Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 211614 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1214 PM EDT SUN SEP 21 2014 .SYNOPSIS... A COLD FRONT WILL PASS THROUGH LATER TODAY. A LARGE AREA OF HIGH PRESSURE WILL BUILD OUT OF CENTRAL CANADA AND PROVIDE GENERALLY FAIR AND COOL WEATHER FOR MOST IF NOT ALL OF THIS WEEK. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... LOW STRATUS HAS DISSIPATED ACROSS PRACTICALLY ALL OF OUR SE ZONES EXCEPT FOR THE IMMEDIATE KMUI VCNTY. EXPECT A PLEASANTLY WARM/MOSTLY SUNNY LATE SEPT AFTERNOON ACROSS MUCH OF THE MID AND LOWER SUSQ VALLEY FOLLOWED BY INCREASING MID LEVEL CLOUDS IN THE 19-21Z PERIOD. WEAKENING AREA OF SHOWERS WITHIN AN EXTENSIVE SHIELD OF MID LEVEL CLOUDS WILL DRIFT ACROSS THE CENTRAL RIDGE AND VALLEY REGION EARLY THIS AFTERNOON...AND LIKELY FIZZLE OUT AS THEY APPROACH THE SUSQ VALLEY...WHERE WARMER TEMPS ALOFT AND RIDGING AT THE SFC AND ALOFT WAS PRESENT. ACROSS THE WESTERN THIRD OF THE STATE...INCREASING UPPER DIFFLUENCE AND POSITIVE LLVL THETA-E ADVECTION WILL LEAD TO ONE OR TWO FAST-MOVING LINES OF SHOWERS DURING THE MID TO LATE AFTERNOON HOURS. AS THE AFOREMENTIONED.../FIRST/ AREA OF MID LEVEL CLOUDS AND SHOWERS MOVES TO THE SUSQ VALLEY LATE THIS AFTERNOON. PERIODS OF SUNSHINE AND HIGHER PWAT AIR OF 1 TO 1.5 INCHES IN THE WAKE OF THIS CLOUD AREA WILL BOOST SFC-BASED CAPES TO 1000-1500 J/KG ACROSS THE CENTRAL AND WRN PARTS OF THE CWA...HELPING TO STRENGTHEN A SECOND LINE OF CONVECTION INTO SOME LOCALLY GUSTY...LOW-TOPPED TSRA. THE LATEST...14Z HRRR FOCUSES THE BULK OF THE CONVECTION /AND ASSOCIATED HIGHER QPF AMOUNTS/ ACROSS THE CENTRAL AND NRN MTNS OF PENN THROUGH 00Z MONDAY. SHOWERS AND PERHAPS A FEW TSRA ENTER THE MID/LOWER SUSQ VALLEY 22-23Z AND CONTINUE INTO EARLY THIS EVENING. THE REAL COLD FRONT/DRY AIR SEEMS LIKE IT WILL BE PASSING THROUGH IN THE AFTN WEST...LATE AFTN CENTRAL AND AROUND SUNSET OR JUST AFTER IN THE EAST. THE BEST LIFT WILL BE ALONG THE FRONT - SO WILL ALSO HOLD THE MENTION OF THUNDER INTO THE EVENING IN THE EAST. TEMPS HAVE A CHANCE TO GET ABOVE 80F AGAIN IN THE SE - BUT EARLY LOW CLOUDS AND SOME FOG COULD BUST THAT FORECAST. THE CLOUDS ARE SHALLOW THOUGH...AND WINDS WILL BE INCREASING FROM THE SSW...WHICH IS A NORMALLY-DRYING INFLUENCE - ESP IN THE EASTERN CWA. SPC STILL MENTIONS THE REGION IN SEE TEXT FOR DAY 1 OUTLOOK OF SEVERE WX. PLUSES FOR ISOLD SVR GUSTS ARE THE WELL-ALIGNED WINDS AND GENERAL INCREASE IN SPEED SHEAR THROUGH THE LOWEST 20KFT. KNOCKS AGAINST SVR WILL BE THE OVERALL LACK OF MOISTURE AND INSTABILITY AND THE LACK OF 50KT WINDS BELOW 15KFT. WILL STILL MENTION THE POSS OF ISOLD SVR GUSTS IN THE HWO...BUT CONFIDENCE CONTINUES TO BE MODERATE TO HIGH FOR A MINIMAL OR EVEN NIL SVR THREAT TODAY. && .SHORT TERM /8 PM THIS EVENING THROUGH 6 PM MONDAY/... AFTER THE FRONT PUSHES THROUGH...THE WINDS OUT OF THE WNW WILL LEAD TO A TYPICAL POST-FRONTAL SET-UP...AND THE RESIDUAL AND LAKE MOISTURE ASCENDING THE MTNS AND COLD AIR MOVING IN ALOFT WILL GENERATE INSTABILITY AND SCT SHRA FOR THE NWRN THIRD OF THE AREA TONIGHT AND PERHAPS THROUGH MID MORNING ON MONDAY. 