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009 FXUS61 KPBZ 231701 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 101 PM EDT Thu Mar 23 2017 .SYNOPSIS... Sunshine and moderating temperatures today. Rain chances return this weekend with a continued warming trend. && .NEAR TERM /THROUGH TONIGHT/... A cold start to the day will give rise to more-seasonal temperature readings this afternoon. The shallow morning inversion on the 12Z KPIT sounding has broken, with warm advection expected to increase in the wake of departing surface high pressure. Despite breaking the morning inversion, full sun amid clear sky or possible thin cirrus, and the expected warm air advection, it will take considerable effort to reach the lower 50s in the ongoing forecast. Given relatively-minimal ensemble spread, confidence is high that it will be a challenge to eclipse the mid-upper 40s today, so maxima were lowered slightly with this update. A weak, low-amplitude disturbance will interact with the strengthening low-level jet overnight to generate light precipitation particularly late tonight and early Fri morning. Although the focus will be in northern counties, latest hi-res models support broader PoP coverage across the forecast area. The strong warm air advection and increasing clouds tonight will inhibit the typical diurnal temperature cycle. Initial cooling and residual dry air may be enough to support wet-bulb values below freezing in very isolated locales for a brief window late tonight at the onset of any precipitation (e.g. a few sheltered valleys in Garrett/Indiana Counties). In general, temperatures are expected to remain above freezing, but a brief period of light freezing rain may occur in those sheltered valleys before warm air advection wins the thermal battle. However, given the northern placement of the upper disturbance, there is a lower confidence in precipitation with southward extent, so it could be that little precipitation occurs in the areas most thermally-favorable for any freezing precipitation. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... The disturbance responsible for overnight precipitation will move east Friday morning, leaving the remainder of the day mostly dry and warm. Another weak disturbance will affect primarily the northern zones Friday night, given the perseverance of an amplifying east-coast upper ridge. With the possible exception of the far north, Saturday looks dry as well. Plenty of subsidence with the eastern ridge firmly in place and any upper level waves will be shoved well to the north of the area. There will be additional cloud cover Saturday, as the atmosphere slowly becomes more saturated. Even warmer temperatures are expected on Saturday. && .LONG TERM /MONDAY THROUGH THURSDAY/... An upper low, ejecting from the Plains into the Great Lakes, will push a front our way on Sunday with good rain chances. The front may linger near the area Sunday night with some showers before another low threatens to bring better rain chances Tuesday. Dry weather and high pressure are expected by the middle of next week. Above-normal temperatures throughout the long term. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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High pressure will keep a majority of clouds at bay through tonight. A shortwave trough crossing along a warm front will bring an increase in clouds and eventually light rain showers by Friday morning. Kept VCSH mention for Pittsburgh and south while northern ports stand the best chance to see borderline MVFR restrictions. Light winds will shift around to the south and gradually increase through the period. An increasing low-level jet will bring a chance for llws before mixing commences Friday morning. Outlook... The next chance for widespread restrictions is not expected until the approach of low pressure early on Sunday.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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