Area Forecast Discussion
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000 FXUS61 KPBZ 142004 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 304 PM EST Tue Nov 14 2017 .SYNOPSIS...
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High pressure will provide dry weather into Wednesday afternoon. Rain chances return with a late Wednesday cold front, with a few snowflakes possibly mixing in on Thursday. Dry weather returns for Thursday night into Friday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Clouds have been a bit slower to clear than previously thought, as the inversion 3-4kft above the ground keeps a thin layer of moisture trapped. The clouds are starting to become more cellular in many areas though, and still expect slow dissipation to continue through the afternoon into the evening, especially when low level flow turns more easterly. A period of mostly clear sky is expected overnight, but some high clouds may approach towards sunrise along the the mid-level ridge axis. Below- freezing morning lows will fall several degrees below climatology.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
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Wednesday will begin dry with seasonable temperatures, but the next upper trough/cold front combo will approach during the afternoon and cross during the evening hours. Models look a touch slower overall, and carried this thinking into the grids, with most of the precipitation arriving after 21Z. Maintained high likely to categorical PoPs with the passage. Northwest flow showers will linger behind the front through Thursday, ending by Thursday evening with the passage of the 850 mb thermal trough. Precipitation type will be all liquid ahead of and just behind the boundary, with light overall QPF. Snow will mix in later Wednesday night into Thursday as subzero 850 mb temperatures return. With the bulk of the moisture below the dendritic growth layer and with surface temperatures remaining above freezing for the most part, very little accumulation is expected at this time. In fact, precipitation may taper off to drizzle during the latter stages due to the loss of cloud-based ice crystals. This will need to be evaluated in future runs. Temperatures will tumble back below normal.
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&& .LONG TERM /FRIDAY THROUGH TUESDAY/...
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Models still differ on timing the significant frontal passage this weekend. The ECMWF continues to lag the GFS, Canadian, and other models, although this appears to be the WPC preference for now. Given the uncertainty, will continue to rely heavily on SuperBlend until a better consensus emerges. This would bring the bulk of the precipitation in the Friday night/Saturday period, mainly as rain. Strong wind gusts remain possible on Saturday ahead of the front and with the frontal passage, with 850 mb winds of 50-60 knots ahead of the boundary. A changover to snow was included Saturday night as cold air crashes in. An extended period of northwest flow showers will then follow into early next week, although the best coverage will occur on Sunday. Would not be surprised to see headline-worthy accumulation in favored lake-effect areas. Below-normal temperatures will continue through Tuesday, when another wave may skirt the region.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/... Stratocu deck will gradually diminish through the rest of the afternoon, though the cloud deck should generally remain VFR through the period as high pressure slides overhead. Light and variable wind will shift to the south tomorrow afternoon ahead of the next low pressure system. .Outlook... Restrictions are likely with a late Wed cold front, and with subsequent upper troughing and cold NW flow Thu. Restrictions are likely again with a Sat cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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