Area Forecast Discussion
Issued by NWS State College, PA

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925 FXUS61 KCTP 101103 AFDCTP Area Forecast Discussion National Weather Service State College PA 603 AM EST Sat Dec 10 2016 .SYNOPSIS... Lake effect snow will continue today with total accumulations around 2 feet across the perennial Northwest Snowbelt. A mixed precipitation event is expected Sunday into early Monday with snow and ice accumulation possible. The winter pattern remains active with another opportunity for snow around midweek followed by a shot of arctic air and frigid temperatures next Thursday/Friday. && .NEAR TERM /THROUGH TONIGHT/... Apologies for the late AFD issuance, we lost an hour due to fire alarm. Long-duration lake effect event continues with an additional 2-4/1-3 inches across much of Warren and McKean County. Total snow accumulations will exceed 2 feet over the snowbelt region in northwest Warren County. HIRES models show LES bands becoming focused more into SW NY later today into early tonight. Outside of the lake effect area, expect a partly to mostly cloudy day with light snow showers and flurries spilling southeast over the Alleghenies into the Central Ridge and Valley region. && .SHORT TERM /SUNDAY THROUGH MONDAY/... Increasing warm advection ahead of mid level wave moving into the Great Lakes should spread light snow into western areas by early Sunday. The main surge of WAA moisture arrives Sunday night into early Monday morning in association with strong 50kt SSW 850mb LLJ. The models show the warm moist air overrunning the cold airmass currently in place which likely results in a ptype transition /snow to sleet-freezing rain/ from south to north. This changeover is most likely to happen in the 00-12z Monday period and impact the Monday morning commute. Confidence in forecast snow and ice amounts is below average given complex nature of wintry mix event and uncertainty in the 850mb 0C line. That being said, a winter weather advisory may be needed and will allow the dayshift to make a final assessment. Steady to slowly rising (non-diurnal) temps early Monday morning should continue to warm through Monday afternoon with any lingering pcpn falling mainly in the form of rain/dz. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Scattered snow showers Monday night across the Western Mtns of PA will diminish as a weak ridge of high pressure at the sfc slides east from the Ohio Valley. Tuesday will begin a cool down in temps over a several day period as progressively cold chunks of arctic air move southeast ahead of the main, sub-500 dam Polar Vortex that will be moving to near James Bay Canada by late Wednesday night. The coldest airmass of this young winter will spread into the region for Thursday and Friday. Temps Thursday could conceivably struggle to get above 10F for highs across the NW mtns. The GEFS shows a small area of -2 to -3 sigma temps at 850 mb with values around -18 F. West-Northwest wind gusting between 25 and 30 mph both Wednesday and Thursday will create wind chills of 5-10 below zero during the morning hours Thursday (mainly across the NW mtns), and only in the single digits during the daylight hours. Skies will become mainly clear with the wind dying off Thursday night as a 1025 mb sfc high build east from the nation`s heartland. This will set the stage for frigid temperatures - but several degrees above record lows. Min temps early Friday could dip to zero to 5 below across the fresh snow covered ground of the Laurel Highlands and NW mtns, and will be in the single digits to teens. Fair and dry (but very cold) weather is expected to persist Friday night. However...a moisture-laden storm will likely impact a large chunk of the region (beginning Friday) with snow changing to mixed precip of from the SW. Saturday and Sunday, clouds will thicken up quickly and precipitation will begin shortly afterward Saturday morning. It`s too early to give specifics on that storm w/resp that storm. 10/00Z EC and GEFS do infer a widespread wintry (snow) precip event...likely changing to some light sleet or fzra as the thicker seeder/feeder cloud shield slides off to the east. && .AVIATION /10Z SATURDAY THROUGH WEDNESDAY/... Cold WNW flow pattern will continue snow showers and MVFR/IFR conditions over the western 1/3 of the airspace. Low VFR to MVFR cigs will prevail at the central terminals with brief MVFR vis possible. VFR over the southeast. Outlook... Sun-Mon...Widespread MVFR/IFR in wintry mix changing to mainly rain by Monday afternoon. Tue...MVFR cigs and -shsn psbl wrn 1/3. VFR central/east. Wed...Restrictions possible with next wintry system. && .CTP WATCHES/WARNINGS/ADVISORIES... Lake Effect Snow Advisory until noon EST today for PAZ005. Lake Effect Snow Warning until noon EST today for PAZ004. && $$ SYNOPSIS...Steinbugl NEAR TERM...Steinbugl SHORT TERM...Steinbugl LONG TERM...Lambert AVIATION...Steinbugl

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