Area Forecast Discussion
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000 FXUS61 KPBZ 220934 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 534 AM EDT Tue May 22 2018 .SYNOPSIS... A few rounds of showers and thunderstorms will remain possible before the passage of a cold front tonight. High pressure then provides a few days of dry weather. Unsettled conditions return during the holiday weekend. Above normal temperatures will continue. && .NEAR TERM /THROUGH TONIGHT/...
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Precipitation coverage/intensity has waned temporarily, but another slug of rain supported by a weak mid-level wave and 250mb divergence from the upper jet is set to move in from the southwest over the next couple of hours. Increased PoPs/QPF especially for the eastern third of the CWA for the morning. Removed thunder for now given the overall lack of lightning and the usual diurnal instability minimum, but it will surely return later in the day. Previous discussion... A relative lull in precip may occur during the late morning/midday hours. Depending on how quickly clouds can break, building instability and a very weak to absent cap should allow some scattered popup showers and storms to develop during the early afternoon hours. More concentrated activity, as well as a slightly better severe risk, will wait for the approach and passage of a cold front during the late afternoon and evening hours. These storms may be able to work with moderate instability, modestly steep mid- level lapse rates, and roughly 35-40 knots of 0-6km bulk shear and allow for a few strong to severe thunderstorms. Think wind is the greater threat, as CAPE profiles aloft seem rather skinny. SPC has a reasonable marginal severe risk across the entire CWA this afternoon and evening. Thunderstorms should weaken by midnight as instability wanes, and only a few showers at most should remain along the southeast ridges overnight. Fog is a possibility, especially across the north, if clouds can clear a bit faster than expected. Temperatures will continue to run above normal.
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&& .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... A few straggling showers may linger along the ridges Wednesday morning. Otherwise, dry weather will dominate this period as the pesky frontal boundary is definitively pushed south by building high pressure. Temperatures will back a bit closer to normal levels, and lower humidity will also be noticed. A quiet Wednesday night may hold the best fog potential as the center of the surface high crosses. Thursday will feature plenty of sunshine and temperatures warming several degrees as 500 mb heights rise. Upper 70s and lower 80s will be common, with dewpoints remaining comfortably low. && .LONG TERM /FRIDAY THROUGH MONDAY/... Mid-level ridging will lead to continued dry weather into Saturday, and 850 mb temperatures climbing to around 16C point to high temperatures in the mid 80s across many areas into the first part of the weekend. Unsettled weather returns for the rest of the holiday weekend. Moisture gets pumped northward around a potential Gulf tropical system, and waves riding over the flattened ridge will provide support for several rounds of precipitation. Given the potential for high PWAT air and warm rain processes, there is some potential for at least isolated areas of excessive rainfall. However, at this distance, NAEFS anomalies and GEFS QPF M-climate do not point to anything highly unusual, and so will wait for further developments before raising any alarms. && .AVIATION /10Z TUESDAY THROUGH SATURDAY/...
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Occasional MVFR conditions are expected in showers through early morning as a warm front lifts N across the area. The showers should become isolated to scattered after sunrise, though some patchy MVFR cigs are expected as CU redevelops. A cold front is expected to approach and cross the region later this afternoon and evening, with another round of showers and thunderstorms. Maintained a VCTS mention in the TAFs until timing can be better determined. Cigs should drop to MVFR after FROPA as winds shift to the WNW. OUTLOOK... Restrictions are possible through early Wed as the cold front exits. Restriction potential returns with weekend low pressure.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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