Area Forecast Discussion
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000 FXUS61 KPBZ 211942 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 342 PM EDT Tue Mar 21 2017 .SYNOPSIS...
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A strong cold front will sweep through tonight, bringing much colder temperatures on Wednesday. A return to warmth is expected by late this week, persisting into early next week as rain chances increase.
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&& .NEAR TERM /THROUGH WEDNESDAY NIGHT/...
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An upper jet is evident on satellite as a cirrus plume spreading across northern Ohio and southern Michigan. This jet will spread across the region late this afternoon and evening, driving a cold front across the forecast area. For the remainder of the afternoon, increasing clouds are expected. An invigorated field of low clouds also is expected as the front passes, but little in the way of precipitation is anticipated along the front. In the wake of the front, a brief window for lake moisture- driven snow showers could impact the I-80 corridor, and perhaps the ridges. Any snow showers could drop a dusting of snow, but wind profiles are not favorable for prolonged snow showers, and the rapidly-drying air mass is not favorable for sustained instability. Cold air is not expected to make it to the ridges in time to promote rapid snow growth, so any accumulation there should be trivial if any snow showers occur. Maxima on Wednesday will be about 15-20F below climatologically- normal values as very cold air lingers in the region amid building high pressure. Clear sky, light wind and very-dry air will promote strong radiational cooling Wednesday night, with temps dropping into the mid-teens in many locations.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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The surface high will translate ewd on Thursday as upper ridging strengthens. Generally, a clear sky is expected, limited mainly by any cirrus spilling over the ridge to the west. Thursday night is a meteorological challenge, as cold (sub- freezing) air will linger at the surface as strong warm air advection begins aloft. Given the sely low-level flow, it is quite plausible that low-level warming will lag the arrival of the warm air aloft, leading to the possibility of a light freezing rain/sleet event. At this time, the possibility has been highlighted in the HWO. The warm air aloft will mix rapidly to the surface Friday morning in the warm sector, with temperatures rebounding to near 60F by afternoon.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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A fairly-active, split-stream jet pattern is expected for the remainder of the forecast, with a series of closed lows expected in the swrn CONUS and a progressive northern stream. Moisture spreading ahead of these southern-stream lows will bring a wetter and cloudier (but warmer) period into early next week. Maxima in the 60s and minima in the upper 40s are expected. Precipitation will be driven by the passage of these ejecting lows, the timing of which is not clear at this time. The most-consistent chance of rain /per MEX trends/ looks to be late Sunday afternoon.
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&& .AVIATION /19Z TUESDAY THROUGH SUNDAY/... Diurnal low-VFR cumulus will dissipate shortly before sunset. Gusty northwest winds will develop this evening behind a crossing front, with an additional round of low-VFR clouds. Cannot rule out the possibility of some MVFR cigs at FKL/DUJ. Clouds should dissipate late Wednesday morning along with wind gusts diminishing. Outlook... The next chance for widespread restrictions should come on Friday with a front tracking across the lower Great Lakes. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ Kramar

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