Area Forecast Discussion
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000 FXUS61 KPBZ 152045 AAA AFDPBZ Area Forecast Discussion...UPDATED National Weather Service Pittsburgh PA 445 PM EDT Sun Apr 15 2018 .SYNOPSIS...
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Rain, will overspread the region by this evening and continue overnight ahead of a cold front. Behind the front, showery precipitation and colder temperatures will dominate through the early part of the week.
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&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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445pm update...only minor changes to previous forecast. Updated PoPs for the evening hours in line with latest hires guidance and radar trends. Temperatures were also slightly adjusted to better portray current conditions. Previous discussion... Elected to expand the Flash Flood Watch to encompass eastern Ohio and the northern WV panhandle. Model consensus of a band of 1.5 to 2.5 inch QPF, perhaps locally higher, was getting harder to ignore. The western counties fall under the right entrance region of a 120-140 knot upper jet during the late afternoon and evening as the trough tilts. Layered frontogenesis and deformation will also be present, along with anomalously high PWAT values of 1.3 to 1.4 inches. Although flash flood guidance values are fairly high in this area, felt that rain rates may support at least isolated flooding concerns. The watch is maintained over the original eastern counties as well where a period of training heavy showers is also possible. The cold front will arrive in the western counties this evening and depart to the east during the predawn hours. Steadier rain will end, to be followed by more showery precipitation as the upper low makes its way into the Ohio Valley.
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&& .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... The upper low will swing across the region behind the boundary on Monday. Periodic shortwaves will then rotate through in the troughing pattern through Tuesday, producing showery precipitation. A mix with and change to snow is still figured first along the higher ridges Monday, and then areawide Monday night into Tuesday morning. Boundary layer warming should allow rain to become dominant again in the lowlands Tuesday afternoon. Any snow accumulation should be minor given the time of year and the antecedent warm conditions. Below normal temperatures will persist. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Precipitation will linger into Tuesday evening north of Pittsburgh, with a brief period of dry weather late Tuesday night into Wednesday in advance of low pressure moving into the region from the Plains. The low should pass just north of the area Thursday morning, sweeping a cold front through. While a flake can`t be ruled out north of I-80 with the initial precipitation, at this point it appears that all precipitation Wednesday night and Thursday would fall as rain. Before precipitation ends Friday, all locations will have a chance for snow Thursday night into Friday morning. High pressure building across the Great Lakes should then keep weather dry into the weekend. Temperatures will be below normal through the extended forecast. && .AVIATION /21Z SUNDAY THROUGH FRIDAY/... Conditions will deteriorate to MVFR/IFR at all sites during the evening hours. Thought that all sites would experience gusts this afternoon, but in the 18Z TAFs pulled the mention of gusts from any terminal that hadn`t had any so far. With a low level jet present ahead of the cold front, have gone ahead and added a period of low level wind shear to all TAFs, although LLWS will likely occur for a shorter time period than is suggested in the current forecast. Even with a wind shift with the cold frontal passage, appears that conditions should remain MVFR at all terminals into Monday afternoon. OUTLOOK... MVFR is anticipated for Tuesday as the area will remain under an upper trough of low pressure. The next chance for restrictions will come late Wednesday and Thursday as another front crosses the area. && .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...Flash Flood Watch until 4 AM EDT Monday for MDZ001. OH...Flash Flood Watch until 4 AM EDT Monday for OHZ039>041-048>050- 057>059-068-069. PA...Flash Flood Watch until 4 AM EDT Monday for PAZ020-021-029-031- 073>076. WV...Flash Flood Watch until 4 AM EDT Monday for WVZ001>004-012-021- 509>514.
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&& $$

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