Area Forecast Discussion
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000 FXUS61 KPBZ 211821 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 121 PM EST Tue Feb 21 2017 .SYNOPSIS... A weak system will pass the region late today with a chance of some showers, however warm conditions will continue through the week. && .NEAR TERM /THROUGH TONIGHT/... Continued with little change to the overall forecast for now. Band of prefrontal rain extending from Michigan into Indiana/Illinois is shrinking with time. This is not surprising given the waning support for lift from the shearing shortwave crossing the Great Lakes. Have continued with slight chance PoPs for the afternoon/evening, but may increase if rain shows more vigor later. Dry mid-level air noted on 12Z PBZ sounding is mixing down and lowering surface dewpoints, and so have decreased those in the grids through the afternoon. Temperatures on track for the most part and only made minor tweaks there. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... Nearly zonal/flat ridging will support fast moving shortwaves through the flow through Thursday. While most of the support for any precipitation should remain well north of the region, increasing moisture in w-sw flow may lead to widely scattered showers until the more amplified low pressure system ejects into the Plains and lifts a warm front across the upper Ohio Valley. Generally kept chance PoPs through the period based on the uncertainty in guidance and lack of deep moisture and lift. With little modification in 850hpa temperatures, expect values to remain 20+ degrees above seasonal averages. It still looks like one our warmest days this week will be Friday, as most ensemble guidance has over 70 degrees here at Pittsburgh. The only thing that could hamper this would be cloud cover and any shower coverage. && .LONG TERM /FRIDAY THROUGH TUESDAY/...
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Warm front will lift north of the area Friday increasing southerly flow into the area. 12Z GFS continues the trend of slowing down the progression of the strong cold front late Friday into early Saturday. Delayed timing should allow for enhanced clearing in the warm sector, and as a result, temperatures will soar. Have kept with the trend of bumping up Friday`s highs, although not quite to the MEX numbers. Will continue with likely PoPs for this boundary, with a chance for thunder, though the overnight passage may be a bit of a limiting factor. Temperatures should return to near normal values, with snow showers as the system departs. Very broad troughing is then expected through early next week, with another system progged for passage in the deterministic guidance.
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&& .AVIATION /18Z TUESDAY THROUGH SUNDAY/...
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VFR conditions expected to persist through the evening with high clouds on the increase. A low pressure system well north of the area will bring a weak cold front tonight. This boundary will result in little more than a few showers, but will lead to an increase in low-level moisture. This will manifest in lowering CIGs down to MVFR for most locations by Wednesday morning. A few locations (FKL/ZZV) could see brief spells of IFR as well. Any lingering restrictions mid Wednesday morning will see gradual improvement through the early afternoon. .OUTLOOK... Restrictions are likely with a Friday night/early Saturday cold front.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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