Area Forecast Discussion
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000 FXUS61 KPBZ 191932 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 232 PM EST Fri Jan 19 2018 .SYNOPSIS... High pressure provides dry and milder weather through Saturday. Light rain chances return by Sunday, with a period of steadier rain possible by Monday night. Cooler weather returns for the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... Mainly cirrus is expected through the night as high pressure slides to the east and warm advection continues. Low temperatures will end up above normal and could be achieved fairly early during the night. Values may steady or rise slightly overnight as the column remains mixed, although any valleys that manage to decouple could cool more than forecast given the remaining snowpack. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... An upper trough will trudge eastward during this period, from the Pacific coast and across the Rockies to the Plains by Sunday night. While flow aloft remains quasi-zonal across our region, low-level southwest flow will continue the warming trend. High temperatures in the 40s both Saturday and Sunday will help to melt much of the snow pack. Clouds will be on the increase Saturday, with a lower stratocumulus deck possibly arriving by the afternoon. Enough moisture should be advected in on weak low- level isentropic lift to support drizzle or light rain starting Saturday night and continuing into Sunday night. Lift and forcing remain weak through this period, and minimal QPF of around or less than a tenth of an inch is forecast in general. There is still a small concern that freezing rain/drizzle may be possible mainly north of Pittsburgh for a time Saturday night, depending on how quickly the boundary layer can cool during the evening. Chances of that remain low however, and do not merit even an HWO mention at this point. && .LONG TERM /MONDAY THROUGH FRIDAY/... As the vertically-stacked low crosses the Mississippi Valley and the Great Lakes Monday and Tuesday, a crossing cold front will provide the focus for the next chance of organized rainfall, mainly Monday afternoon and night. The moisture plume ahead of the front remains deep but fairly narrow, and the system is still expected to be progressive as the upper trough takes on a negative tilt. Models and ensembles have been fairly consistent in keeping the QPF under control with this system, generally a half-inch or less. Given the loss of much of the snow pack prior to this, large-scale flooding issues are still not projected to be a concern. However, localized issues due to ice jams will remain quite possible, and this threat has been addressed in the HWO for now. Behind the system, temperatures will drop back to seasonable levels for Tuesday and Wednesday, with any lingering showers turning over to snow by Tuesday night. A minor ridge accumulation is possible during this period. High pressure should allow Thursday and Friday to feature dry weather and another warming trend to close out the week. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... VFR will prevail for much of the period as high pressure remain in place. Diurnal mixing will support a SSW with gusts to 20kts both this afternoon and next. Model guidance suggest moisture, trapped under building inversion aloft may lead to some afternoon restrictions tomorrow. Will make subtle mention of this at PIT with low confidence for now. .OUTLOOK... Restriction potential returns with the new week and an approaching frontal system. && .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.