Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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605 FXUS61 KPBZ 161742 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 142 PM EDT Fri Apr 16 2021 .SYNOPSIS... Scattered showers will end this evening. Weak upper level disturbances will provide spotty opportunities for light rain this weekend, and temperatures will remain below normal. && .NEAR TERM /THROUGH TONIGHT/... Upper level low pressure is currently situated near the southern New England coast. It will slowly drift eastward tonight, leading to a slow rise in 500mb heights for our area. Shower coverage will slowly taper off as moisture becomes more shallow and as subsidence increases from approaching weak high pressure. Some clearing will also work into the region, especially portions of eastern Ohio and northern West Virginia. With at least partial clearing, lighter wind, and below normal temperature, frost concerns are present with the start of the growing season. Think that there is some potential for patchy frost in eastern Ohio, as going a bit below NBM temperatures seems justified, with some areas dropping to 35/36 and the potential for clearing. However, the approach of high clouds towards morning lends some uncertainty, as well as the potential for at least a fewer low clouds to persist through the night. Will keep patchy frost in the grids and mention in HWO, but will hold off on advisory issuance for now. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Flattening ridging and weak surface high pressure cross on Saturday, which should keep the daytime dry for much of the area. However, a very weak 500mb wave will cross in the vicinity of the Mason-Dixon Line during the day. Combined with lingering low-level moisture, just enough lift may be realized for some spotty light rain south of Pittsburgh. Otherwise, continued northwest flow and low-level moisture underneath an inversion will continue to support clouds in the area. Temperatures will moderate but remain some 5 degrees below normal. The next mid-level shortwave will be a bit stronger, but remain generally south of the region as it crosses the lower Ohio Valley and the southern Appalachians Sunday/Sunday night. Again, any rain will be spotty and light. Temperatures will continue to creep upward in weak temperature advection, but remain just below normal. && .LONG TERM /MONDAY THROUGH THURSDAY/... As the shortwave crosses the southern Appalachians, 500mb ridging will arrive in the upper Ohio Valley in its wake. This will provide dry weather and seasonable temperature for Monday and Monday night. A deeper trough will be carved out over the Upper Midwest on Tuesday, the advance of which will push a frontal boundary across the region by Wednesday. Some timing differences exist among the various models, but there seems to be agreement on the fact that moisture will be fairly limited (PWAT below an inch), and so rain will remain relatively light. The Wednesday temperature forecast in particular could be greatly impacted by the eventual timing. Once the front moves east, drier weather and below-normal temperature will take hold for the remainder of the work week. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... Scattered showers remain a concern through the afternoon due to the days heating. Expect these to dissipate. However, moisture flow off the lake, upslope due to the terrain, and weak lift from a remnant trough will keep cloud cover over the area through much of the TAF period/ Locations such as ZZv and MGW to the south and west will break into VFR conditions earlier whereas FKL and DUJ will remain in IFR and below longer. Gusty W-NW winds from 15-20 kts will persist through this afternoon before lessening this evening. .Outlook... Restrictions are likely thru Fri night as the upr low slowly exits. Restrictions are psbl again Sat night thru Mon with a crossing trough. && .PBZ WATCHES/WARNINGS/ADVISORIES... PA...None. OH...None. WV...None. && $$

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