Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 250213 AFDCTP Area Forecast Discussion National Weather Service State College PA 1013 PM EDT Mon Apr 24 2017 .SYNOPSIS... A storm system over the southeastern states will begin to make slow progress northward along the coast over the next several days. && .NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
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As of 10PM radar shows the main east-west band of light rain along I-80 with more intermittent light rain covering the area south to the MD border. Tweaked pops for the next few hours to reflect the more spotty nature of the light rain and possible drizzle, but overall forecast for a damp mild night has not changed. Models are in good agreement in bringing widespread rain over the region overnight through Tuesday, with the heaviest amounts of .50-.75" most likely over the eastern 1/2 of the CWA. Overnight lows will average in the 40s which will be some 5-10 deg above normal.
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&& .SHORT TERM /7 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... The guidance is very consistent with timing and placement of the major features. Deep easterly flow will slide up the coast into PA through the short term period. The confidence is highest for the best rains to occur tomorrow afternoon, especially through the eastern half of the region. However, the tilt of the trough which the upper low is associated with is a little fuzzy. With a more- negative tilt it may move a little faster, and bands of rain may move more quickly. This would probably keep the rain lighter at any one location. Looking at latest plumes keep precip total/accumulation around 0.5 through the period. Most of this rain should be out of stable profiles, so thunder and big totals are not likely. Temps will be seasonably mild overnight tonight. Maxes on Tues will be homogeneous in the u50s to low 60s in the far northwest where skies will see some sun. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Moist and anomalously strong (approx -3 sigma) southeasterly flow off the Atlantic will bring occasional rain/showers to the eastern 1/2 to 2/3rds of the CWA Tuesday night with QPF likely averaging just another 1-2 tenths in most places across the Susq Valley and Western Poconos (less across the central and western mtns). Min temps will be on the mild side - in the upper 40s across the western mtns and lower 50s elsewhere. The slowly weakening (1004-1006mb) sfc low, and filling upper low will be moving NE twd Cape Cod late Wed/Wed night. Bkn-Ovc cloud cover on the western fringe of the departing low will bring a slight chc for showers across the eastern part of our CWA (mainly Wednesday morning), while increasing sunshine greets residents over the western half of the state. A fairly sharp and slightly anomalous upper ridge will slide across the Appalachian Chain and Mid Atlantic Piedmont Wednesday night and Thursday bringing dry conditions and well above normal temps min and max temps Wed night and Thu will be at least 12-15F above normal with even greater departures over nearly 20 deg F above normal across the northern and western mtns. Late this week and over the upcoming weekend persistent and quite strong southwesterly flow aloft will be accompanied by a few embedded shortwaves and associated sfc warm/weak cold frontal boundaries. This will bring periods of unsettled weather with uncertain timing with respect to exact onset/ending timing of the showers. The best chcs for rain appear to be Thursday night and again later Sunday into Monday as the broad lift from the RE region of an upper level jet (140-150 kt) and quite potent sfc cold front slides east from the Ohio Valley. Well above normal max/min temps (though probably not record level temps) will persist Friday through Sunday, before a gradual cool off begins Monday. Main forecast concern for the Fri-Sat period, when medium range models indicate a peak in temps (with maxes in the 70s to around 80) will be the location of a warm/stationary frontal boundary across northern and western PA. Clouds and some showers could lead to a temp bust by several deg or more on the high side (with observed temps possibly holding in the 60s across the northern mtns). && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Low pressure lifting up the east coast will spread lowering clouds and spotty light rain into central Pa overnight. Model soundings and SREF prob charts suggest MVFR conditions will become likely by late this evening across southern Pa and after midnight across the northern half of the state. As the storm system moves closer, expect a steadier rain to develop Tuesday. With the exception of BFD/IPT, model soundings support IFR CIGs across central Pa Tuesday. Outlook... Wed...AM drizzle/low CIGs possible. Thu...AM fog possible. Isolated PM tsra impacts possible west. Fri...Isolated PM tsra impacts possible east. Sat...Isolated PM tsra impacts possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Dangelo/Ceru LONG TERM...Lambert AVIATION...Fitzgerald

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