Area Forecast Discussion
Issued by NWS State College, PA

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545 FXUS61 KCTP 131052 AFDCTP Area Forecast Discussion National Weather Service State College PA 552 AM EST Wed Dec 13 2017 .SYNOPSIS... A deep northwest flow of cold air will be over the region through this afternoon, resulting in snow showers across the Northwest Mountains and Laurel Highlands. A weak ridge of high pressure will bring a lull in the winds and snowfall for several hours this afternoon, followed by a fast-moving clipper system tonight that will bring periods of light to moderate snow to perhaps the entire region. Several inches of additional snow can be expected by Thursday morning across the Western Mountains, while a general 1 to 3 inches falls across the central Mountains, with slightly lesser amounts throughout the Susquehanna Valley. Another ridge of high pressure will slide across the region Thursday and Thursday night with cold but mainly dry conditions. More snow showers will occur Friday afternoon into Saturday morning. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A gusty West-Northwest flow this morning will continue to push several streamers of Lake Effect Snow showers well inland from Lake Erie with an additional Coating to 2 inches expected across the northern and western mtns of the state. mainly flurries will occur to the SE of a KAOO to KUNV and KIPT line. Winds will slacken steadily later this morning and this afternoon as a weak ridge of high pressure slides quickly east across the state, bringing some brief partial clearing (mainly to the eastern half of the state) along with dry conditions. High temps today will range from the Lower 20s across the Northern and Western mtns, to the mid and upper 20s headed SE across the central Mtns to the Lower Susquehanna Valley. The passage of upper trough axis and pressure fall/rise couplet early today will be accompanied by gusty winds and winds chills in the single digits above and below zero. Latest Bufkit soundings continue to support frequent gusts between 30-35kts early this morning. Heavy winter coats, hats, and good gloves/mittens will be in order for the morning commute to work and school, especially at the bus stops this morning. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/...
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A fairly vigorous Alberta Clipper (994-996 MB) will race east from the Ohio Valley and likely move cross the southern part of the state tonight. Large scale uvvel at the nose (thermally indirect, left exit region) of a 115-120 kt upper jet and low to mid level warm advection, will result in thickening clouds late today followed quickly by a rather large shield of light (to briefly moderate) snow near and to the north of its sfc warm front. Best dynamics and low level orographic lift will favor up to 3-4 inches of snow across the Laurel Highlands with gradually lesser amounts occurring to the north and east across the state. A second/separate Winter Weather Advisory was recently issued from the NW mtns to the Laurel Highlands for the 23Z Wed - 13Z Thursday period and well Collaborated with surrounding WFOs. As expected with a clipper, model omega/temp time-sections indicate fairly high snow/water ratios (perhaps around 20:1) with max lift occurring within, or just below, the DGZ. These high snow/water ratios could tip the scale for Advisories to be expanded east across several Central PA counties encompassing KAOO, and KUNV where a fluffy 3 or 4 inches may accumulate from the latest model consensus and SREF mean of around 0.20-0.25 inches of LEQ.
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Highly sheared and rather shallow cold airmass with a gusty NW wind of 20 to 25 mph will follow for Thursday with Partly to mostly sunny skies SE of the Allegheny Plateau. Flurries with a few isolated-sctd snow showers will occur from KJST to KFIG and KBFD, with accums generally less than an inch. Clearing and quite cold conditions for Thursday night under the center of high pressure. Min temps will vary from the single digits over the NW mtns, to the teens throughout the Susq Valley and Southern Tier. A weak, elongated vort lobe will push east through the region late Friday/Friday night as low pressure moves across southern/central Ontario, Canada. Expect to see isolated to scattered snow showers across mainly the Northern and Western mtns of the state, with generally light snow accums in the typical Lake Effect/orographically enhanced locations. High Pressure consolidates off the Mid Atlantic Coast for Sunday with the large scale flow becoming southwesterly and milder air (temps 8-10 F above normal) flooding the eastern half of the Lower 48 States. Clouds will thicken up from the southwest late Sunday through Monday with a likelihood of rain showers.
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&& .AVIATION /12Z WEDNESDAY THROUGH SUNDAY/... IFR conds in snow showers and and blowing snow will affect mainly the northwest mountains for the next 12 to 24 hours. MVFR and a few snow showers will affect the central mtns with VFR elsewhere. A short wave could bring light snow into western areas Wednesday afternoon into Thursday. This could lower CIG/VIS in many western areas from KJST-KAOO-KUNV but this is beyond our current forecast period. Outlook... Wed...Snow showers with IFR NW Mtns. Sct snow showers with MVFR NW half. Otherwise VFR. Wed night...Alberta Clipper could bring light snow and more widespread reductions. Thu-Fri...Sct snow showers NW. Reductions west and southwest mts. Sat...Mainly VFR. Perhaps a snow shower north and east early. Sun...Mainly VFR. Perhaps a few showers late. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 1 PM EST this afternoon for PAZ005-010-017. Winter Weather Advisory from 6 PM this evening to 8 AM EST Thursday for PAZ004-005-010-017-024-033. Lake Effect Snow Warning until 1 PM EST this afternoon for PAZ004. && $$ SYNOPSIS...Lambert NEAR TERM...Lambert SHORT TERM...Lambert LONG TERM...Lambert AVIATION...Grumm/Gartner is the U.S. government's official web portal to all federal, state and local government web resources and services.