Area Forecast Discussion
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927 FXUS61 KPBZ 211743 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1243 PM EST Tue Nov 21 2017 .SYNOPSIS... A cold front will bring the next chance for precipitation tonight. Dry weather and below average temperature are expected for the remainder of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Temperatures are off to a roaring start this morning as a very dry column has allowed for insolation to maximize early, which has in turn allowed for vertical mixing to increase earlier than normal. This has quickly pushed temperatures up well above normal. With a leading wave aloft passing at the moment, the few high clouds it is generating should move east fairly quickly later this morning, resulting it full sunshine through the afternoon. This will allow for further warming on gusty southwest winds. As a result, high temperatures have been pumped upward fairly substantially for the afternoon. Speaking of the southwest wind, model soundings suggest 35-40 kts off the deck through the early afternoon below the inversion level. While full dry adiabatic mixing is not really supported, a good deal of that momentum should be capable of mixing downward, thus wind gusts were increased into the range of 30 kts through the afternoon, with the highest values expected to the north and in the ridges. Fries && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/... Cold front will quickly swing through the area this evening and into the overnight hours. Model are showing sufficient upper level support and low-level forcing to continue with likely POPs, mainly over the northern half of the region. The cold airmass behind the front does not look deep enough to sustain a very long period of post frontal snow showers. Forecast soundings are showing saturation levels dropping quickly, well below the dendritic snow growth layer. Minor snow accumulations are possible, but should be limited mainly to the I 80 corridor and ridges. Less than an inch is anticipated in those areas. High pressure will then ensure a dry midweek and Thanksgiving holiday, with sub average temperatures. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Ensemble forecasts are showing the next cold front dropping through the area on Saturday, followed by the next trough setting up over the Eastern CONUS, which will hold into the beginning of next week. Cold surface high is expected to build back in late Sunday into Monday. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... VFR conditions will carry through the late evening. Strong southwesterly surface flow will gradually dissipate after sunset as the strong low-level jet exits to our east. Clouds will increase overnight in advance of an approaching cold front. Ceiling drop to MVFR is expected in concert with the onset of rain along the front. Cold air pouring in behind will lead to a transition to snow and possible visibility restrictions in the heaviest, mainly northern ports. Ceilings may drop to IFR for a time at FKL/DUJ in the pre-dawn hours, but are largely expected to stay MVFR elsewhere. Sustained cold advection will keep MVFR ceilings in for much of the day Wednesday. Any improvement to VFR would likely come to ZZV or HLG first where moisture will begin to erode. Passage of the front will shift winds to west-northwesterly through the balance of the TAF period. .Outlook... The next chance for restrictions is forecast with an early Saturday cold front. && .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.