Area Forecast Discussion
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000 FXUS61 KPBZ 180536 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 136 AM EDT Mon Sep 18 2017 .SYNOPSIS... High pressure centered over the region will bring a prolonged period of dry weather, along with unseasonably warm temperatures through the coming week. && .NEAR TERM /THROUGH TODAY/... High pressure will continue to hold sway through the morning and into the daytime on Monday as a frontal boundary currently straddling Indiana into Michigan inches eastward. This front is set to run into a wall of high pressure and drier air aloft concurrent with its upper forcing shearing off rapidly northeastward toward Quebec. As this occurs, all convective activity currently along the front should translate well north of the area on Monday. Before that time, however, a clear overnight with very weak boundary layer flow will transition into a Monday with a bit of an increase in mid and high clouds as well as the current boundary layer moisture resulting in fairly pervasive cumulus development. However, with the surface trough impinging upon the western fringe of the area, easterly flow into the ridges will probably be weaker than in previous days. This would seemingly result in a lower chance of showers in the heat of the day in the terrain. Otherwise, continued elevated dewpoints due to a lack of afternoon ventilation spurred by cumulus development each and everyone one of the last couple days will result in saturated valleys through morning. This means a deja vu forecast for fog through sunrise. Even with a decent bit of cloud cover, a warm air mass already in place and at least some sun breaks through the day should result in yet another above normal afternoon as highs jump toward the lower 80s in most spots. Fries && .SHORT TERM /TONIGHT THROUGH 6 PM TUESDAY/... Very little weather of interest is expected through the early week period locally. A narrow high amplitude ride will remain anchored from the western Gulf northeastward through western Pennsylvania, framed by Hurricane Jose to the east and an upper level trough to the west. The approaching trough will rapidly shear out as it approaches Tuesday, with the surface boundary never reaching the area. Given strong mid level capping and the subsidence west of Jose, any threat of afternoon showers would be extremely isolated either afternoon. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Once the nor`easter formerly known as Hurricane Jose departs the eastern seaboard, mid level heights will continue to rise over the eastern CONUS. 500mb heights exceeding 590dm are an almost certain bet by Thursday, and will continue through the weekend. Such values would be several standard deviations above climatology for late September. Using today`s high temperatures as a baseline (14.5C 850mb, calm winds, significant Cu coverage), see no reason why forecast highs Thursday through Sunday won`t be at least several degrees warmer than those advertised by the model blends, in the mid to perhaps even a few upper 80s. Have made upward adjustments, and this beginning to calendar autumn may end up being one of the warmest stretches of the year. Additionally, there is a near zero chance of rainfall through the balance of the forecast period. This becomes noteworthy as some areas (including locally here at NWS PBZ) are abnormally dry over the past month and will likely be heading into early drought conditions. Also, for those who have noticed an accelerated (nearly 1 month) head start to the foliage change in the local area, this will undoubtedly be halted by the stretch of much above normal temperatures. Bookbinder && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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Deterioration to IFR is expected overnight in fog as crossover temperatures are reached. Used persistence for most ports. A return to VFR is expected within a couple of hours after sunrise as the fog mixes out and dissipates. VFR is expected under upper ridging for the rest of the TAF period, though a diurnal CU cig and increasing mid/high clouds are expected. .Outlook... Patchy morning fog restrictions are possible through Thu with ridging in place.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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