Area Forecast Discussion
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000 FXUS61 KPBZ 211942 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 342 PM EDT Sun May 21 2017 .SYNOPSIS... Periods of rain and some thunderstorms will continue until the passage of the cold front overnight. Rain chances will return Tuesday with the approach of mid-atlantic low pressure. && .NEAR TERM /THROUGH TONIGHT/...
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Area of rain, associated with a shortwave ahead of the cold front, will slowly move across the region through the afternoon. Enhancement along the lifting surface warm front will support heavier rain and a few embedded thunderstorms as is already indicated by radar and progged by hi-res/mesoscale guidance. Modest instability and 30kts of shear in the low levels may support a few strong storms, especially in closer proximity to the cold front this eve over Ohio but the more potent cells crossing the warm front may also need to be watched, since directional shear is greatest there. Will continue to carry categorical PoPs for this first swath of precipitation but carry likelies through tonight until the cold front passes. High PWAT values will support some efficient rainfall but up to this point, very little training has occurred. Thus, generally think water issues will be localized. Front should be approaching the ridges by Monday morning, with showers ending everywhere by midday. With expected cloud cover and precipitation, temperatures both today and tonight should be just around or slightly above seasonal averages.
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&& .SHORT TERM /MONDAY THROUGH WEDNESDAY/...
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Conditions should improve by Monday afternoon under building high pressure and last through at least the start of Tuesday. The models continue to differ on the evolution of low pressure moving across the Tennessee valley on Tuesday. At this time, have opted to bump PoPs up based on some of the newer guidance and ensembles, as now the GFS seems to be the outlier. Departure of this low will be quickly followed by yet another system, again, which is being resolved a little differently between deterministic models. Opted to stay close to a model blend for midweek based on the uncertainty. Temperatures are expected to be near seasonal averages through the period.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
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Upper trough and embedded shortwaves will start to shift eastward toward the end of the week, but it`s influence should maintain at least low chances for precipitation through the period based on model consensus. Temperatures will generally stay just below seasonal averages through the start of the weekend.
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&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/...
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Area of rain and embedded thunder will continue to move across the upper Ohio Valley, bringing temporary MVFR and IFR restrictions as heavier showers pass over a terminal. Some improvement in cigs is expected before the cold front approaches tonight. Coverage of showers and thunderstorms should increase from what is currently being observed across western Ohio. Expect deterioration in conditions where a thunderstorm passes, with IFR conditions again possible. Improvement is expected later tonight (west)and Monday morning (east) as winds shift westerly and skies quickly clear. .Outlook... The next chance for widespread restrictions and precipitation is expected Wednesday night into Thursday.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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