Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 182015 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 415 PM EDT MON AUG 18 2014 .SYNOPSIS... SEVERAL DAYS OF DRY WEATHER WILL GIVE WAY TO SOME UNSETTLED CONDITIONS THIS WEEK AS WEAK WEATHER SYSTEMS BRING A FEW CHANCES FOR SHOWERS THIS WEEK. SHOWERS FROM A WEAK LOW TRACKING SOUTH OF THE REGION WILL BRUSH THE SOUTHERN THIRD OF PENNSYLVANIA TONIGHT...BUT A BETTER CHANCE OF SHOWERS IS EXPECTED WEDNESDAY INTO THURSDAY AS A LOW FROM THE GREAT LAKES REGION APPROACHES. DRIER AIR IS LIKELY TO REBUILD OVER THE COMMONWEALTH THIS WEEKEND AS HIGH PRESSURE REESTABLISHES ITSELF FROM NEW ENGLAND TO THE NORTHERN MID ATLANTIC COAST. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A NICE AFTERNOON IN PROGRESS ACROSS CENTRAL PA. UPPER TROF UNDERCUTTING A PREVAILING SHORTWAVE RIDGE AXIS IS TRACKING ACROSS THE VIRGINIAS...INCREASING DEEP LAYER MOISTURE ACROSS FAR SOUTHERN PA AND PRODUCING UPSLOPE FLOW AND LCL BKN-OVC CIGS INTO THE LAURELS. RADAR SHOWS LITTLE IF ANY SHOWER ACTIVITY THUS FAR... BUT SLGT TO CHC POPS WILL BE ON THE RISE TONIGHT AS THE MOISTURE INCREASES. SUFFICIENT MOISTURE FOR SHOWERS NOT EXPECTED TO TRACK MUCH FARTHER EAST THAN FRANKLIN/ADAMS COUNTIES TONIGHT...AS WEAK SHORTWAVE TRACKS OFF OF THE NORTHERN MID ATLANTIC COAST BY 12Z. STILL...UPSLOPE FLOW MAY KEEP A FEW SHOWERS POSSIBLE OVER THE LAUREL HIGHLANDS AND SOUTH CENTRAL MOUNTAINS INTO TUE MORNING. MINS WILL BE MILDER THAN RECENT MORNINGS WITH LOW TO MID 50S EXPECTED NORTH AND LOWER 60S ACROSS THE SOUTH. A BIT OF MUGGINESS WILL BE FELT IN THE AIR...AND SOME LCL MVFR/IFR CONDS IN VALLEY FOG ARE EXPECTED ACROSS ESPECIALLY CENTRAL AND NORTH CENTRAL PA. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... MOST AREAS WILL SEE A BREAK IN SHOWER ACTIVITY ON TUESDAY... IN BETWEEN THE WEAK FORCING SHIFTING OFF THE COAST AND DEEPER UPPER LOW DRIFTING INTO THE CENTRAL GLAKS. UNDER A SHORTWAVE RIDGE AXIS...MOST AREAS WILL BE DRY...BUT CANNOT RULE OUT A SHOWER ACROSS THE SOUTH IN THE FLATTER SLIGHTLY CYCLONIC UPPER FLOW IN A RICHER AMBIENT MOISTURE ENVIRONMENT (PW ~1.7"). CLOUD COVER SHOULD BE SIMILAR TO TODAY WITH GREATEST AMTS OF SUNSHINE FOUND NORTH...AND LESS BREAKS ACROSS THE SOUTH. MAXES SIMILAR TO...RANGING FROM MID 70S NORTH TO LOWER 80S SOUTH. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
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MID TO LATE WEEK CONTINUES TO LOOK LIKE A TUMULTUOUS TIMEFRAME FOR WEATHER...GEFS/CMC...LOOK FOR SLIGHTLY ANOMALOUS PWATS WEDNESDAY INTO THURSDAY...HOWEVER OPERATIONAL RUNS FROM THE GFS/EC/CANADIAN CONTINUE THE TREND OF SLOWING THE SYSTEMS EASTWARD PROGRESSION. AS THE UPPER LEVEL CURRENTLY OFF THE NEW ENGLAND COAST SLOWLY MOVES TO THE NORTHEAST...THE RIDGE SHOULD TILT NEGATIVELY AND SLOWLY FLATTEN. THIS SHOULD ALLOW FOR THE TROUGH CURRENTLY STRADDLING THE CANADIAN...MINNESOTA BORDER...BEFORE ENTERING THE GREAT LAKES ON WEDNESDAY. THIS LOW...MOVING BELOW HIGH BUILDING INTO NORTHERN CANADA AND SPECIFICALLY HUDSON BAY...HAS WEAK FLOW ALOFT. THIS SHOULD ALLOW IT TO SLOWLY MEANDER EASTWARD. CONSIDERING IT IS CUTOFF FROM MAJOR MOISTURE SOURCES...PRECIPITATION WILL BE GENERALLY LIGHT WITH SLIGHTLY HIGHER AMOUNTS POSSIBLE IN THUNDERSTORMS. THIS PROGRESSION SHOULD DELAY FRONTAL PASSAGE AND ANY ORGANIZED PRECIPITATION TO LATE WEDNESDAY NIGHT INTO THURSDAY. GFS IS THE FASTEST WITH THE CANADIAN/EC FURTHER WEAKENING AND SLOWING EASTWARD PROGRESSION OF THE SYSTEM. BROAD MODEL AND ENSEMBLE SUPPORT FOR LIKELY POPS BY THURSDAY ...AS THE SFC FRONTAL BOUNDARY ASSOCIATED WITH UPPER LEVEL ENERGY DRIFTING EASTWARD THRU THE CENTRAL GREAT LAKES PUSHES SLOWLY EASTWARD ACROSS THE CWA. USED A BLEND OF MODELS LEADING TOWARD THE EC AND MOS GUIDANCE. BY FRIDAY THE CONFIDENCE IN THE MEDIUM RANGE FORECAST DROPS OFF AS ENSEMBLES SHOW GREAT VARIABILITY IN TIMING AND PLACEMENT.THOUGH THE WEEKEND IS TRENDING TOWARDS A DRIER SOLUTION. THE UPPER LEVEL LOW THAT MOVES THROUGH MID WEEK COULD BECOME QUASI-STATIONARY JUST OFF THE COAST. DEPENDING ON ITS POSITION COULD ALLOW FOR WEAK SHORT WAVES THROUGH THE REGION THAT COULD ALLOW FOR CHANCE POPS.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/... VFR CONDITIONS PREVAILING THIS AFTERNOON...BUT ISOLD SHRA/TSRA WILL MOVE INTO SOUTHWEST AIRFIELDS LATE AFTN/EVE. MVFR CIGS WITH ISOLD/SCT SHRA POSSIBLE AT KJST AND KAOO TONIGHT. KUNV AND KMDT WILL LIKELY REMAIN DRY. SCT FOG LIKELY CENTRAL AND NORTHERN AIRFIELDS TUE 09Z-13Z. UNSETTLED WEATHER CONTINUES INTO MID WEEK...WITH SCATTERED SHOWERS AND THUNDERSTORMS BOTH WED AND THU. OUTLOOK... TUE...RAIN/LOW CIGS POSSIBLE...MAINLY SOUTHERN PA FIRST HALF DAY. WED-FRI...VFR IN GENERAL...BUT RESTRICTIONS IN SCATTERED SHRA/TSRA. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DEVOIR NEAR TERM...DEVOIR SHORT TERM...DEVOIR LONG TERM...CERU AVIATION...JUNG/DEVOIR/GARTNER

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