Area Forecast Discussion
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000 FXUS61 KPBZ 211120 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 720 AM EDT Fri Jul 21 2017 .SYNOPSIS... Relatively quiet today, a shower or storm is possible over the southern half of the area. More activity expected this weekend, perhaps with more strong storms and heavy rain Saturday and Saturday night. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Quick morning update to adjust early morning PoPs based on the latest radar observations and trends as convection has diminished, for now. Otherwise, forecast remains as is this afternoon. Previous... Will keep low chance to slight chance PoPs across the southern counties today, as whatever is left of Thursday`s weak boundary gets hung up over Central West Virginia. A weak upper level wave is expected to dive southward toward the boundary this afternoon. Very warm temperatures aloft will provide a cap, thus the low chance PoPs. Rest of the area looks warm, muggy and dry.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/... Model differences arise again this weekend with the timing and strength of a shortwave that will dive through the region in the northwest flow aloft. For now will lean away from the very energetic NAM solution for Saturday/Saturday night. Because of these large differences in the models, have low confidence at this point for most of the weekend. The next major shortwave trough is expected to bring showers and storms to the area sometime on Saturday and continue into Saturday night. In addition to the upper level wave, a surface cold front will drift through the area Saturday night. By favoring a solution closer to the GFS, have slowed likely PoPs on Saturday, focusing them more toward the afternoon hours. There will be many factors at play on Saturday, which will determine the strength of the convection. Amount of sunshine, very warm air aloft, timing of wave, timing of surface front and the possibility of surface reflection developing along the front which will impact the speed at which the boundary moves through. Hopefully, a model consensus will develop over the next few runs. Differences continue into Sunday, as does the low confidence in the forecast. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... A general Great Lakes/northeast U.S. trough will be carved out by Monday, with this pattern holding into mid-week. Temperatures will fall back to near or just below normal during this period. After lingering showers, Tuesday and Wednesday appear dry with high pressure settling over the region. A return to northwest flow may herald increasing rain chances Thursday. && .AVIATION /11Z FRIDAY THROUGH TUESDAY/...
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After patchy fog clears mid-morning...VFR conditions expected through the day. Slight chance of shra/tsra at southern locations but not enough confidence in coverage for inclusion in the TAF at this time. .OUTLOOK... Additional rounds of storms are expected through the weekend, and morning fog is possible as well.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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