Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 191106 AFDCTP Area Forecast Discussion National Weather Service State College PA 606 AM EST Thu Jan 19 2017 .SYNOPSIS... High pressure will build northeast across Pennsylvania today, providing dry conditions through early Friday. Low pressure over the midwest will push a warm front north across the commonwealth during the day Friday bringing a several hour period of steady rain. Relatively mild conditions will persist for the next several days. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Another night/early morning spent under an extensive blanket of low clouds and patchy light fog, as lowering inversion will keep llvl moisture trapped beneath it for much of central PA. Most places will see a 5-8 kt west to west-northwest breeze through the mid morning with some gusts into the mid and upper teens across the NW mtns and Laurel Highlands. Min temps will be fairly homogeneous...ranging from the lower to middle 30s throughout Northern and western PA to near 40F in the larger metro areas across the lower Susq Valley. Subsidence inversion base lowers by about 1000 feet throughout today which should yield some breaks in the increasingly shallow strato cu deck. High temps today will be in the lower-mid 40s across the Northern and Western Mtns, and 45 to 50F from the Central mtns to the Lower Susq Valley. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
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1020 MB sfc ridge builds NE and over central PA and upstate New York late today and tonight as a sharp upper ridge builds over the NE states (sliding from the spine of the Appalachians to the Eastern Seaboard by midday Friday). The first half of tonight will start off partly to mostly cloudy, then turn overcast in many places by 12Z Friday. The main weather maker for early in this period will come in the form of a warm front that will lift north over the state during the day Friday. Operational model and EFS consensus us for a few periods of rain to occur Friday - primarily during the daylight hours as the nose of a 35-40 kt south-swrly LLJ helps to transport a few bands of relatively strong 925-850 mb Theta-E convergence and uvvel over the state. Consensus Model QPF ranging from 1-2 tenths of an inch across the Mtns north and east of KIPT, to between 3 and 4 tenths of an inch in the SW agrees well with the concept categorical - 100 percent pops in our gridded forecast (and depicted by the latest several runs of the NBM).
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The upper ridge is forecast to re-establish itself over the eastern U.S. over the upcoming weekend, bringing mild and mainly dry conditions Saturday, through at least the mid morning hours on Sunday. Daytime temperatures across most of Central Pennsylvania will be well above normal, but the departures for overnight lows should be greater by several degrees more throughout the entire extended period. The ridge axis will shift to the Hudson Valley and Eastern Seaboard early Sunday as a sfc backdoor cold front drifts swwd into PA and stalls out as a potent and moisture laden nearly stacked low lifts NE from the deep south to the Delmarva region by 12Z Tuesday. Temps could be marginal at the start of pcpn overnight Sunday for some ice or snow, and soundings via the GFS/GEFS and EC appear cold enough for Sunday night through Monday night for a mix of rain/snow (or even periods of all wet snow at times across the northern mtns of PA. However, the bulk of pcpn across the Central Ridge and Valley Region looks to be rain at this point. Some guidance, especially the ECMWF, is suggesting enough cold air may arrive at the end of the pcpn for wintry p-types to reach as far south as I-80 and the Laurel Highlands. Another short wave ridge will slide east from the Ohio Valley and move over the Commonwealth Wednesday, accompanied by light wind and fair/generally dry conditions.
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&& .AVIATION /12Z THURSDAY THROUGH MONDAY/... 09Z TAFS sent. Strong inversion will keep low clouds around the area this morning. Some minor changes made. Earlier discussion below. High confidence that blanket of low clouds will continue through the overnight with IFR restrictions persisting over the west and MVFR for much of the central and the east (though KUNV/KAOO may dip to IFR for a couple of hours bracketed by sunrise as inversion continues to lower. Other concern with plenty of low level moisture trapped will be potential for fog. Winds becoming light will promote formation of fog, with most areas settling between 2-4sm. High pressure building in for Thursday will finally mix enough drier air down from aloft to erode clouds - initially breaking in the SE starting mid morning and spreading to the NW by early/mid afternoon. Next trouble will be on Fri as the surface ridge gets squeezed and upper ridging is poked to the east by a strong short wave trough rotating poleward from a central CONUS upper cut-off. Warm advection will bring in clouds and deteriorating flying conditions into MVFR/IFR in the early morning SW and around noon in the NE. Outlook... Fri...Restrictions developing early. Rain/Snow north and rain south early. Rain areawide in the afternoon. Fri night...Widespread restrictions in areas of drizzle. Sat...MVFR/VFR cigs. Sun...Widespread IFR/MVFR restrictions. RA advances fm S-N. Mon...Widespread IFR restrictions in -RA. LLWS poss. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Lambert/Gartner AVIATION...Martin/RXR is the U.S. government's official web portal to all federal, state and local government web resources and services.