Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 210853 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 453 AM EDT MON JUL 21 2014 .SYNOPSIS... AN UPPER LEVEL WILL SLIDE EAST ACROSS PENNSYLVANIA TODAY. A COLD FRONT WILL MOVE SOUTHEAST FROM THE GREAT LAKES AND CROSS THE COMMONWEALTH LATE WEDNESDAY AND WEDNESDAY NIGHT. A REFRESHINGLY COOLER AND LESS HUMID AIRMASS WILL OVERSPREAD THE COMMONWEALTH THURSDAY THROUGH SATURDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 08-0830Z KCCX RADAR LOOP SHOWS SCATTERED LIGHT SHOWERS DRIFTING NE ACROSS THE LAUREL HIGHLANDS REGION FROM WVA /IN ASSOCIATION WITH A WEAK SHORT WAVE IN THE SW FLOW ALOFT...AHEAD OF AN UPPER LEVEL SHEAR AXIS THAT WAS LOCATED ACROSS THE OHIO VALLEY/. ANOTHER VORT MAX WILL BE DIVING SE TWD THE BASE OF THE WEAK UPPER LEVEL TROF...AND MOVING ACROSS THE NW MTNS DURING THE AFTERNOON AND EARLY EVENING HOURS. POCKETS OF UVVEL ASSOCIATED WITH BOTH OF THESE FEATURES WILL COMBINE WITH AN AXIS OF HIGH PWAT AIR /1.5-1.75 INCHES/ TO CREATE SCATTERED SHOWERS AND ISOLATED AFTERNOON TSRA. THE GREATEST CONCENTRATION OF CONVECTION IS EXPECTED TO BE ACROSS THE LAURELS /AND TO A LESSER DEGREE OVER THE NRN MTNS/ WHERE SLIGHTLY COOLER MID-LEVEL TEMPS AND A LIGHT SERLY LLVL UPSLOPE FLOW WILL BE FOUND. THIS SCENARIO IS SUPPORTED BY A BLEND OF THE LATEST 06Z HRRR...07Z RAP...AND 03Z SREF WHERE ML CAPES OF 800-1200 J/KG ARE SHOWN. CONVECTIVE INSTAB ELSEWHERE ACROSS CENTRAL AND NERN PA IS MINIMAL. BASIN AVG QPF WILL BE GENERALLY ONE TENTH OF AN INCH OR LESS ACROSS THE WRN HALF OF THE CWA...THOUGH SOME AREAS COULD SEE AROUND 0.25 OF AN INCH /ESP NEAR AND TO THE SOUTH OF KJST/. OTHERWISE...LIGHT WIND WITH TVARIABLE AMOUNTS OF HIGH BASED STRATOCU AND ALTOCU CLOUDS /AND AREAS OF LIGHT FOG ACROSS THE NORTH/ WILL OCCUR THIS MORNING WITH JUST AN ISOLATED SHOWER POSSIBLE ACROSS THE NE HALF OF THE CWA. CONSENSUS BLEND OF ALL AVAILABLE 00Z THROUGH 06Z GUIDANCE YIELDS HIGH TEMPS THIS AFTERNOON RANGING FROM THE UPPER 70S TO LOW 80S...WHICH IS A TAD COOLER THAN NORMAL FOR MID SUMMER. SFC DWPTS CLIMBING WELL INTO THE 60S WILL ALSO MAKE IT FEEL MORE MUGGY. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... A VERY SIMILAR NIGHT /TO SUNDAY NIGHT/ IS EXPECTED WITH JUST SOME ISOLATED /MAINLY EVENING/ SHOWERS...FOLLOWED BY PARTLY CLOUDY SKIES WITH NEAR NORMAL MIN TEMPS RANGING FROM THE U50S IN THE NORTH...TO THE LOWER 60S THROUGHOUT THE CENTRAL MTNS...AND MID 60S ACROSS THE LOWER SUSQ RVR VALLEY. TUESDAY WILL BE NOTICEABLY WARMER AND HUMID WITH PARTLY SUNNY SKIES AND APPROX 1.5 PWAT AIR HELPING TO FUEL ML CAPES OF 800-1400 J/KG ACROSS THE WRN MTNS...AND GENERALLY LESS THAN 500 J/KG ACROSS THE MIDDLE AND LOWER SUSQ VALLEY. UNIMPRESSIVE...MID-LEVEL LAPSE RATES OF JUST OVER 5C/KM WILL KEEP MOST OF THE CONVECTION ISOLATED /AND ACROSS THE HIGHER TERRAIN OF NRN AND WRN PENN/ DURING THE AFTERNOON AND EVENING HOURS. HIGH TEMPS TUESDAY AFTERNOON WILL BE IN THE LOWER 80S ACROSS THE MTNS...AND MID TO UPPER 80S THROUGHOUT THE VALLEYS OF CENTRAL AND SOUTHERN PENN. