Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 200935 AFDCTP Area Forecast Discussion National Weather Service State College PA 435 AM EST Fri Jan 20 2017 .SYNOPSIS... A weakening warm front will push across the state today. Relatively mild conditions will persist through the weekend before cooler air makes a return next week. A complex storm system is expected to move off the Mid Atlantic coast Monday and Tuesday and could bring a return of wintry weather. && .NEAR TERM /THROUGH TONIGHT/... A weakening warm front extends from northern KY eastward through southern Va. Milder air is making progress northeastward bringing a shield of rain along with it. Guidance suggests the rain will overspread the region around or shortly after sunrise. The biggest issue with the advance of the rain is whether surface temps rebound enough to prevent a period of freezing rain. Latest HRRR is colder and shows spotty Freezing rain along the leading edge as the rain progresses northeast. Being the hours of the morning commute, we have issued an Advisory for a few hour period of freezing rain to cover the possibility of some light icing. The precip will continue off to the northeast with improving conditions expected for the afternoon as the steady rain turns to just scattered showers. As we have seen so many times this season, the low level cold air will be stubborn to dislodge, so while it will be quite mild over SWRN Pa today, the ridge-valley area of central Pa will stay locked in with temps only in the upper 30s to mid 40s. With just some scattered showers early tonight, the overnight temperatures will stay steady or only fall back slowly as we become ensconced in a mild SW flow between high pressure over the Mid Atlantic and a stronger low moving through the upper Midwest. Lows in the 30s and 40s will be some 15-25 deg above normal for the dead of winter. && .SHORT TERM /SATURDAY/... Saturday will be mild with a fair amount of cloudiness, but mostly rain free. I cannot rule out a stray shower, especially over the NW, but the chances are very low and I chose the more optimistic forecast not mentioning rain. Highs will average in the 40s and 50s, well above normal. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... The upper ridge is forecast to re-establish itself over the eastern U.S. early in the period, as a very complex storm system gathers over the southern Rockies by Saturday evening. This southern stream low is tracked through the southern states before turning northeast over the eastern US early next week. Meanwhile the models build high pressure over eastern Canada and gradually ooze colder air south into the NERN US. By late Monday into Tuesday morning, the parent upper low is made to track into the Mid Atlantic states. The deterministic GFS has the southernmost track, through eastern NC then up just off the coast. The GEFS has a slightly more northern track through VA. The ECMWF and its ensemble partner are more north taking the storm up through eastern PA. The ECMWF tracks its sub 990mb surface low through the Del Marva up along the NJ coast is what we look for as a "sweet spot" for snowstorms locally. Temperatures are marginally cold so it`s still questionable what the precip type will be. But it`s the most interesting pattern we have seen this winter for the snow-birds among us. After our early week storm system, the eastern ridge is made to make a rapid rebound, even if for just a short time around midweek. A fast moving shortwave quickly chews the top off the ridge we are made to evolve into a cyclonic westerly flow by week`s end. It will turn cooler, but not especially so as there really is no truly cold air over North America at the current time. && .AVIATION /10Z FRIDAY THROUGH TUESDAY/...
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09Z TAF updates sent. Band of rain over the Ohio Valley just starting to push into southwestern PA. Have to watch for pockets of freezing rain this morning. Earlier discssion below. Satellite showing a few breaks in the low cloud cover at BFD at 03Z, which has resulted in fog development. GLMP MELD suggests some improvement is possible at BFD after about 07Z, as a southeast breeze develops, causing fog to disperse a bit. However, confidence in significant improvement is low and will continue to forecast IFR/LIFR conditions through dawn at BFD. Elsewhere, VFR conditions currently observed across southern PA at 03Z. However, a calm wind and mclear skies have allowed temps to fall close to the dewpoint late this evening. Thus, feel radiation fog will form over much of central/southern Pa between 04Z-07Z. Can`t rule out a brief dip to IFR visibility before thickening mid and high clouds arrive late tonight, diminishing the fog threat. Based on latest SREF and downscaled NAM, believe IPT stands the best chance of significant vis reductions overnight. An approaching warm front will bring a period of rain and low CIGs to the entire region on Friday. Based on current model data, arrival time of rain should range from 12Z-13Z at JST to 17Z-18Z at IPT. The rest of central PA should see rain/low CIGs develop in between those times. The steady rain will exit the area between 20Z-00Z. However, low clouds/drizzle are expected to linger into the evening over most of central PA. Outlook... Sat...Low CIGs likely, mainly in the morning. Sun...IFR/MVFR CIGs likely. Rain advances fm S-N. Mon...Rain/low CIGs likely with snow possible central Mtns. Tue...AM rain/snow and low CIGs possible.
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&& .CTP WATCHES/WARNINGS/ADVISORIES...
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Freezing Rain Advisory until 10 AM EST this morning for PAZ017>019-024>028-033>036-056-063>065.
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&& $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...La Corte LONG TERM...La Corte AVIATION...Fitzgerald/Martin

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