Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 072238 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 638 PM EDT TUE JUL 7 2015 .SYNOPSIS... A WEAK RIDGE WILL BRING VERY WARM AND HUMID CONDITIONS TO THE REGION TODAY. AN APPROACHING COLD FRONT WILL MOVE THROUGH OVERNIGHT...THEN STALL OUT ALONG OR JUST SOUTH OF THE MASON DIXON LINE FOR MUCH OR THE REST OF THE WEEK KEEPING UNSETTLED CONDITIONS IN THE FORECAST FOR THE NEXT COUPLE OF DAYS. HIGH PRESSURE SHOULD RETURN FOR FRIDAY AND BRING SLIGHTLY COOLER AND NOTABLY LESS HUMID WEATHER WITH LITTLE CHANCE FOR RAIN. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... AN OVERACHIEVING BOWING LINE SEGMENT...AIDED BY A CELL MERGER OVER THE NORTHWEST MOUNTAINS...PRODUCED A FAIRLY LONGLIVED PATH OF WIND DAMAGE ACROSS MCKEAN AND POTTER COUNTIES EARLY THIS EVENING. THE CLUSTER OF STORMS RESPONSIBLE FOR THESE ISOLATED SEVERE WIND GUSTS WAS TRAVERSING MY NORTHERN TIER COUNTIES...AND THE BOW HAS MOVED NORTH OF THE PA/NY BORDER. ATTENTION SHIFTS UPSTREAM TO LOCALLY STRONG CELLS JUST WEST OF MY CWA. CELL MOTION ORTHOGONAL TO INDIVIDUAL DOPPLERS MAKING SAMPLING DIFFICULT. IN GENERAL...THIS ACTIVITY SHOULD BE WEAKENING AS IT ENTERS MY NORTHWEST COUNTIES LATER THIS EVENING. SOME TRAINING POTENTIAL EXISTS AS THE SLOW MOVING FRONT PROGRESSES SOUTHEASTWARD. ACCOMPANYING COLD FRONT WILL MOVE INTO THE NORTHWEST ZONES LATER THIS EVENING AND SLOWLY SOUTHWARD ACROSS THE COMMONWEALTH OVERNIGHT. SHOWER COVERAGE SHOULD DIMINISH AS THE FRONT MOVES SOUTH. TEMPERATURES WILL BE GENERALLY MILD OVERNIGHT AS MOST OF THE AREA WILL BE CLOUDY AND HUMID WITH SCATTERED SHOWERS. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... THE SURFACE COLD FRONT WILL STALL OUT CLOSE TO THE MASON DIXON LINE ON WEDNESDAY. THE CHANCE OF SHOWERS AND THUNDERSTORMS WILL SHIFT TOWARDS THE SOUTHERN HALF OF PENNSYLVANIA TOMORROW. QPF VALUES WILL BE LESS THAN A THIRD OF AN INCH IN OUR COUNTIES. MAX TEMPS WEDNESDAY WILL BE AROUND 10 DEGREES COOLER THAN TODAY AS CLOUDS WILL DOMINATE THE SKY. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... THE LINGERING QUASI-STATIONARY FRONTAL ZONE EXTENDING FROM THE MID ATLANTIC COAST WWD INTO THE OHIO VALLEY IS EXPECTED TO REMAIN A FOCUS FOR PCPN ON DAY 3/THURS. THERE IS REASONABLY GOOD MODEL AGREEMENT IN A CONVECTIVELY ENHANCED PERTURBATION/SFC WAVE EMERGING FROM THE SRN PLAINS AND PROGRESSING EWD AROUND THE PERIPHERY OF A SUBTROPICAL RIDGE OVER THE SOUTHEAST STATES. THE GLOBAL MODELS TEND TO HAVE A NORTHERN BIAS WITH QPF AXES ASSOCD WITH THESE MESO FEATURES...AND THEREFORE FOLLOWED WPC LEAD WITH CLUE FROM THE HI-RES MODELS IN SHIFTING MAX POPS SWD OF CONSENSUS. THERE IS THE POTENTIAL FOR THIS FEATURE TO MAINTAIN INTENSITY OR RE-INTENSIFY AS IT REACHES CENTRAL PA THURSDAY AFTERNOON..IN WHICH CASE IT WOULD BE ACCOMPANIED BY SEVERE WX AND HEAVY RAINFALL RISK. LATER FORECASTS SHOULD BE ABLE TO PROVIDE GREATER VISIBILITY AND INCREASED CONFIDENCE IN THE EVOLUTION AND POTENTIAL IMPACTS ASSOCD WITH