Area Forecast Discussion
Issued by NWS State College, PA

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113 FXUS61 KCTP 212317 AFDCTP Area Forecast Discussion National Weather Service State College PA 717 PM EDT Tue Mar 21 2017 .SYNOPSIS... Look for a relatively short lived but significant change in the weather later tonight and Wednesday as a frontal system bring much colder air back to the region for Wednesday and Thursday. A period of snow or ice is possible ahead of the returning warm air later in the week. A milder pattern will persist through the weekend with opportunities for rain into early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Big temperature changes later this evening as strong cold front will push across the region. The front will bring gusty winds but will be mainly dry with just a few mainly light snow showers over the usual spots in NW PA. A short northerly fetch and dry air should limit any accumulation to a brief coating over Northern Alleghenies. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... It will be cold with a good deal of the area not breaking freezing /15-25 degrees below average/. A strong ridge of surface high pressure will build into the area with decreasing winds and clear skies by afternoon. This will set the stage for strong radiational cooling and very cold temperatures by Thursday morning. && .LONG TERM /THURSDAY THROUGH TUESDAY/... WAA pattern quickly follows what could be winter`s last gasp with moderating temperatures into the second half of the week. Models indicate risk for snow/ice mix ahead of the warm air as pcpn spreads into retreating shallow low-level cold layer (associated with 1035mb high pressure area that briefly pauses along the coast) Thursday night-AM Friday. Max POPs are over the NW 1/3 of the area based on a multi-model consensus blend but ZR risk extends into the interior zones based on WPC probabilistic winter pcpn guidance. Risk for mix/ZR continues into mid Friday morning before temperatures warm above freezing. Models continue to show the warm front lifting north into NY by Friday night, becoming quasi-stationary and setting up a west-east oriented baroclinic zone. Location of this boundary will be key as it will be a focus for pcpn into the weekend. Models and ensembles are in decent agreement with the general synoptic pattern evolution across the CONUS with a series of upper troughs moving into the Southwest U.S. and losing amplitude as they eject/dampen out downstream across the Central Plains and east of the MS River. The lead wave and associated frontal system is progged to reach the area by Sunday which coincides with max POPs based on NBM/WPC/ECENS blend. The first wave will plow the path for a weakening second wave lifting through and bringing chances for showers early next week - though by then precip type looks to remain plain rain. Above average temperatures are expected over the weekend with the warmest day likely on Saturday with some sites approaching 70F over southern PA. Sunday should also be mild but a bit cooler due to likelihood of rain. Operational EC/GFS/CMC are somewhat at odds early next week with EC/CMC more bullish than GFS with shallow cool air to seeping southward east of the Appalachians. && .AVIATION /23Z TUESDAY THROUGH SUNDAY/...
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Strong cold front to the northwest, weak system over Ohio moving east, and severe strorms over the south. There could be a few lower clouds and light snow showers late at BFD and JST, mainly due to dynamics, but moisture is limited. Not expecting the 3 systems to combine into anything major over central PA. Did cut back on lower clouds late, for 00Z TAF package. Wed should be mainly VFR after mid morning, as very low dewpoints work in. Gusty northwest winds. More in the way of adverse weather for Friday, into next week, as a cold front remains nearby, and split flow keeps colder air to the north, and moisture from the south nearby. Outlook... Thu...No sig wx expected. Fri...Showers/reduced CIGS possible, mainly BFD. Sat-Sun...Showers/reduced CIGS possible.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Ross NEAR TERM...Ross SHORT TERM...Ross LONG TERM...RXR/Steinbugl AVIATION...Martin

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