Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 020823 AFDCTP Area Forecast Discussion National Weather Service State College PA 323 AM EST Fri Dec 2 2016 .SYNOPSIS... A large and deep storm system will move slowly through Quebec over the next couple of days keeping a prolonged period of cool northwest flow over the local area. High pressure will build in for a brief time Sunday before the next frontal system approaches early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Temps expected to go almost nowhere until mid morning as extensive cloud cover, neutral temp advection, and good mixing in lower layer of atmosphere keeps things static. With the temps at or above freezing everywhere, the light and quick-moving precip across the north is likely to not stick much through morning. The little heating we do get today and the downslope flow will be enough to push the temps in the SE into the m40s. However, the NW half of the area will stay below 40F. Most likely precip type is snow/snow grains/snow pellets judging by the cloud and sub-cloud temp profile. Despite light precip falling for much of the day in the NW third of the CWA the surface temps should allow for little if any accums through the daylight. Have continued with a bare mention of snow accums in the NW. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... The stacked low pressure over Quebec gradually moves into the Canadian Maritimes. The flow off the lakes will be highly persistent with lake effect precip expected to last into Sat Night. A weak/subtle feature will slide across the lower lakes this evening/early tonight, and could briefly enhance the snow rates and push snow bands into the central mountains. Tonight is the most likely time for any kind of accums to occur. However, only about half of the area goes below freezing. The wind does not slacken and the clouds will be pesky. Thus, the temps will not get more than 6 to 10F colder than daytime temps. Saturday looks like much of the same. Second verse same as the first. Have inched the temps up a little higher than guidance in the SE where the downslope could help them out. Still, these numbers are within a few degs of normals for the first part of Dec. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Sunday brings a brief respite as high pressure moves over the state. Sunday evening and night, a period of light snow is looking likely as a northern stream shortwave races through the region with a burst of warm advection. QPF looks to be on the order of a tenth of an inch or less, but occurring overnight many places could see their first coating of snow of the young season by Mon morning. Snow is more likely in the NW than SE. Another ridge moves through on Monday as progressive weather pattern becomes more active. On Tues there is decent agreement in bringing the SW US upper low up through the Ohio Valley as a shearing out shortwave and diffuse surface low. Unless cold air damming traps enough chilly air in the low levels to make for some freezing rain, the precip type with this midwest system looks to be mainly rain. The end of the week brings some model disagreement with the GFS/GEFS being faster than the ECMWF with the next large upper trof and frontal system. Either way, precip looks like a good bet around the Thu/fri period as all solutions eventually bring this trough through. So predictability is increasing, but timing issues remain. Best bet for precip at this point is mainly rain over the SE as decent push of warm air lifts ahead of the system, with a rain/snow mix further north where warm air will not infiltrate as much. Behind the trough, looks like a chilly weekend in store with a potential sharp dropoff in temps. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... Early AM satellite loop shows stratocu covering most of Central Pa associated with slow moving low pressure over Southern Quebec. 07Z radar is showing lake effect snow showers affecting Northwest Pa, where KBFD is experiencing IFR conditions. Latest GLMP MELD supports predominantly IFR conditions at KBFD for the balance of the morning. Elsewhere, model soundings indicate falling CIGs this morning, as a slight wind shift from WSW to WNW causes moisture from the Great Lakes to spread south. GLMP MELD suggests IFR CIGs and snow showers are possible later this morning at KJST. Downsloping flow east of the mountains should result in progressively better conditions further east, with tempo MVFR possible at KAOO/KUNV and VFR at KIPT/KMDT/KLNS. Weak diurnal heating/mixing should result in a modest increase in CIGS by this afternoon, likely resulting in CIGS between 1-2KFT at KBFD/KJST and VFR elsewhere. However, passing snow showers will still occasionally drop vsbys below 3SM at KBFD/KJST through evening. The entire region will continue to see breezy conditions last through the next 24 hours. Clearing skies have resulted in lighter winds at KMDT/KLNS early this morning. However, Bukfit soundings support winds between 10-20kts across the entire region later today and evening, with occasional gusts near 25kts. Outlook... Sat...SHSN with ocnl IFR vsby at KBFD/KJST, mainly in the morning. Sun...Light snow/reduced vis possible at night, mainly NW Mtns. Mon...No sig wx expected. Tue...Mixed precip/low CIGs possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Dangelo/Gartner NEAR TERM...Dangelo SHORT TERM...Dangelo LONG TERM...La Corte/RXR AVIATION...Fitzgerald

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