Area Forecast Discussion
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516 FXUS61 KPBZ 301141 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 741 AM EDT Fri Sep 30 2016 .SYNOPSIS... Upper level low pressure will continue to linger near our region into this weekend. Showers will be most numerous today, with more scattered activity this weekend. && .NEAR TERM /THROUGH TONIGHT/...
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Early update to cancel wind advisory, POPs will need to be adjusted by midday as bands of showers rotate across the region on the front side of closed upper low over Kentucky. Temperatures will be seasonably cool. Tonight the upper level closed low and an associated occluded boundary will lift northward, with continued dry air entrainment behind it. This will push the bulk of the shower activity ahead of it. PoPs will thus decrease from the south with time, with most showers north of Pittsburgh by 12Z. Temperatures were nudged towards the lower side of the guidance envelope, with a model blend used with the previous forecast.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY/... The mature low pressure system that has plagued our area much of this week will linger through the weekend, bringing additional rain chances. By Saturday, the occluded front will have gradually lifted north spreading the best rain chances north of I-80. An expansive feed of dry air wrapping around the south and east of the low will push into our southern counties, resulting in a drying trend through the day. Model differences exist on the evolution and track of the low Sunday into Monday, but the overall trend is to push the track further south and slow it`s progress. This seems prudent, given the extreme northern trajectory of the upper-level jet stream, and the subsequent inability to capture the low and sweep it east. As a result of this slower southern solution, have introduced chance PoPs Sunday afternoon, mainly north of Pittsburgh, as low nears northern Ohio. Temperatures through the weekend will be slightly above normal. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
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Model consensus exists on the eventual departure of the low pressure system early next week and building a broad ridge through the Great Lakes by middle of next week. This will result in several days of dry weather. With little difference across model guidance, the Superblend was largely utilized in the extended. Temperatures will be back above normal for the first week of October. With the anomalously strong ridge in place, forecast temperatures were bumped a degree or two above the Superblend numbers.
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&& .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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Bands of showers continue to rotate around closed upper low over Kentucky. Most terminals will start out MVFR with IFR at KDUJ, with graqdual improvement through the day to VFR outside of shower bands. Any thunder chance looks to be isolated with only a VCTS mention at KZZV due to proximity of cloder air aloft. Winds will be east around 10 Kts with a few gusts to 20 Kts. Showers will consolidate more towards the occluded front this afternoon and advance northeastward tonight with the boundary. MVFR ceilings should accompany this activity. Ceilings late tonight are tricky, as models want to drop values to IFR or even worse, but suspect that this may be a bit pessimistic south of I-80. Elected to continue with MVFR for now. .OUTLOOK /FRIDAY NIGHT THROUGH MONDAY/... Scattered restrictions can be expected into Monday as the upper level low lingers, then slowly lifts north of the region.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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