Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 300234 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1034 PM EDT MON JUN 29 2015 .SYNOPSIS... A WARM FRONT WILL MOVE NORTHEAST ACROSS THE STATE OVERNIGHT BRINGING SHOWERS TO PRIMARILY THE NORTHWEST HALF OF THE STATE. WARMER AND MORE UNSTABLE AIR WILL ENCOMPASS THE REGION TUESDAY HELPING TO TRIGGER NUMEROUS SHOWERS AND SCATTERED AFTERNOON THUNDERSTORMS AS A TROUGH OF LOW PRESSURE AT THE SURFACE AND ALOFT APPROACHES FROM THE WEST. EXPECT AN UNSETTLED WEATHER PATTERN TO PERSIST INTO THE UPCOMING HOLIDAY WEEKEND AS A BROAD BUT WEAKENING UPPER LEVEL TROUGH REMAINS POSITIONED OVER THE LOWER 48 EAST OF THE CONTINENTAL DIVIDE. && .NEAR TERM /UNTIL 8 AM TUESDAY MORNING/...
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10 PM UPDATE... ALL IS GOING ACCORDING TO PLAN. THUNDER NEAR KHLG COULD SURVIVE INTO THE CWA...BUT RAP LI/S DO NOT GO BELOW 0 OVER THE NEXT FEW HRS. SHOWERS WILL CONTINUE. WILL KEEP HIGH POPS IN THE NW HALF OF THE AREA OVERNIGHT. BUT LI/S DO DROP AS WE NEAR SUNRISE. 8 PM UPDATE... SHOWERS NOW WANING OVER THE NE...BUT A SECOND BATCH OF SHOWERS ASSOCIATED WITH A WELL-DEFINED SHORT WAVE TROUGH IS OVER SWRN PA AND HEADED THIS WAY. AIR IS STILL PRETTY DRY OVER THE SERN COS. WILL HOLD SCT TO LOW LIKELY POPS IN THE NWRN HALF FOR THE NIGHT...AS THE SE IS UNFAVORED BY THE FLOW PATTERN AND RELATIVELY LOWER RELATIVE HUMIDITIES. TEMPS COOLED OFF A LITTLE QUICKER THAN EXPECTED WITH THE RAIN/EVAPORATIVE COOLING...BUT STILL ON TRACK TO GET TO THE FCST MINS. PREV... WEAK SFC RIDGING HELPED TO PROVIDE A DRY AND PARTLY TO MOSTLY SUNNY DAY FOR THE REGION. THIS FAIR AND DRY WEATHER WILL CONTINUE THROUGH EARLY TONIGHT ACROSS THE EASTERN HALF OF THE STATE...WHILE CLOUDS QUICKLY INCREASE AND AREAS OF SHOWERS SPREAD ACROSS THE WESTERN MTNS BEFORE DUSK. 12Z OPER MODEL...LATEST 09Z SREF...AND HRRR CONSENSUS FAVORS A LIKELIHOOD OF SHOWERS OVER NW PA TONIGHT WITH MODEST QPF AMOUNTS IN THE 0.25 TO 0.50 INCH RANGE AS THE SFC LOW REACHES LAKE ERIE BY 12Z TUE AND IT/S ATTENDANT WARM FRONT LIFTS NE ACROSS THE REGION USHERING SLIGHTLY ABOVE NORMAL PWAT AIR. LOW TEMPS TONIGHT WILL VARY FROM THE U50S ACROSS THE NORTH...TO THE LOWER AND MID 60S ELSEWHERE.
