Area Forecast Discussion
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000 FXUS61 KPBZ 210518 AAC AFDPBZ Area Forecast Discussion...UPDATED National Weather Service Pittsburgh PA 118 AM EDT Wed Jun 21 2017 .SYNOPSIS...
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The risk for showers and storms return today and will continue into the weekend. The best chance for widespread activity will arrive on Friday.
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&& .NEAR TERM /THROUGH TODAY/...
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The overnight forecast will be composed using latest radar/satellite trends and a blend of hires guidance. Rather vigorous shortwave will swing across Lake Erie and dive southeastward overnight through PA. The strongest part of the wave will rotate eastward, meaning the large scale ascent moving southward will decrease overnight. There is a weak surface boundary situated in close proximity with the upper level energy and it will slowly push southward overnight as well. The current activity has developed ahead of the boundary, fueled by the aforementioned shortwave, and is moving more to the east, following the main energy aloft. Will show a slow southward progression of low chance/slight chance PoPs overnight, but expect most of the showers to dissipate once the heart of the wave is gone. The weak boundary will sag southward overnight, stalling just north of PIT around dawn. A stalled front will lay across the middle of the region through much of the day. This front will become the focal point for additional development this afternoon. Would expect a combination of daytime heating, although it may be curbed by cloud cover, and an afternoon shortwave, to be the trigger to get showers and possibly a storm to fire this afternoon. The strength of development would likely be predicated on how much sun we see. Convective temps will be in the upper 70s, so sunshine will help to push surface readings to those levels. If convection does fire, it will move southward late this afternoon and into the evening with the shortwave driving the surface boundary to the south. Activity will dissipate during the evening hours due mainly to the loss of daytime heating.
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&& .SHORT TERM /TONIGHT THROUGH FRIDAY/...
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The unsettled pattern continues into Thursday with a shortwave moving across the area. Again, stuck with low chance pops, primarily across northern counties. The most active weather period for the week still appears to occur Friday into Friday night. Models are in good agreement that another cold front will enter the region from the west late Friday and move through Friday night. Showers will overspread the area well ahead of the surface boundary Friday morning, as a series of shortwaves move across the southern half of the area. If these waves end up tracking as forecasted, would think most of the rain for the first half of the day would be over the south, until the front arrives. This may help to curb stronger convection with the boundary. Still much to be worked out for the Friday forecast.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... The chance of showers will linger south and east of Pittsburgh Saturday along the back side of the front, and an additional shortwave could spark showers on Sunday. High pressure should build in for Monday and Tuesday, resulting in quiet weather. Temperatures will remain below normal through the extended forecast. && .AVIATION /05Z WEDNESDAY THROUGH SUNDAY/... General VFR is expected to be marred only be scattered, high based showers later tonight and Wednesday as a shortwave trough traverses the region. Sfc wind will back from west to south with the approach of that disturbance, then veer to the west with passage on Wednesday afternoon. .OUTLOOK... Widespread restrictions are likely Friday with the encroachment of a cold front. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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