Area Forecast Discussion
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000 FXUS61 KPBZ 132208 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 508 PM EST Wed Dec 13 2017 .SYNOPSIS...
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Rapidly moving low pressure will spread more snow over the region tonight. Winter weather advisories remain in effect for much of the region.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Changes for the eve update were primarily cosmetic and timing- related as the leading swath of light snow has nearly completed passage over the area. The main event is still to come as strong, but rapidly moving low pressure will cross the region tonight, with snow resuming following an early eve break. Advisory level snow (2-5 inches) is still projected north of the low center, which is progged to cross ZZV as per rapidly falling surface pressure on the obs. The late afternoon update included the addition of counties in a layer through the major Interstate junctions, where impact of a couple inches may be higher, especially during the evening, and early morning rush hours. Previous... Stratiform snow will transition to snow showers behind the departing surface low late tonight, and this is when the accumulation focus will shift toward the ridges as low level flow goes northwest. Much of the ridge accumulation will occur after 06Z, with activity scattering out fairly rapidly after sunrise as mixing layers collapse. Keeping a 2-4 inch range in the ridges. Wind gusts on the higher ridges bear watching, as instability could partially mix down 40-50 knot winds just off the surface in tight isobar packing behind the low.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... Flow will have backed a bit towards the west and southwest by Thursday evening, and as such expect virtually all of the snow shower activity to shut off by that time. Dry weather will continue through at least Friday morning with high pressure zipping by to the south. A weak shortwave will cross into the eastern Great Lakes Friday afternoon and track north of the region Friday night. Snow shower activity from this will commence Friday afternoon and linger into Saturday morning. The lack of a good moisture feed and overall weak forcing point to fairly light snow amounts, although an inch or two will be possible north of Pittsburgh over the period. Activity ends by evening. Temperatures remain below normal, but will start to moderate Saturday as 500 mb heights start to rise. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Flow goes zonal over our area by Sunday as our trough lifts out and energy digs into the southwest U.S. This will result in continued temperature moderation towards more seasonal levels. The next system arrives on Sunday and will be mainly a rain producer from the southern branch of the jet stream. The pattern could remain unsettle thereafter with weak waves in the west- southwest flow aloft, with perhaps another cooldown by the middle of next week. && .AVIATION /22Z WEDNESDAY THROUGH MONDAY/...
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Expect further condition deterioration overnight to IFR as fast moving low pressure spreads snow over the area. Conditions will improve rapidly on Thursday although MVFR stratocu are expected to persist into the afternoon as cold northwest upslopes off the lakes. .Outlook... Next chance for restrictions is Friday into Saturday.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...Winter Weather Advisory until 10 AM EST Thursday for MDZ001. OH...Winter Weather Advisory until 7 AM EST Thursday for OHZ039>041- 049-050. PA...Winter Weather Advisory until 7 AM EST Thursday for PAZ007>009- 013>016-020>023-029-031-073>075. Winter Weather Advisory until 10 AM EST Thursday for PAZ076. WV...Winter Weather Advisory until 7 AM EST Thursday for WVZ001>003- 509-510. Winter Weather Advisory until 10 AM EST Thursday for WVZ511>514.
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&& $$

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