Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 231959 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 359 PM EDT TUE SEP 23 2014 .SYNOPSIS... HIGH PRESSURE CENTERED OVER WESTERN PENNSYLVANIA WILL DRIFT NORTHEAST TO THE MAINE COAST BY WEDNESDAY AFTERNOON. A LOW PRESSURE SYSTEM WILL TRACK UP THE MID ATLANTIC COAST WEDNESDAY AND THURSDAY...THEN OUT TO SEA BY FRIDAY. DEEP AND MODERATELY STRONG EASTERLY FLOW WILL BETWEEN THESE TWO WEATHER FEATURES WILL TRANSPORT DEEP...ABUNDANT MOISTURE FROM THE WESTERN ATLANTIC...LEADING TO PERIODS OF RAIN WEDNESDAY NIGHT INTO THURSDAY ACROSS THE EASTERN HALF OF THE STATE. AN ANOMALOUS UPPER RIDGE WILL MIGRATE EASTWARD FROM THE GREAT LAKES TO PENNSYLVANIA THIS WEEKEND BRINGING A STRING OF SUNNY...WARM DAYS. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... VISIBLE SATL IMAGERY CONTINUES TO DISPLAY NEARLY CLOUD-FREE SKIES OVER ALL OF PENNSYLVANIA THANKS TO A SPRAWLING 1031 MB SFC HIGH CENTERED JUST NORTH TO THE GREATER PITTSBURGH AREA. A SPLENDID AFTERNOON /AND FIRST FULL DAY OF FALL/ WILL CONTINUE WITH LIGHT WIND AND TEMPS IN THE 60S...TO NEAR 70F IN THE LARGER METRO AREAS THROUGHOUT THE LOWER SUSQ VALLEY. TRANQUIL CONDS EXPECTED TONIGHT AS SFC HIGH PRESSURE DRIFTS SLOWLY NE ACROSS THE COMMONWEALTH. WEAKEST LLVL P-GRADIENT WILL BE OVR THE N MTNS...WHERE A CALM WIND AND CLEAR SKIES SHOULD PROMOTE AREAS OF LATE NIGHT VALLEY FOG. FURTHER SOUTH...A DEVELOPING EASTERLY BREEZE SHOULD LESSEN THE FOG POTENTIAL...BUT PATCHY 1/2-1SM VALLEY FOG STILL APPEARS LIKELY. WAA ALOFT AHEAD OF UPPER LOW OVR THE SE CONUS MAY SPREAD INCREASING /ALBEIT MAINLY THIN/ CIRRUS INTO SOUTHERN PA VERY LATE TONIGHT. LOWS TEMPS TONIGHT WILL BE MAINLY IN THE LOWER TO MID 40S. A FEW SPOTS ACROSS THE NORTH WILL LIKELY DIP INTO THE U30S. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... A DECENT AMOUNT OF SUNSHINE IS EXPECTED EARLY IN THE DAY. CIRRUS WILL GRADUALLY SPREAD NORTH-NORTHWEST DURING THE MIDDAY AND AFTERNOON HOURS...WITH A THICK ALTOSTRATUS DECK EXPECTED ACROSS THE LOWER SUSQ VALLEY /AND POSSIBLY ACROSS THE SCENT MTNS AS WELL/ BY 22Z WED. LIGHT RAIN WILL BE KNOCKING ON THE DOORSTEP OF THE LOWER SUSQ VALLEY LATE WEDNESDAY AFTERNOON AS THE NOSE OF A HIGHLY ANOMALOUS ESE 850 MB JET /-3 TO -4 ST DEVIATIONS/...AND PWATS IN EXCESS OF 1.5 INCHES BECOMES AIMED RIGHT INTO THAT REGION. POPS WILL BE ESSENTIALLY ZERO ACROSS PRACTICALLY ALL OF THE CWA THROUGH 00Z THURSDAY...BUT INCREASE TO 20-30 PERCENT TO THE SE OF A KTHV AND KLNS LINE. TEMPS WED SHOULD BE FAIRLY UNIFORM IN THE U60S TO ARND 70F DUE TO THE THICKEST CLOUDS ARRIVING OVR THE NORMALLY WARMER SOUTHERN COUNTIES. SHOULD CLOUDS THICKEN UP FASTER THAN ANTICIPATED ACROSS THE SOUTH...DAYTIME TEMPS MAY HAVE TO BE TRIMMED BY A FEW TO SEVERAL DEG F. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
