Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 170230 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1030 PM EDT THU APR 16 2015 .SYNOPSIS... HIGH PRESSURE MOVING OFF THE NEW ENGLAND COAST THIS AFTERNOON WILL GIVE WAY TO WEAK LOW PRESSURE MOVING ACROSS THE GREAT LAKES ON FRIDAY. THIS SYSTEM WILL BRING SOME SHOWERS AND PERHAPS A THUNDERSTORM TO THE AREA TONIGHT INTO FRIDAY. FAIR WEATHER WILL RETURN TO THE AREA LATE FRIDAY...AS HIGH PRESSURE BUILDS SOUTHWARD FROM QUEBEC. A COMPLEX FRONTAL SYSTEM WILL BRING MORE SHOWERS TO THE AREA LATE SUNDAY INTO TUE...AS A SOUTHERLY FLOW OF AIR DEVELOPS EAST OF A COMPLEX FRONTAL SYSTEM ACROSS THE PLAINS EARLY NEXT WEEK. && .NEAR TERM /THROUGH FRIDAY/...
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SURGE OF 0.75" TO 1" PW HAS OVERSPREAD ALL OF CENTRAL PA THIS EVENING...SPREADING WIDESPREAD SHOWERS ACROSS THE REGION. THE SHOWERS ARE MOST NUMEROUS AND ORGANIZED ALONG AN 850 MB SPEED MAX CURRENTLY LIFTING INTO NORTHEAST PA AND THE CATSKILLS. CYCLONIC CURVATURE ALOFT AND WEAK BOUNDARY LAYER FORCING WILL PERSIST OVERNIGHT BEHIND THIS FEATURE...KEEPING SCT-NMRS LIGHT SHOWERS GOING INTO THE PRE DAWN HOURS. MOST AREAS WILL SEE A TENTH OF AN INCH OR LESS OF RAIN. THESE LIGHT SHOWERS WILL LAST INTO THE FIRST PART OF FRIDAY. H5 HEIGHTS RISE AFTER 18Z FRI...AND DEEP LAYER MOISTURE DECREASES AND WEAK HIGH PRESSURE BUILDS INTO THE OHIO VALLEY AND WESTERN PA BY LATE AFTERNOON. CLOUDS WILL DECREASE FROM NW TO SE DURING THE AFTERNOON. TEMPERATURES WILL RISE INTO THE LOWER 70S ACROSS THE SE ON FRIDAY...WITH MID TO UPPER 60S FOR HIGHS ELSEWHERE.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY/... VERY LOW DEWPOINTS WORK INTO THE AREA LATER FRIDAY INTO SAT. FIRST PART OF THE WEEKEND SHOULD BE DRY...WITH TEMPERATURES IN THE 70S. THERE WILL BE A LARGE RANGE FROM DAY TO NIGHT...GIVEN THE DEWPOINTS. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... 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 /02Z FRIDAY THROUGH TUESDAY/... AN AREA OF LIGHT SHOWERS WILL CONTINUE TO PROGRESS ACROSS THE AREA THROUGH THE EVENING HOURS...GRADUALLY MOISTENING THE ATMOSPHERE AND EVENTUALLY ALLOWING FOR MVFR/IFR CONDITIONS TO DEVELOP FOR THE SECOND HALF OF THE OVERNIGHT. IMPROVING CONDITIONS WILL DEVELOP FROM WEST TO EAST ON FRIDAY...AS WINDS SHIFT TO THE NW. TERMINALS SHOULD IMPROVE TO VFR DURING THE AFTERNOON AND CONTINUE THROUGH AT LEAST THE FIRST HALF OF SUNDAY. OUTLOOK... SAT...NO SIG WX EXPECTED. SUN...SHOWERS/LOW CIGS POSS LATE. MON-TUE...SHOWERS/LOW CIGS EXPECTED. && .FIRE WEATHER... VERY DRY AIR OVER THE AREA BUT THE WIND IS LIGHT ENOUGH TO NOT EXACERBATE FIRE DANGER. CLOUDS AND SHOWERS WILL CONTINUE TO MOVE OVER THE REGION TONIGHT AND EARLY FRIDAY...FURTHER REDUCING THE THREAT FOR WILD FIRE SPREAD. SAT...VERY DRY AGAIN...BUT WITH A LIGHT WIND. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...MARTIN NEAR TERM...DEVOIR/MARTIN SHORT TERM...MARTIN LONG TERM...RXR AVIATION...LA CORTE FIRE WEATHER...

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