Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 230922 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 522 AM EDT TUE SEP 23 2014 .SYNOPSIS... HIGH PRESSURE WILL DRIFT EAST ACROSS PENNSYLVANIA TODAY THEN PASS OFF THE NEW ENGLAND COAST WEDNESDAY. A LOW PRESSURE SYSTEM WILL TRACK UP THE MID ATLANTIC COAST WEDNESDAY AND THURSDAY...THEN OUT TO SEA BY FRIDAY. AN ANOMALOUS UPPER RIDGE WILL MIGRATE EASTWARD FROM THE GREAT LAKES TO PENNSYLVANIA THIS WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... EARLY AM 11-3.9 MICRON SATL IMAGERY SHOWING DENDRITIC PATTERN OF VALLEY FOG ACROSS NORTHERN AND WESTERN PA. RADIATIONAL COOLING UNDER A MCLEAR SKY AND LGT WIND WILL RESULT IN FOG BECOMING MORE WIDESPREAD AND LOCALLY DENSE TOWARDS DAWN IN THE VALLEYS OF THE ALLEGHENY MTNS. A MORE PERSISTENT NWRLY BREEZE SHOULD PRECLUDE WIDESPREAD FOG EAST OF THE ALLEGHENIES...BUT WILL MENTION AT LEAST PATCHY FOG ALL THE WAY INTO THE SUSQ VALLEY. DWPTS AT 09Z ARE STILL RUNNING IN THE U30S OVER MUCH OF THE ALLEGHENY PLATEAU...A BIT HIGH FOR WIDESPREAD FROST. HOWEVER...BASED ON CURRENT MESONET DATA...WILL MAINTAIN PATCHY FROST IN THE EARLY AM FORECAST FOR THE NORTHERN MTNS AND LAUREL HIGHLANDS. HIGH PRESSURE WILL BE POSITIONED DIRECTLY OVR PA LATER TODAY. THE RESULTING LACK OF MIXING COULD DELAY THE FOG BURN OFF UNTIL LATE MORNING IN THE DEEP RIVER/STREAM VALLEYS OF THE ALLEGHENIES. AFTER THE FOG LIFTS...EXPECT ABUNDANT SUNSHINE AND LIGHT WIND FOR THE LATE MORNING AND AFTERNOON HOURS. GEFS MEAN 925 TEMPS BTWN 12-14C SHOULD TRANSLATE TO HIGHS BTWN 65-70F FROM NW TO SE. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... TRANQUIL CONDS EXPECTED TONIGHT AS SFC HIGH REMAINS OVR THE AREA. WEAKEST 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 WILL LIMIT THE FOG POTENTIAL. ALSO...WAA ALOFT AHEAD OF UPPER LOW OVR THE SE CONUS MAY SPREAD INCREASING CIRRUS INTO SOUTHERN PA LATE TONIGHT. ALTHOUGH MOST OF THE REGION SHOULD DAWN BRIGHT...EXPECT INCREASING CIRRUS TO OVERSPREAD CENTRAL PA FROM THE SOUTH ON WEDNESDAY...AS AFOREMENTIONED UPPER LOW OVR THE SE CONUS DRIFTS NORTH. ALL CURRENT MDL DATA KEEPS ASSOC SFC COASTAL LOW/PLUME OF ATLANTIC MOISTURE JUST SOUTH OF PA...SO CONFIDENCE IS HIGH THAT ANY RAIN WILL HOLD OFF THRU THE DAYLIGHT HRS. TEMPS WED SHOULD BE FAIRLY UNIFORM ARND 70F DUE TO THE THICKEST CLOUDS ARRIVING OVR THE NORMALLY WARMER SOUTHERN COUNTIES. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... SIGNIFICANT CHANGES MADE TO THE WED NITE/THURSDAY FCST...AS ALL MED RANGE GUIDANCE NOW TRACKS COASTAL LOW ACROSS THE DELMARVA. THIS SCENARIO WILL LIKELY BRING A PERIOD OF RAIN TO AT LEAST THE SE COUNTIES ON THURSDAY. TIGHT PRES GRADIENT BTWN HIGH EAST OF NEW ENG AND SFC LOW RIDING UP THE E COAST IS RESULTING IN ANOMALOUS EASTERLY WINDS/PWATS IN THE 00Z GEFS ACROSS SE PA WED NIGHT AND THURSDAY. GEFS AND OPER MDL QPF ALL SUPPORT AT LEAST LIKELY POPS ACROSS THE LOWER SUSQ VALLEY DURING THIS PERIOD AND A CHC OF RAIN AS FAR WEST AS THE ALLEGHENY PLATEAU. SOME ENSEMBLE AND OPER RUNS INDICATE A SUBSTANTIAL RAINFALL OF OVER AN INCH IS POSSIBLE ACROSS PARTS OF SE PA. 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 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 AS THE 00Z NAEFS CLOUD OUTPUT SUGGESTS. GEFS AND ECMWF 925TEMPS NEAR 20C SHOULD SUPPORT HIGH TEMPS ARND 10F ABOVE NORMAL...WITH AFTN READINGS BTWN 75-80F OVR MUCH OF THE AREA. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... CLOUDS DECREASED WITH VFR CONDITIONS FOR THE NEXT 24-48 HOURS. UPPER LEVEL LOW PRESSURE SYSTEM WILL BRING CLOUDY SKIES AND A CHANCE FOR SHOWERS WED NIGHT AND THU TO AT LEAST KMDT AND KLNS. OUTLOOK... WED...PATCHY FOG IN THE MORNING...OTHERWISE VFR. THU...LOW CIGS AND AREAS OF -RA/DZ PSBL. FRI-SAT...PATCHY FOG IN THE MORNING...OTHERWISE VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... FROST ADVISORY UNTIL 9 AM EDT THIS MORNING FOR PAZ033. && $$ SYNOPSIS...FITZGERALD NEAR TERM...FITZGERALD SHORT TERM...FITZGERALD LONG TERM...FITZGERALD AVIATION...ROSS

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