Area Forecast Discussion
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000 FXUS61 KPBZ 060553 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1253 AM EST Tue Dec 6 2016 .SYNOPSIS... Low pressure is expected to spread precipitation across the region Tuesday. A Thursday cold front will return snow shower chances and much colder temperatures for the end of the week. && .NEAR TERM /THROUGH TODAY/... The low clouds have now almost completely eroded out of the northeast counties, leaving just the advancing high clouds. Clearing north of Pittsburgh has allowed temperatures to fall off a bit more than previously forecast, and have made adjustments there as well as in sky cover. This might have implications on initial precipitation type, although advancement of the precipitation shield may occur a bit more slowly than currently depicted in the grids. Left PoPs/weather grids alone for now pending fuller examination of 00Z data. Previous discussion follows for the system that arrives on Tuesday...As the high exits late tonight, a shortwave and associated weak surface low is progged to track from the Mississippi Valley region, reaching the Upper Ohio Valley region Tuesday. Deep layer moisture, ascent and low level jet support should result in widespread rain across much of the region. With southeast upslope flow, cold air is expected to remain across the higher terrain SE of PIT, where a winter weather advisory has been issued to highlight a freezing rain threat. With the low level jet, gusty winds are also expected in the higher terrain. The cold temperatures should persist until the flow veers to the southwest Tuesday evening, and precipitation exits. Areas toward DUJ could also see a wintry mix with some light snow or ice accumulation possible, though confidence in advisory level precip in this area is lower. Included an HWO mention for this potential. && .SHORT TERM /TONIGHT THROUGH THURSDAY/... The shortwave and precip are progged to exit Tuesday night as the surface low weakens, and coastal development occurs. Ridging should return dry weather for Wednesday. A cold front is progged for a Thursday passage, with subsequent upper troughing progged across much of the eastern CONUS. Maintained high chance to likely snow shower pops for this scenario. The boundary layer flow should remain WSW preventing any lake enhancement. Temperatures are expected to be a few degrees below average Wednesday, with readings 10 to 15 degrees below average for Thursday. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Upper troughing and cold W-WSW flow should persist across the eastern CONUS through Friday maintaining snow shower chances. A less amplified pattern is progged from the weekend through early next week, with several crossing shortwaves progged. Maintained a mention of chance pops from Saturday night through early next week. Much below average temperatures are expected to moderate with the less amplified pattern by early next week. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
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VFR will prevail through the early morning hours before deeper moisture associated with a northeastward traversing low pressure approaches. Most if not all of the model guidance then deteriorates conditions to MVFR and eventually IFR as moisture spreads across the terminals. Strong warming aloft should support a mainly rain event across the TAF sites, save for KFKL and KDUJ where a period of wintry mix may occur for several hours. There may be some frozen precipitation at onset further south depending on how quickly we can saturate, but with low confidence, this was not mentioned in the TAFs at this time. An ese wind is expected through much of the day, veering to southwesterly and westerly as the coastal low becomes the primary low pressure system. Some low level wind shear may be possible at KLBE with a strong low level jet in place early this morning, before we start mixing, but will wait to see if this materializes as much of the bufkit guidance shows some mixing will occur. .OUTLOOK... Improvements look possible on Wednesday before the next cold front brings the chance for both cig and vsby restrictions in snow showers.
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MD...Winter Weather Advisory from 4 AM early this morning to 10 PM EST this evening FOR MDZ001. OH...None. PA...Winter Weather Advisory from 4 AM early this morning to 10 PM EST this evening FOR PAZ074-076. WV...Winter Weather Advisory from 4 AM early this morning to 10 PM EST this evening FOR WVZ512>514.
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