FXUS64 KHUN 101143 AFDHUN AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE HUNTSVILLE AL 543 AM CST WED MAR 10 2010 .UPDATE... 12Z AVIATION FORECAST. && .AVIATION... UNSETTLED WEATHER WILL CONTINUE ACROSS THE TENNESSEE VALLEY THROUGH THE PERIOD. CONVECTION CURRENTLY AFFECTING CENTRAL MISSISSIPPI AND ALABAMA WILL DRIFT NORTH...AND BRING GREATER CHANCES FOR SHOWERS AND THUNDERSTORMS TO THE AREA INTO TONIGHT. IFR CEILINGS OVER NW ALABAMA SHOULD IMPROVE TO MVFR BY THE LATE MORNING...WITH MVFR CEILINGS PREVAILING ELSEWHERE THROUGH THE DAY. THE HEAVIER SHOWER ACTIVITY MAY TEMPORARILY REDUCE VISIBILITY/CEILINGS TO IFR OR LOWER AT TIMES. && .DISCUSSION... /ISSUED 354 AM CST WED MAR 10 2010/ SENSIBLE WEATHER IMPACTS THROUGH EARLY NEXT WEEK WILL BE DOMINATED BY A COMPLEX AND BROAD UPPER LEVEL-LOW AS IT MOVES SLOWLY EWRD FROM THE CENTRAL PLAINS TO THE EAST COAST. RESOLVING SOME OF THE FINER DETAILS REMAINS RATHER DIFFICULT WITH THIS LATEST FORECAST PACKAGE...ALTHOUGH CONFIDENCE IS INCREASING SLIGHTLY WITH SOME OF THE SMALLER SCALE FEATURES AND TIMING SPECIFICS OVER THE NEXT COUPLE OF DAYS. MOST FORECAST PARAMETERS WERE NUDGED IN A DIRECTION AS INDICATED BY THE LATEST FORECAST TRENDS...BUT NO WHOLESALE CHANGES WERE MADE TO THE PREVIOUS FORECAST. WITH THAT BEING SAID...CONFIDENCE IS STILL SOMEWHAT LOW PARTICULARLY FOR FRIDAY...WHERE MODEL DIFFERENCES ARE PERHAPS THE GREATEST. CONFIDENCE IS FAIRLY HIGH HOWEVER...THAT THE UPPER LOW WILL SLOWLY MOVE EWRD ACROSS THE TN/OH VALLEYS ON SAT THRU MON...LEADING TO A COOL...CLOUDY AND POSSIBLY SHOWERY PERIOD. SHORT TERM (TODAY THROUGH FRIDAY)... EARLY MORNING REGIONAL RADARS SHOW A FAIRLY NARROW LINE OF SHRA WITH EMBEDDED DEEPER CONVECTION STRETCHING FROM SRN MISS INTO NRN GA. OUR AREA HAS BEEN ON THE NRN SIDE OF THIS LINE FOR MUCH OF THE NIGHT...WITH CULLMAN...MARSHALL...DEKALB AND JACKSON COUNTIES RECEIVING THE VAST MAJORITY OF THE PRECIP. AS A SFC LOW DEEPENS IN THE SOUTHERN PLAINS AND A STRONG SHORT WAVE ROUNDS THE BASE OF THE UPR TROUGH...LOW/MID LEVEL WINDS WILL TEND TO BACK ACROSS THE AREA TODAY. THIS WILL MAINTAIN A FAIRLY STRONG SFC THETA-E GRADIENT...AS SLIGHTLY COOLER/DRIER AIR MOVES IN FROM THE SE. WARM/MOIST SRLY FLOW ATOP THE GRADIENT WILL MAINTAIN SHRA IN THE REGION...AND ALLOW THE BAND CURRENTLY TO OUR SOUTH TO MOVE NWRD. IN ADDITION...DEEP LYR LIFT WILL INCREASE AS AN UPR JET STREAK MOVES INTO THE SOUTHEAST...AND A LOW/MID LVL