Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 221846 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 246 PM EDT MON SEP 22 2014 .SYNOPSIS... A LARGE AREA OF HIGH PRESSURE OVER THE MIDWEST...WILL BUILD EAST ACROSS THE MID ATLANTIC REGION TUESDAY BEFORE DRIFTING OVER THE NEW ENGLAND STATES FOR THE LATTER HALF OF THE WEEK. THIS DOMINANT WEATHER FEATURE WILL PROVIDE GENERALLY FAIR AND COOL WEATHER FOR THE ENTIRE WEEK. && .NEAR TERM /THROUGH TONIGHT/... DEEP...AND WELL-ALIGNED NWRLY FLOW AND ASSOCIATED LAKE EFFECT CLOUDS/ISOLATED LIGHT SHOWERS ACROSS THE ALLEGHENIES WILL CONTINUE THROUGH EARLY TONIGHT...BEFORE THE MEAN BOUNDARY LAYER FLOW GRADUALLY WEAKENS BY 5 KTS OR SO AND CONTRACTS THE CLOUD COVER BACK TWD THE SOUTH SHORE OF LAKE ERIE. THE CLOUDS WILL BE TOUGH TO BREAK UP COMPLETELY...AND BASED ON SEVERAL FACTORS INCLUDING MODEL FCST OF HIGH RH/S IN THE 925-850 MB LAYER...THE 850 MB RIDGE AXIS WELL TO THE WEST OF PENN THROUGH 12Z TUESDAY...AND ANOTHER /ALBEIT WEAKER/ 850 MB THERMAL TROUGH DRIFTING SE ACROSS LAKE ERIE IN THE 06-09Z PERIOD TUESDAY...MVFR CIGS MAY HANG ON FOR MOST OR ALL OF THE NIGHT INVOF KBFD AND POINTS WEST. LLVL TRAJECTORIES APPEAR FAVORABLE TO KEEP PLENTY OF CLOUDS ACROSS THE LAUREL HIGHLANDS AS WELL THROUGH THIS EVENING. THE THINNER...AND MAINLY BKN STRATO CU THAT WILL BE PRESENT FOR THE REST OF TODAY ACROSS THE CENTRAL AND SE ZONES SHOULD SCT OUT EARLY TONIGHT...THANKS TO THE MEAN SFC-850 MB FLOW DECREASING TO AROUND 10 KTS. TEMPS SHOULD RISE JUST ANOTHER 1-3 DEG F THIS AFTERNOON...WITH MAX TEMPS RANGING FROM 50-55F ACROSS THE NRN AND WRN MTNS...TO THE MID AND UPPER 60S THROUGHOUT THE LOWER SUSQ VALLEY. THESE READINGS WILL GIVE US AN EARLY TASTE OF AUTUMN THAT OFFICIALLY BEGINS HERE AT 0229Z TUESDAY. THE HIGHS WILL BE A SOLID 6-10F BELOW NORMAL /WITH THE GREATEST DEPARTURES OF 12-14F BELOW NORMAL ACROSS THE NW MTNS. LOW TEMPS EARLY TUESDAY WILL REACH FROSTY LEVELS ACROSS THE HIGHER TERRAIN OF SOMERSET COUNTY...WHERE A FROST ADVISORY WAS POSTED FROM 07-13Z TUESDAY. ELSEWHERE...PATCHY FROST IS POSSIBLE FOR RURAL VALLEYS...EXCEPT FOR THE LOWER SUSQ VALLEY. LOWS WILL BE IN THE U30S TO AROUND 40F IN MOST LOCATIONS THROUGHOUT THE CENTRAL RIDGE AND VALLEY REGION...WITH LOWER 40S IN THE LARGER SERN PENN METRO AREAS SUCH AS YORK...HARRISBURG...AND LANCASTER. