Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 181002 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 602 AM EDT THU SEP 18 2014 .SYNOPSIS... A TROUGH OF LOW PRESSURE OVER EASTERN NORTH AMERICA WILL SLOWLY WEAKEN INTO SATURDAY BEFORE RE-INTENSIFYING LATER ON SUNDAY ONCE AGAIN. OVERALL IT SHOULD BE A RELATIVELY COOL AND DRY PERIOD WITH A BRIEF WARM UP OVER THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A COMPACT MID/UPPER SHORT WAVE WAS SLIDING EAST ACROSS SOUTHERN PENN EARLY TODAY...WHILE A COLD FRONT WAS SAGGING SLOWLY SOUTH FROM SRN ONTARIO. THESE TWO WEATHER FEATURES /AND A RESULTANT AREA OF WEAK THETA-E ADVECTION AROUND THE 850 MB LEVEL/...WERE LEADING TO AREAS OF BKN HIGH-BASED STRATO CU AND LOW-END ALTO CU CLOUDS THAT WILL HANG AROUND THROUGH AT LEAST THE MID MORNING HOURS. LIGHT AND VARIABLE WIND...AND A TIGHT 1-3F T/TD SPREAD AT 07Z WILL LEAD TO AREAS OF FOG INCREASING IN BOTH COVERAGE AND THICKNESS ACROSS THE REGION EARLY THROUGH 12Z TODAY. VSBYS IN MOST PLACES WILL ONLY DROP TO 1-3SM DUE TO THE AFOREMENTIONED CLOUDS. THE VSBY WILL LIKELY DIP TO UNDER 1/4SM FOR A FEW HOURS EITHER SIDE OF SUNRISE IN SOME OF THE NORTHERN PENN DEEPER VALLEYS CONTAINING LARGER STREAMS AND RIVERS. LOWS TEMPS WILL VARY FROM 39F IN THE COLDEST SPOTS IN THE NRN MTNS...TO THE MID AND UPPER 40S THROUGHOUT MUCH OF CENTRAL AND SOUTHERN PENN. ANOTHER DRY AND SEASONABLY COOL DAY IS EXPECTED. A WEAK FRONTAL BOUNDARY WILL DRIFT SOUTH ACROSS THE REGION DURING THE LATE MORNING AND EARLY AFTERNOON HOURS...BRINGING SLIGHTLY COOLER AIR AND JUST SCATTERED CLOUD COVER. HIGH TEMPS THIS AFTERNOON WILL RANGE FROM THE L60S ACROSS THE NORTH...TO THE LOWER 70S IN THE SOUTH /OR JUST A FEW DEG F BELOW NORMAL/. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... TONIGHT WILL BY QUITE COLD WITH FROST POSSIBLE ACROSS THE COLDEST VALLEYS. A FROST ADVISORY MAY HAVE TO BE ISSUED /DURING THE DAY TODAY/ FOR PORTIONS OF WESTERN PA FOR FRIDAY MORNING. CURRENT LATEST...00Z NUMERICAL GUIDANCE IS INDICATING BORDERLINE TEMP/DEWPONTS FOR WIDESPREAD FROST UP NORTH ATTM...SO AFTER COORDINATION WITH SURROUNDING WFOS...DECISION WAS TO DELAY THE ISSUANCE OF ANY FLAGS UNTIL THE DAYSHIFT CAN BOOST CONFIDENCE IN EITHER DIRECTION WITH MORE DEFINITIVE GUIDANCE. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... WARMER AIR AND HIGHER MOISTURE WILL ADVECT INTO THE REGION THIS WEEKEND ON INCREASING SW FLOW AROUND A HIGH PRESSURE AREA /RETREATING TO THE EAST/. AT THE SAME TIME...TROUGH BEGINS TO CARVE INTO ZONAL FLOW OVER THE GREAT LAKES AS A SYSTEM APPROACHES PA FOR SUN/MON. THE RESULT WILL BE A PAIR OF ABOVE NORMAL TEMPERATURE DAYS SAT-SUN WITH TEMPS MAINLY IN THE 70S...AND