Area Forecast Discussion
Issued by NWS State College, PA

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799 FXUS61 KCTP 191543 AFDCTP Area Forecast Discussion National Weather Service State College PA Issued by National Weather Service Binghamton NY 1043 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 /THROUGH TONIGHT/... Updated at 1030 AM... A tricky cloud forecast for today as lots of low level moisture remained trapped underneath an inversion this morning per the 12z PIT sounding. High pressure will crest over the area this afternoon with a light west- northwest flow. This pattern should allow for some clearing especially south and east of the mountains... with clouds hanging on longer over our northern and western counties. Latest cloud trends showing some clearing trying to develop over the lower Susquehanna Valley while clouds hang on farther north and west. Based on these factors will allow for clearing over the Susquehanna Valley today and a few breaks over the central mountains... but remaining mostly cloudy across the northern mountains. Expect temperatures to climb to near 50 over the southeast where some sunshine is expected... with lower 40s over our central mountains and upper 30s across the northern mountains where little sunshine is expected. Previous discussion is below. 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 /FRIDAY THROUGH FRIDAY NIGHT/... 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). && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... 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 through Monday afternoon. The trend in most operational models and ensembles has been further to the south and east with this particular late weekend/early week system. This places parts of the fcst area in the sweet spot for potentially several inches or more of heavy, wet snow (especially later Monday/Monday night across the nrn and wrn mtns of PA at elevations of 1400 ft or higher), as the mean 850 mb low in the GEFS and EC tracks NE along the I-95 corridor in VA and adjacent SERN PA/Southern NJ. U-wind anomaly at 850 mb peaks at -4 to -5 sigma during much of Monday as a 45-55kt easterly llj develops between this approaching low, and the aforementioned colder airmass pushing swwd from SERN Canada and the New England states. Rainfall amounts are expected to be in the 1 - 1.5 inch range across roughly the SE half of PA with lesser amounts to the NW. 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. && .AVIATION /16Z THURSDAY THROUGH MONDAY/... Strong inversion will keep lower clouds across the region early on today. Partial clearing late, but high clouds will not be that far off. Looks like any rain on Friday will be after sunrise. 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... NEAR TERM... SHORT TERM... LONG TERM... AVIATION...

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