Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 070650 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 250 AM EDT TUE JUL 7 2015 .SYNOPSIS...
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A WEAKENING UPPER LOW WILL TRACK EAST ACROSS THE REGION TONIGHT. A WEAK RIDGE WILL BRING VERY WARM AND HUMID CONDITIONS TO THE REGION TODAY. A COLD FRONT WILL APPROACH TONIGHT...THEN STALL OUT ALONG...OR JUST SOUTH OF THE MASON DIXON LINE FOR MIDWEEK. A FEW WAVES OF LOW PRESSURE WILL RIPPLE EAST ALONG THIS BOUNDARY BRINGING THE LIKELIHOOD FOR SHOWERS AND THUNDERSTORMS WEDNESDAY AFTERNOON AND EVENING...AND AGAIN ON THURSDAY. HIGH PRESSURE WILL BUILD IN FOR FRIDAY AND BRING SLIGHTLY COOLER AND NOTABLY LESS HUMID WEATHER WITH LITTLE CHANCE FOR RAIN.
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&& .NEAR TERM /THROUGH TODAY/...
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LAST VESTIGES OF THE GREATLY WEAKENED UPPER TROUGH ARE SEEN AS JUST A FEW HIGHLY ISOLATED /BUT BRIEFLY HVY/ RAIN SHOWERS DRIFTING NORTH ACROSS THE REGION EARLY THIS MORNING. PLENTY OF CLOUDS AND PATCHY FOG WILL BE AROUND EARLY TODAY AS THIS FEATURES DEPARTS TO OUR EAST. FOR THE LATE MORNING AND AFTERNOON HOURS. DEEP SWRLY FLOW...SLIGHTLY DECREASING SFC DEWPOINTS...AND MID- LEVEL WARMING WILL COMBINE TO BRING US A VERY WARM DAY WITH TEMPERATURES A FEW- SVRL DEG F ABOVE NORMAL...AND LITTLE CHANCE FOR RAIN IN MOST PLACES. A WEAK LEE TROUGH OVER AND TO THE EAST OF THE SUSQ VALLEY...AND A COLD FRONT WELL OFF TO THE NW WILL BRING LOW CHCS FOR PULSE SHOWERS/TSRA TO OUR EASTERN ZONES DURING THE MID TO LATE AFTERNOON HOURS...AND PERHAPS SOME MORE ORGANIZED/STRONGER MULTI-CELL TSRA CLUSTERS ACROSS THE FAR NW LATE IN THE DAY INTO TONIGHT. HIGH TODAY WILL LIKELY BE THE WARMEST THIS WEEK...AND ABOUT 3-4 DEG ABOVE NORMAL. 8H TEMPS TEMPS NR 17C SHOULD TRANSLATE TO MAX TEMPS WELL INTO THE 80S OVER MOST OF CENTRAL PA.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...
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SFC COLD FRONT SLIDES SLOWLY TO THE SOUTHEAST ACROSS THE COMMONWEALTH TONIGHT THROUGH WED MORNING...BEFORE STALLING OUT NEAR...OR JUST TO THE SOUTH OF THE MASON-DIXON LINE. MAIN FCST PROBLEM/CHALLENGE FOR THE UPCOMING SHIFTS WILL BE TO TRY TO PIN DOWN /VIA SOME SEMBLANCE OF MODEL CONSENSUS/ THE LOCATION AND TIMING OF CONVECTIVE FEATURES/AREAS OF LOW PRESSURE THAT WILL FORM AND RIDE EAST ALONG THIS BOUNDARY WEDNESDAY INTO THURSDAY. CURRENTLY...A GEFS/NAM/SREF BLEND POINT TWD THE BEST CHC FOR RAIN WITH EMBEDDED TSRA FOCUSED ACROSS THE SOUTHERN THIRD TO HALF OF PENN WEDNESDAY...WHERE PWAT WILL STAY AOA 2.0 INCHES. THE SHARP GRADIENT TO MUCH LOWER PWAT /AOB 0.75 OF AN INCH/ WILL STAY NEAR OR JUST TO THE NORTH OF THE PENN/NEW YORK BORDER WHERE CHCS FOR RAIN WILL BE QUITE LOW WEDNESDAY AND MOST OF WED NIGHT. MAX TEMPS WEDNESDAY COULD EASILY TURN OUT TO BE SEVERAL DEG F OR MORE BELOW CURRENT FCST VALUES DEPENDING ON THE TIMING AND EXTENT OF CONVECTION ACROSS THE CENTRAL AND SOUTH. CURRENT TEMP FCST BUSTING ON THE LOW SIDE FOR WEDNESDAY`S HIGH IS A VERY LOW PROBABILITY. WILL BE ADJUSTING THESE TEMPS WITH 03Z SREF AND 06Z OP GUIDANCE WHERE NEEDED.