SHORT WAVE WILL AID IN INSTABILITY. THUS...EXPECTING MOST LOCATIONS TO RECEIVE SHOWERS TODAY...WITH SOME EMBEDDED TSRA. THE BEST CHANCES WILL BE IN SERN AREAS...WITH A GRADUAL TAPERING OF LOWER POPS TO THE NW. ISOLATED LOCATIONS PARTICULARLY IN THE SOUTH COULD RECEIVE OVER ONE INCH OF RAINFALL...IF CONVECTION TRAINS OVER THE SAME AREA. WILL CONTINUE TO EVALUATE THE FLASH FLOOD THREAT THIS MORNING. AS THE SFC LOW WRAPS UP IN THE CENTRAL PLAINS...A COLD FRONT TRAILING THE LOW WILL MOVE QUICKLY EWRD INTO THE TN VALLEY BY THURSDAY MORNING. EXPECTING A LINE OF SHRA WITH EMBEDDED TSRA TO MOVE INTO NWRN AL AHEAD OF THE FRONT BEFORE DAWN ON THURS. THE LINE WILL RAPIDLY CROSS THE AREA...REACHING THE AL/GA BORDER PROBABLY BY MID-MORNING. ALTHOUGH THE SVR WX THREAT APPEARS MARGINAL...DEEP LAYER SHEAR/INSTABILITY WILL PRESENT A STRONG OR PERHAPS DAMAGING WIND THREAT. ALTHOUGH CHANCES LOOK VERY SLIGHT...COULD NOT RULE OUT A BRIEF ISOLD TORNADO EMBEDDED WITHIN THE LINE...GIVEN THE POTENTIAL FOR SFC-BASED PARCELS AND MARGINALLY SUFFICIENT INSTABILITY. THE BEST CHANCES FOR ANY STRONG/SVR TSRA WILL LIKELY BE IN THE WEST...WHERE BETTER INSTABILITY/SHEAR WILL RESIDE. THE FRONT WILL CROSS THE AREA ON THURS MORNING/AFTN...BRINGING THE PRECIP TO AN END FROM WEST TO EAST. A WEAK SHORT WAVE MAY ROUND THE SE SIDE OF THE MAIN UPR TROUGH DURING THE AFTN...GIVING RISE TO AN ISOLD OR SCT TSRA DURING THE AFTN. OTHERWISE...EXPECTING PARTIALLY CLEARING SKIES IN THE AFTN. THIS MAY BE THE LAST OPPORTUNITY TO SEE THE SUN ESPECIALLY IN NRN AREAS THROUGH EARLY NEXT WEEK. SHORT TERM GUIDANCE CONTINUES TO INDICATE YET ANOTHER WEAK SFC LOW MAY DEVELOP IN THE SE AHEAD OF THE MAIN UPR TROUGH...BRINGING ANOTHER ROUND OF SHRA AND MAYBE TSRA ON FRI. WILL RETAIN THE PREVIOUS FCST THAT HINTED AT THIS SOLUTION. WILL LIKEWISE KEEP THE MENTION OF ISOLD TSRA IN THE EAST...WHERE INSTABILITY MAY BE SUFFICIENT. LONG TERM (SATURDAY THROUGH TUESDAY)... AFTER A SECONDARY TROUGH MOVES ACROSS THE AREA ON FRI...THE REGION WILL REMAIN IN W TO NW FLOW INTO EARLY NEXT WEEK. THE UPR LOW WILL MOVE SLOWLY EWRD ACROSS THE REGION...FINALLY EXITING OFF THE EAST COAST PERHAPS BY MON. SHALLOW MOISTURE/LIFT WILL MAINTAIN THE PRESENCE OF LOW CLOUDS AND LIGHT SHRA OR PERIODS OF DZ THROUGH AT LEAST THRU SUN. AS A RESULT...KEPT FCST TEMPS A LITTLE BELOW GUIDANCE/CLIMO. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ AVIATION...RSB DISCUSSION...KDW