Area Forecast Discussion
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000 FXUS61 KPBZ 150607 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 107 AM EST Thu Feb 15 2018 .SYNOPSIS... A weak disturbance will keep light rain chances through this morning before low pressure and a cold front results in widespread rain later today and tonight. Precipitation should taper off Friday as the front exits. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Weak ascent in warm advection and saturated lower levels should continue the light rain, drizzle and fog overnight. QPF should be very light overnight with very little upper support. Temperatures should slowly rise overnight with the warm advection. && .SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY/... Surface low pressure will move through the Ohio Valley Thursday night, dragging a cold front across the area. The period of heaviest rainfall is expected to be Thursday night, with rainfall rates decreasing on Friday; heaviest rainfall should occur along the Mason-Dixon line in southwestern Pennsylvania and northern West Virginia. See the hydrology section below for more information. Confidence was high enough to issue an areal flood watch in addition to the flood watch at individual river points. As precipitation ends Friday, there could be a brief period of snow, but any accumulation would be minimal. The better chance for snow accumulation will occur with a quick moving storm Saturday afternoon and evening. While the center of the low pressure system will pass well to the southeast, precipitation could spread across the area and change from rain to snow. Models are still varying in how the storm is depicted, and it`s too far to nail down any details. High pressure will briefly move into the region for Sunday, yielding dry conditions. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Deep swly flow will persist in the ern and central CONUS through much of next week as an H5 trough becomes entrenched in the swrn CONUS and upper high pressure persists in the wrn Atlantic. This stagnant upper- air pattern will support strong return flow, warm advection and an omnipresent frontal boundary, with multiple rounds of rain/showers beginning Mon morning and continuing through much of the week. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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Persistent low-level moisture will maintain IFR/LIFR restrictions with low ceilings and areas of fog/drizzle until mid-morning when there is a chance cigs raise to low end MVFR levels briefly for a couple hours. By mid-afternoon increased lift ahead of an approaching front will result in moderate to heavy rain at times through the evening....maintaining IFR or lower restrictions.
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&& .HYDROLOGY... Rain should overspread the area Thursday afternoon as low pressure and a cold front approaches and crosses the area, with areas of moderate to heavy rain Thursday night. Rainfall should taper off Fri as the front exits. This should result in rises on the Mon and Ohio Rivers and their tributaries through the weekend. Overall rainfall amounts in the aforementioned area are expected to range from 1.5 to 2.25 inches. A flood watch remains in effect for these areas, along with various river flood watches for specific points along the Ohio and Mon rivers. && .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...Flood Watch from this evening through Friday afternoon for MDZ001. OH...Flood Watch from this evening through Friday afternoon for OHZ059-068-069. PA...Flood Watch from this evening through Friday afternoon for PAZ021-029-031-073>076. WV...Flood Watch from this evening through Friday afternoon for WVZ001>004-012-021-509>514.
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