Area Forecast Discussion
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000 FXUS61 KPBZ 160131 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 831 PM EST Fri Dec 15 2017 .SYNOPSIS...
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An upper trough has brought snow showers to the region for tonight and early Saturday. Temperatures will begin to moderate to near seasonal averages this weekend.
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&& .NEAR TERM /THROUGH SATURDAY/...
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No changes were needed for the eve update as snow shower coverage is in decline as expected with passage of the mid level trough axis. Previous... A quick early eve update was issued to adjust snow shower coverage as encroaching shortwave is generating more coverage than previously anticipated, although accumulation is not expected to be problematic. Previous... Upper level shortwave will makes it`s approach this evening, with the bulk of the lift and moisture north of PIT. That being said, a brief period of light snow is anticipated further south as lapse rates steepen into the dendritic layer for a time, but accumulation is generally expected to be light. Snow will continue north of I-80, through at least the first half of Saturday, with a strengthening low-mid level jet providing for some enhancement over the region. This will be where the highest accumulations will reside, though 24 hour values are still expected to be under advisory level thresholds. The aforementioned jet will also support some stronger gusts in the terrain tonight though the window is rather short before the inversion strengthens enough to hold the greatest gusts from mixing down. High pressure will begin to build eastward for the latter half of the day, ending any snow showers as the wind shifts more wsw and drying takes place through the column. Sunshine and weak warm advection should allow us to get closer to seasonal averages, with the exception being the north where cloud cover may linger for much of the day.
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&& .SHORT TERM /SATURDAY NIGHT 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 /02Z 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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