MESOSCALE UPDATE

AREA FORECAST DISCUSSION...UPDATED FOR MESOSCALE AND AVIATION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
637 AM CDT WED MAR 19 2008

UPDATE...MESOSCALE UPDATE.

WITH WEAKENING OF STORMS IN EASTERN MISSISSIPPI...IT APPEARS THAT THE SEVERE WEATHER PARAMETERS ARE POINTING AGAINST A SIGNIFICANT THREAT FOR THE NEXT SEVERAL HOURS. IN SPITE OF IMPRESSIVE SHEAR PROFILES ALOFT...THE MAIN INHIBITING FACTOR IS THE WARM TEMPERATURES AND LIMITED BOUNDARY LAYER INSTABILITY.

WE ARE STILL WATCHING TRENDS CLOSELY FOR LATER THIS MORNING...IN THE 15Z TO 17Z TIME FRAME. THERE ARE SOME INDICATIONS IN BOTH THE NAM AND RUC OF SOME MID LEVEL COOLING...WHICH COMBINED WITH SURFACE HEATING...MAY SUFFICIENTLY DESTABILIZE THE ATMOSPHERE TO SUPPORT CONVECTION. STILL THINKING THE MAIN THREAT WILL BE THUNDERSTORM WINDS...BUT AT 15Z...RUC13 0-3KM SRH IN EXCESS OF 300 M2/S2 AND BAND OF MUCAPE OF ABOUT 500 J/KG ROUGHLY ALONG A JASPER/TUSCALOOSA/ UNIONTOWN AXIS INDICATE THE TORNADO THREAT IS STILL WORTH WATCHING.

ANOTHER CONCERN NOT YET TO BE COMPLETELY DISMISSED...IS THE POSSIBILITY OF ISOLATED TO SCATTERED SHOWERS/THUNDERSTORMS RE-FIRING ALONG THE COLD FRONT AS IT WORKS ACROSS THE AREA THIS AFTERNOON IN THE 20-22Z TIME FRAME. SUFFICIENT CAPE/INSTABILITY APPEARS TO BE AVAILABLE...BUT UPPER WARM UPPER LEVEL TEMPS AND DECREASING HELICITY/SHEAR APPEAR TO KEEP THE THREAT MARGINAL AT BEST.


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