Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 060948 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 548 AM EDT MON JUL 6 2015 .SYNOPSIS... WARM AND HUMID CONDITIONS WILL MOVE BACK INTO PENNSYLVANIA EARLY THIS WEEK. A WEAKENING...BUT MOISTURE LADEN WAVE OF LOW PRESSURE AT THE SURFACE AND ALOFT WILL DRIFT NORTH INTO THE REGION TODAY BRINGING WITH IT NUMEROUS...MAINLY AFTERNOON SHOWERS...ALONG WITH ISOLATED THUNDERSTORMS THAT COULD DUMP LOCALLY HEAVY RAIN. AFTER A MAINLY RAIN-FREE TUESDAY...A COLD FRONT WILL PUSH SOUTHEAST ACROSS THE STATE TUESDAY NIGHT. THE COLD FRONT WILL STALL OUT NEAR...OR JUST SOUTH OF THE MASON DIXON LINE LATER THIS WEAK. THIS BOUNDARY WILL ACT AS A PATHWAY FOR A FEW WAVES OF LOW PRESSURE TO RIPPLE EAST ALONG AND BRING A FEW MORE ROUNDS OF SHOWERS AND THUNDERSTORMS LATE WEDNESDAY...AND AGAIN THURSDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... EARLY MORNING RADAR/SATELLITE BLEND SHOWS SHOWERS SPREADING INTO THE SOUTHERN TIER COUNTIES OF PENN...ASSOCIATED WITH A SLOW MOVING UPPER TROUGH OVER WEST VA. ANOMALOUSLY HIGH PWAT AIR OF 45-50MM WILL SPREAD NORTH OVER THE ENTIRE CWA BY LATE THIS AFTERNOON. MOISTURE FLUX...HELPED ALONG BY A PLUS 2 SIGMA /20-25 KT/ SOUTHERLY FLOW AT 850 MB...WILL BE FOCUSED RIGHT ACROSS THE REGION LATE THIS MORNING AND THIS AFTERNOON. SREF/S PROB OF CAPE EXCEEDING 1000 J/KG IS LOWEST ACROSS THE NCENT MTNS THIS AFTERNOON AND THIS EVENING...AND 70-80 PERCENT INVOF KMDT...KTHV AND KLNS. MODEST HEATING OF THIS AIR MASS SHOULD PRODUCE NUMEROUS PM SHRA/TSRA. CONTINUE TO LEAN TOWARD SREF AND GEFS POPS...WHICH SUPPORT CATEGORICAL POPS OVR MUCH OF CENTRAL PA INCREASING DIFLUENCE AHEAD OF THE AFOREMENTIONED UPPER TROUGH WILL COMBINE WITH THE MDTLY HIGH MIXED LAYER INSTABILITY AND SHEAR TO PRODUCE FREQUENT-SHOWERS /AND THE OUTSIDE CHC OF A THUNDERSTORM/. MDL BLENDED QPF OF A 1/4 TO 1/2 INCH SEEMS REASONABLE FOR BASIN AVERAGE AMOUNTS. HOWEVER ...CONVECTION-ALLOWING MDLS IMPLY LOCALIZED AMTS IN EXCESS OF 2 INCHES IN PLACES THAT SEE A FEW TRAINING TSRA. GIVEN THE WET GROUND AND 1HR FFG VALUES LESS THAN AN INCH OVR MUCH OF CENTRAL PA...WILL MAINTAIN THE MENTION OF LOCAL FLOODING IN THE HWO. BEST CHC OF LOCALLY EXCESSIVE RAINFALL SHOULD BE ACROSS THE WESTERN AND SOUTHERN COUNTIES...WHERE MDL INSTABILITY THE GREATEST. WEAK FLOW ALOFT AND PRACTICALLY NON- EXISTENT DCAPE DUE TO LACK OF MID LVL DRY AIR SIGNALS A LOW CHC OF SVR WEATHER. GREATER PROBABILITY FOR HIGH CAPE /EXCEEDING 2000 J/KG/ EXISTS ACROSS THE LOWER SUSQ VALLEYS AND ADJACENT COMMUNITIES THIS AFTERNOON AND EARLY THIS EVENING. SPC HAS ACCOUNTED FOR THIS AREA OF LOCALLY HIGH PRECIP POTENTIAL...INSTABILITY...AND WEAK TO MDT SOUTHERLY LLVL SHEAR BY PLACING SCENT PENN AND ADJACENT PORTIONS OF THE LOWER SUSQ VALLEY