Area Forecast Discussion
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000 FXUS61 KPBZ 300829 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 429 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/... Strong upper low will linger over the lower Ohio Valley today, and then begin to lift towards the lower Great Lakes tonight. Drier air visible on water vapor loops is becoming entrained by the system, which has pushed most of the rain west of the ridges. The departure of the rain has allowed mountain wave activity to become visible across the wind advisory area. Occluded boundary continues to linger just to our south across central Ohio and West Virginia. A few locations have received heavy rainfall totals of 2 to 2.5 inches over the past 12 hours, particularly in the flood advisory area. Will continue to focus higher PoPs closer to the occluded boundary today, which should move little and place the most precipitation across southeast OH, extreme southwest PA, and northern WV. Rainfall totals and rates will be lower today, with generally a half inch or less expected during the daylight hours. Kept some thunder chances across our southwest counties, where some modest instability remains possible. If any storms do manage to stand up, there may once again be enough shear to allow one or two to become strong. Will keep the wind advisory going for now with the visible wave activity and still favorable soundings, although observations to this point have come in below criteria. Weakening of the low level jet may allow the advisory to be canceled a bit early. Tonight, the stacked low and occluded boundary will begin to 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. && .SHORT TERM /SATURDAY THROUGH MONDAY/... 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 /MONDAY NIGHT THROUGH FRIDAY/... 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 next week. With little difference in 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. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... Bands of showers are continuing to rotate over the area, although coverage should wane a bit towards sunrise. Conditions will bounce between VFR and MVFR through the night, with some brief drops to IFR still possible. DUJ, in moist easterly flow, should remain mainly IFR through sunrise. VFR will become a bit more prevalent during the day Friday as moisture drops off a bit. Wind gusts of 15 to 25 knots are expected at most terminals during the afternoon as the surface pressure gradient tightens a bit. Wind gusts of 35 to 40 knots are still possible in downsloping off of the ridges in the LBE area, although these winds may not be seen at the airport proper. .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. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...Wind Advisory until noon EDT today FOR MDZ001. OH...None. PA...Wind Advisory until noon EDT today FOR PAZ073>076. WV...Wind Advisory until noon EDT today FOR WVZ510>514. && $$

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