Area Forecast Discussion
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000 FXUS61 KPBZ 300109 AAB AFDPBZ Area Forecast Discussion...UPDATED National Weather Service Pittsburgh PA 809 PM EST Tue Nov 29 2016 .SYNOPSIS... Several crossing disturbances will result in periodic rain chances in the forecast through the mid week. && .NEAR TERM /THROUGH WEDNESDAY/...
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810pm update...no major changes from last update. Continued to tweak the PoPs overnight and adjusted temperatures. Previous discussion follows... Another surface low originating near Texas will be pulled up the Mississippi Valley and along the Ohio Valley late tonight. This will again bring increasing clouds along with organized rain that will last through Wednesday. The rain will be supported by deep moisture, ascent along the deformation zone, and low level jet support is expected with it`s passage. Location of primary rain band will be dependent on the exact track of the low and the aforementioned deformation zone. Latest NAM/GFS/SREF trend the low further west than the previous forecast, bringing the best rain chances almost directly over Pittsburgh and through the heart of the forecast area. Have adjusted PoPs to account for this trend, but overall, the forecast remains largely the same. Everyone should see at least some rain from late tonight through Wednesday. Temps will remain well above average tonight ahead of the rain. The arrival of the low and associated cold front make Wednesday high temps a little more difficult, but they will remain above average.
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... Model differences remain with regard to the rapidity of the exit of precipitation from the area on Wednesday night. Likewise, upper troughing starts to move farther eastward into the Great Lakes region with the frontal passage on Wednesday night, low level flow really fails to turn NW immediately. Thus, drier air should move into the area with the best chance for any showers of rain or snow behind the front remaining mostly north of I-80. Low level flow starts to get a smaller northerly component by Thursday night into Friday as the upper low continues to migrate slightly farther east. This may allow for a few rain and snow showers to start to develop into the ridges, as well. Temperatures will trend decidedly downward behind the frontal passage on Wednesday night. However, it will really only get us cool enough to allow for mixed rain and snow showers with little accumulation expected most anywhere. Fries && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Ridging will likely move closer and closer to the area through the weekend with low level flow gradually losing any northerly component. This should allow for showers to wind down with drier air again returning to the CWA. After the weekend, model solutions start to diverge with regard to potential activity crossing the area Sunday night into Monday. They also diverge in terms of thermal profiles when any potential activity does. A blend of models was used in this portion of the forecast with very low confidence as a result. From Monday onward, model and ensemble solutions actually start to converge upon more amplified ridging developing over the area as a deep low starts to develop in the southern Rockies. This should allow temperatures to head back upward again from the early to the middle part of next week as rain again develops. Fries && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... VFR conditions to begin the forecast period with high clouds streaming out ahead of the next low pressure system, which is approaching from the southwest. Expect deterioration to MVFR and IFR in the hours surrounding sunrise as rain spreads in. These restrictions will hold into the afternoon hours, with the passage of a frontal boundary allowing for some slow improvement after 18Z. Winds will remain light out of the south and southeast tonight. Models show a low level jet passing to the southeast of Pittsburgh mainly between 12Z and 18Z. While surface winds will gust to between 20 and 25 knots at the surface in this area, there is also a threat of low level wind shear with strong winds at the top of a fairly shallow inversion. Will include LLWS in the MGW and LBE TAFs, with the possibility of westward expansion depending on the track of the low level jet. .OUTLOOK... Periodic restrictions are again likely, especially over FKL and DUJ, as colder air moves back over the region during the latter half of the week. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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