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000 FXUS64 KHUN 101141 AAA AFDHUN AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE HUNTSVILLE AL 541 AM CST WED FEB 10 2010 .UPDATE... UPDATED FOR 12Z AVIATION DISCUSSION. && .AVIATION.../12Z TAFS/ BRIEF MVFR CEILINGS CAN BE EXPECTED AT BOTH KMSL AND KHSV THROUGH ROUGHLY 14Z. DECIDED TO INCLUDE -SN TO ACCOUNT FOR SOME SNOW FLURRIES THIS MORNING AT KHSV...ALTHOUGH VISIBILITIES WILL NOT BE IMPACTED DUE TO THE -SN. VFR CONDITIONS WILL THEN DEVELOP WITH BKN-OVC CEILINGS BETWEEN 3500-5000 FEET EXPECTED TODAY. NORTHWEST WINDS WITH GUSTS UP TO 25 KTS WILL BE POSSIBLE BUT WILL DECREASE LESS THAN 7 KTS SUSTAINED AFTER 00Z. && .DISCUSSION... /ISSUED 337 AM CST WED FEB 10 2010/ SHORT TERM (TODAY THRU SATURDAY)... A COMPLEX WX PATTERN IS ONCE AGAIN TAKING SHAPE ACROSS THE CNTRL TN VALLEY AREA THIS EARLY MORNING. AN UPPER LOW FEATURE OVER THE OH VALLEY CONTINUES TO GRADUALLY SHIFT EWD TOWARD THE MID ATLANTIC BASIN...AS WEAK EMBEDDED DISTURBANCES/WAVES ALOFT TRAVERSE EWD UNDERCUTTING THE TROUGH PATTERN. THIS IS NOT ONLY ALLOWING CONTINUED CAA INTO THE REGION...BUT IS ALSO PROVIDING FOR SOME ISOLATED FLURRIES/LIGHT SNOW SHOWERS ACROSS THE EXTREME PORTIONS OF NE AL...ALTHOUGH THESE LIGHT SHOWERS SHOULD COME TO AN END LATER THIS MORNING WITH THE EXITING UPPER LOW. CONDITIONS THOUGH SHOULD REMAIN QUITE COLD...ESPECIALLY WITH BREEZY SFC WINDS OUT OF THE NW PERSISTING THROUGH THE AFTERNOON HRS. CAA ALSO LOOKS TO CONTINUE INTO THE EVENING/OVERNIGHT HRS AS WEAK HIGH PRESSURE SETTLES INTO THE LOWER/MID MS VALLEY LATER TODAY. OVERALL TEMPS MAY WARM A FEW DEGREES GOING INTO THU AS THE SFC HIGH CONTINUES TO WEAKEN AS IT GRADUALLY MOVES TOWARD THE E. NOT XPCTING MUCH IN THE WAY OF ANY CLOUDS EXITING THE AREA AS A PREDOM ZONAL FLOW ALOFT PREVAILS ACROSS THE SE REGION INTO FRI. THE FORECAST PACKAGE THEN BECOMES A BIT OF A CHALLENGE HEADING INTO THE WEEKEND PERIOD. THE LATEST GLOBAL MODELS REMAIN CONSISTENT WITH SOME TYPE OF LOW PRESSURE AREA DEVELOPING IN THE WRN GULF DURING THE LATE THU/EARLY FRI PERIOD. THE MODELS THEN BECOME SOMEWHAT DIVERGENT WITH THE TRACK OF THIS SYSTEM ON FRI. HAVE OPTED TO USE A BLEND OF THE 00Z NAM/ECMWF WITH THE HANDLING OF THIS FEATURE FRI AND SAT. THIS WOULD BASICALLY HAVE THE LOW PRESSURE CENTER MOVING EWD ALONG THE CNTRL GULF COAST FRI BEFORE EXITING INTO THE SRN ATLANTIC SAT. THIS IS BECOMING QUITE THE POPULAR TRACK FOR GULF