Area Forecast Discussion
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000 FXUS61 KPBZ 261837 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 237 PM EDT Fri May 26 2017 .SYNOPSIS... Rain chances return tonight, continuing at times through the holiday weekend with another area of low pressure. && .NEAR TERM /THROUGH SATURDAY/...
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The last few sprinkles/light rain showers will dissipate over the next few hours as flat ridging builds in for the late afternoon/evening hours with a brief dry interlude. Models agree on bringing what will likely be an MCS into the CWA overnight along/ahead of a warm front, although the exact track is disagreed on. Favoring a more southerly track as depicted by the HRRR into the richer instability pool, which is supported by CAMs as well. Have thus upped to likely PoPs from PIT on south. Most of the severe threat from this MCS should be suppressed to the south as well, although damaging wind gusts cannot be totally ruled out in southeast Ohio given a short period of strong mid-level flow. The complex should weaken overnight as it crosses, ending as mainly stratiform rain across the southeast CWA by sunrise. Rainfall amounts should remain under control, although isolated locations could receive heavy rainfall, particularly along a line from Zanesville to Morgantown. The passage of the MCS should help to push the front back south towards southern WV/central KY during the day Saturday. This will keep much of the daytime convection, especially that of severe strength, out of the CWA. The track of the MCS and any boundaries it leaves behind will help to determine favorable convective zones. For now, will still allow for some scattered activity during the afternoon, but the better CAPE and shear profiles will lie towards central and southern WV. There may be sufficient instability for a few strong to borderline severe storms south of Pittsburgh, hence the day 2 SPC marginal risk in this area, but the threat is not high. Temperatures will not stray too far from seasonal levels tonight and tomorrow.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
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Saturday evening should be fairly quiet as any convection wanes. Moisture will be on the increase once again overnight, however. A shortwave crossing the upper Midwest and Great Lakes through Sunday will help to push the boundary back north as a warm front, to be followed by a cold frontal passage late Sunday or Sunday night. Deepening moisture and a period of isentropic lift will justify likely PoPs with the system, with enough instability for thunderstorms as well, although likely too low for a severe concern. Behind the front, a few showers may linger into Memorial Day, although the day may well end up mostly dry for a good portion of the area. Temperatures generally will remain near or just above climatology.
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&& .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
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Broad upper troughing will develop behind the Sunday cold front, with that pattern lingering through most of next week. Shortwaves rotating through the trough will provide occasional chances for mainly scattered showers. Temperatures will generally remain near or just below normal values.
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... As of 17Z, ZZV and MGW had VFR ceilings, and ceilings should trend upward into VFR levels slowly from south to north through the rest of the afternoon. Little more than drizzle is expected through the afternoon as well. Low pressure and an area of showers and thunderstorms currently over Iowa and Illinois will track east this afternoon/evening and should hold together into the forecast area. There is still some uncertainty as to the track by the time the low pressure system arrives, but the current forecast keeps the highest chance of thunderstorms to ZZV/HLG/MGW between midnight and sunrise. Once low pressure passes, some showers may continue, but the greater flight impact will come from IFR ceilings that will develop. IFR should persist through the morning, with ceilings eventually lifting to VFR during the afternoon. .Outlook... Showers continue through much of the period with episodic restrictions. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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