFTING NORTH OF THE REGION ON THURSDAY AS A WARM FRONT. WITH LITTLE UPPER FORCING EXPECT CHANCE POPS TO REMAIN WITH THE BOUNDARY IN THE AREA ON WEDNESDAY.


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