Area Forecast Discussion
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000 FXUS61 KPBZ 171256 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 756 AM EST Sun Dec 17 2017 .SYNOPSIS... Another upper level disturbance will result in scattered light precipitation developing later this afternoon. Warmer temperatures, cloudy skies, and light drizzle can be expected Monday and Tuesday. && .NEAR TERM /THROUGH TONIGHT/...
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Update this morning included a reconfiguration of the PoP fields for the afternoon. Pushed off onset a bit later given hi-res model output showing this, as well as the dry low levels sampled by the 12Z PBZ sounding. However, did increase PoPs for the mid/late afternoon, especially across the south, as a weak mid- level wave provides a brief but decent shot of isentropic lift at 295/300K. Minor tweaks were made to other parameters. Previous discussion... Fog development north of a stationary boundary running roughly along I-80 will diminish by mid-morning as southwesterly flow increases ahead of an approaching shortwave out of the midwest. This feature will lift the aforementioned boundary north of the forecast area as a warm front. Scattered showers are expected later in the afternoon and into the evening as the mid-level feature passes over. Counties north of Pittsburgh may see mixed precipitation but surface temperatures are expected to be warm enough that no problems are anticipated.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... Latest guidance shows decent continuity with previous runs with zonal flow aloft and the forecast area remaining within the warm sector through Tuesday. Weak forcing and saturated lower levels also continue to be forecast...and expect extensive cloud coverage, patchy drizzle, and periods of light rain to persist through the period. Despite expected cloud cover, warm advection should lead to temperatures at least near seasonal averages with a somewhat limited diurnal range through Tuesday. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Tuesday night the upper level flow will amplify and the aforementioned boundary is progged drop back south over the area...finally scouring low-level moisture but also resulting in temperatures 10 degrees lower on Wednesday. Some locations may see some light snow Wednesday but no significant accumulations are expected. Drier and warmer conditions are expected the latter part of the week as zonal flow is reestablished. Models have slowed the arrival of the next system to impact the region to late Friday early Saturday. Changes in the extended were largely based on latest Superblend guidance. && .AVIATION /13Z SUNDAY THROUGH THURSDAY/... Outside of variable morning fog for FKL and DUJ this morning, all other terminals will remain VFR. VFR conditions will carry through this afternoon before moisture increases behind a warm front lifting northward. Eventual deterioration is expected areawide later tonight with ceilings falling and mist/drizzle making an entrance. Light southerly flow will hold through the balance of the TAF period. .Outlook... Restrictions are likely 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. && $$

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