Area Forecast Discussion
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811 FXUS61 KPBZ 160454 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1154 PM EST Fri Dec 15 2017 .SYNOPSIS...
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Snow showers will continue into Saturday, mainly north of Pittsburgh. Temperatures will begin to moderate to near seasonal averages this weekend.
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&& .NEAR TERM /THROUGH SATURDAY NIGHT/...
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Upper-level trough axis is shifting east of the area at this time, per latest Mesoscale Analysis from SPC. This means that the back edge of the accumulating snow showers, currently near the I-70 corridor south of Pittsburgh, will continue to push east early this morning. A lull in widespread snow will then occur for several hours in between two weak disturbances. Scattered showers may continue north of I-80, but it will take until the pre-dawn hours Saturday for the low-level wind to organize such that our northern zones get scraped by a lake effect band. A strengthening low and mid-level jet will move overhead early Saturday, providing some modest support for more widespread snow showers. Still, with warm and dry advection beginning to occur, areas south and west of Pittsburgh will likely remain outside of the snow showers. High pressure will begin to nose in from the south midday Saturday, pushing lingering downlake snow showers further north and leading to some level of clearing. That said, will continue to carry likely snow showers north of I-80 through the afternoon where favorable fetch continues. All of this will lead to a sharp gradient in sky and thus temperatures as well. Locations south of I-76 should warm up much warmer than areas further north, which will likely stay in the clouds. Any remaining snow showers will cease and lift north by Saturday evening. With high pressure continuing its northern push, dry weather will carry through Saturday night. Saturday`s low temperatures will remain near seasonal averages.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY/... High pressure will remain in control through the first half of sunday before precipitation begins to move in with an approaching shortwave. An area of isentropic lift will provide modest ascent as this wave approaches with some question as to precipitation type. At this time it looks, given the time of day, that the bulk of the precip will fall as rain, though some snow may initially mix in over the north. Once this wave departs, it appears we will be rather quiet, though waves passing over the weak upper ridge may bring some chance for rain and snow across the region. At this time kept PoPs rather low, near climo, with temperatures expected to warm to above averages with some adjustments likely depending on the placement of a warm front. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... With no blocking pattern in place, weak ridging will quickly shift east with the approach of another system for the middle of the week. The models are handling precipitation with this system differently so opted to stay a near a blend of guidance with some minor adjustments. Temperatures will remain a few degrees above average until the trough midweek. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... A crossing shortwave/reinforcing cdfnt will bring snow showers and MVFR cig/vis mainly north of PIT tonight. FKL, and to a lesser extent DUJ, have a chance of getting occasional IFR conditions in a couple heavier snow showers. Heaviest snow showers should occur through midnight. After a lull overnight as the disturbance departs, a fresh injection of moisture will bring another round of snow showers and MVFR ceilings. Flight conditions will start to slowly improve from south to north by the end of the TAF period. .Outlook... The next chance for general restrictions arrives by Sunday with an advancing warm front. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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