Area Forecast Discussion
Issued by NWS State College, PA

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764 FXUS61 KCTP 290538 AFDCTP Area Forecast Discussion National Weather Service State College PA 138 AM EDT Sat Apr 29 2017 .SYNOPSIS...
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A nearly stationary frontal boundary will be located over the Keystone state for much of the time this weekend. A few disturbances aloft will move over this front and bring periods of showers and thunderstorms. A strong trough and cold front will move across the region on Monday, followed by much cooler temperatures.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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Northeast extent of a series of MCSs (stretched all the way back to the southern plains) will move across the CWA early today bringing several hours period of MDT to ocnly HVY rain (with embedded TSRA across the southern few layers of counties). Rainfall amounts should average around one inch across the south...near or slightly under 0.75 of an inch along the I-80 corridor, with 0.25 of an inch or less along the PA/NY border. Overnight, lows will range from the mid 50s across the NW...to the mid 60s across the Lower Susq Valley (that current lies just to the SE of the stalled out frontal boundary). These temps will be about 15-20 deg above normal.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/...
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Guidance agrees in bringing the warm front slowly northward today, but differences exist as to how far north it manages to progress. Warm and muggy air will pool along and just to the south of the boundary. Models develop a fair amount of CAPE, they just differ on whether the most unstable air will favor the Maryland border areas or extend up into the Central Mountains. SPC has the region under a marginal risk for severe storms, and with moderate deep layer shear expected, this looks reasonable. Look for the best chance of showers and storms to be from mid day into the afternoon. Highs will vary from around 70 along the NY border to the mid/upper 80s over the SE. If we end up with more sunshine than currently expected, I would not rule out a high temp near 90 in a couple of places. With dewpoints well up into the 60s over at least the southern half of the CWA, it will begin to feel humid.
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&& .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Upper level ridge tries to builds in for Saturday night through Sunday but continued southerly flow/instability and a weak warm front lifting through the Ohio Valley and W PA will lead to continued chances for showers and even a tsra - mainly in the NW half of the area. Temps remain very warm into Monday. A 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 lift northward. Models showing strength/timing issues so not getting to specific this far out, but looks like unsettled weather pattern continues. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... Complex weather pattern across the region. Radar and short term models indicate area of showers/rain moving in from the west. Although there is some embedded thunder, it seems to be having difficulty making it over the western mountains. Have increased rain chances in TAFS over the next 2 to 4 hours. With dry atmosphere in place, have not included restrictions in flying conditions (cigs/vsby), although there may be some isolated restrictions in heavier showers/thunderstorms. Short term models indicate that most of the shower activity will diminish before sunrise. A wavering frontal boundary is expected to set up across the region tomorrow. Thinking right now for aviation purposes is to lean towards northern areas to be in the cool sector, with occasional showers and lower ceilings and less chance of thunder. Central areas are in the battleground region. Scattered showers and thunderstorms possible right through the period. Reluctantly, have included VCTS for large blocks of time in the forecasts, as timing very difficult. Southeastern areas may be in the warm sector Saturday. While there is a risk of thunder here as well at KMDT and KLNS, activity may be more isolated than across the KJST/KAOO/KUNV corridor. Have therefore left thunder out of these (KMDT/KLNS)TAFs for now. Outlook... Sat-Sun...Sct showers/Tstorms. Areas of sub-VFR north, and also associated with any thunderstorms. Mon...Breezy. Showers/thunderstorms likely with periods of sub- VFR. FROPA. Tue-Wed...Breezy with a chance of showers NW 1/2. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte/Lambert NEAR TERM...Lambert/Martin SHORT TERM...La Corte/Martin LONG TERM...RXR AVIATION...Jung

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