Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 272355 AFDCTP Area Forecast Discussion National Weather Service State College PA 755 PM EDT Mon Mar 27 2017 .SYNOPSIS... An area of low pressure will move along or just south of the Mason-Dixon line late tonight and Tuesday. High pressure will build down out of southern Canada and bring cooler and drier weather for Wednesday and Thursday. A new storm system will approach for the end of this week with the potential for more inclement weather. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Early evening GOES-16 visible loop shows the last vestiges of stratus have been scoured out of the Susq Valley as the surface warm front lifts north of the region. Partly to mostly sunny skies in the warm sector have push temperatures into the 60s over most of the area at 21Z, with low 70s noted over the south central valleys. Clouds will return with a renewed chance of showers once again tonight, as the next wave of low pressure moves into Ohio. Near term models suggest an arrival time of around midnight across the southwest counties and after midnight elsewhere. Lows will be very mild in the 40s to lower 50s. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... Latest NAM/GFS show the surface wave taking a track over or just south of the PA-MD border during the day Tuesday bringing occasional showers that will taper off from NW to SE during the afternoon. The guidance once again shows the development of some instability over southern areas so a thunderstorm cannot be ruled out. It will likely be subject more to the amount of sunshine that can develop than dynamic forcing. It will be another mild day in the 60s in most locations. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... The long term period will start with a frontal system and associated precipitation exiting the region and heights building aloft. Building high pressure will push the warm moist air off to our south Tuesday night into Wednesday. Wednesday should be a relatively nice day (though with some mdt northerly wind gusts at times, as high pressure builds in from the northwest. The dry air and high pressure are in all of the most recent guidance, implying Wednesday and Thursday should be relatively nice days. High pressure, dry air, and normal to slightly below normal 850 hPa and 925 hPa temperatures imply near normal daytime highs. Most of the 26/00-06Z U.S. and int`l model guidance (and EFS) indicates more of southern...shearing storm track for late in the week...thanks to a stronger and more wwd position of a deep nrn stream vortex across the Canadian Maritimes. The trend of the big model discrepancy for late this week and this weekend (between the GFS and EC over the past several days) has trended toward the GFS and its ENS members with southern stream energy and its moisture being prevented from amplifying with an associated storm track to our west. Rather, what we see is a shift of the primary southern stream sfc low track to our south as the potent midweek southern stream sfc/upper low (that will be trying to take the turn northeast across the Mid Miss Valley twd the Great Lakes) encounters great resistance from the notably stronger WNW upper jet core defining the northern stream that will be situated from the Upper Glakes to the Mid Atl Coast. With this type of consensus storm track, pops will be somewhat less for Friday and Saturday (compared to a heavily weighted EC/ECENS solution) and limited to mainly the southern half of PA where some rain (or even an elevation-dependent rain/wet snow mix) with expansive cooler and drier air north of PA. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... VFR conditions this evening will deteriorate with lowering ceilings and dropping visibilities as lower atmosphere moistens rather rapidly tonight on light southeast flow. Approaching system will bring showers into most areas overnight, with damp rain/shower activity lasting through Tuesday. This will bring significant restrictions to flying conditions, with widespread MVFR to IFR expected. Cooler, drier air filters in behind the system late Tuesday night into Wednesday with a slow improvement in conditions. VFR conditions Thursday, before a large rain-making system affects the area Thursday Night through Saturday. Outlook... Tue...IFR/MVFR across the region in showers/light rain. Wed...Morning restrictions, gradually improving to VFR most areas. Thu...VFR/No sig wx. Thurs Night-Sat...Sub-VFR restrictions/rain likely. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...Fitzgerald/La Corte SHORT TERM...La Corte LONG TERM...Lambert/Gartner AVIATION...Jung/La Corte

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