Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 021653 AFDCTP Area Forecast Discussion National Weather Service State College PA 1153 AM EST Fri Dec 2 2016 .SYNOPSIS...
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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 and a gusty wind over the local area. High pressure will build in for a brief time Sunday before the next frontal system approaches early next week.
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&& .NEAR TERM /UNTIL 7 PM THIS EVENING/...
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Shallow and relatively warm strato cu deck will support little in the way of precip across most of the northern and western mtns of the state this afternoon and evening as the mean llvl flow will remain westerly with little tap of significant moisture off the upper Great Lakes. Significant breaks in the cloud deck will occur across the Middle and Lower Susq valley at times. The Central Ridge and Valley Region will be in between with bkn-ovc high-based strato cu this afternoon and evening with nothing more than a sprinkle or flurry. With the temps mainly in the mid 30s this afternoon across the NW mtns where frequent snow showers will occur, expect to see less than an inch or snow accumulation, which will be confined to grassy areas for the rest of the daulight hours. Elsewhere over Central and Southeastern parts of the Forecast Area, high temps will be in the low-mid 40s. Some locations to the east of I-83 and south of I-81 could reach 50F during the early to mid afternoon.
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&& .SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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The stacked low pressure over Quebec gradually moves into the Canadian Maritimes. The mean boundary layer flow off the Great Lakes will be persistent with lake effect precip expected to spread a little more inland (developing south across the Laurel Highlands) and 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 in fact, could increase by 5-10 kts in the sustained and gust department) thanks to the axis and left rear, thermally direct descending branch of a strong 150-160 kt upper jet lifting north from the Central Appalachians. Clouds will be pesky and lionger across much of the CWA tonight through Saturday. Therefore, the overnight min 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.
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&& .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 /18Z FRIDAY THROUGH WEDNESDAY/...
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Late morning satellite loop continues to show stratocu covering most of Central Pa associated with slow moving low pressure over Southern Quebec. Cold air flowing over Lk Erie is producing lake effect snow showers across Northwest Pa. Will stick with persistence at KBFD/KJST this morning and forecast predominantly MVFR conditions. However, still believe ocnl dips to IFR are likely with passing snow showers at KBFD as the latest GLMP MELD indicates. Downsloping flow east of the mountains should result in progressively better conditions further east, with tempo MVFR possible this morning 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 could 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. Bukfit soundings support winds between 10-20kts across the entire region today and tonight, with occasional gusts around 25kts (especially late tonight and early Saturday). 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.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/Gartner NEAR TERM...Dangelo/Lambert SHORT TERM...Dangelo/Lambert LONG TERM...La Corte/RXR AVIATION...Fitzgerald

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