Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 171616 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1216 PM EDT FRI APR 17 2015 .SYNOPSIS... A WEAK TROUGH WILL CROSS THE AREA THIS AFTERNOON. HIGH PRESSURE WILL THEN MOVE IN. A DRY COLD FRONT WILL SLIP DOWN FROM THE NORTH ON SATURDAY. A COMPLEX FRONTAL SYSTEM WILL BRING RAIN UP FROM THE SOUTHWEST LATE SUNDAY INTO TUESDAY. && .NEAR TERM /UNTIL 8 PM THIS EVENING/...
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A WEAK SURFACE TROUGH WILL SLIDE EAST ACROSS THE REGION THIS AFTERNOON SPARKING SCATTERED SHOWERS AND A FEW LOW-TOPPED TSRA ACROSS THE SUSQ VALLEY AND SCENT MTNS...WITH A FEW HOUR PERIOD CONTAINING ISOLATED SHOWERS A LITTLE FURTHER TO THE NW UNTIL CFROPA TIME. BREAKS IN THE DUAL LAYERED CLOUD COVER WILL CREATE AREAS OF SFC BASED CAPE BETWEEN 750-1000 J/KG ACROSS THE SE THIRD OF THE CWA. 0-1KM SHEAR IN THIS AREA IS ONLY AROUND 10 KTS...AND 0-3 KM SHEAR NOT MUCH GREATER AT 15-20 KTS. THEREFORE...ANY TSRA WILL BE THE PULSE VARIETY AND GENERALLY BRIEF. TEMPS APPEAR ON TRACK TO REACH OUR FCST LATE AFTERNOON HIGHS OF 60-65F ACROSS THE NORTHERN AND WRN MTNS...AND THE LOWER 70S IN THE SE.
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&& .SHORT TERM /8 PM THIS EVENING THROUGH SUNDAY/... ANY SHRA/TSRA IN THE FAR SE AROUND SUNSET WILL MOVE QUICKLY EAST AS THEY WEAKEN. THERE SHOULD BE GOOD CLEARING OVERNIGHT...BUT IT MAY COME SLOWLY AT FIRST. THE RESIDUAL MOISTURE AND A DIMINISHING WIND DUE TO A HIGH PRESSURE AREA NOSING IN FROM THE OHIO VALLEY MAY BODE WELL FOR PATCHY FOG. HOWEVER...SUBSIDENCE WILL BE DRYING OUT THE AIR AS WELL. MINS WILL HOLD IN THE 40S AND L50S. SATURDAY SHOULD BE FAIR WITH A GENERALLY LIGHT WIND. HOWEVER...A VERY POTENT SHORT WAVE WILL ZIP THROUGH NEW ENGLAND AND DRAG A DRY BACKDOOR FRONT THROUGH IN THE MIDDLE OF THE DAY. THIS COULD KICK THE WINDS UP...ESPECIALLY OVER THE NE. MAXES WILL BE INTO THE 70S FOR MOST...BUT PERHAPS ONLY THE M-U60S IN THE HIGHER ELEVATIONS/NW. UPPER RIDGE STAYS JUST TO THE WEST SAT NIGHT...AND SHOULD KEEP IT MAINLY CLEAR. TEMPS MAY GET FROSTY IN THE NRN MTNS...WITH 40S ELSEWHERE. THE LIGHT N/E WIND MAY BE ENOUGH TO KEEP TEMPS FROM REALLY FALLING OFF. SUNDAY LOOKS MAINLY DRY AT THIS POINT...WITH MOST GUIDANCE NOT BRINING ANY RAIN INTO THE AREA UNTIL AFTER 21Z. WILL KEEP CHC POPS IN THE SW FOR LATE IN THE DAY. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... GOOD TO ABOVE AVERAGE CONFIDENCE NOW IN EXTENDED RANGE FORECAST WITH LATEST 16/12Z MODELS CONTINUING THEIR TREND OF MUCH BETTER AGREEMENT ON EVOLUTION OF OVERALL PATTERN AND TIMING. THE KEY ELEMENTS OF THE FCST ARE NOW BECOMING RATHER CLEAR: 1) THE WEEKEND SHOULD TURN OUT TO BE DRY! 2) A POTENTIALLY SIGNIFICANT RAINFALL EVENT IS BEING SIGNALED BY THE MODEL AND ENSEMBLE DATA FOR LATE SUNDAY NIGHT INTO MONDAY AND 3) BEYOND MONDAY THE PATTERN LOOKS BLOCKY WITH A CORE OF NEGATIVE HEIGHT ANOMALIES CENTERED OVER THE MIDWEST/GREAT LAKES/NORTHEAST. THE UPPER LOW EXITING THE FOUR CORNERS REGION INTO THE CENTRAL PLAINS WILL MERGE WITH NORTHERN STREAM ENERGY DROPPING SWD ACROSS SOUTHERN CANADA...EVENTUALLY CARVING OUT A BROAD LW TROUGH OVER THE EASTERN U.S. AT THE SFC...A DEEPENING LOW WILL