Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 261954 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 354 PM EDT TUE MAY 26 2015 .SYNOPSIS... HIGH PRESSURE AT THE SFC AND ALOFT WILL REMAIN ANCHORED JUST OFF THE EAST COAST THROUGH THE END OF THIS WEEK. A COLD FRONT WILL LIKELY PUSH ACROSS THE REGION SATURDAY NIGHT...THEN STALL JUST SOUTH OF THE STATE EARLY NEXT WEEK. && .NEAR TERM /UNTIL 10 PM THIS EVENING/... DEEP SOUTH-SOUTHWESTERLY FLOW ON THE WESTERN PERIPHERY OF THE DOMINANT COAST RIDGE WILL CONTINUE TO TRANSPORT GULF OF MEX MOISTURE NORTHWARD INTO CENTRAL PA. WATER VAPOR LOOP AND RAP 300-400 MB WIND PROGS INDICATE THAT A WELL-DEFINED...ALBEIT COMPACT SHORT WAVE WILL BE MOVING NE ACROSS LAKE ERIE LATE THIS AFTERNOON...WHILE AN ASSOCIATED 45-50 KT JETLET CROSSES NRN AND WRN PENN. ENHANCED MESOSCALE LIFT FROM THIS FEATURE WILL TEAM UP WITH THE GROWING CAPE VALUES /LOCALLY AS HIGH AS 1000-1500 J/KG/ ACROSS THE ALLEGHENY PLATEAU TO PRODUCE INCREASINGLY NUMEROUS SHOWERS...AND A FEW TSRA LATE THIS AFTERNOON AND EARLY THIS EVENING. BLEND OF THE LATEST NAM/SREF AND HRRR CONTINUE TO FAVOR THE NRN MTNS...AND PORTIONS OF THE LAUREL HIGHLANDS FOR THE GREATEST CHC OF SHOWERS/SCTD TSRA. FOR AREAS SOUTH AND EAST OF KCBE TO KSEG AND KAVP LINE...THE PERIOD THROUGH 21Z SHOULD REMAIN DRY. HOWEVER...DIFFERENTIAL HEATING AT THE SE EDGE OF THE MID LEVEL CLOUD SHIELD...AND A RIBBON OF HIGHEST 850 MB THETA-E AIR ADVECTING EAST INTO THE MIDDLE SUSQ VALLEY SHOULD HELP TO FOCUS AND ENHANCE ANOTHER AREA OF SHOWERS THERE LATE TODAY. SPC PAINTS THEIR MARGINAL RISK OF SVR TSRA ACRS ROUGHLY THE WRN HALF OF PENN THIS AFTERNOON AND EVENING. BASIN AVG RAINFALL WILL BE GENERALLY AROUND 0.10 OF AN INCH IN MOST PLACES THROUGH MIDNIGHT...WITH SOME SPOTTY 0.25-0.50 INCH AMOUNTS IN TSRA. TEMPS ARE NEARING THEIR HIGHS FOR THE DAY RANGING FROM THE MID- UPR 70S OVR THE ALLEGHENY PLATEAU...TO THE M80S ACROSS THE LOWER SUSQ VALLEY. && .SHORT TERM /10 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... DIURNALLY-DRIVEN CONVECTION WILL DIE OFF AFTER SUNSET THIS EVENING. THE REST OF THE NIGHT WILL LIKELY FEATURE WARM AND TRANQUIL CONDS WITH VARIABLE AMOUNTS OF MAINLY ALTO CU CLOUDS. SOME LOWER OROGRAPHICALLY GENERATED CLOUDS AND HAZE ARE POSSIBLE BEFORE DAYBREAK...ESPECIALLY ACROSS THE WEST FACING SLOPES OF THE LAURELS AND NW MTNS WHERE LLVL WINDS WILL VEER AROUND TO THE WSW AROUND 10Z. HIGH PWAT AIR MASS WILL RESULT IN MID SUMMER MIN TEMPS...WITH LOWS IN THE M/U60S MOST PLACES. A FEW ILL-DEFINED/VERY WEAK AND SMALL SCALE SHORT WAVES LIFTING NORTH ACROSS THE CENTRAL APPALACHIANS IN THE HEAT OF THIS SOUPY AIRMASS COULD SPARK SOME ISOLATED SHOWERS...BUT POPS AFTER MIDNIGHT TONIGHT WILL BE GENERALLY BELOW 20 PERCENT. A MORE POTENT SHORTWAVE LIFTING THRU THE GRT LKS WILL INTRODUCE A BETTER CHC OF SHRA/TSRA ON WEDNESDAY. MDL TIMING OF THIS FEATURE SUGGESTS SHOWERS COULD ARRIVE EARLY IN THE DAY ACROSS THE W COUNTIES...WITH A GREATER RISK OF PM TSRA ACROSS EASTERN PA. GEFS MEAN CAPES PEAK ARND 1200 J/KG ACROSS THE SE COUNTIES WED AFTN. HOWEVER...MID LVL WINDS AND ASSOCIATED DEEP-LYR SHEAR ARE NOT PARTICULARLY STRONG IN THE LATEST MDL DATA...SO THE SVR WX THREAT JUST MRGL...AND THAT`S WHAT SPC COVERS PRACTICALLY ALL OF THE CWA WITH IN THEIR DAY 2 CONVECTIVE OUTLOOK. MCLDY SKIES WILL HOLD TEMPS DOWN A BIT...BUT CONSALL STILL SUGGESTS HIGH TEMPS BTWN THE M70S- L80S...SEVERAL DEG ABV NORMAL FOR LATE MAY. