Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 181117 AFDCTP Area Forecast Discussion National Weather Service State College PA 617 AM EST Wed Jan 18 2017 .SYNOPSIS... A cold front will push east across the region today, and will be accompanied by a few brief rain showers. High pressure will follow and bring mainly dry conditions later today, right into early Friday. Low pressure over the midwest will push a warm front north across the commonwealth Friday, that will be preceded by a several hour period of light rain. Daytime Temperatures across most of Central Pennsylvania will be 10 to 13 degrees above normal with departures even several degrees more for overnight lows. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A rather vigorous, 115 kt westerly upper level speed max rounding the base of a compact, but quite potent upper level shortwave trough will bring plenty of clouds and a scattering of light rain showers this morning. Westerly sfc wind gusts around 30 kts earlier across the Laurel Highlands (linked to the thermally direct descending branch of the aforementioned jet streak) has moved east across the stagnant, stable and foggy airmass across scent PA and the wind gusts have been greatly limited mixing down to the sfc. Will consider canceling the Dense Fog Advisory a few hours early as only several pockets of 1/4SM fog remain at 08z. A light to moderate westerly sfc breeze will develop across the Central Ridge and Valley Region and the Susq Valley, helping to mix out the shallow, cool, moist near sfc air during the mid morning hours. This will help to quickly improve vsbys. Look for a rather murky start to the day today, with low clouds gradually lifting and breaking up by late morning into the afternoon as a secondary cold front brings a stronger push of cooler-drier air to the region. The new airmass will not be especially chilly, with the cold air very marginal and barely deep enough to produce much more than isolated-sctd light snow/rain showers in the wake of the secondary cfront (thanks to 850 mb temps of just -2 to -4C). The most numerous snow showers will occur as usual just inland from Lake Erie and across our far NW zones. A light coating of snow could occur there at elevations over 2000 ft MSL. Low temps early today will range from the mid 30s acrs the northern and central mtns, to the lower 40s in the south. Gradual improvement is expected as the Wednesday wears on...but it will be a slow process as 5h low drops ESE to the Del Marva by afternoon...helping a secondary front drop across the area to signal improvement in the afternoon. Skies will be mostly cloudy throughout with some brightening mid to late afternoon south central and southeast. Highs will range from the upper 30s north to around 50F southeast. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... A shallow, bkn-ovc layer of mild and mainly non-precipitating strato cu (topped by periods of Alto Cu clouds) will hang around late today and tonight as the primary 850 mb ridge axis stays west of our area (and across the upper Great Lakes and Middle Ohio River Valley). Isolated to scattered flurries or brief rain/snow showers will drift over the Allegheny Plateau of northern and western PA. Little or no accumulation is expected. Some breaks in the low cloud deck will develop late today/tonight over the SE 2/3rds of the CWA, and remain through the day Thursday. Low temps tonight in the upper 20s to Lower 30s will be near to slightly below normal high temps typically experienced in the area during Mid January. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
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1020 MB sfc ridge builds NE and over central PA and upstate New York Thursday night with a sharp upper ridge builds over the NE states (sliding from the spine of the Appalachians to the Eastern Seaboard by midday Friday). The main weather maker for early in this period will come in the form of a warm from 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 40-45 kt swrly LLJ helps to transport a few bands of relatively strong 925-850 mb Theta-E convergence over the state. Rainfall amounts should be between 2 and 4 tenths across much of the forecast area during the Friday period. The upper ridge re-establishes 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. Another wave approaches/lifts into the OH valley late in the weekend into next Monday. Again, temps could be marginal at the start of pcpn overnight Sunday for some ice or snow, but the bulk of pcpn looks to be rain at this point. However, some guidance suggesting enough presence of cold air to for wintry p-types across northern PA.
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&& .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... Transition to westerly flow will spell improving conditions east of the Allegheny Front with VLIFR-IFR trending to MVFR/VFR by 15z. IFR to LMVFR cigs will likely persist at KBFD/KJST through the period before slowly improving on Thursday. Outlook... Thu...BCMG VFR west. No sig wx. Fri...Sub-VFR likely with rain moving SW-NE during the day. Sat...Sub-VFR possible with chc of rain increasing south-north. Sun...Sub-VFR likely with rain developing. && .CTP WATCHES/WARNINGS/ADVISORIES...
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&& $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Lambert/Gartner AVIATION...Steinbugl

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