Area Forecast Discussion
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000 FXUS61 KPBZ 162007 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 307 PM EST Sat Dec 16 2017 .SYNOPSIS... Snow ends north of interstate 80 this evening. The next upper level disturbance approaches Sunday afternoon with increasing rain chances, though some snow may mix in Sunday night. Temperatures will moderate to above seasonal averages through the beginning of the week. && .NEAR TERM /THROUGH SUNDAY/... Area of convergence along a lifting boundary continues to support some light snow north of I-80. Expect this to move north and dissipate through the rest of the afternoon as high pressure builds to the south. Little additional accumulation is expected. Building ridge will lend to a quiet night tonight. Warmth aloft should hold temperatures up slightly, given mostly clear skies and light wind - though it doesn`t appear we will fully decouple. Stayed close to persistence for lows. Next system will approach Sunday afternoon, though this is all mid-level driven as shortwave lifts across the upper Ohio valley. Light precipitation will spread across the region through the evening but warm advection in advance of the system should support mainly rain. A mix is possible to our north, where temperatures may lag a bit with lingering cloud cover. For now, with consideration to the differences in the model profiles, will continue to mention a rain/snow mix though there may be a brief window for freezing rain. Current thinking is there should be enough daytime heating to warm surfaces and limit this potential. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... Shortwave will depart quickly to the east Sunday night, leaving nearly zonal flow aloft and some uncertainty to boundary placement through the period as additional weak shortwaves pass. With no considerable lift apparent in the guidance but plenty of moisture, expect mostly cloudy conditions and very light precipitation. At this point, profiles are not even well saturated above the boundary layer which suggests little more than drizzle through this time frame. Made only modest adjustments to the PoPs through the short term to reflect some of the newer guidance but generally think chance is appropriate given the likelihood of drizzle versus measurable rain. Despite expected cloud cover, warm advection should lead to temperatures at least near seasonal averages. && .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 /20Z SATURDAY THROUGH THURSDAY/... Near and north of I-80, MVFR ceilings will linger through most of the period as clouds remain locked in. Snow showers may still produce brief MVFR/IFR visibilities until mostly shutting off by 00Z. Ceilings may drop to IFR during the overnight/early hours for a period before lifting by mid-morning once mixing kicks in. Further south, building high pressure will keep conditions VFR through the period. Mid clouds will mostly clear out this afternoon, with scattered clouds at most tonight. Overcast conditions may return by midday Sunday ahead of a weak disturbance, with most light precipitation holding off until after 18Z. .Outlook... Restrictions are possible from Sunday night through Tuesday, as abundant low-level moisture may become trapped underneath an inversion for an extended period. IFR conditions are possible at times. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.