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... HIGH PRESSURE WILL BUILD EAST FROM THE OHIO NE UP THE OHIO VALLEY AND BECOME CENTERED RIGHT OVER THE REGION TUESDAY AFTERNOON. AFTER SOME LOCALLY DENSE RIVER VALLEY FOG AND PATCHY FROST IN A FEW OF THE COLDER SPOTS EARLY TUESDAY...EXPECT ABUNDANT SUNSHINE AND LIGHT WIND FOR THE LATE MORNING AND AFTERNOON HOURS. TUESDAY WILL BE A MUCH MILDER DAY WITH TEMPS RISING ABOUT 25F DURING THE DAY...AND REACHING ABOUT 10F MILDER THAN MONDAY/S HIGHS IN THE NW - BUT STAYING SIMILAR TO MONDAY IN THE LOWER SUSQ. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... HIGH PRESSURE WILL PARK ITSELF OVER NEW YORK AND NEW ENGLAND WITH +2 TO +3 SIGMA ABOVE NORMAL MSLP ANOMALIES BY WEDNESDAY-THURSDAY. THE MODELS SEEM TO BE IN FAIR AGREEMENT SHOWING A BLOCKING 500 HPA ANTICYCLONE TO THE NORTHWEST AS A MASSIVE 500 HPA POSITIVE HEIGHT ANOMALY OF +2 TO +3 SIGMA DEVELOPS OVER CENTRAL CANADA BY THURSDAY AND INTO FRIDAY. THE MODELS AND ENSEMBLE MEANS DO WELL FORECASTING ANTICYCLONES SO THERE SEEMS TO BE MORE OF A CONSENSUS ON THE FAIR WEATHER FORECAST NEXT WEEK. EXPECT DIURNAL VALLEY FOG AND LOW CLOUDS LIKELY TO AFFECT THE REGION EACH MORNING ONCE THE BIG HIGH TAKES HOLD....AND CONTINUING DAILY INTO NEXT WEEKEND. THAT MASSIVE HIGH SHOULD CONTINUE THE DRY FAIR WEATHER THROUGH NEXT WEEKEND. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... EXTENSIVE MVFR TO VFR BKN-OVC STRATO CU CLOUD DECK CONTINUES TO COVER ALL BUT PORTIONS OF SCENT PENN AT MID AFTERNOON. THE CLOUD SHIELD IS STARTING TO ERODE TWD THE NW AND EXPECT THIS TREND TO CONTINUE LATE THIS AFTERNOON AND THIS EVENING. EXCEPTIONS WILL BE AT KJST AND KBFD WHERE MVFR CIGS AREA EXPECTED TO CONTINUE UNTIL AT LEAST 07Z TUESDAY. AFTERWARD...HIGH PRESSURE RIDGING IN FROM THE OHIO VALLEY /AND BECOMING CENTERED OVER PENN TUESDAY AFTERNOON/ WILL BRING MAINLY CLEAR SKIES AND LIGHT WIND LATER TONIGHT THROUGH TUESDAY. THE LARGE SPREAD OF 25 DEG F OR SO BETWEEN THE AIR AND REGIONAL STREAMS AND RIVERS /COUPLED WITH CURRENT SFC DEWPOINTS IN THE LOWER 40S/ WILL LEAD TO LOCALLY DENSE VALLEY FOG FOR SEVERAL HOURS EARLY TUESDAY. THE FOG SHOULD IMPACT MAINLY KIPT...KUNV AND KAOO AIRFIELDS. GENERALLY TRANQUIL WEATHER WITH MAINLY VFR CONDITIONS SHOULD PREVAIL THROUGH WED...WITH THE EXCEPTION OF SOME PATCHY MORNING VALLEY FOG. OUTLOOK... WED-SAT...MAINLY VFR...BUT WITH DAILY RESTRICTIONS IN MORNING FOG POSSIBLE. && .CTP WATCHES/WARNINGS/ADVISORIES... FROST ADVISORY FROM 3 AM TO 9 AM EDT TUESDAY FOR PAZ033. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...GRUMM/CERU AVIATION...LAMBERT

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