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THE MODELS CONTINUE TO SHOW INCONSISTENCY IN A RUN BY RUN BASIS AS THE NAM/EC/GEFS/SREF AND GFS NOW BACK PRECIP EASTWARD...THOUGH STILL WESTWARD ENOUGH TO AFFECT CENTRAL PA. GFS REMAINS THE MOST CONSISTENT OF THEM AS IT CONTINUES THE HEAVIEST PRECIP IN THE DELMARVA REGION. MADE CHANGES TO THE WED NITE/THURSDAY FCST...DUE TO THE CHANGE IN TRACK OF THE COASTAL LOW ACROSS THE DELMARVA. THIS SYSTEM SHOULD BRING MOIST EAST TO SOUTHEASTERLY FLOW AND ACCOMPANYING RAINSHOWERS TO AT LEAST THE SE COUNTIES ON THURSDAY. THE EC BRINGS THE PRECIP NORTHWARD THROUGH CENTRAL PA BEFORE IT SHIFTS NORTHEASTWARD AND HEADS UP THE COAST. A TIGHT PRESSURE GRADIENT BETWEEN THE HIGH EAST OF NEW ENG AND SFC LOW RIDING UP THE EAST COAST SHOULD AMPLIFY THE ANOMALOUS EASTERLY WINDS/PWATS IN THE 12Z GEFS...THOUGH THE HIGHEST PWATS SHOULD ONLY AFFECT SE PA WED NIGHT THROUGH THURSDAY MORNING. SOME ENSEMBLE AND OPERATIONAL RUNS INDICATE A SUBSTANTIAL RAINFALL OF OVER AN INCH IS POSSIBLE ACROSS PARTS OF SE PA. GIVEN THE VARIABILITY BETWEEN THE OUTPUTS HAVE QPFS IN THE 0.75 TO ONE INCH RANGE. HAVE INCREASED MIN TEMPS WED NIGHT AND LOWERED MAX TEMPS WED SIGNIFICANTLY DUE TO THE EXPECTED CLOUD COVER/RAIN. GENERAL AGREEMENT AMONG MED RANGE GUIDANCE THAT COASTAL LOW WILL EXIT THE MID ATLANTIC COAST THURSDAY NIGHT INTO FRIDAY...BRINGING A RETURN TO FAIR AND MILD WX. ANOMALOUS UPPER LVL RIDGE OVR THE GRT LKS IS THEN PROGGED TO SLIDE EAST INTO PA OVR THE WEEKEND...BRINGING THE AREA A PERIOD OF FAIR AND WARM WX THAT SHOULD LAST INTO EARLY NEXT WEEK. LG SCALE SUBSIDENCE BENEATH THIS SYSTEM SHOULD RESULT IN MCLEAR SKIES THRU THE WEEKEND. MID LEVEL TEMPERATURES IN THE GEFS AND ECMWF SHOULD SUPPORT HIGH TEMPS ARND 10F ABOVE NORMAL...WITH AFTN READINGS BTWN 75-80F OVR MUCH OF THE AREA THROUGH THE WEEKEND. ANOTHER LOW LOOKS TO BE APPROACHING THE REGION BY THE MIDDLE OF NEXT WEEK. DUE TO THE LARGE VARIATION IN TIMING HAVE ONLY CHANCE POPS TUESDAY INTO WEDNESDAY.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/... VFR CONDITIONS WILL PREVAIL FOR THE NEXT 24-30 HOURS...WITH JUST A FEW...TO SVRL HOUR PERIOD OF PATCHY 1/2SM EXPECTED...MAINLY VALLEY FOG BETWEEN 09-13Z WED. A DEVELOPING...DEEP AND MDTLY STRONG EASTERLY FLOW /BETWEEN HIGH PRESSURE OVER THE NEW ENGLAND STATES...AND UPPER LEVEL LOW PRESSURE SYSTEM/SFC TROUGH OVER THE SE U.S./ WILL BRING CLOUDY SKIES AND A CHANCE FOR RAIN WED NIGHT AND THU...ESP ACROSS THE EASTERN HALF OF PENN. WIDESPREAD IFR TO MVFR CIGS /AND VSBYS IN THE SAME CATEGORY/ APPEAR LIKELY WED NIGHT THROUGH THURSDAY. OUTLOOK... WED...PATCHY FOG IN THE MORNING...OTHERWISE VFR. WED NIGHT AND THU...LOW CIGS AND AREAS OF -RA/DZ LIKELY. FRI-SUN...PATCHY 1/2SM FOG IN THE MORNING...OTHERWISE VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...FITZGERALD/CERU AVIATION...LAMBERT

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