Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 191806 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 206 PM EDT TUE AUG 19 2014 .SYNOPSIS...
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A MASSIVE RIDGE WILL BUILD OVER EAST-CENTRAL CANADA FOR THE NEXT WEEK. ANOTHER STRONG RIDGE WILL BUILD OVER THE SOUTHERN UNITED STATES. SHORT-WAVES IN THE WEAK FLOW MOVING UNDER THE CANADIAN BLOCK WILL SLOW DOWN AND WEAKEN AS THEY MOVE THROUGH OUR REGION. THIS WILL LEAD TO A POTENTIALLY PROLONGED PERIOD OF UNSETTLED WEATHER. BUT IT SHOULD PROTECT US FROM THE LATE SEASON HEAT BUILDING TO OUR SOUTH.
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&& .NEAR TERM /UNTIL 9 PM THIS EVENING/... A WEAKLY ORGANIZED BROKEN LINE OF SHOWERS AND ISOLATED THUNDERSTORMS IS TRYING TO WORK ITS AWAY ACROSS OUR WEST-CENTRAL COUNTIES FROM CENTRE COUNTY DOWN TO THE MARYLAND BORDER. BUMPED UP POPS AND ADDED TEXTURE TO THE GRIDS WITH 3KM HRRR AND 4KM NAM ESTIMATED POPS/QPF. RADAR SHOWS VERY LIGHT RAIN. LOCAL GAGES SHOW ABOUT 0.10 IN WESTERN AREAS OF STATE COLLEGE. BUT SOME STREAKS ON RADAR OF 0.1 TO 0.4 INCHES. IN SOMERSET COUNTY...STRONGER CELLS SHOWS CLOSE TO AN INCH OF ESTIMATED RAINFALL. RADAR AND HRRR IMPLY BEST CHANCE RAIN WILL BE FROM CAMBRIA AND SOMERSET COUNTIES EASTWARD TO HUNTINGTON AND FRANKLIN COUNTY AS THE STRONGEST ELEMENTS HEAD SLOWLY EAST. THE 3KM AND 4KM MODELS IMPLY MOST OF THIS CONVECTION DIES OFF A FEW HOURS EITHER SIDE 6 PM. && .SHORT TERM /9 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... SREF AND NAM CONTINUE TO SHOW CHANCE TO SLIGHT CHANCE OF SHOWERS OVERNIGHT. MOST AREAS RAINFREE IN HRRR AFTER 0000 UTC TONIGHT THROUGH 0600 UTC. BUT THE HRRR DOES SHOW OVERNIGHT CONVECTION IN THE MIDWEST MOVING INTO WESTERN PA AFTER 0600 UTC. CHANCE RAIN WILL CLEARER INCREASE BEFORE SUNRISE IN WESTERN AREAS. THE SURGE OF CAPE AND PW INTO WESTERN PA IN THE SREF AND NAM...SIMILAR TO OLDER GEFS/GFS IMPLY SOME MORE ORGANIZED RAIN POSSIBLE ON WEDNESDAY. USED A BLEND TO GET THE POPS AND THE 12KM NAM TO ADD SOME TEXTURE TO CONVECTION AND RAIN AREA THAT APPEARS TO BE POISED TO MOVE WEST TO EAST ACROSS THE REGION WEDNESDAY. THE SREF POPS/PDF IMPLIES SHOWERS COMING INTO WEST AROUND 1500 UTC AND MOST OF CENTRAL TWO THIRDS OF REGION BY LATE EVENING. SREF IS KIND OF OPTIMISTIC SOUTHEAST PA COULD HAVE YET ANOTHER MOSTLY RAIN FREE DAY WEDNESDAY. THE KEY FEATURES ARE THE RETROGRADING RIDGE OVER EASTERN CANADA WHICH IS TAKING THE UMPH OUT OF THE SYSTEMS CUTTING UNDER THIS FEATURE. IN MOST MODELS THE NEAR 1SD ABOVE NORMAL PW SURGES WEAKEN AS THE MOVE INTO PA. THUS MORE OPTIMISTIC...SREF-LIKE IN THE WEST THAN THE EAST WITH RAINFALL AND NOT REALLY CONFIDENT GOING LIKELY. