Area Forecast Discussion
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937 FXUS61 KPBZ 161033 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 533 AM EST Sat Dec 16 2017 .SYNOPSIS... Light snow this morning, mainly north of Pittsburgh. Temperatures will begin to moderate to near seasonal averages this weekend. && .NEAR TERM /THROUGH TONIGHT/... Light snow beginning to move back into the area from the west. This activity is associated with a strengthening low-level jet moving overhead and coincides with noted cooling on GOES-16 Clean IR channel. This snow will slide southeast, over the area but will start to fight warm and dry advection from the southwest. High pressure will begin to nose in from the south midday Saturday, pushing lingering downlake snow showers further north and leading to some level of clearing. That said, will continue to carry likely snow showers north of I-80 through the afternoon where favorable fetch continues. All of this will lead to a sharp gradient in sky and thus temperatures as well. Locations south of I-76 should warm up much warmer than areas further north, which will likely stay in the clouds. Any remaining snow showers will cease and lift north by Saturday evening. With high pressure continuing its northern push, dry weather will carry through Saturday night. Saturday`s low temperatures will remain near seasonal averages. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... High pressure will gradually take over the area Sunday, but the dry weather will be fleeting. Despite brief ridging aloft locally, a wave ejecting out of the southern Plains will ride over the ridge Sunday afternoon bringing light precipitation back to the area. The weakening disturbance will stream southern moisture northward along an axis of modest isentropic ascent. Models still differ on the placement of the main precipitation band Sunday, but more importantly on the boundary layer temperatures and subsequent precipitation types. Will continue to use a blend for the placement of high chance PoPs and will keep p-types fairly broad. Regardless of precipitation type, this system looks to have relative minor impact on the forecast area. The weak wave will depart quickly to the east Sunday night, leaving a period of mostly zonal flow aloft. Monday and Tuesday`s precipitation forecast appear a bit nebulous at this time. With abundant low-level moisture left below a strong mid- level inversion, it looks as if clouds and light precipitation or drizzle could plague the area in the beginning of the week. With a lack of organized ascent, precipitation chances will hinge on weak waves passing through the zonal flow. Will follow the previous forecast and continue to keep PoPs in the neighborhood of climatology. Temperatures will continue to warm to above average values Monday and Tuesday, despite continuous cloud cover expected. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... A broad trough will drop into the central CONUS Tuesday night sweeping a cold front through the area. This could re-invigorate showers Tuesday night into Wednesday, but will help drive temperatures back to near-normal values. Upper-level flow returns to zonal behind the front, bringing a drier and warmer trend until the latter part of the week. Models still have another system/cold front for Friday, but strength and placement of the low have changed with newest guidance. Will hold close to the SuperBlend for precipitation details, and look for clarity in the coming guidance packages. && .AVIATION /10Z SATURDAY THROUGH WEDNESDAY/... MVFR this morning as light snow showers can be expected this morning with improvement to VFR in the afternoon...except for FKL/DUJ where IFR cig/vis restrictions are possible and persistent MVFR for much of the day. .Outlook... The next chance for general restrictions arrives by Sunday with an advancing warm front. Model guidance shows good consensus with abundant low level moisture in the warm sector. Based off analogs...ports could see continued restrictions (including IFR and lower at times) through Tuesday. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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