Area Forecast Discussion
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063 FXUS61 KPBZ 282203 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 603 PM EDT Sun Aug 28 2016 .SYNOPSIS... Thunderstorm chances will continue through the evening as a weak boundary crosses the region. Warm but less humid conditions will be introduced under building high pressure through midweek. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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Thunderstorms have fired along the frontal boundary that is currently sinking south across the area. The storms are tapping into a highly unstable air mass with 3000+ J/kg of CAPE, and inverted-V soundings mean that downbursts are a threat. TPIT terminal doppler radar showed one such storm likely produced strong winds in Columbiana County. Will also need to watch rainfall totals as individual cells are moving slowly, and with high rainfall rates due to anomalously high precipitable water, localized flooding is possible. Little to no activity further south away from the boundary so far, as there is little support for lift. Upped PoPs and adjusted timing in the grids. Extended life of slight chance PoPs a little further into the night as well given boundary and lingering instability. Minor updates otherwise.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... Newest model guidance pushes the aforementioned boundary south of the region by Monday afternoon as reinforcing shortwaves help deepen a trough over the Northeast U.S. through midweek. The surface front may continue to provide focus for diurnally- enhanced convection over the mountains in WV, but building surface high under northwest flow should suppress precip by Tuesday. A second and more notable boundary, as far as temperatures change, will approach on Wednesday. At this time, it appears that instability and moisture will be rather meager with this fronts passage so very low pops were kept, based on a blend of guidance and timing differences through Wednesday. Temperatures should moderate to near normal with northwest flow/cool advection by Wednesday. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Troughing over the eastern CONUS will result in cooler temperatures the remainder of the week before ridging builds back in this weekend. Dry conditions are forecast under dry northwesterly flow and ridging later in the period. && .AVIATION /22Z SUNDAY THROUGH FRIDAY/... Warm air aloft has been capping off convective development thus far, however, weak surface convergence, slightly cooler temperatures aloft, and the passage of a weak wave in the mid and upper levels looks more likely than not enough to trigger convection by late afternoon into early evening. Outflows from early convection should be deep enough to continue initiate storms from northwest to southeast heading into early evening but will diminish as instability lessens. Do to the degree of uncertainty in timing have opted to utilize mention of VCTS in latest TAFs but will update as details emerge through the afternoon. .OUTLOOK /MONDAY THROUGH THURSDAY/... Restrictions are possible Monday mainly S of PIT as the front completes its passage, and again with another crossing front Wednesday. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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