Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 291938 AFDCTP Area Forecast Discussion National Weather Service State College PA 338 PM EDT Sat Apr 29 2017 .SYNOPSIS... A nearly stationary frontal boundary will remain over the forecast area for much of the weekend. A strong Cold front will move across the region on Monday, followed by cooler air for midweek. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... The leading edge of yet another decaying MCS is moving through my western zones. Unstable air as measured by CAPE is pretty much confined to the Mason-Dixon line southward, but RAP analysis indicates mid level lapse rates are a fairly respectable 6-7C/km or higher so there is at least some elevated instability. The HRRR survives these showers as they move through central and eastern PA through late afternoon, with the northern 2/3 or so of the region standing the highest chance of getting wet. The frontal system over PA is hard to find in the meso anal but the more humid air over the south seems to be separated by a boundary that extends from near PIT eastward to near the PA border and into the soupier dewpoints over the lower Susq. Satellite loop shows tops warming at a pretty good clip as the convection leaves the more unstable airmass of the Ohio Valley. The thin high clouds over the SE have done little to thwart warming with readings of 80+ already for much of the area. The latest HRRR takes this MCS and streaks it east and out of the area by nightfall, with a period of dry weather indicated into the wee hours of Sunday, before new convection from the Midwest and OH Valley begin to approach my western areas. I used blended POPs to bring a small chance of rain back in for the second half of the overnight. Lows will range from the mid 40s over the north to around 60 over the south. Well above normal for the last days of April. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... The warm front will try to crawl back north into the CWA Sunday presenting a high temperature forecast problem. Near term deterministic models show a cool-air damming scenario hanging rather tough. The surface based LI field is usually a great indicator of this. The ECMWF/NAM/GFS are all in good agreement with the warm air working into my western higher elevations while the ridge-valley areas east of the Alleghenies stay in the clouds and cooler air. If things work out as expected highs will vary from around 60 in the Poconos to around 80 in Somerset county. Again the main focus for Sunday will be for showers/thunderstorms to once again develop and/or move into the region. With the most unstable air expected to be over the western sliver of my CWA, that`s where I would expect the best chance for measurable rain. Once again I used blended MOS POPs for this given that the best focusing mechanism will be well west of the region. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
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Upper level ridge builds across the Mid Atlc Region Sunday night and Monday and a warm front will be lifting through the Ohio Valley and W PA. This weather feature will lead to continued chances for showers and even a tsra - mainly in the NW half of the area. Upper low now over the four corners region is forecast to lift through the central Plains on Sunday then the Great Lakes on Monday. This will serve to send pieces of energy along the surface boundary. Temps should return/rise to very very warm levels on Monday. The massive and deepening cyclone lifting into the western Great Lakes Sun night into Monday will push a strong cold front through PA Mon into Mon night, accompanied by a round of potentially potent showers and thunderstorms (likely reaching western half of CWA in the afternoon and eastern half during the evening). Once this front passes by much chillier air will advect into PA on cyclonic flow with unsettled light showery weather persisting mainly for the northern part of the state right into Wednesday. Chance for a more widespread light rain arrives Thu into Fri as a low progged to develop along the southern Appalachians and the lift northward. Models showing strength/timing issues so not getting to specific this far out, but looks like unsettled weather pattern continues.
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&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/... BFD has seen their ceiling fall to IFR as low level moisture backs in behind the shallow cold front. The remainder of the flying area is VFR. A decaying area of showers and thunderstorms is moving east across the area from about JST-AOO northward. Terminals will tend to remain VFR with reductions associated with the showers through late afternoon. A more general decrease in ceilings will occur this evening and overnight as cool-moist air settle south behind a weak back door cold front. The exception will be the lower SUSQ Valley where ceilings should stay just above 3000`. Sunday will see conditions improve only slowly over much of central and northern PA as the warm front tries to return northward. Scattered showers/thunderstorms will once again be possible, especially over western areas during the afternoon. Outlook... Mon...Breezy. Showers/thunderstorms likely with periods of sub- VFR. FROPA. Tue-Wed...Breezy with a chance of showers NW. Thu...Widespread sub-VFR developing ahead of a warm front. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...La Corte LONG TERM...Lambert/Gartner AVIATION...La Corte is the U.S. government's official web portal to all federal, state and local government web resources and services.