TAKING A RUN AT 80F IN THE SE. WE/LL ALSO GET A BREAK FROM OUR RUN OF CHILLY OVERNIGHTS AS LOWS REMAIN WELL INTO THE 40S AND 50S. A PERIOD OF LOW/STRATUS AND PATCHY DRIZZLE IS POSSIBLE FOR A FEW HOURS EARLY SATURDAY...OTHERWISE SHOWER ACTIVITY SHOULD REMAIN CONFINED TO THE UPPER MIDWEST THROUGH EARLY SUNDAY. THE CENTER OF THE APPROACHING LOW PRESSURE SYSTEM WILL REMAIN WELL TO OUR NORTH...BUT A WEAK COLD FRONT WILL PUSH THROUGH PA SUNDAY INTO SUN NIGHT. THIS WILL BE THE BEST CHANCE OF RAIN/SHOWERS THROUGH DURATION OF THE EXTENDED FORECAST. THE LATEST ECMWF IS THE WETTEST WITH QPF POTENTIALLY UP TO 0.25...WHILE THE GFS BRINGS LIGHTER AMOUNTS. THE 500 HPA TROUGH BEHIND THE FRONT DEEPENS OVER THE REGION MONDAY INTO TUESDAY. THIS WILL KEEP MENTION FOR SCT INSTABILITY SHOWERS MONDAY INTO TUESDAY...MAINLY IN HIGHER TERRAIN OF N/W CWA. COOLER AIR ON NW FLOW WILL GRADUALLY FILTER BACK INTO THE REGION...WITH MONDAY/S HIGHS ABOUT 8-10F COOLER AND TUESDAY FALLING ANOTHER 5F OR SO. OVERNIGHT LOWS WILL SLIP BACK INTO THE 40S MON NIGHT...WITH SOME MID/UPPER 30S POSS IN THE NORTHERN MTNS TUE NIGHT. TROUGH LIFTS TO THE NE BY MIDWEEK AS HIGH PRESSURE SETTLES BACK IN. AS FLOW AGAIN TURNS AROUND TO THE SW...REGION SHOULD SEE ANOTHER GRADUAL WARMUP FOR LATE WEEK. && .AVIATION /10Z THURSDAY THROUGH MONDAY/...
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HIGHLY VARIABLE FLYING CONDITIONS EXIST EARLY THIS MORNING ACROSS CENTRAL PENNSYLVANIA...WITH CONDITIONS RANGING FROM VLIFR TO VFR OVER THE REGION. THE PATCHY NATURE OF THE FOG HAS MADE FOR HIGHLY CHANGABLE CONDITIONS AT SOME INDIVIDUAL AIRFIELDS...WITH CIGS AND VSBYS VARYING FROM VFR TO VLIFR IN JUST A FEW MINUTES. LATEST UPDATES ATTEMPT TO CAPTURE PREVAILING CONDITIONS...BUT PILOTS SHOULD BE PREPARED FOR RAPIDLY CHANGING LOCAL FLYING CONDITIONS EARLY THIS MORNING. GIVEN THE PATCHY NATURE OF THE FOG...MOST LOCATIONS WILL BE BACK TO VFR CONDITIONS BY 13Z TO 14Z. LATER TODAY...A MOISTURE STARVED COLD FRONT WILL PUSH SOUTHEAST THRU THE REGION. EXPECT VFR CONDITIONS ACROSS ALL OF CENTRAL PENNSYLVANIA FOR THE BALANCE OF THE DAY INTO THE EVENING. THEN ONCE AGAIN...FOG DEVELOPMENT WILL REDUCE FLYING CONDITIONS THURSDAY OVERNIGHT INTO FRIDAY MORNING. A FRONTAL SYSTEM WILL REINTRODUCE THE CHANCE OF SHOWERS AND POSSIBLE THUNDERSTORMS FOR SUNDAY INTO SUNDAY NIGHT...FOLLOWED BY HIGH PRESSURE AND FAIR WEATHER FOR THE START OF NEXT WEEK. OUTLOOK... FRI...PATCHY AM FOG POSSIBLE...MAINLY NORTH. SAT...AM LOW CIGS/FOG POSSIBLE. SUN...SLIGHT CHC OF PM TSRA IMPACTS W MTNS. MON...NO SIG WX EXPECTED.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT/RXR AVIATION...JUNG

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