Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 280548 AFDCTP Area Forecast Discussion National Weather Service State College PA 148 AM EDT Tue Mar 28 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 THIS MORNING/...
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Isolated showers breaking out early this morning across the Central and West Central Mountains...with scattered coverage increasing over the Laurel Highlands. This in response to approaching midwestern upper trough pushing through the lower Ohio Valley...inducing northward increase of deep layer moisture into central PA from WV and VA. PW increasing to over 1.0" up to the I-80 corridor at this hour...as sfc low tracks into south central OH...and moisture pools along and north of inverted sfc extending from the WV pandhandle ESE to Chesapeake Bay. Shower arrival is right on time with previous forecasts, and while showers look to be mostly hit or miss...POPs will increase to around 50pct. Developing frontogenetical forcing across the northwest mountains is likely to result in a better chance of steady rain up there toward dawn. Increasing easterly low level flow ahead of aforementioned sfc low pressure will promote nearly homogeneous min temps within a few degrees of 50F across the entire area.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... Weak surface low will track just south of the Mason Dixon Line Tuesday. However, bulk of the latest near term model guidance indicates the best chance of rain will be across the northern mountains, where models place a developing band of fgen forcing. A cool, rainy day appears likely in this part of the state, while thin spots in the overcast and only scattered showers allow temps to rise into the 60s over much of central Pa. Along the southern tier, readings could reach the low 70s if warm front manages to lift north of the Mason Dixon. The guidance continues to show the development of some instability over southern areas by afternoon, where a thunderstorm cannot be ruled out, especially in the vicinity of warm front along the MD border. Showers should wind down from west to east Tuesday evening, as weak surface low passes off the Mid Atlantic coast. && .LONG TERM /WEDNESDAY 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 /06Z 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...DeVoir/Fitzgerald SHORT TERM...Fitzgerald/La Corte LONG TERM...Lambert/Gartner AVIATION...Jung/La Corte

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