Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 061153 AFDCTP Area Forecast Discussion National Weather Service State College PA 653 AM EST Tue Dec 6 2016 .SYNOPSIS... Low pressure over the Tennessee Valley will track northeast through Pennsylvania late today and tonight. A cold front will sweep southeast across the area Thursday. A low pressure system is likely to track west of Pennsylvania through the Great Lakes Sunday and Monday. && .NEAR TERM /THROUGH TONIGHT/...
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Overrunning precip ahead of approaching sfc low is spreading into northern Virginia and W Virginia as of 12Z and latest near term models support arrival across the Laurels/SC Mtns by 14Z-15Z. Model soundings indicate enough evaporational cooling potential at onset to support a rain/snow/sleet mix across the southern valleys during the late AM to early PM hours. However, with surface temps mainly above freezing, don`t anticipate significant travel issues across the Lower Susq Valley. Main focus will be over the high terrain of the Laurels, where model soundings indicate a light accum of freezing rain is likely. Further north, model soundings, as well as SREF and NCAR ensemble, all indicate a mainly snow event north of I-80. Surface high is in ideal position over New Eng to hold in the relatively cold air over Pa. Marginal surface temps could limit accums a bit in the valleys. However, over the higher terrain of Northern Pa, model blended QPF is supportive of snow totals around 3 inches by the time precip tapers off late this evening. Based on coordination with BUF/BGM, have lowered snow amts from WPC guidance and held off on a winter wx advisory across Northern Pa, but will have to revisit this possibility on the day shift. Will maintain the advisory across the Laurel Highlands. However, current feeling is that the freezing rain will be isolated to only the highest terrain and thus the impact will be fairly low. Deep moisture will exit the area with passage of mid level shortwave late this evening. However, model soundings remain nearly saturated below 850MB, indicating the likelihood of linger drizzle late tonight. Superblend and high res NAM both indicate temps creeping above freezing even across the N Mtns late tonight.
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&& .SHORT TERM /WEDNESDAY/... Surface high pressure building into the region should supply a dry Wednesday to Central Pa. However, low level moisture trapped beneath inversion and weak mixing will likely result in stubborn low clouds across the NW Mtns. A downsloping westerly breeze should result in partly to mostly sunny skies east of the Mtns. Temperatures there should respond by rising into the low-mid 40s, while cloud cover holds readings to the mid 30s across the NW Mtns. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Broad and weak to moderate large scale lift/low to mid level warm advection develops late Wednesday night across the mtns of Wrn PA, and spreads across the remainder of Central PA Thursday ahead of an approaching arctic front and beneath the thermally direct segment of a 150kt 300mb jet moving by just to our north. Although moisture will be lacking with this feature, the fairly impressive large scale forcing, in conjunction with 00Z GEFS precip probs, supports mention of SHSN (SHRASN Lower Susq) across the entire area Thursday. The subsidence inversion base lifts rapidly up to 7-10 kft agl Thursday afternoon, right through Friday night. The mean wind in the 925-850mb layer veers from about 270 deg to 295-310 deg Friday and Friday night creating the likelihood of a significant/heavy Lake Effect/orographic snow event for the NW Mtns (i.e. mainly the snowbelt of NW Warren county). Will highlight this potential in the HWO. Gusty NW winds could top 40 mph at times Friday. A large area of high pressure and modified arctic airmass will slide off the east coast Sat night and Sunday. The coldest temps of the season so far will occur Sat night/early Sunday with lows in the lower to mid teens across the snow covered ground of the NW/Ncent Mtns...and upper teens to low 20s elsewhere. 00Z ECENS and NAEFS both track a surface low west of Pa through the Grt Lks late Sunday into Monday. There could be a bit of light snow in the WAA ahead of this feature, then milder/showery conditions appear likely Monday before trailing cold front and colder air arrive Mon night/Tues. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... MVFR cigs over the northwest airspace should trend to VFR over the next several hours. Elsewhere expect VFR with increasing/thickening high clouds. Cigs will lower from south to north later this morning with precip spreading over the airspace by the afternoon. P-types should transition from frozen/freezing to rain/drizzle across the western 2/3 of the airspace into Tuesday night. The southeast airspace should see mostly rain with some sleet possible at the onset. Confidence in ptypes is marginal given complex and evolving thermal structure/evaporative cooling in the boundary layer. Elevation and pcpn rates will also be a factor. A period of LLWS is possible at BFD/JST from roughly 6/18z-7/03z. Overall, expect flying conditions to deteriorate with high confidence in sub-VFR Tuesday afternoon into Tuesday night. Outlook... Wed...A.M. low cigs becoming mainly VFR. Thu-Fri...Becoming windy with periods of snow showers. Mainly MVFR/IFR west to MVFR/VFR east. Sat...Decreasing winds. Low cigs/-SHSN psbl NW. VFR east. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until midnight EST tonight for PAZ024- 033. && $$ SYNOPSIS...Fitzgerald NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald LONG TERM...Fitzgerald/Lambert AVIATION...Gartner/Steinbugl is the U.S. government's official web portal to all federal, state and local government web resources and services.