Area Forecast Discussion
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000 FXUS61 KPBZ 192250 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 550 PM EST Thu Jan 19 2017 .SYNOPSIS... Rain will return to the region late tonight and Friday as the next upper level system moves through. The mild pattern continues through the weekend. && .NEAR TERM /THROUGH FRIDAY/...
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Hi-res and synoptic models have largely come into agreement with regard to the overspread of rainfall through the night tonight into Friday morning. This favors a timing for the start of rainfall around Pittsburgh likely just before 12z/7am. Even while dewpoint depressions are rather wide off the ground this evening, warm advection working in tandem with moisture transport keep the thermal profiles way, way, way above freezing off the deck. When you combine this with the fact that boundary layer wet bulb temperatures are already above freezing, this means all areas should experience purely liquid precipitation. Rain will continue to the northeast on Friday as the negatively- tilted mid-level trough axis shifts northeastward. Rain will end behind the axis from southwest to northeast in the latter half of the day as both lift and layer moisture wane. Fries
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&& .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/... Although different models show isolated showers through this period, have decided to go with a dry forecast Friday night and Saturday, and chance pops Saturday night since there should not be much to provide any sort of organized lift. This should be the warmest stretch of the forecast, with lows only dropping into the 40s and many locations reaching the 60s on Saturday. && .LONG TERM /SUNDAY THROUGH THURSDAY/... A strong upper low will develop over the Southern Plains Sunday and track eastward into early Monday, before turning toward the northeast Monday night and Tuesday. While the GFS and ECMWF keep the surface low moving along the Atlantic coastline, the NAM keeps the surface low as far west as Kentucky, and have not used the NAM during the early part of the extended forecast. The GFS and ECMWF are trending farther east with the track of the system, and while they are in good agreement, this track may result in the widespread precipitation shield also being farther to the east. Nevertheless, have still kept likely pops in the forecast for now from Sunday through Monday night. After a brief break in precipitation Tuesday, GFS and ECMWF are in good agreement showing low pressure moving across the Great Lakes Wednesday and Thursday, and have gone with chance pops. Although temperatures will be lower with multiple storm systems, the forecast remains well above normal warmth. && .AVIATION /22Z THURSDAY THROUGH TUESDAY/... IFR cigs will persist as low level moisture remains trapped under building high pressure. A brief break is possible overnight shortly before the next disturbance returns rain and IFR/LIFR cigs. .OUTLOOK... Restrictions are likely with low pressure Friday, and again on Sunday. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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