LOWS THIS WINTER WITH MOISTURE ADVECTING NWD AHEAD OF THE SFC LOW. WITH A POLAR AIR MASS FAIRLY ENTRENCHED ACROSS THE AREA...ANY PRECIP THAT DEVELOPS ALMOST CERTAINLY WOULD BE ALL SNOW...BEGINNING WITH THE OVERNIGHT HRS THU...AND THEN PROGRESSING FROM W TO E THROUGH FRI...BEFORE TAPERING OFF FRI EVENING. QPF AMOUNTS THIS FAR N ARE NOT THAT HIGH THUS FAR...LESS THAN 1/4 OF AN INCH. THIS TRANSLATES TO APPROX 1/2 TO 1 INCH OF SNOW ACCUMULATION...WITH THE HIGHER AMOUNTS SLATED FOR THE SRN AREAS...OR MORE IN LINE WITH THE AXIS OF MOISTURE INFLOW. THERE IS SOME UNCERTAINTY WITH THE ORIGIN AND TRACK OF THE SFC LOW AND THE STRENGTH OF THE MOISTURE RETURN GIVEN THIS IS CLOSE TO 72 HRS OUT AND THERE IS SOME MODEL DISCREPANCY. HOPEFULLY FUTURE MODEL RUNS WILL BECOME A BIT MORE CONSISTENT WITH THE TIMING AND PLACEMENT OF THIS NEXT UPCOMING WINTER EVENT. 09 LONG TERM (SUNDAY THRU WEDNESDAY)... A POTENT UPPER LEVEL LOW WILL DIVE SOUTHEAST ACROSS THE MISSISSIPPI RIVER VALLEY ON SUNDAY AS A SURFACE LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT APPROACH THE AREA. WITH ENOUGH MOISTURE AVAILABLE...LIGHT PRECIPITATION SHOULD BEGIN BY DAYBREAK ACROSS NORTHWEST ALABAMA AND SPREAD EAST ACROSS THE TENNESSEE VALLEY ON SUNDAY. AT THIS TIME...IT APPEARS TEMPERATURES WILL BE BELOW FREEZING DURING THE MORNING HOURS TO WARRANT SNOW ESPECIALLY ACROSS NORTHWEST ALABAMA. THE QUESTION REMAINS HOW WARM TEMPERATURES WILL GET ON SUNDAY AFTERNOON WITH PRECIPITATION FALLING CAUSING EVAPORATIVE COOLING. WITH THAT SAID...CONTINUED A RAIN/SNOW MIX FOR SUNDAY AFTERNOON FOR THE ENTIRE AREA...ALTHOUGH CONFIDENCE REMAINS LOW ON WHETHER TEMPERATURES WILL BE COLD ENOUGH FOR ALL SNOW. LUCKILY...PRECIPITATION AMOUNTS SHOULD REMAIN LIGHT WITH ROUGHLY A TENTH OF AN INCH IN QPF ADVERTISED. BY SUNDAY NIGHT...THE ABOVE MENTIONED UPPER LOW WILL QUICKLY MOVE NORTHEAST AS A LONGWAVE UPPER TROUGH SETTLES OVER THE AREA. MOSTLY CLOUDY SKIES WILL CONTINUE SUNDAY NIGHT WITH A FEW SNOW FLURRIES POSSIBLE OVERNIGHT. A CONTINUED COLD PATTERN WILL REMAIN ON MONDAY WITH LOWS IN THE LOW TO MID 20S AND HIGHS IN THE MID TO UPPER 30S. HIGH PRESSURE BEGINS TO BUILD OVER THE REGION ON TUESDAY AS TEMPERATURES REMAIN WELL BELOW NORMAL. PERIODS OF CLOUDINESS CAN BE EXPECTED MID WEEK AS SEVERAL MOISTURE STARVED UPPER LEVEL DISTURBANCES MOVE ACROSS THE AREA. KNS && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ AVIATION...KNS DISCUSSION...09/KNS
