Area Forecast Discussion
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000 FXUS61 KPBZ 092003 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 256 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 /THROUGH TONIGHT/...
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Shortwave will pivot over the forecast area tonight but the overall strength of the system will weaken considerably with the jet core downstream the longwave axis and left entrance region over the forecast area. With weak dynamics for lift and relatively dry moisture profiles in the dendritic growth zone...only see potential for a short period of light snow in most locations as the trough passes. Most of the forecast area will see minimal accumulation (trace to 1"). Localized areas of up to 2" are possible north of I-80 with higher, but still sub-advisory amounts on the higher elevations where ensuing upslope flow will support prolonged accumulation potential before the inversion falls. A small handful of the typical spots in the ridges where snow development is highly favored may see accumulations >3".
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY/...
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Sunday afternoon and early evening are expected to remain dry, but another weak short wave is projected to cross overnight. Model consensus shows limited moisture to work with 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.
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&& .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
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Conditions for a continuing lake and elevation enhanced snow showers is expected to continue through Wednesday until boundary layer flow backs to the west and southwest on Wednesday night. As unidirectional flow and a deep cold mixing layer are still expected to prolong accumulating snow potential on Wednesday, no changes were 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.
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&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/...
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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.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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