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... THURSDAY LOOKS LIKE ANOTHER UNSETTLED DAY...AS UPPER LOW MAKES IT/S CLOSEST PASS TO PA...TRACKING ACROSS UPSTATE NY. COOL TEMPS ALOFT...COMBINED WITH DIURNAL HEATING...SHOULD YIELD NUMEROUS SHRA AND TSRA BY AFTN. HAVE RAISED POPS TO THE LIKELY CATEGORY BASED ON 00Z OPER AND GEFS OUTPUT. SOUTHERLY LL JET AND PLUME OF HIGH PWATS WILL HAVE PASSED NE OF THE AREA THURSDAY...LIMITING THE THREAT OF ANY HVY RAINFALL. MDL BLENDED QPF IS IN THE QUARTER TO HALF INCH RANGE THURSDAY. THE NUMEROUS SHOWERS AND COOLER TEMPS ALOFT WILL RESULT IN HIGH TEMPS BLW NORMAL FOR AUGUST...WITH MAXES MAINLY IN THE 70S. LATEST MED RANGE GUIDANCE POINTING TOWARD DRIER WX FRIDAY INTO EARLY NEXT WEEK...AS SUBTROPICAL HIGH IS PROGGED TO EDGE TOWARD THE REGION FROM THE MIDWEST. DAILY RING OF FIRE CONVECTION ON NE PERIPHERY OF THIS RIDGE WILL THREATEN WESTERN PA DURING THE FRI-SUN TIME FRAME...WHILE EASTERN PA IS LIKELY TO REMAIN DRY. DESPITE APPROACH OF UPPER RIDGE...NO BIG WARMUP EXPECTED...AS LARGE SFC HIGH OVR THE CANADIAN MARITIMES WILL CIRCULATE AN EASTERLY FLOW INTO CENTRAL PA. THERE MAY BE ISSUE WITH AM LOW CLOUDS/FOG DUE TO THE EXPECTED MOISTLY SERLY FLOW OVR THE AREA. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... RADAR SHOWS SOME ORGANIZED SHOWERS AND THUNDERSTORMS FROM NEAR KFIG SOUTH TO THE MARYLAND BORDER. THESE SHOWERS AND STORMS WILL SLOWLY MOVE EASTWARD THIS AFTERNOON. AREAS OF MVFR AND LOCALLY IFR ARE POSSIBLE ALONG THE LINE AND WITHIN THE SHOWERS AND THUNDERSTORMS. MODELS ALL SUGGEST POPCORN SHOWERS POSSIBLE OVER MOST OF CENTRAL PA AND THE MORE ORGANIZED ACTIVITY OVER THE SOUTHERN HALF OF THE STATE THROUGH THIS EVENING. THINGS SETTLE DOWN OVERNIGHT...MORE PATCHY FOG AND LOW CLOUDS.SO MORE AREAS OF MVFR AND IFR. WEDNESDAY WILL SEE RAIN AND SHOWERS LIKELY IN WESTERN PA BY MID- LATE MORNING SLOWLY SPREADING EAST. VFR IN EAST BUT AREAS MVFR LIKELY IN AM FOG AND THEN SHOWERS IN WESTERN AREAS. OUTLOOK... TUE...MAINLY VFR...WITH SHRA/TSRA POSSIBLE. WED...MORNING FOG/LOW CLOUDS SHRA/TSRA LIKELY WEST CHANCE EAST. THU-FRI...MORNING FOG CHANCES EACH DAY. OVERALL VFR...BUT INCREASING CHANCES OF MAINLY AFTERNOON SHRA/TSRA AND ASSOCIATED RESTRICTIONS. SAT...MAINLY VFR. STILL CHANCE OF SHRA...BUT DECREASING CHANCES. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS... NEAR TERM...GRUMM SHORT TERM...GRUMM LONG TERM...FITZGERALD AVIATION...GRUMM

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