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... THE 07/00Z MODEL AND ENSEMBLE GUIDANCE IS PROVIDING A FAIRLY CONSISTENT SIGNAL THAT THE AREA WILL REMAIN IN A LOW AMPLITUDE QUASI-ZONAL MID/UPPER FLOW PATTERN WITHIN THE NORTHERN STREAM WESTERLIES. AS MIGHT BE EXPECTED IN THIS PATTERN...THERE IS LOW PREDICTABILITY/CONFIDENCE GIVEN DEGREE OF SPREAD AND MEANINGFUL DIFFERENCES ASSOCIATED WITH SHORTWAVE DETAILS. THIS LARGELY UNSETTLED AND RECENTLY PERSISTENT WEATHER PATTERN FOR THE LOCAL AREA WILL BE MODULATED TO SOME EXTENT BY RETROGRESSION OF UNSEASONABLY STRONG UPPER TROUGH/RIDGE COUPLET OFF THE WEST COAST AND OVER THE SOUTHEAST AND SCENTRL U.S. THERE IS BROAD SUPPORT FOR ANOTHER MEAN TROUGH TO DEVELOP OVER THE NORTHEAST/MID ATLANTIC STATES BY NEXT WEEK/JULY 13TH AS ENERGY EJECTING FROM CA UPPER LOW EVOLVES DOWNSTREAM IN THE WESTERLIES AND TEAMS WITH VORTEX OVER HUDSON BAY. IN TERMS OF SENSIBLE WEATHER...A WELL-DEFINED COLD FRONT ENTERS CENTRAL PA EARLY WEDNESDAY ACCOMPANIED BY SHOWERS/TSTMS...THEN BECOMES WAVY AS IT STALLS OUT FROM NEAR THE OH RIVER/MASON DIXON LINE. EXPECT ONE OR MORE EPISODES OF PCPN THRU LATE WEEK MOST LKLY DUE TO MCS REMNANTS OR CONVECTIVELY INDUCED LOWS TRACKING EWD FROM THE MID MS/OH VLY...BUT TOO DIFFICULT TO PIN POINT TIMING/LOCATION AT THIS POINT. FWIW THE MODEL BIAS IS USUALLY TOO FAR NORTH WITH MCS ACTIVITY. PCPN RISK SHOULD EVENTUALLY BE ENHANCED TOWARD THE END OF THE PERIOD INTO EARLY NEXT WEEK AS CA LOW ENERGY AND ASSOCIATED SFC SYSTEM REACHES THE GREAT LAKES. WHAT WE CAN SAY WITH RELATIVE CERTAINTY IS THAT WE DO NOT EXPECT ANY HEAT WAVES OR EXTENDED PERIODS OF DRY WEATHER OVER THE NEXT 7+ DAYS. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... SENT 03Z TAF PACKAGE. STILL SOME SHOWERS AND STORMS ACROSS THE EAST. EARLIER DISCUSSION BELOW. CONDITIONS OVER THE STILL MAINLY RAIN FREE LOWER SUSQ VALLEY...WITH REDUCED CONDITIONS CONTINUING OVER THE LAUREL HIGHLANDS WHERE SHOWERS ARE MORE NUMEROUS. EXPECT SHOWER ACTIVITY TO INCREASE IN COVERAGE AND SPREAD FROM SOUTH TO NORTH THROUGH THE AFTERNOON. SHOWERS WILL TEND TO BE SLOW-MOVING AND COULD PRODUCE HEAVY DOWNPOURS AND LOCAL IFR CONDITIONS. THE UPPER LOW WILL WEAKEN AS IT ENTERS CENTRAL PA OVERNIGHT...BUT WE SHOULD MAINTAIN A RISK FOR SCT SHOWERS. EXPECT CIGS/VSBYS TO TREND GRADUALLY LOWER OVERNIGHT GIVEN DIURNAL COOLING...VERY HUMID AIRMASS AND LIGHT WINDS...WITH AT LEAST MARGINAL RESTRICTIONS LIKELY AT MANY SITES INTO TUESDAY MORNING. LOWER CONDITIONS TUESDAY MORNING WILL IMPROVE BY MID MORNING TO MID DAY. A COLD FRONT WILL APPROACH THE AIRSPACE FROM THE LOWER LAKES/OH VALLEY BY LATE IN THE DAY AND SHIFT SLOWLY SEWD INTO THE AIRSPACE TUE NIGHT/WED BEFORE STALLING OUT NEAR PA/MD BORDER THURS INTO FRIDAY. OUTLOOK... WED-SAT...VFR/MVFR WITH PERIODS OF SHRA/AFTN TSTMS. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LA CORTE/LAMBERT NEAR TERM...LAMBERT SHORT TERM...LA CORTE/LAMBERT LONG TERM...GARTNER/STEINBUGL AVIATION...LA CORTE/MARTIN

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