Area Forecast Discussion
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833 FXUS61 KPBZ 091649 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1149 AM EST Fri Dec 9 2016 .SYNOPSIS... Occasional snow showers will continue through tonight, especially north of Pittsburgh, and will taper off on Saturday. Accumulating snow is expected for much of the region on Sunday. && .NEAR TERM /THROUGH TONIGHT/...
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flow continue to be west to northwest coming off the lakes this afternoon, but an approaching shortwave tonight will again turn the flow more west to southwest, diminishing lake enhanced snow showers. There will be a bit of an uptick in snow showers with the shortwave overnight. Have only raised snow amounts about a half inch across portions of Mercer and Venango counties mainly this afternoon and evening. No changes to temperatures, and remainder of forecast is unchanged.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY/... By daybreak Saturday, only the extreme northern edge of the forecast area will remain near the downlake moisture plume. Will linger chance PoPs in this area for now, but little additional accumulation is expected. Surface high pressure will bring dry weather through late Saturday evening, but the next system will already be approaching from the west. A complex system will move into the region by Sunday, stretching into the new work week. Modest isentropic lift along a weak warm front will lead to the onset of snow by daybreak Sunday. Models differ slightly with the placement of this initial band, but the mean of guidance centers the highest PoPs over the northern and western counties. This boundary will be the focus for light to moderate snow through Sunday afternoon, while a system organizes in the Midwest. An amplifying upper-level trough will push the deepening surface low through the southern Great Lakes Sunday night into Monday. As the warm front lifts north, we end up in the warm sector, with strong warm air advection. A non-diurnal temperature trend will bring a change from snow to rain Monday morning, at least for the southern half of the forecast area. Guidance has been inconsistent with the track of the low, subsequent warm air advection and precipitation types. At this time, chose to be a little general with a rain/snow mix Monday morning, until finer details can be hashed out. Regardless, accumulating snow is likely from Sunday afternoon into Monday, primarily north of Pittsburgh. There is also a possibility of pockets of freezing rain in the favorable mountain locations Monday morning, where easterly flow dams up the colder air. Will carry a mention in the HWO for this system. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... Any lingering shower activity behind the cold front Monday night should transition back to snow with falling temperatures. Transient high pressure will briefly lead to drier period into Tuesday. Largely zonal flow will then bring several disturbances through the latter part of next week. With significant guidance differences existing through this time, SuperBlend was relied on heavily. After near normal temperatures Monday, temperatures will drop back below normal through the end of next week. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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Broad upper troughing maintain mainly MVFR conditions through Saturday morning for most ports. Scattered snow showers are also expected through the evening, though the best chance of local IFR conditions should be N of I 80 where some lake enhancement should occur. Gusty W winds should also persist this afternoon with a tight pressure gradient, before diminishing this evening. Conditions should improve to VFR by Saturday afternoon as high pressure briefly builds in. .OUTLOOK... Widespread restrictions are likely Sunday and Monday, and again Wednesday, with crossing areas of low pressure.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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