Area Forecast Discussion
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000 FXUS61 KPBZ 112231 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 531 PM EST Wed Jan 11 2017 .SYNOPSIS... Several periods of rain will continue through the week until more seasonable temperatures return by Friday. A wintry mix is expected over the weekend. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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A wall of deep moisture is moving in from the SW at the moment and encroaching on Pittsburgh as I type this. PWAT values are set to increase rapidly in the next few hours likewise...with current values around one-half of an inch surging to over 1 inch within in the next couple of hours. A coupled upper jet structure combined with strong moisture advection from the southwest is responsible for the rapidly expanding rain shield moving in that will last much of the evening. As this gradually advances northeast, and the best upper divergence departs likewise, rain showers will move with it as we emerge into the warm sector across the southeastern half of the CWA for the overnight hours into Thursday. Fries
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY/... The next cold front will bring more rain on Thursday mainly during the afternoon and evening hours. Some parts of the region may receive more rainfall due to the lack in eastward progression of the front until the trough axis helps push the front out of the area late Thursday. The boundary is expected to sag south of the forecast area on Friday. High pressure will build over the eastern Great Lakes behind the front keeping the area dry on Friday. This feature will play a crucial role in determining the weather type for the weekend. As of now, confidence is increasing for the existence of a wintry mix to occur on Saturday over much of the forecast area as overriding warm air encroaches with the northward shift of the aforementioned boundary. There is, however, uncertainty in the northward extent of the boundary and therefore used the superblend to maintain chance to likely PoPs. Sufficient cold air damming should help result in freezing rain to occur, with the largest ice accumulation amounts progged over Garrett and Tucker Counties. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... The weekend front will linger across southern portions of the forecast area and may continue to cause a wintry mix, and with uncertainty as to exactly where the front will be, have kept likely pops generally contained to locations well south of Pittsburgh on Sunday. GFS and ECMWF diverge in model solutions for Sunday night and Monday with a system in the Plains, and have made minimal changes to this portion of the forecast. Temperatures should be near or slightly above normal. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... VFR will deteriorate to mvfr with areas of IFR in rain showers overnight as a frontal boundary pushes north. Low level wind shear also expected as southwest low level jet over 50 KTs crosses region. Some improvement across the far south Thursday morning, otherwise continued IFR as cold front crosses Thursday afternoon. .OUTLOOK... Periodic restrictions in a possible wintry mix can be expected for the weekend, especially across southern ports. && .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.