Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 122306 AFDCTP Area Forecast Discussion National Weather Service State College PA 606 PM EST Tue Dec 12 2017 .SYNOPSIS...
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A deep northwest flow of cold air will be over the region through Wednesday afternoon. This will result in snow showers across the mountains tonight and early Wed. Low pressure will track across southwestern Pennsylvania Wednesday night. This low will bring a period of light snow to the area late Wednesday into early Thursday. A complex weather pattern will be across the region this weekend, and early next week. This will result in some snow showers from time to time, but a moderating trend into next week.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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IR loop at 2230Z showing breaking clouds across eastern Ohio and northwest Pa, as low PWAT arctic air overspreads the region on northwest flow. Surface dewpoints range from the 20s over eastern Pa to the single digits in the west. Although the dry air will hinder lake effect snow overall, long fetch Lake Huron band is progged by models to slip southward across northern Pa late tonight. Have timed highest POPs to correlate with arrival of this band based on latest NAM/Canadian 925mb thte fields. Based on model blended qpf and an expectation of snow/water ratios near 20/1 (max omega occurring within DGZ), believe additional snowfall between 00Z-12Z will range from up to 6 inches over the snowbelt of northwest Warren County, to a fresh coating across the northeast quadrant of the forecast area. Despite favorable upslope flow, believe overnight accums across the Laurel Highlands will be only an inch or less due to the aforementioned dry air. For most of the forecast area, the cold air and low wind chills will be the main story overnight. Temperatures falling into the teens, combined with gusty winds, will result in wind chills in the lower single digits late tonight across the southeast counties and the lower single digits below zero across the Allegheny Plateau. Passage of upper trough axis and pressure fall/rise couplet late tonight will likely be accompanied by an increase in wind gusts during the early morning hours. Latest Bufkit soundings support frequent gusts between 25-35kts early Wed morning. Heavy winter coats, hats, and good gloves/mittens will be in order if going out tonight, especially at the bus stops Wednesday AM.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Key point is it will be a very cold day with lots of wind. Windchill values will be below 0F in the northwest and range the single digits above zero over the southeast. Bundle the kids up for school. A very cold December kind of day. Snow guns should be blazing at ski resorts. The snow should continue though at lesser rates in the northwest and in the higher terrain of the southwest mountains. Clouds will increase during the day as a fairly vigorous Alberta Clipper zips on towards us. Most models weaken it as it passes over us. But as the rule of clippers go this one should pass just to our south, the old school sweet spot. Most of the larger scale models imply 0.1 to 0.25 inches of QPF. Highest in southwest mountains, possible. Most of the potential snow will fall after this period. But the GEFS and SREF imply some snow could arrive in the southwest in the late afternoon or early evening. Most of the snow will fall after 7 PM. I did up QPF and POPS some Wednesday night. Amounts still below advisory. System is moving awful fast for much snow. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Complex pattern for late in the week into next week. I did lower temperatures and dewpoints for the first part of the weekend, as the northern system looks stronger now, may result in cold air building southward into the area. Also cut winds and gusts down, as I have done the last few days, given the trend away from a deep low on Sunday. Models show southern branch of the westerlies trying to come into play on the large scale next week, but for now did not go real high with POPS. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... The cold front is still working its way across our easternmost counties. Behind the initial surge of cold air winds have come around to the west/northwest with gusty winds in the higher elevations. Gusty winds will slowly spread east. Low cigs are behind the front. But most of the MVFR/IFR is in the higher terrain. Snow and blowing snow will affect the southwestern mountains and northwestern areas for the next 12 to 24 hours. Blowing snow too. KBFD and KJST will be the two spots to check the weather carefully before take off. Most other areas main concern will be increasing and gusty winds. Some snow showers will affect KAOO and KUNV at times but nothing significant nor long lasting but periods of MVFR will happen. Farther east mainly gusty winds. 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 Wednesday for PAZ005- 010-017-024-033. Lake Effect Snow Warning until 1 PM EST Wednesday for PAZ004. && $$ SYNOPSIS...Lambert/Martin NEAR TERM...Fitzgerald SHORT TERM...Grumm/Martin LONG TERM...Martin AVIATION...Grumm/Martin

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