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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UPPER LEVEL TROUGH WILL DEEPEN AS IT PROPAGATES EASTWARD. EXPECT COLD FRONT TO MOVE THROUGH PA...WEDNESDAY NIGHT INTO THURSDAY MORNING. THIS WILL BRING NORTHWESTERLY FLOW AND COOLER AND DRIER AIR. HIGH PRESSURE AT THE SURFACE AND ALOFT WILL BUILD OVER THE REGION THROUGH FRIDAY...REDUCING ANY PRECIPITATION CHANCES THROUGH THE LATTER HALF OF THE WEEK AS THE BULK OF MED RANGE GUIDANCE IMPLIES DRIER WX AS LOWER PWAT AIR MASS WORKS INTO CENTRAL PA. A COLD FRONT WILL LIKELY BRING AN END TO THE SUMMER-LIKE WARMTH/HUMIDITY NEXT WEEKEND. A FAIR AMT OF AGREEMENT AMONG MED RANGE GUIDANCE FOR RAINY WX SATURDAY NIGHT INTO SUNDAY ALONG AN INCOMING FRONTAL BOUNDARY. SCATTERED SHOWERS COULD FOLLOW SUNDAY/MONDAY AS WAVE OF LOW PRES RIDES EASTWARD ALONG STALLED FRONTAL BNDRY SOUTH OF PA.
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&& .AVIATION /20Z TUESDAY THROUGH SUNDAY/... VFR SHOULD CONTINUE FOR THE BULK OF THE TIME AT MOST SITES OVER THE NEXT 24 HOURS. HIGHEST CONFIDENCE IN BRIEF 1-3HR PERIOD OF 3-6SM VISIBILITY RESTRICTIONS IN BR/HZ IS AT MDT/LNS AROUND DAYBREAK TUESDAY. A SLIGHTLY LONGER...SEVERAL HOUR PERIOD OF MVFR CIGS AND BORDERLINE VSBYS IS FCST INVOF KJST AND KBFD BETWEEN 08-15Z AS SFC WINDS VEER MORE TO A FAVORABLE WSW UPSLOPE COMPONENT. BRIEF...15-30 MINUTE MVFR TO IFR CIGS AND SIMILAR VSBYS WILL ACCOMPANY THE HEAVIER SHRA AND SCTD TSRA LATE THIS AFTERNOON AND EARLY THIS EVENING. THESE REDUCTIONS IN CIGS AND VSBYS WILL BE POSSIBLE AT ANY GIVEN AIRFIELD...BUT MAINLY IMPACTING AIRFIELDS ACROSS THE NW HALF OF PENN. BASED ON THE FAIRLY LOW COVERAGE OF THE TSRA EMBEDDED IN THE FIELD OF MORE NUMEROUS SHOWERS...DECIDED NOT TO EXPLICITLY MENTION TSTMS IN MOST OF TERMINALS AT THIS TIME...BUT DID INCLUDE VCTS AT KUNV AND KIPT WHERE THE LATEST RUNS OF HIGH RESOLUTION MODELS INDICATE THE BEST CHC OF THUNDER AND GREATEST DEG OF INSTABILITY. A SUMMER-TIME PATTERN WILL PERSIST THROUGH THE WEEK WITH REPLAY OF PATCHY MORNING FOG GIVING WAY TO VFR AND AFTN ISOLD-SCT TSTMS. IT APPEARS THAT THE MORE DEFINED TSTM RISKS THIS WEEK WILL BE WEDNESDAY AFTERNOON AND EVENING...AND AGAIN SATURDAY AFTERNOON AND EVENING...ALONG AND AHEAD OF A RATHER STRONG COLD FRONT PRESSING SE FROM THE GREAT LAKES. OUTLOOK... WED-FRI...PATCHY A.M. MVFR FOG/BR. ISOLD-SCT P.M. TSTMS. SAT-SUN...PATCHY A.M. MVFR FOG/BR. SCT-NMRS P.M TSTMS W/COLD FROPA...MAINLY 19Z SAT-01Z SUNDAY. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...FITZGERALD/LAMBERT LONG TERM...FITZGERALD/CERU AVIATION...LAMBERT

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