Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 291229 AFDCTP Area Forecast Discussion National Weather Service State College PA 729 AM EST Tue Nov 29 2016 .SYNOPSIS... A frontal system will move through the area today. A new wave will form on the trailing cold front and move through the region Wednesday. A cooler northwest flow will develop for the end of the week into the weekend. && .NEAR TERM /THROUGH TONIGHT/... A plume of deep Gulf of Mexico moisture in advance of potent shortwave is supporting an expansive area of rain late this evening from the Grt Lks south thru the Ohio Valley. Regional radar loop at 11Z shows rain through central PA and HRRR indicates the rain will continue to move through Central Pa this morning. Expect the area of rain to diminish as it moves into eastward and breaks in the precipitation should occur this afternoon. Steady or slowly rising temperatures anticipated today under thickening cloud cover and WAA. The inversion noted in model soundings should keep the winds from becoming too strong/gusty in the central and eastern counties. However, model soundings support gusts of 25-30kts across the higher terrain of the Alleghenies. a second, shortwave lifting northeast from the Ohio Valley is expected link up with plume of +2-3SD PWATS to produce a second batch of heavier rainfall across southeast Pa between 12Z-18Z. Latest model guidance indicates the rain could linger into late afternoon across Lancaster Co, but a general drying trend from west to east is anticipated during the late AM and afternoon. Model-blended QPF between tonight and Tuesday ranges from a quarter inch or less across Mckean/Potter Counties, to around three quarters of an inch through the lower Susquehanna valley. The WAA will allow for highs today in the upper 50s. These forecasted highs are 10 to 15 degrees above normal. It may then be a dismal/damp but mild night Tuesday night. A wave develops along the old front over the Deep South while another front spins off-east of the midwestern storm center. Will keep chc-low likely pops in for the very last part of Tues night in the west. && .SHORT TERM /WEDNESDAY/... The front that is moving through the area today will become nearly stationary over the central Gulf states today, setting the stage for a new wave to form under the right entrance region of a powerful upper level jet streak Wednesday. This new storm will bring a quick return of surge of moisture for late tonight through Wednesday with a widespread .50" to .75" of rain expected to fall over most of the region. We could also see some rare November thunder as guidance hints at the development of some modest instability as the storm enters the region. Still too low a probability to include in the forecast, for now. The rain will taper to showers Wednesday afternoon as the surface wave scoots quickly to the southern New England coast by evening. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... As the storm pulls away it will set the stage for an extended period of breezy west-northwest flow. The upstream airmass doesn`t look especially cold (fairly close to seasonal normals), but the cold air flowing over the still quite warm lakes will be enough to provide an extended period of widespread cloudiness and frequent lake enhanced snow or even rain showers over the the NW mountains down into the Laurel Highlands, possibly lasting all weekend. By Sunday the medium range guidance begins to diverge significantly with the ECMWF popping an upper ridge through the NERN US while the GFS/GEFS have a much flatter ridge and keep us under the WNW flow aloft longer. Attention then turns to the upper low the models forecast to develop over BAJA by Saturday. The ECMWF and ECENS take this eastward and open it up more quickly than the GFS/GEFS which translates into a new widespread rainfall event Sunday night into Monday, while the GFS/GEFS don`t bring up the southern stream energy until Tuesday. This puts the end of the extended forecast in the very low confidence category. Temperatures Wednesday will be quite mild, some 15-20 deg above normal, before falling back to chillier and closer to normal readings for Thursday into the weekend. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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Warm front lifting out of the Ohio Valley will cross central PA this morning. Restrictions in the form of low CIGS are expected through 21z across the western and central TAF sites. BFD, JST and AOO are IFR and lower with MVFR elsewhere. Expect these low cigs to continue through early afternoon. As the front passes through MDT and LNS they should drop to IFR between 12Z to 15Z. A brief break in pcpn should occur later this afternoon, after 20Z, until the next front moves in on Wednesday. Much colder air and prolonged NW flow will follow the second front. Outlook... Tue...Low cigs/rain, mainly in the morning W and all day in the SE. Wed...Rain/low cigs possible. Thu-Sat...Sct SHSN w/ocnl IFR in BFD-JST. Isold SHSN AOO-UNV- IPT. VFR Elsewhere.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...Ceru SHORT TERM...Ceru LONG TERM...La Corte AVIATION...Ceru/RXR is the U.S. government's official web portal to all federal, state and local government web resources and services.