Area Forecast Discussion
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000 FXUS61 KPBZ 241241 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 841 AM EDT Wed May 24 2017 .SYNOPSIS... Unsettled weather will return for the remainder of the week as an upper-level disturbance moves slowly across the Ohio Valley. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As a deep upper low slowly migrates toward the western Great Lakes today, a couple of weak short waves troughs embedded in southwesterly flow aloft are set to transit the area. This fact combined with a rather haphazard low/mid-level deformation field have allowed for scattered showers to continue to develop across the area early this morning, and it is expected this trend will continue through much of the day. Between these weak waves, however, episodic thinning of the clouds will allow for breaks of sun at times during the day today. More coherent shower activity will start to encroach on the area late in the day as the upper low over the western Great Lakes starts to migrate eastward. Even still, due to abundant layer moisture ahead of this system, clouds will be common through the day with diurnal ranges looking rather subdued as a result. Fries && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... The upper low will gradually first dig into the mid-Mississippi Valley before slowly ejecting toward our area. This will all take through Thursday to occur. As it does so, lapse rates will steadily increase due to mid-level cooling even as boundary layer temperature remain rather subdued due to rain cooling and abundant cloud cover. As such, chances of thunderstorms and showers will remain in the forecast with generally below normal temperatures. By Friday, the upper low will have shifted toward New England with northwesterly flow in control and a bit of drier air working into the region. This will be rather short-lived, however, as the H5 ridge axis looks to shift through the area by Saturday with broad southwesterly flow becoming established. This will allow for more humid and warmer conditions to arrive for the weekend. However, it will also bring in chances of showers and thunderstorms yet again. In fact, some solutions have featured an MCS traversing the region on Saturday. Stay tuned on that. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... The pattern going into next week looks to continue to amplify as an upper low again drops into the Mississippi Valley with a downstream ridge popping up rapidly along the eastern seaboard. Unfortunately for us, we will be stuck between these two areas with broad southwesterly flow remaining in place and thus abundant moisture streaming toward the area. As a result, shower chances will remain with temperatures not too far from normal. && .AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
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VFR conditions are expected to deteriorate through midday as low level moisture increases with a crossing shortwave. Maintained a VCSH mention in the TAF with sct shower coverage expected. Improvement back to VFR is expected by late morning/early afternoon before deterioration back to MVFR in showers late in the day with approaching low pressure. Increasing SE winds are expected today with an increasing pressure gradient, with a few 20-25kt gusts especially for the higher terrain ports. .Outlook... Restrictions are likely through Thu night, and again over the weekend, with low pressure.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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