Area Forecast Discussion
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000 FXUS61 KPBZ 150218 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 918 PM EST Thu Dec 14 2017 .SYNOPSIS... Cold conditions will give way to temperature moderation after Friday and early Saturday snow showers. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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The late eve update featured adjustments to hourly trends of clouds and temperature as high cloudiness is already increasing on the van of a shortwave trough digging over the Northern Lakes. Overnight lows were forecast about a dozen degrees under the averages.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
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That Great Lakes shortwave trough will approach the Upper Ohio Valley Region late in the day. Persistent clouds and an increasing chance for snow showers can be expected amid increasing low-level instability and weak synoptic lift. If any instability can be realized, the convective thermal profile is favorable for efficient snow production, although mixing layer wind would have to better align for sustained accumulation. So, although QPF is low, snow ratios might be quite high and could lead to non- trivial snow accumulation, especially in north of the I-80 corridor. Snow chances will peak Fri evening and begin to wane late Fri night as nwly flow resumes and the upper shortwave trough exits ewd. Any lingering showers will translate nwd as wind backs to wswly.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Residual snow showers may linger into Sat, but will decrease in coverage as warmer air invades the region and heights rise. Flow will become zonal by Sun in the Great Lakes region as a shortwave trough strengthens in the swrn CONUS. Ahead of this system, warm-air advection will help restore temperature to near-seasonal values during the weekend and into next week. An impulse ejected from the trough in the swrn CONUS may bring light rain to the region on Sun afternoon-evening, but it will be a decaying system by the time it approaches the Great Lakes. A better chance for precipitation comes mid-week as the swrn CONUS trough phases into a nrn stream disturbance and drives a cold front through the region. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... General VFR is anticipated overnight despite lingering high- based stratocu. A drop back to MVFR is possible during the day Friday as the next disturbance approaches. Snow is expected at FKL and possibly at DUJ Friday afternoon with visibility restrictions. .Outlook... Next chance for restrictions is late Friday into Saturday. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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