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... LARGE UPPER RIDGE BUILDING NORTH 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 WEAK 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. MEDIUM RANGE MODEL FORECASTS CONTINUE TO BRING A FRONT AND INCREASED CHANGES FOR PRECIPITATION TOWARD PA IN THE WEDNESDAY/THURSDAY TIME FRAME AND SHOW ANOTHER...POTENTIALLY STRONGER SYSTEM LATE NEXT WEEKEND. IN THE MEANTIME...SURFACE HIGH PRESSURE AXIS TO OUR EAST WILL KEEP GENERALLY FAIR WEATHER ACROSS PENNSYLVANIA EARLY IN THE WEEK. LOW LEVEL MOISTURE WILL ATTEMPT TO CREEP BACK INTO THE REGION ON WEAK RETURN FLOW MONDAY NIGHT AND TUESDAY. DEEPEST MOISTURE WILL REMAIN FARTHER WEST OVER OHIO VALLEY. KEPT MENTION OF ISO/SCT TSTMS MON- EARLY WED /MAINLY ACROSS THE WEST/. A WARMING TREND BEGINNING ON MONDAY...WILL CONTINUE RIGHT THROUGH WED...WHEN TEMPS ARE EXPECTED REACH THEIR PEEK FOR THE WEEK IN THE IN THE UPPER 80S TO AROUND 90F IN THE SUSQ VALLEY...AND GENERALLY IN THE MID 80S ELSEWHERE. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... GENERALLY FOLLOWED A BLEND OF PERSISTENCE /LAST NIGHTS SFC OBS AND EARLY MORNING TRENDS/ WITH CURRENT CONDS FOR THE 21/06Z SCHEDULED TAFS. DESPITE RELATIVELY HIGH BLYR MSTR/THIN T-TD SPREADS...COMBO OF SCT-BKN MID CLOUDS WITH LACK OF OBSERVED RAFL SEEMS TO BE KEEPING RESTRICTIONS AOA MVFR FLGT CATS. MVFR TO LOW END VFR CIGS AND VSBYS SHOULD IMPROVE TO VFR /SCT-BKN CU WITH BASES AROUND 5KFT AGL/ BY LATE MORNING/AFTN. LIFT ASSOCD WITH LEFTOVER BROAD/WEAK UPPER TROUGH CENTERED JUST WEST OF THE APPALACHIAN SPINE...COUPLED WITH MEAGER INSTABILITY SHOULD BE ENOUGH TO GENERATE WDLY SCT SHRA/ISOLD TSRA ACRS THE AIRSPACE THIS AFTN. CVRG AND PROBS OF PCPN ARE TOO LOW TO MENTION IN POINT BASED TAFS ATTM. PARTIAL CLEARING EXPECTED WITH THE LOSS OF DAYTIME HEATING...GIVING WAY TO PATCHY FOG/LOWERING CIGS OVERNIGHT MAINLY E OF THE ALLEGHENY FRONT. OUTLOOK... TUE...MAINLY VFR. SCT A.M MVFR FOG/CIGS. WDLY SCT AFTERNOON AND EVENING SHOWERS/THUNDERSTORMS. WED-THU...SLOW NW-SE MOVG COLD FROPA WILL LKLY BRING SCT SHOWERS AND THUNDERSTORMS. FRI...NO SIG WX. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT/GARTNER AVIATION...STEINBUGL

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