Area Forecast Discussion
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000 FXUS61 KPBZ 092200 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 500 PM EST Sat Dec 9 2017 .SYNOPSIS... Cold weather continues. Most locations will see a period of light snow tonight, early Monday morning, and again on Tuesday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... An early eve update was issued with minor adjustments to hourly trends. The overall forecast remains on track as a shortwave will pivot over the forecast area tonight. Differential vorticity advection/resulting ascent and already sparse mid level moisture are apparently fading and mid level frontogenesis issues will not be a problem given the position of the extensive jet over the Eastern CONUS. The bottom line is that most of the forecast area will see minimal accumulation (trace to 1") as this system is pulled northeastward tonight. Localized areas of up to 2" are possible north of I-80 as are higher, but still sub-advisory amounts on the higher elevations where ensuing upslope flow in the wake of the trough will likely support prolonged accumulation potential before the inversion falls. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/... Sunday afternoon and early evening are expected to remain dry, but another weak shortwave is projected to cross overnight. Model consensus shows limited moisture and given the quick passage, expect only very light snow accumulation potential. The persistent longwave trough is forecast to be reinforced on Monday via another shortwave digging toward the axis-base. Snow showers are likely to spread over the Upper Ohio Region as the associated cold front front crosses on Monday night. Deep cold flow on northwesterly wind will upslope off the Lakes and support snow showers through Tuesday. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... Conditions for lake and elevation enhanced snow showers/squalls are expected to continue through Wednesday as unidirectional flow and a deep cold mixing layer develop in the amplified trough. No changes were thus made to the ongoing mention in the Hazardous Weather Outlook. Another shortwave is forecast for a late Thursday approach and early Friday passage. Cold and snow showers chances were thus maintained for that period. Relief is anticipated for next weekend as the advance of a Western CONUS trough flattens flow over the remainder of the country. && .AVIATION /22Z SATURDAY THROUGH THURSDAY/... VFR areawide will gradually diminish west to east with low MVFR or high IFR expected tonight in light snow showers. Upstream observations show low MVFR ceilings with occasional IFR visibilities. Will continue to carry the MVFR ceilings and monitor the visibilities as the snow moves in. Ceiling restrictions are then expected to linger through early Sunday morning before improvement is achieved by midday. A SW to W wind shift is expected overnight, with wind gusts picking up to 20kts due to steepening lapse rates in cold advection. .Outlook... Scattered restrictions in light snow are expect Sunday night into Monday. The next chance for widespread restrictions will come with low pressure progged for Monday night/Tuesday. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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