TRACK NEWD THROUGH THE GREAT LAKES WITH ABOVE NORMAL PWS BEING DRAWN NWD ALONG AND AHEAD OF ITS TRAILING COLD FRONT VIA STRONG SLY FLOW. AIDED BY THE MAGNITUDE OF THE MSLP...850MB WINDS AND PW ANOMALIES THE PATTERN RECOGNITION SUGGESTS THE POTENTIAL FOR A SYNOPTIC TYPE HEAVY RAINFALL EVENT LATE SUNDAY NIGHT INTO MONDAY. AS THE PARENT UPPER TROUGH TAKES ON A SLIGHT NEGATIVE TILT...IT ALSO APPEARS THAT A TRIPLE POINT LOW WILL FORM ALONG THE FRONT OVER THE SRN MID ATLC STATES...WHICH USUALLY SLOWS THE PROGRESSION AND ENHANCES RAINFALL. CURRENT FORECAST GRIDS ARE IN VERY GOOD SHAPE...AND MAINTAINED THE TREND OF INCREASED POPS FOCUSED AROUND DAY 3.5-4/SUNDAY NIGHT-MONDAY WITH ADDED CHC FOR +RA FROM THE SOUTH CENTRAL MTNS INTO THE SUSQ VLY. BASED ON CAPE FORECASTS...ADDED A MENTION OF CHANCE TSTM TO THE WEST MONDAY AS WELL WITH MOISTURE STREAMING IN ON NOTABLE 850MB SOUTHERLY JET. TEMPS SHOULD TREND COOLER INTO MIDDLE/LATE WEEK WITH SHOWERY /YET LIGHT/ REGIME ASSOCIATED WITH BROAD CYCLONIC FLOW ALOFT WITH CLOSED UPPER LOW CENTERED INVOF THE UPPER GREAT LAKES. DETAILS ON PRECIP DO REMAIN SKETCHY FOR THIS PERIOD...WITH LACK OF GOOD CONSENSUS IN GUIDANCE AFTER WED WITH DIVERGING SOLUTIONS IN POSITION OF BROAD TROUGH OVER S CANADA/NORTHEAST U.S. && .AVIATION /16Z FRIDAY THROUGH TUESDAY/... A WEAK TROUGH OF LOW PRESSURE WILL PUSH EAST ACROSS THE STATE THIS AFTERNOON. BRINGING A FEW...GENERALLY BRIEF SHOWERS AT CENTRAL AND SERN PENN TAF SITES. A FEW BRIEF TSRA MAY IMPACT TAF SITES SE OF A LINE FROM KSEG TO KAOO. TSRA ARE EXPECTED HAVE JUST ISOLATED COVERAGE AND NOT POSE ANY SIGNIFICANT WIND THREAT AS BULK SHEAR IN THE LOWEST 3 KM AGL IS FROM THE WEST AND MAINLY UNDER 20 KTS. NR TERM MDL SOUNDINGS INDICATE LOW LVL MOISTURE ASCENDING THE ALLEGHENY MTNS WILL CONTINUE TO PRODUCE IFR CIGS AT KBFD THRU ARND 18Z. AS FLOW VEERS TO THE WEST...UPSLOPING FLOW MAY ALSO RESULT IN A PERIOD OF IFR CIGS AT KJST BTWN 14Z-18Z. FURTHER EAST...DOWNSLOPING FLOW WILL LIKELY YIELD NO WORSE THAN BRIEF MVFR CIGS IN SCTD SHOWERS/TSRA AFTER 16Z. GENERALLY IMPROVING CONDS EXPECTED THIS AFTN ACRS THE CENTRAL AND WEST...AS WESTERLY FLOW DRAWS DRIER AIR INTO THE REGION. HOWEVER...CAN/T RULE OUT A BRIEF SHRA/TSRA AT KMDT/KLNS BTWN 19Z- 00Z ASSOC WITH PASSAGE OF UPPER LVL DISTURBANCE. A RIDGE OF HIGH PRES WILL BUILD INTO THE AREA TONIGHT...BRINGING WIDESPREAD VFR CONDS AND LGT WIND THIS EVENING. CAN/T RULE OUT PATCHY RADIATION FOG LATE AT NIGHT/EARLY SAT AM. OUTLOOK... SAT-SUN...NO SIG WX EXPECTED. MON...SHOWERS/LOW CIGS EXPECTED. TUE...NO SIG WX EXPECTED. && .FIRE WEATHER... WETTING RAINFALL HAS DECREASED THE WILD FIRE SPREAD THREAT FOR NOW. HOWEVER...DEWPOINTS WILL BE VERY LOW ON SATURDAY. A WEAK BACK DOOR FRONT WILL LIKELY KICK UP THE WIND A BIT OVER THE NORTHEASTERN COUNTIES LATER ON SATURDAY. IF FUELS DO DRY OUT BY SAT AFTERNOON...THE CONDITIONS MAY BE WORTHY OF A RED FLAG WARNING. FURTHER GUIDANCE FROM DISTRICT FIRE MANAGERS WILL HELP IN DETERMINING WHETHER A RED FLAG WARNING MAY BE NECESSARY. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO/LAMBERT NEAR TERM...LAMBERT SHORT TERM...DANGELO LONG TERM...RXR AVIATION...LAMBERT FIRE WEATHER...

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