Area Forecast Discussion
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000 FXUS61 KPBZ 260930 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 530 AM EDT Wed Apr 26 2017 .SYNOPSIS... High pressure provides sunshine and very warm temperatures today. Continued warmth is forecast for Thursday, when an approaching front brings shower and thunderstorm chances. && .NEAR TERM /THROUGH TONIGHT/...
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530 AM...low clouds have expanded in coverage a bit over the last couple of hours, particularly in southeast Ohio, with patchy valley fog also developing. Have increased coverage and persistence of clouds in the grids, but still expect plenty of sunshine to develop by midday once mixing gets going. Rest of forecast on track for now. Previous discussion... Thereafter, quiet weather is anticipated through tonight as a 500 mb ridge ambles across. Heights will rise in response to a digging trough across the Plains, leading to a significant warmup today. Readings will be some 10 to 20 degrees warmer than yesterday, with many locations reaching or topping 80 degrees. Some high clouds may arrive later tonight, but with lower levels remaining mixed due to an increasing tight pressure gradient, temperatures will remain quite mild overnight, with low temperatures around 15 degrees above seasonal norms.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY/... Main event this period is still the ejection of the Plains trough into the Great Lakes by Thursday afternoon. This negatively tilted feature will push a frontal boundary across the CWA during the late afternoon/early evening. Exact timing remains a bit problematic, and appears to be a touch faster on latest model runs. Have maintained mostly likely PoPs for this event. The severe threat remains somewhat uncertain. While deep layer shear will certainly be present in the forecast pattern, instability is the main question. Given afternoon temperatures in the lower to mid 80s across much of the area with upper 50s dewpoints, think that instability may be sufficient to overcome mid-level capping, which could be mitigated by mid to late afternoon anyway as cooler 700 mb temperatures arrive. Overall, think that BUFKIT soundings may be underplaying the potential CAPE. SPC has expanded a marginal risk over most of our area in the new day 2 outlook, and would not be surprised to see higher probabilities in later updates. Will maintain the HWO mention of severe risk. Precipitation pulls out behind the front during the evening hours. Dry weather returns for Friday with high pressure. Although temperatures will moderate a bit, broad southwest flow aloft points to continued above normal temperatures. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... An active pattern is figured for the weekend into early next week. A few shortwaves will cross in continued moist southwest flow along the front of a broad trough, leading to rain chances for Saturday and Sunday. Timing remains tricky, but Saturday night currently looks to be the period with the lowest coverage in the warm sector. Temperatures remain above normal. The trough lifts out as a closed upper low into the Great Lakes by Monday, pushing a fairly strong boundary across us. Given system strength, the amount of moisture, and a possibly negative tilt to the upper trough, strong storms appear possible. Behind this system, quieter weather and seasonable temperatures are expected into the middle of next week. && .AVIATION /10Z WEDNESDAY THROUGH SUNDAY/... Biggest question overnight is fog. How much will develop and how low will vis drop. For the most part, went with a drop at all ports to at least MVFR, with tempo LIFR possible in fog prone locations. This is a low confidence forecast and will be monitored throughout the night. Improvement to VFR is expected after sunrise with south- southeast wind remaining under 10kts. .Outlook... The next chance for general restrictions is expected with late week low pressure. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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