FXUS64 KHUN 101638 AFDHUN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HUNTSVILLE AL 1038 AM CST MON NOV 10 2014 .UPDATE... NO CHANGES TO THE FCST ATTM. && .SYNOPSIS... /ISSUED 310 AM CST MON NOV 10 2014/ AN ACTIVE WINTER PATTERN IS IN STORE FOR THIS FORECAST AS WE PLUNGE FROM MID FALL STRAIGHT INTO MID WINTER CONDITIONS. TEMPERATURES BY WEDNESDAY THROUGH SUNDAY WILL ACTUALLY FEEL MORE LIKE JANUARY/FEBRUARY THAN NOVEMBER. CURRENTLY AN AMPLIFIED RIDGE PREVAILS OVER THE EASTERN PACIFIC (GULF OF ALASKA), A DEEPENING TROUGH EXISTS OVER THE CENTRAL ROCKIES AND GENERALLY ZONAL FLOW PREVAILS ACROSS THE EASTERN HALF OF THE CONUS. IN ADDITION, A SPLIT FLOW REGIME PREVAILS WITH THE POLAR JET OVER THE NORTHERN STATES WHILE THE SUBTROPICAL JET PREVAIL ACROSS THE SOUTHERN PORTIONS OF THE GULF OF MEXICO. THE PHASING OF THESE TWO JETS IS EXPECTED LATER THIS WEEK. NEVERTHELESS WILL MAINLY FOCUS ATTENTION ON THE DEEPENING TROUGH OVER THE CENTRAL ROCKIES, WHICH WILL BE THE PRIMARY PLAYER FOR SENSIBLE WEATHER IMPACTS OVER THE TN VALLEY TUESDAY INTO WEDNESDAY. THIS TROUGH WILL BE RESPONSIBLE FOR PUSHING A SHALLOW, VERY COLD ARCTIC AIRMASS RAPIDLY SOUTHEAST. SL.77 && .DISCUSSION... HIGH PRESSURE OVER THE SERN US WILL KEEP SKIES MAINLY SUNNY TODAY. THERE IS CURRENTLY WEAK WAA ACROSS THE TN VALLEY WHICH WILL HELP TEMPS TO RISE TO NEAR 70 BY THE AFTN. 07 && .AVIATION... /ISSUED 532 AM CST MON NOV 10 2014/ FOR 12Z TAFS... VFR CONDITIONS SHOULD CONTINUE THIS TAF PERIOD. LIGHT WINDS THIS MORNING WILL BECOME SOUTHERLY 10-15KT...WITH A FEW GUSTS NEAR 20KT. WINDS SHOULD DIMINISH AND BECOME SE 5-10KT AFTER SUNSET. MOSTLY CLEAR SKIES SHOULD CONTINUE TODAY...WITH FEW HIGH CLOUDS MOVING IN AFTER SUNSET. RSB && .PREV DISCUSSION... /ISSUED 310 AM CST MON NOV 10 2014/ BEFORE THE ARCTIC FRONT ARRIVES, WARMER WEATHER WILL PREVAIL TODAY (ENJOY IT WHILE IT LASTS) AS A SFC RIDGE CENTERED OVER CENTRAL ALABAMA SHIFTS EAST. THIS WILL BRING A SOUTHERLY FLOW LATE THIS MORNING INTO THE AFTERNOON. COMBINED WITH DAYTIME HEATING, HIGHS TODAY SHOULD REGISTER IN THE UPPER 60S/CLOSE TO 70 DEGREES. MODEL GUIDANCE HAS BEEN TRENDING WARMER WITH TEMPERATURES TODAY AND HAVE BLENDED SEVERAL MOS GUIDANCE VALUES TO REFLECT THE OVERALL TREND. THEN FOR TONIGHT, QUIET AND COOL CONDITIONS SHOULD PREVAIL WITH SOUTHERLY WINDS LIKELY STAYING HIGH ENOUGH TONIGHT (4-7KTS) TO KEEP FOG FORMATION MINIMAL. ANOTHER WARM DAY IS IN STORE ON TUESDAY AS MID-HIGH LEVEL CLOUDS INCREASE, AND A SOUTHERLY FETCH INCREASES (10-15 MPH) AHEAD OF THE APPROACHING TROUGH/SFC FRONT. MODEL GUIDANCE DOES DEPICT A SOMEWHAT SLOWER ONSET OF PRECIPITATION ON TUESDAY WITH THE POSSIBILITY OF ISOLATED SHOWER ACTIVITY AHEAD OF THE FROPA LATE TUESDAY MORNING INTO THE AFTERNOON. GIVEN THE ANTECEDENT DRY ENVIRONMENT (SFC-UPPER LEVELS) CURRENTLY IN