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&& .SHORT TERM /8 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... THE LEAD SHORTWAVE IS FCST TO WEAKEN INTO THE LOWER GREAT LKS EARLY TUESDAY. HOWEVER...A DEEPENING MEAN TROUGH OVER THE OHIO RIVER VALLEY WILL HELP TO DEVELOP A SECONDARY SFC LOW ACROSS NRN INDIANA AND OHIO...AND SEND A FEW PULSES OF SHORTWAVE ENERGY EAST ACROSS PENN. THESE FEATURES WILL COMBINE WITH THE FORMATION OF A DISTINCT LEE TROUGH IN THE BLYR TO FOCUS NUMEROUS SHOWERS AND AFTERNOON TSRA ACROSS THE CENTRAL MTNS...THEN LATER IN THE AFTERNOON/EARLY EVENING MAINLY OVER THE SUSQ VALLEY. DEEP LAYER SHEAR VALUES WITHIN THIS CONVECTIVE ZONE ARE SUPPORTIVE OF ORGANIZED MULTI-CELL UPDRAFTS AND LINE SEGMENTS. A SECOND AREA OR A FEW NARROW BANDS OF LESS INTENSE SHRA/TSRA SHOULD BE FOUND ACROSS WESTERN PENN AND THE ALLEGHENIES LATER TUESDAY AFTERNOON AND EVENING...CLOSER TO THE SFC LOW AND MEAN UPPER TROUGH. SPC DAY 2 OUTLOOK HAS MAINTAINED A MARGINAL RISK FOR SVR TRSA ACROSS ALL OF THE CWA. BASED ON MDTLY STG...20 KT 0-1 KM SHEAR PROFILES ACROSS THE EASTERN ZONES TUES AFTERNOON...ALONG WITH POOLING OF LLVL MOISTURE RELATIVELY HIGHER ML CAPE AHEAD OF THE AFOREMENTIONED LEE TROUGH...A LATER UPGRADE TO SLIGHT RISK ACROSS THAT AREA MIGHT BE IN THE CARDS. TUESDAY WILL LIKELY OFFER THE GREATEST CHC FOR PRECIP UNTIL AT LEAST THURSDAY AFTERNOON AND EVENING. AFTER A VERY CHILLY AND RAINY WEEKEND...THE WARMTH AND SLIGHT MUGGINESS ON TUESDAY WITH DEWPOINTS 5-10F THAN THE ACTUAL DAYTIME TEMPS WE HAD SATURDAY WILL FEEL QUITE WELCOME. HIGH TEMPS TUESDAY AFTERNOON WILL BE IN THE L-M 70S ACROSS THE MTNS...AND AROUND 80F THROUGHOUT THE SUSQ VALLEY. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... THE LARGE UPPER LEVEL LOW OVER NORTHERN CANADA THAT WILL BE DOMINATING THE WEATHER PATTERN OVER THE NEXT WEEK WILL BRING A DEEPENING TROUGH THAT WILL CONTINUE TO ADVECT WARM MOIST SOUTHWESTERLY FLOW INTO THE REGION TUESDAY NIGHT INTO WEDNESDAY. MID LEVEL PERTURBATIONS AND SHORT WAVE TROUGHS SHOULD ENHANCE LAPSE RATES. DAY 2 OUTLOOK IS CURRENTLY MARGINAL FOR ALMOST ALL OF PENNSYLVANIA. SO EXPECT ANY TSTMS THAT FORM TUESDAY AFTERNOON INTO EVENING TO LINGER TUESDAY NIGHT INTO POSSIBLY WEDNESDAY. AS THE MAIN TROUGH LIFTS AND EXITS THE REGION WEDNESDAY THE CONVECTIVE ENVIRONMENT SHIFTS THE BEST INSTABILITY WITH LARGER VORTICIES DUE TO A SHORT WAVE THAT SHOULD ALLOW FOR LOW LVL LAPSE RATES TO BE STRONGER THROUGH ALONG A FRONTAL BOUNDARY. MODELS CONTINUING TO TREND MORE ZONAL FLOW LATE WEDNESDAY