Area Forecast Discussion
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000 FXUS61 KPBZ 122233 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 533 PM EST Tue Dec 12 2017 .SYNOPSIS... Sharply colder temperatures and bitterly cold wind chills expected through Wednesday. A few lake-effect snow bands will bring localized accumulating snow, with a more widespread snow event expected to bring several inches to the region Wednesday afternoon into Wednesday night. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Light, but numerous convective snow showers continue to dust the area, with a more singular thin band extending from Cleveland to Moon Township/Pittsburgh with traces back to Lake Michigan. Overall, the threat of accumulating snow through tonight has largely diminished as temperatures are now in the teens with dewpoints already in the single digits limiting the extent of deep moisture. Overnight, hi-res convective models vary on the degree to which additional lake-effect bands will form. With these fast moving clippers, flow trajectories are not stagnant to develop persistent bands across the narrow lake fetch given the overall wind direction. Let the lake- effect snow warning ride up north for now, given some of the convective allowing output, but really think that a couple inches across the rural north will be more common than an isolated 4-6" additional amount beyond what`s fallen. Outside of these extremely narrow snow bands, the main headline overnight will be with bitterly cold wind chills. Arctic air continues to spill southward with temps bottoming out overnight in the low to mid teens, which should push wind chills down in the 0 to -5 degree range most areas (colder WV mountains). && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/... After a brief break tomorrow morning, strong WAA aloft will quickly overspread the area during the afternoon ahead of another clipper - this one a bit further south than its predecessor with a progged surface low track along I-70. Areas along and north of the surface low should see a steady light to moderate snow beginning Wed afternoon and continuing overnight. Despite the Canadian origins of this wave, substantial large scale isentropic ascent and sufficient Pacific moisture should yield a widespread 2-4" snow event for the affected areas. Will almost certainly need a winter weather advisory headline, but after collaboration did not want to confuse the ongoing headlines with the second event, so have held off for now. Winds will once again become quite gusty across the Laurel Highlands into the WV/MD mountains late Wednesday night as classic post-frontal isobar stacking occurs west of the mountains. Could see gusts again over the 30 mph for a several hour window around 12Z Thursday. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Brief cold advection follows behind the departure of Wednesday night/Thursday`s system. This will be short-lived, however, as a general retrogression of the upper trough toward the high plains seems in store for next weekend. This will result in more normal temperatures returning to the region, but with the threat of a southern jet branch storm that should bring primarily rain across the area on Sunday. && .AVIATION /22Z TUESDAY THROUGH SUNDAY/...
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Periods of moderate snow will result in intermittent IFR conditions along a relatively narrow band of snow impacting BVI-PIT-AGC-LBE. General MVFR with scattered show showers elsewhere. General MVFR conditions with scattered light snow IFR expected during periods of moderate snow...mainly along a relatively narrow band of snow impacting BVI-PIT-AGC-LBE Expect some improvement later today outside of the terminals impacted by lake-enhanced snow but general MVFR should prevail. Flow will swing to the wnw with gusts to near 30kts. .Outlook... Periodic restrictions in snow showers and northwest flow will continue through Wednesday. Another system will bring more snow and restrictions to many of the terminals Thursday.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...Winter Weather Advisory until 7 AM EST Wednesday for MDZ001. Wind Chill Advisory until 1 PM EST Wednesday for MDZ001. OH...None. PA...Winter Weather Advisory until 1 PM EST Wednesday for PAZ007- 016. Lake Effect Snow Warning until 1 PM EST Wednesday for PAZ008- 009-015. Winter Weather Advisory until 7 AM EST Wednesday for PAZ023- 074-076. WV...Winter Weather Advisory until 7 AM EST Wednesday for WVZ510>514. Wind Chill Advisory until 1 PM EST Wednesday for WVZ512>514.
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