UNDER A MARGINAL RISK FOR SVR TSRA LATE THIS AFTERNOON INTO THIS EVENING. TEMPS WILL START OUT BE MILD EARLY TODAY...WITH DAYBREAK LOWS RANGING FROM THE U50-L60S ACROSS THE NRN HALF OF PENN...TO NR 70F OVER THE LOWER SUSQ VALLEY. HIGHS THIS AFTERNOON /IN THE INCREASING MUGGINESS/ WILL BE IN THE MID 70S ACROSS THE LAUREL HIGHLANDS AND U70S TO NEAR 80F ELSEWHERE. DEWPOINTS ARE PROGGED TO CREEP INTO THE UNCOMFORTABLE RANGE BTWN 65-70F. && .SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY NIGHT/... THE HEART OF A VERY WARM AND MUGGY AIRMASS WILL BE OVER THE STATE TONIGHT AND TUESDAY WITH MAINLY RAIN-FREE CONDITIONS BETWEEN 04-20Z TUESDAY. LATER TUESDAY AFTERNOON ISOLATED TO SCATTERED CONVECTION WILL FORM INVOF A LEE TROUGH...AND IN ADVANCE OF A SFC COLD FRONT APPROACHING FROM THE OHIO VALLEY. MUCH OF THE ENERGY PUSHING THIS FRONT EASTWARD APPEARS THAT IT/LL BE SHEARING OFF TO THE ENE ACROSS SRN ONTARIO AND QUEBEC. STILL A CLOSE CALL ENOUGH CALL FOR ADEQUATE DEEP-LAYER SHEAR TO BRING SCATTERED SHOWERS...AND ISOLATED STRONG TO POSSIBLY SVR TSRA /MAINLY ACROSS THE WEST/ LATE IN THE DAY TUESDAY AND TUESDAY NIGHT. WARMING TEMPS IN THE MID LEVELS /FROM 7C...UP TO 9C TUESDAY AFTERNOON AND EVENING/ WILL HELP TO GREATLY LIMIT/CAP OFF SHOWERS AND TSRA ACROSS MUCH OF CENTRAL PENN AND THE SUSQ VALLEY. HIGH TUESDAY WILL LIKELY BE THE WARMEST THIS WEEK...AND ABOUT 3-4 DEG F ABOVE NORMAL. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... 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 /09Z MONDAY THROUGH FRIDAY/... 07/09Z UPDATE...ADJUSTED TAFS FOR IFR CIGS AT JST/LNS/IPT. 07/06Z...EXPECT SHOWER ACTIVITY TO INCREASE IN COVERAGE AND SPREAD FROM SOUTH TO NORTH THROUGH THE AFTERNOON...AS AN UPPER LEVEL LOW CURRENTLY OVER WV/KY AND SFC WARM FRONT LIFTS NEWD ALONG THE CENTRAL APPALACHIANS. LOW VFR TO MVFR CIGS ARE FCST ACROSS MUCH OF THE AIRSPACE THRU THE PERIOD. SHOWERS WILL TEND TO BE SLOW-MOVG AND COULD PRODUCE HEAVY DOWNPOURS AND LCL IFR VISBYS. THE UPPER LOW WILL WEAKEN OVER CENTRAL PA INTO TNGT BUT STILL MAINTAIN SCT SHOWER RISK...THEREFORE SIMPLY WENT WITH VCSH AFT 00Z. CIGS/VSBYS SHOULD TREND GRADUALLY LOWER OVERNIGHT GIVEN DIURNAL COOLING...HIGH LOW LEVEL MSTR/NARROW T-TD SPREADS AND LGT WINDS...WITH AT LEAST MARGINAL RESTRICTIONS LKLY AT SEVERAL SITES INTO EARLY TUESDAY. LOWER CONDITIONS TUESDAY MORNING SHOULD IMPROVE BY AFTN. A COLD FRONT WILL APPROACH THE AIRSPACE FROM THE LWR LKS/OH VLY BY LATE IN THE DAY AND SHIFT SLOWLY SEWD INTO THE AIRSPACE TUE NGT/WED BEFORE STALLING OUT NEAR PA/MD BORDER THURS INTO FRIDAY. OUTLOOK... TUE-FRI...VFR/MVFR WITH PERIODS OF SHRA/AFTN TSTMS. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...STEINBUGL AVIATION...STEINBUGL

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