NIGHT INTO THURSDAY. WITH AN AMPLIFYING TROUGH SWINGING THROUGH THURSDAY AFTERNOON. THIS TREND SHOULD ALLOW FOR MORE A MORE SUMMERTIME REGIME THURSDAY INTO THE WEEKEND. IN THE WAKE OF THURSDAY/S TROUGH THE GFS/GEFS/EC BEGIN TO DIVERGE IN SOLUTIONS. HOWEVER WITH DRIER AIR ADVECTING IN AND THE CONSENSUS, THOUGH THE TIMING DIFFERS, THAT A RIDGE SHOULD BUILD OVER PA THROUGH THE FIRST HALF OF THE WEEKEND. THIS COULD LIMIT ANY CONVECTION TO ALONG THE MASON DIXON LINE AND ONLY A SLIGHT CHANCE FOR PRECIPITATION CURRENTLY SUNDAY EVENING. SO DESPITE A SERIES OF MID- LEVEL DISTURBANCES MOVING DOWNSTREAM FROM THE UPPER/MID MISSISSIPPI VALLEY THROUGH THE MID ATLC REGION...500MB HEIGHTS SHOULD BE IN RECOVERY MODE WHICH SHOULD ALLOW DAYTIME TEMPERATURES TO TREND WARMER INTO THE JULY 4TH HOLIDAY WEEKEND. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... VFR CONDITIONS DOMINATING THE REGION THIS EVENING...WITH LIGHT SHOWERS DRIFTING IN FROM THE SW. THIS AREA OF SHOWERS WILL EXPAND OVERNIGHT TO ALL BUT SE COUNTIES AS A WELL-DEFINED SHORT WAVE TROUGH HELPS TO LIFT A WARM FRONT NORTHWARD. MAY SEE AN ISOLATED TSTM IN FAR WESTERN COUNTIES...BUT VERY UNLIKELY THROUGH 12Z. LOW LEVEL SW JET OF AROUND 30 KTS SWINGS IN FROM THE SW...AND WILL BRING MARGINAL LLWS TO KJST-KAOO ALONG WITH MVFR CIGS FOR MAINLY WESTERN HIGHER TERRAIN. SURFACE WINDS WILL REMAIN LIGHT AREAWIDE. MVFR CONDITIONS WILL REMAIN LIKELY FOR WESTERN HIGHER TERRAIN THROUGH LATE MORNING TUE /WITH BRIEF MVFR CIGS POSS CENTRAL MTNS/. AN UPPER LEVEL DISTURBANCE OFF TO OUR WEST WILL BRING A COUPLE ROUNDS OF SHOWERS AND SCT AFTERNOON TSRA. AN UNSETTLED PATTERN WITH A SERIES OF FRONTS WILL BE AFFECTING THE REGION MUCH OF THIS WEEK. THE BEST CHANCES OF RESTRICTIONS WILL BE TUESDAY INTO WEDNESDAY. OUTLOOK... TUE...MVFR CIGS LIKELY WEST. OTHERWISE MAINLY VFR. LOCAL RESTRICTIONS IN SHRA/SCT TSRA. ISO TSTMS MAY BE STRONG IN THE AFTERNOON. WED...MVFR CIGS LIKELY WEST. OTHERWISE MAINLY VFR. LOCAL RESTRICTIONS IN SCT SHRA/TSRA. THU...MAINLY VFR. ISOLATED TSRA MAINLY SOUTH OF I-80. FRI...MAINLY VFR. ISOLATED TSRA SOUTH. SAT...MAINLY VFR. CHANCE SHRA/TSRA. && .CLIMATE... JUNE 2015 HAS BEEN A WET MONTH ACROSS MUCH OF CENTRAL PA. THROUGH 6/28...OUR TWO LCD CLIMATE SITES /HARRISBURG AND WILLIAMSPORT/ ARE RANKED 8TH AND 6TH RESPECTIVELY FOR THE WETTEST JUNE ON RECORD. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...DANGELO/LAMBERT SHORT TERM...LAMBERT/STEINBUGL LONG TERM...CERU/STEINBUGL AVIATION...RXR CLIMATE...

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