Issued by NWS State College, PA
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-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --000 FXUS61 KCTP 211356 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 856 AM EST SAT NOV 21 2009 .SYNOPSIS... HIGH PRESSURE SHOULD PROVIDE RELATIVELY DRY WEATHER OVER THE REGION THROUGH SUNDAY. EASTERLY FLOW AND A WAVE COMING OUT OF THE GULF SHOULD INCREASE THE CHANCE OF RAIN LATE SUNDAY INTO MONDAY. THE PATTERN OVER NORTH AMERICA IS CHANGING...THE ENSEMBLES SHOW A TROUGH ATTEMPTING TO ESTABLISH ITSELF OVER EASTERN NORTH AMERICA WITH A RIDGE OVER NORTHWESTERN CANADA. A SERIES OF WAVES WILL CARVE OUT THE TROUGH BRINGING UNSETTLED WEATHER TO THE REGION NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...-- Changed Discussion --NAM BUFKIT PROFILES SHOW A CLASSIC BOUNDARY LAYER INVERSION AROUND THE 296K TO 298K LEVELS ACROSS CENTRAL AND WESTERN PA BETWEEN 3K AND 5K FEET. WITH CENTER OF 1023 MB SFC HIGH MOVING ONLY SLOWLY EASTWARD ACROSS THE OHIO VALLEY TODAY...DO NOT EXPECT SUBSTANTIAL ENOUGH MIXING TO CLEAR THE STRATUS FROM THE CENTRAL AND SOUTH CENTRAL MOUNTAINS WESTWARD ACROSS THE ALLEGHENIES...BUT THERE SHOULD BE ENOUGH DOWNSLOPING THROUGH THE MID AFTERNOON HOURS TO PRODUCE NUMEROUS BREAKS IN THE STRATUS OVER THE SOUTHEAST... ONCE THE HIGH CLOUD SHIELD STREAMS EAST OF THE AREA BY EARLY AFTERNOON. OVERALL...A TYPICAL NOVEMBER SKY ACROSS CENTRAL PA. CORE OF THE COLD AIR AT 850 MB ASSOCIATED WITH 5H TROF ALOFT SINKING SOUTHWARD VEROM THE CENTRAL AND EASTERN GLAKS WILL DROP SOUTH OF THE REGION BY LATE THIS AFTERNOON AND EVENING...EASING THE LOW LEVEL LAPSE RATES AND HELPING TO WEAKEN THE BOUNDARY LAYER INVERSION. STILL EXPECTING MAXES TO RANGE FROM THE UPPER 40S OVR THE ALLEGHENIES...TO THE MID 50S AIDED BY SUNBREAKS ACROSS THE SUSQ RIVER VALLEY.-- End Changed Discussion --&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... LG SCALE SUBSIDENCE IN WAKE OF DEPARTING SHORTWAVE SHOULD RESULT IN CLEARING SKIES TONIGHT. HOWEVER...LGT WINDS ASSOCIATED WITH SFC HIGH SHOULD RESULT IN PATCHY RADIATION FOG TOWARD DAWN. ALTHOUGH THE CLEARING SKIES WILL ALLOW TEMPS TO BECOME COOLER THAN THIS MORNING...MINS STILL LIKELY TO BE 5-10F ABV NORMAL WITH READINGS GENERALLY IN THE M/U30S. AFTER PATCHY AM FOG...RIDGING AT SFC AND ALOFT SHOULD PRODUCE A MSUNNY AND MILD SUNDAY. NAEFS SUPPORTS THE HIGHER MAV MOS TEMPS...RANGING IN THE L/M50S MOST SPOTS. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... AN ACTIVE SPLIT FLOW PATTERN IS FCST TO CONTINUE THROUGH MUCH OF THE PD BY LONG TERM GUIDANCE. SEVERAL UPR LEVEL TROFS ARE FORECAST TO TRAVERSE THE CONUS IN BOTH THE NRN AND SRN STREAM FLOW WITH VARYING LEVELS OF INFLUENCE ON PA. OVERALL HOWEVER...MOST OF THE NEXT WEEK LOOKS TO BE DRY WITH CONTINUED ABOVE NORMAL TEMPERATURES. THE FIRST TROF...IN THE SRN STREAM...IS FCST TO MOVE ACROSS THE GULF COAST TDY...THEN LIFT NE ALONG THE MID ATLC COAST LATE SUNDAY. THE WAVE WILL BE LIFTING INTO THE NRN STREAM MEAN UPR RIDGE WITH HIGH PRESSURE IN PLACE AT THE SFC. MODEL TRENDS ARE FOR A SMALLER...FARTHER EAST SOLUTION OF THE SFC LOW ASSCD WITH THE SRN TROF AND FORECASTS DRIER THAN PVS RUNS. GFS APPEARS AN OUTLIER WITH A SIG WET FORECAST FOR MONDAY ACROSS MUCH OF PA...AND SUCH HAVE LOWERED POPS FOR THIS TIME PD FOLLOWING THE MULTITUDE OF OTHER LONG TERM GUIDANCE. HIGHEST ENSEMBLE POPS ARE MONDAY DURING THE DAY INTO MONDAY NIGHT. SOME TIMING ISSUES. LOWERED THE POPS INTO THE 30-50 PERCENT RANGE MONDAY DURING THE DAY AND UPPED THEM MONDAY NIGHT INTO TUESDAY DUE TO THE UNCERTAINTY IN THE TIMING. PRETTY WEAK SYSTEM AND THE RAIN SHOULD BE VERY LIGHT. AMPLIFICATION IN THE NRN STREAM IS FCST TO OCCUR OVER THE GREAT LAKES BY TUE...WITH A WEAKENING SFC FRONT REACHING WRN ON WED AS SUPPORTING CLOSED UPPER TROF LIFTS INTO SERN CANADA. A STRONGER UPR TROF/COLD FRONT IS FCST TO MOVE THROUGH PA THANKSGIVING NIGHT...IF CURRENT TIMING HOLDS...WITH A NOTICEABLE COOL DOWN IN STORE FOR SHOPPERS NEXT FRIDAY. ANY SHOWER ACTIVITY OVER NW PA COULD BE IN THE FORM OF SNOW THUR-FRI AS 850 TEMPERATURES FALL BELOW 0C. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... HIGH PRESSURE BUILDING INTO THE REGION TODAY. MOISTURE LAYER TRAPPED UNDER SUBSIDENCE INVERSION WILL BRING IFR/MVFR CIGS FOR SEVERAL HOURS THIS MORNING IN HIGHER TERRAIN TAFS...BUT THESE SHOULD MIX OUT TO VFR BY EARLY AFTERNOON. VFR WILL BE THE RULE IN THE EAST WITH SLIGHT DOWNSLOPE COMPONENT IN LIGHT WESTERLY WINDS. OUTLOOK... SUN...AREAS OF MVFR/IFR CIGS EARLY IN HIGHER TERRAIN...OTHERWISE VFR. MON...MVFR LCL IFR. PSBL SHRA IN THE AFTN. TUE...MVFR/IFR CIGS. SHRA IN THE AM. WED...MVFR TO VFR EARLY. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...GRUMM NEAR TERM...FITZGERALD SHORT TERM...DEVOIR/FITZGERALD LONG TERM...GRUMM/GARTNER AVIATION...RXR
