Area Forecast Discussion
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000 FXUS61 KPBZ 181842 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 242 PM EDT Sun Mar 18 2018 .SYNOPSIS... High pressure will maintain dry weather and seasonal temperature into Monday. Low pressure then is likely to bring a wintry precipitation mix to the region Monday night and Tuesday. && .NEAR TERM /THROUGH TONIGHT/... A few high clouds are possible tonight as high pressure moves ewd and flow aloft becomes more zonal. Given the lack of clouds and expected light wind, radiational cooling will support a rapid drop in temp post-sunset. && .SHORT TERM /MONDAY THROUGH TUESDAY/... A generally-sunny morning will be supplanted by increasing clouds through the day as low pressure from the Plains crosses srn IL/IN. The response to the approaching sfc reflection of this wave will be nely sfc wind and attendant reinforcement of a cold sfc airmass. Models remain in general agreement on a swd focus for precipitation Mon night and Tue, echoing the earlier swd deviation noted by the previous forecast. The reasoning noted by the previous shift seems in line with current model depictions, so little deviation from their wx process was made. Some combination of FZRA and snow will affect the higher elevations amid stronger warm-air advection aloft, while rain (and eventually snow) will affect the lowlands as cooler air advects swd into the trough. Where snow does occur, snow ratios will be limited owing to warm air aloft approaching 32F--- especially in the ridges--- which ought to preclude need for anything more significant than an advisory. Where headlines are concerned, snow totals or FZRA presence are likely to warrant a Winter Weather Advisory in the ridge zones. Added Indiana County to the Hazardous Weather Outlook map, as the higher terrain in the ern section of the county could be affected by such wx. For at least a portion of Tue, shortwave ridging in advance of a digging Lower Ohio storm system should diminish PoPs, while temperature rises into the 40s amid warm advection ahead of low pressure encroaching upon the Lower Ohio. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... The ECM, GFS and ensembles are in general agreement on formation of an Eastern CONUS-to-coastal, southern-stream trough for the mid- to late-week period. This pattern suggests periodic, active wx for the remainder of the extended timeframe. Given the projected weakness of the upper- and mid-level wind field, a damp, light snow/snow showery period is envisioned for Wednesday as cold advection in the low levels is intensified on the wrn flank of coastal low pressure. Thereafter, a dry, but cool, period is expected to close the work week as surface high pressure builds under nwly flow aloft. A wet and cloudy Saturday appears probable as the upper-air pattern amplifies, and waves in the nrn and srn streams interact as they approach the region. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/... VFR conditions will continue through the TAF period under high pressure. High clouds will begin to appear overnight and thicken somewhat on Mon. West to northwest wind of around 10 knots will become light and variable tonight, and become light out of the northeast on Mon. OUTLOOK... Restriction potential returns with low pressure Mon night through Wed. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$ Kramar is the U.S. government's official web portal to all federal, state and local government web resources and services.