Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 242233 AFDCTP Area Forecast Discussion National Weather Service State College PA 633 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 /THROUGH TUESDAY/... Rain continues to advance from the south. Showers remain scattered as lower atmosphere is fairly dry. Have tried to refine the timing and northward extent of the rain and opaque cloud cover for the near term. Overall, the timing is similar between all the guidance. QPF will be light today, on the order of a tenth of an inch or less south of I-80 and a tenth to quarter of an inch south of the turnpike. Maxes should be above normals in the north but below normal in the south. Temps through southern and central PA are in low 60s where the mainly sunny Northern portion of PA has reached the 70s. && .SHORT TERM /TUESDAY NIGHT 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. Moisture will slowly infiltrate the lower levels and rainfall will become more widespread overnight into Tuesday morning. The confidence in occurrence of the decent rain is highest 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 /22Z MONDAY 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 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... Tue...Rain/low CIGs likely. Wed...AM rain/low CIGs possible. Thu...AM fog possible. PM tsra impacts possible. Fri...PM tsra impacts possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo NEAR TERM...Dangelo/Ceru SHORT TERM...Dangelo/Ceru LONG TERM...Lambert AVIATION...Fitzgerald/Ceru is the U.S. government's official web portal to all federal, state and local government web resources and services.