PLACE, SATURATION WILL LIKELY BE CONFINED TO THE LOW TO MID-LEVELS IF WARM AIR/MOISTURE ADVECTION SHOWED BY THE NAM/GFS VERIFY. THIS WILL TRANSLATE TO LIGHT- MODERATE SHOWER ACTIVITY AHEAD AND ALONG THE FRONT WITH QUICK DRYING/SUBSIDENT PROFILE ONCE THE SFC AND MID-LEVEL VERY COLD/DRY AIR PASSES OVER THE REGION EARLY WEDNESDAY MORNING. DID INCREASE POPS, ESPECIALLY OVER NW AL WHERE A GULF MOISTURE TONGUE LOOKS TO RESIDE. SO, WE WILL GO FROM WARM/MOIST TO VERY COLD/DRY RATHER QUICKLY ON TUES NIGHT INTO WEDNESDAY MORNING. THE FRONT SHOULD ENTER NW AL BY 00Z-03Z (6PM-9PM) AND EXIT (DEKALB/MARSHALL COUNTY) BY 06-09Z (MIDNIGHT-3AM) WEDNESDAY MORNING WITH BRISK NORTHERLY WIND OF 10-15 MPH. WINDS MAY GUST UP TO 20 MPH AS THE PRESSURE GRADIENT INCREASES AS THE 1050 MB POLAR HIGH CENTERED OVER THE NORTHERN PLAINS SLOWLY SHIFTS SE. NEEDLESS TO SAY, THE TEMPERATURE FORECAST FOR WEDNESDAY IS CHALLENGING, BUT HAVE KEPT A 5-6 DEGREE TEMPERATURE GRADIENT FROM NW TO SE (WARMEST OVER SE PORTIONS OF THE CWA). CLOUDS SHOULD BE SLOW TO CLEAR WHICH, COMBINED WITH STRONG CAA, WILL HAMPER MODIFICATION OF THE AIRMASS ON WEDNESDAY. TEMPERATURES WILL PLUMMET OVERNIGHT WITH LOWS DROPPING INTO THE 30S FOR EARLY THURSDAY MORNING WITH DAYTIME HIGHS IN THE 40S FOR BOTH THURSDAY AND FRIDAY (AND LOWS IN THE 20S BOTH FRI/SAT MORNING) AS THE POLAR SFC HIGH SLOWLY SHIFTS EAST OVER THE OH AND MS RIVER VALLEYS. DUE TO THE PLACEMENT OF THE HIGH, VERY COLD CHARACTERISTICS OF THE AIRMASS, AND LOW SUN ANGLE, IT WILL TAKE SOME TIME TO MODIFY (WARM) THIS AIRMASS. THUS, WHAT WOULD BE TYPICAL FOR JAN/FEB TEMPS HERE WILL ACTUALLY BE THE NORM FOR A FEW DAYS IN MID NOV. THEN, AS THE POLAR AND SUBTROPICAL JETS PHASE ON WEDNESDAY INTO THURSDAY, THE CONUS WILL REMAIN IN A QUASI-NW FLOW REGIME WITH THE CANADIAN POLAR LOW EJECTING SEVERAL MID-LEVEL SHORTWAVE TROUGHS SOUTHWARD TOWARDS THE SOUTH/SOUTHEAST US. THIS SETUP WILL MEAN THAT BY THE END OF THE FORECAST PERIOD, ANOTHER MID-LEVEL SHORTWAVE TROUGH WILL PUSH A REINFORCING COLD FRONT SOUTH ON SATURDAY JUST AS THE SFC AIRMASS BEGINS TO MODIFY (HIGHS IN LOW 50S ON SAT). AT THIS POINT, THE MODELS DO SHOW THE POSSIBILITY OF RAIN SHOWERS AND A HINT OF AN OVERRUNNING SCENARIO OCCURRING CLOSE TO OUR AREA (COULD MEAN WINTRY PRECIP) ON SAT NIGHT INTO EARLY SUNDAY MORNING. STILL TOO MUCH UNCERTAINTY AND MODEL VARIABILITY LIKELY THIS FAR IN ADVANCE. THUS, WILL KEEP PRECIP LIQUID AT THIS TIME WITH ABOVE FREEZING TEMPS ON BOTH SATURDAY AND SUNDAY. HOWEVER, FOR THE THURSDAY THROUGH FRIDAY TIME FRAME STILL FORECASTING TEMPS THAT ARE BETWEEN 15-25 DEGREES BELOW NORMAL FOR THIS TIME OF YEAR! SL.77 && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT WEATHER.GOV/HUNTSVILLE.
Posted on: Mon, 10 Nov 2014 16:38:35 +0000
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