THIS SYSTEM. THE MEDIUM RANGE MODEL AND ENSEMBLE GUIDANCE REMAINS CONSISTENT IN ITS PROJECTION THAT THE FLOW ALOFT WILL STEADILY EVOLVE TOWARD AN AMPLIFIED TROUGH/RIDGE/TROUGH PATTERN FROM WEST TO EAST ACROSS THE LOWER 48. THIS SHOULD OCCUR BY WAY OF NRN PAC ENERGY FEEDING INTO A TROUGH ALONG THE WEST COAST...A STRENGTHENING UPPER RIDGE THAT RETROGRADES WWD FROM THE SOUTHEAST INTO THE PLAINS EVENTUALLY EXPANDING NWD OVER THE ROCKIES INTO WRN CANADA...AND DOWNSTREAM TROUGHING FROM THE BUILDING RIDGE OVER THE EAST EXTENDING SWD FROM HUDSON BY VORTEX. A 24-48HR PERIOD OF DRY WEATHER...WHICH HAS BEEN QUITE ELUSIVE AS OF LATE...COULD BE IN STORE FOR THE AREA BY THE END OF THE WEEK AS WEAK RIDGING FOLLOWS IN THE WAKE OF THE D3 CONVECTIVE LOW. THE PLACEMENT OF PIVOTING FRONTAL BOUNDARY AND ASSOCIATED MSTR/PW AXIS WILL BE CRUCIAL FOR DETERMINING PCPN RISK INTO THE WEEKEND...WITH THE LATEST MODEL CONSENSUS KEEPING MOST OF THE ACTIVITY TO THE NW OR SW OF CENTRAL PA. THE OTHER FACTOR WILL BE WHAT HAPPENS TO ENERGY EJECTING FROM UPPER LOW MOVING ONSHORE CA IN THE SHORT RANGE. THERE IS REASONABLE AGREEMENT IN PRINCIPLE THAT THIS ENERGY SHOULD ROUND THE BUILDING ROCKIES/HIGH PLAINS RIDGE AND THEN HELP TO CARVE OUT THE DEVELOPING ERN TROUGH DOWNSTREAM. HOWEVER SOLUTIONS HAVE NOT LOCKED ONTO HOW SHEARED THE ENERGY WILL BECOME...WHICH ALONG WITH A FEW ADDITIONAL FACTORS LEADS TO DIFFERENCES IN THE DEPTH OF THE TROUGH AND TIMING OF NEXT PCPN OPPORTUNITY. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... MOST OF CWA REMAINS VFR THIS EVENING...AS REGION REMAINS IN THE WARM SECTOR AHEAD OF AN APPROACHING COLD FRONT OVER THE OHIO VALLEY. BUT THUNDERSTORMS ARE ALREADY IMPACTING THE NW MTNS AND KBFD AT 22Z...BRINGING SHORT-LIVED REDUCTIONS TO BOTH CIG AND VSBY ALONG WITH SOME GUSTY WINDS. AS THE FRONT ENTERS NW PA THIS EVENING...SHOWERS AND THUNDERSTORMS WILL CONTINUE TO IMPACT THE NW MTNS AND KBFD THROUGH THE EVENING HOURS. EXPECT ANOTHER WAVE OF TSTMS TO SLIDE ACROSS THROUGH 03Z...FOLLOWED BY A COUPLE HOUR PERIOD OF STRATIFORM RAIN WITH FROPA AS CIG RESTRICTIONS BEGIN. AS THE COLD FRONT PUSHES SLOWLY SOUTH ACROSS THE AIRSPACE OVERNIGHT...SCATTERED TO NUMEROUS SHOWERS/TSTMS WILL IMPACT CENTRAL MTNS STARTING MID EVEING...WITH JUST SCT TSTMS POSS IN THE SE OVERNIGHT. BY MORNING...CONDITIONS WILL BE MVFR/IFR IN ALL BUT FAR SE. THE FRONT WILL SETTLE SOUTH WEDNESDAY BEFORE STALLING OUT ALONG THE MASON DIXON LINE. WAVES OF LOW PRESSURE WILL MOVE ALONG THE FRONT AND BRING PERIODS OF SHOWERS/THUNDERSTORMS ALONG WITH REDUCED CONDITIONS INTO THURSDAY. OUTLOOK... WED...SHOWERS/TSTMS LIKELY SOUTH...SCATTERED NORTH. THU...SHOWERS/TSTMS LIKELY. CIG RESTRICTIONS LIKELY NORTH...LOCAL RESTRICTIONS SOUTH. FRI-SUN...MAINLY VFR. CHC OF SHOWERS/TSTMS SW 1/3 OF AIRSPACE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LA CORTE NEAR TERM...DEVOIR/LA CORTE SHORT TERM...LA CORTE LONG TERM...GARTNER/STEINBUGL AVIATION...RXR

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