Area Forecast Discussion
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000 FXUS61 KPBZ 100415 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1115 PM EST Fri Dec 9 2016 .SYNOPSIS... Cold northwest flow will continue a few bands of snow showers into Saturday. Low pressure will bring accumulating snow Sunday, mixing with and changing to rain later Sunday night and Monday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Low level flow has turned decidedly southwest, bringing in some drier air in the lower levels. however, flow up toward 850 mb remains stubbornly northwesterly with model indications revealing little trend toward any more westerly or southwesterly component at this level over the next six hours or so. Luckily, this is leaving us with a fair amount of directional shear in the lower levels of the atmosphere, preventing a true dominant band of snow downwind from Lake Erie. However, given that northwesterly flow remains in the most unstable portion of the column which is also co-located with the dendritic growth layer, it seems the current radar depiction over Mercer and Venango Counties will likely linger for several more hours. It seems reasonable thus given snow rates over the past few hours to expect around two more inches of snow in the more decent lake effect bands over northern Mercer and Venango County through the night. The lake effect snow advisory was thus extended until 5 AM. Elsewhere, flurries will be possible as somewhat unstable lapse rates remain even with a much drier column. Fries
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... High pressure will begin to move east Saturday with flow becoming westerly as weak shortwave exits. Temperatures will continue well below average. Complex low pressure will approach Sunday and move across the Great Lakes Monday. Warm advection snow will develop across the region Sunday and continue into Sunday evening, before mixing briefly with freezing rain and then changing to plain rain except for areas north of I-80 where cold air will hang in until mid morning Monday. With surface low so far west, warm air should be able to move north fairly quickly, keeping snow accumulations in check for the most part. Best estimate for now is 4-6 inches north of SR 422 in PA, with only an inch or two across Pittsburgh. Areas south of Pittsburgh will have little in the way of accumulation. Some light icing possible mainly in the ridges for a time Sunday night. Warm advection will push temperatures into the upper 30s to mid 40s Monday before a cold front drops temperatures back toward normal in the afternoon. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Main feature will be an arctic cold front Tuesday night crossing east of the ridges early Wednesday. Temperatures will be 15 to 20 degrees below average through late week. While snow showers will be scattered mainly across the north, no significant snow is expected. && .AVIATION /04Z SATURDAY THROUGH WEDNESDAY/... Broad upper troughing will maintain mainly MVFR conditions for most locations outside of FKL and DUJ where scattered snow showers will result in continued IFR. Improvement 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. && .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...None. OH...None. PA...Lake Effect Snow Advisory until 5 AM EST Saturday FOR PAZ007. WV...None.
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