Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 241525 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1125 AM EDT THU JUL 24 2014 .SYNOPSIS...
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HIGH PRESSURE AND A REFRESHINGLY COOLER AND LESS HUMID AIRMASS WILL PUSH SOUTHEAST FROM THE GREAT LAKES REGION TODAY AND STAY WITH US RIGHT INTO SATURDAY. A WARM FRONT WILL SLIDE EAST OUT OF THE OHIO VALLEY LATE SATURDAY FOLLOWED BY A WAVY...SLOW MOVING COLD FRONT FOR SUNDAY INTO SUNDAY NIGHT. PERIODS OF SHOWERS AND THUNDERSTORMS WILL AFFECT CENTRAL PENNSYLVANIA AND THE ALLEGHENY PLATEAU SATURDAY NIGHT THROUGH SUNDAY NIGHT.
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&& .NEAR TERM /UNTIL 7 PM THIS EVENING/...
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COLD AIR ALOFT AND GOOD SOLAR HEATING GENERATING LOTS OF CU OVER THE ENTIRE REGION. WEAK/MODERATE SHORT WAVE TROUGH IS ALSO PRODUCING LARGER-SCALE LIFT TO AID IN THE CLOUD FORMATION. BUT BREAKS WILL STILL BE THERE THROUGH THE DAY AND EVENTUALLY THE DRY AIR WILL START TO MIX THOROUGHLY AND START TO DISSIPATE THE CLOUDS IN LOTS OF AREAS DURING THE MID-LATE AFTERNOON...ESPECIALLY THE DOWNSLOPE REGIONS. BY SUNSET A LOT OF THE CLOUDS WILL BE GONE...WITH THE GREATEST COVERAGE OVER THE SW/SC MOUNTAINS. TEMPS LOOK ON TRACK FOR THIS SCENARIO.
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&& .SHORT TERM /7 PM THIS EVENING THROUGH 6 AM FRIDAY/...
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HIGH PRESSURE BUILDING INTO THE STATE FROM THE OHIO VALLEY WILL BRING CLEAR TO PARTLY CLOUDY SKIES TO ALL OF THE REGION TONIGHT. ANOMALOUSLY LOW PWAT AIR OF ONLY AROUND ONE-HALF OF AN INCH /OR LESS/ WILL COMBINE WITH A COOL POOL AT 850 MB...AND LIGHT WIND... TO BRING A VERY CHILLY MID-SUMMER NIGHT. LOW TEMPS AT DAYBREAK FRIDAY WILL VARY FROM AROUND 40F ACROSS THE PERENNIAL COLD SPOTS ACROSS THE NORTH...TO BETWEEN 50 AND 55F THROUGHOUT THE SUSQUEHANNA VALLEY. RECORD MINS LOOK LIKE THEY WILL BE IN JEOPARDY IN AT LEAST A FEW SITES TONIGHT. THIS COULD BRING FOG DUE TO THE COLD AIR OVER THE WARMER WATERS. BUT THE AIR IS GOING TO BE VERY DRY. THESE FACTORS WILL BE AT ODDS WITH EACH OTHER...MAKING THE FOG FORECAST THERE PRETTY TOUGH.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/... OVERALL SCENARIO REMAINS UNCHANGED IN THE LONG TERM PERIOD AS A LARGE UPPER RIDGE BUILDING OVER THE FOUR CORNERS REGION IS FORECAST TO EXPAND NORTH AND EAST INTO THE ROCKIES AND PLAINS DURING THE PERIOD. DOWNSTREAM...THIS WILL LEAD TO MODERATE TO STRONG LONG WAVE TROFFING OVER THE EASTERN THIRD OF THE COUNTRY. UPPER LOW TO THE EAST OF HUDSON BAY WILL BE STRENGTHENED AT TIMES BY SHORTWAVE ENERGY IN THE STRONGER JET STREAM FLOW ACROSS CANADA. SOUTHWARD EXTENSION OF THIS LOW/TROF WILL AT TIMES DURING THE PERIOD STRENGTHENING THE TROFFING ACROSS THE NORTHEASTERN U.S./OUR REGION. THE TREND OF MEDIUM RANGE MODEL GUIDANCE IS FOR STRONGER/DEEPER TROFFING DOWNSTREAM ACROSS THE EASTERN U.S...DEVELOPING AN ALMOST FULL LATITUDE TROF EXTENDING FROM THE EASTERN CANADA LOW SWD TO FLORIDA. THIS WILL LIKELY SERVE TO EXPAND AND PROLONG THE CHANCES FOR PCPN THIS WEEKEND. A POTENTIALLY STRONGER SYSTEM /STRONGER THAN THE ONE THAT USHERED IN THE COOL AND MUCH LESS HUMID AIRMASS OVERNIGHT WEDNESDAY NIGHT/ WILL AFFECT THE REGION FOR THE SECOND HALF OF THE UPCOMING WEEKEND. THE TREND OF STRONGER TROUGHING MENTIONED ABOVE HAS LEAD TO SLOWER ARRIVAL AND DEPARTURE OF THE FRONTAL SYSTEM IN THE DAILY PROGS. THE ECMWF IN LATEST RUN HAS SLOWED UP THE PROGRESSION OF THIS UPPER LEVEL LOW...WHERE THE GFS OPERATIONAL AND ENSEMBLES HAVE SPED UP ITS PROGRESSION THROUGH THE GREAT LAKES REGION. A WARM FRONT WILL BE ON OUR WESTERN DOORSTEP LATE SATURDAY NIGHT AND SUNDAY...AS THE EC CONTINUES TO SLOW ITS PROGRESSION SO EXPECT THE WARM FRONT TO MOVE IN CLOSER TO MIDDAY SUNDAY. HAVE THUS ADJUSTED POPS/TIME. ASSOCIATED COLD FRONT DOES NOT CROSS THE STATE TIL MONDAY...WHERE SURPRISINGLY AT THIS POINT...THE EC AND GFS COME CLOSELY IN PHASE. THIS LARGE UPPER LEVEL LOW COULD BECOME QUASI STATIONARY OVER SOUTHERN CANADA...GREAT LAKES REGION WHICH COULD LEAD TO A POTENTIAL PROLONGED PERIOD OF SHOWERS AND THUNDERSTORM THROUGH THE MIDDLE OF NEXT WEEK. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... SEVERAL MORE HOURS OF CLOUDS. CLEARING FROM NW TO SE. CLOUDS HAVE LIMITED FOG OVERNIGHT. THUS MAINLY LOOKING AT VFR CONDITIONS BY LATE MORNING ACROSS THE REGION. HIGH PRESSURE WILL KEEP DECENT CONDTIONS ACROSS PA INTO SAT MORNING. A STRONG WARM FRONT WILL BRING A CHANCE OF SHOWERS AND THUNDERSTORMS TO THE AREA FROM LATE SATURDAY INTO SUNDAY. STILL A CHC OF SHRA/TSRA ON MON. OUTLOOK... FRI...PATCHY AM FOG...OTHERWISE VFR. SAT...PATCHY AM FOG...OTHERWISE MAINLY VFR. PM TSRA/MVFR POSS W. SUN...SHRA/TSRA WITH WARM FRONT PASSAGE MON...MORE WIDESPREAD SHRA/TSRA WITH COLD FRONT PASSAGE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...DANGELO/LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT/GARTNER AVIATION...MARTIN

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