8H TEMPS DO DIP INTO THE LOWER SINGLE DIGITS MONDAY AND MAXES MAY BE LIMITED TO THE M50S IN THE MTNS BUT STILL GET CLOSE TO 70F IN THE DOWNSLOPE- WARMED SOUTHEASTERN PIEDMONT. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... HIGH PRESSURE BUILDS IN AS THE LONG TERM IS BEGINNING AND IT SORT OF PARKS ITSELF OVER NEW YORK AND NEW ENGLAND WITH +2 TO +3 SIGMA ABOVE NORMAL MSLP ANOMALIES BY WEDNESDAY-THURSDAY. THE MODELS SEEM TO BE IN FAIR AGREEMENT SHOWING A BLOCKING 500 HPA ANTICYCLONE TO THE NORTHWEST AS A MASSIVE 500 HPA POSITIVE HEIGHT ANOMALY OF +2 TO +3 SIGMA DEVELOPS OVER CENTRAL CANADA BY THURSDAY AND INTO FRIDAY. THE MODELS AND EFS DO WELL FORECASTING ANTICYCLONES SO THERE SEEMS TO BE MORE OF A CONSENSUS. ON THE FAIR WEATHER FORECAST NEXT WEEK. EXPECT DIURNAL VALLEY FOG AND LOW CLOUDS LIKELY TO AFFECT THE REGION EACH MORNING ONCE THE BIG HIGH TAKES HOLD....AND CONTINUING DAILY INTO NEXT WEEKEND. THAT MASSIVE HIGH SHOULD CONTINUE THE DRY FAIR WEATHER THROUGH NEXT WEEKEND. TEMPERATURES ON MONDAY AND MONDAY EVENING WILL BE BELOW NORMAL...HOWEVER OUTSIDE OF MONDAY...TEMPERATURES THERE WILL BE A PERIOD OF NEAR NORMAL TEMPERATURES. && .AVIATION /16Z SUNDAY THROUGH THURSDAY/... LOW CLOUDS AND FOG THAT RESULTED IN IFR/LIFR ACROSS THE EASTERN AIRFIELDS EARLIER THIS MORNING...WILL GRADUALLY MIX OUT AND DISSOLVE THROUGH 16Z. CLOUDS DECK ASSOCIATED WITH FIRST LINE OR TWO OF SHOWERS WERE MAINLY IN THE MVFR CATEGORY...BUT CAUSING SOME BRIEF IFR CIGS/VSBYS IN THE NORTHWEST. THESE TRANSIENT... BUT ADVERSE CONDITIONS WILL SPREAD ACROSS THE ALLEGHENY FRONT AROUND 16Z...BEFORE REACHING THE SUSQ VALLEY IN A LIKELY WEAKENED STATE. A SECOND AND PROBABLY STRONGER LINE OF SHOWERS AND TSRA ALONG THE TRUE COLD FRONT WILL WILL MOVE ACROSS THE WESTERN MTNS THROUGH 20Z BEFORE REGION THE CENTRAL ZONES AFTER 21Z. ELSEWHERE...MAINLY VFR WILL DEVELOP/PERSIST THROUGH THE EARLY AFTERNOON...AND STAY INTACT ACROSS THE LOWER SUSQ VALLEY PERHAPS UNTIL DUSK. THE COLD FRONT WILL ENCROACH ON THE REGION TODAY...LIKELY REACHING KBFD AROUND 18Z...KUNV AROUND 21Z...AND THE SOUTHEAST AIRFIELDS AROUND 00Z. PRIOR TO THE ACTUAL FRONT...A FEW PRE- FRONTAL BAND/S/ OF SHOWERS AND EMBEDDED TSRA EXPECTED. EXPECTING SOME POST FRONTAL SHOWERS TO POTENTIALLY LINGER IN THE NORTHWEST SUNDAY. HOWEVER...IN GENERAL...AFTER FRONTAL PASSAGE...VFR CONDITIONS SHOULD PREVAIL INTO MID/LATE WEEK WITH THE EXCEPTION OF SOME PATCHY MORNING FOG. OUTLOOK... MON...AM LOW CIGS POSS W MTNS. TUE...AM FOG POSS W MTNS. WED...AM FOG POSS...MAINLY NORTHERN PA. THU...PATCHY AM FOG POSSIBLE. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO/LAMBERT NEAR TERM...DANGELO/LAMBERT SHORT TERM...DANGELO LONG TERM...GRUMM/CERU AVIATION...JUNG

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