Area Forecast Discussion
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000 FXUS61 KPBZ 251005 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 505 AM EST Sun Feb 25 2018 .SYNOPSIS... Rain will end today as a cold front crosses. A welcome period of dry and mild weather will take hold for the first part of the work week as high pressure takes control. && .NEAR TERM /THROUGH TONIGHT/... Warm front pushing northward across the region currently, driven by a 50 to 60 knot low level jet. Precipitable water values are just about at their maximum, and warm cloud depth/low level RH are favorable for efficient rain, but rainfall rates/totals have generally come in below expectations. Convection firing across the lower Ohio Valley earlier may at least be partially responsible, robbing some of the moisture transport into the region. Issued flood warnings have yielded little in the way of flooding reports. Will allow the flood watch to continue for now, but some counties in Ohio could be trimmed off during the next few hours. Cold frontal passage occurs in the 12Z-18Z window today, with gusty winds developing behind the boundary with downward momentum transport. Hi-res models depict a line of low-topped showers developing along the boundary, after a relative lull in rainfall as the low-level jet departs. Have used the HRRR to time this activity across, with most precipitation departing with the front by 18Z. Clouds will linger for a few hours behind the front, but expect decent clearing areawide by sunset. By this time, high pressure will start to nose in from the lower Ohio Valley, loosening the pressure gradient and allowing wind gusts to diminish. Temperatures will continue to shoot up towards sunrise, pushing 60 degrees across the south. Steady or slowly falling temperatures are expected behind the front this afternoon. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... The region will receive a much needed dry spell during this period. High pressure will expand from the lower Ohio Valley tonight and eventually center itself over the central Appalachians by Tuesday. After lingering clouds depart tonight, plenty of sunshine is figured for both Monday and Tuesday. Temperatures will be a bit cooler Monday, but still above normal, with readings in the upper 40s to mid 50s. Developing southwest flow behind the high Tuesday will allow a bit of warming, with some 60 degree readings reappearing near the Mason-Dixon Line. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Moisture from the southern stream reappears on Wednesday, bringing a chance of light rain as a warm front approaches from the Tennessee Valley. A split-flow pattern tracks low pressure centers to the north and south of our region, eventually phasing into a single low off of the east coast. Details of this remain murky, but rain appears likely Thursday and Thursday night in this pattern. Cooler air arrives starting Thursday night, knocking temperatures back towards climatology and possibly allowing snow to mix in along I-80. Accumulation potential appears meager. Showery precipitation will continue in northwest flow through Friday night, with increasing snow coverage, before tapering off Saturday as midlevel ridging approaches. && .AVIATION /10Z SUNDAY THROUGH THURSDAY/...
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With the warm front lifting north of the area and the cold front yet to come this morning, we find ourselves temporarily in the warm sector of the broad low pressure system. VFR or at worst MVFR ceilings have been common in the warm sector and will continue until the frontal passage from west to east this morning. In the wake of the front, dry air will allow clouds to scatter out and ceilings to raise. VFR is then expected through the balance of the TAF period. Low-level wind shear will be alleviated with the frontal passage, but a surface wind shift will also accompany. Winds will quickly shift from southerly to westerly behind the front, gusting into the 20-30kt range and possibly (temporarily) higher. OUTLOOK... High pressure building in for early this week will limit restriction potential.
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&& .HYDROLOGY... With rainfall totals coming in below expectations, any flooding of the mainstem rivers should fall in the minor flood spectrum at worst. Also, as of this writing, few reports of small stream and creek issues have been received in the locations where areal flood warnings and advisories are in effect. Perhaps some flooding will be discovered with daylight, but overall, the threat of widespread high water issues is decreasing. Still, the flood watch will remain intact for now, and mudslides remain a concern given the saturated ground and continued runoff. No river flood warnings are in effect at this time, but remain possible as the effects of the recent rain are considered. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...Flood Watch through this evening for MDZ001. OH...Flood Watch through this evening for OHZ039>041-048>050- 057>059-068-069. PA...Flood Watch through this evening for PAZ007>009-013>016- 020>023-029-031-073>076. WV...Flood Watch through this evening for WVZ001>004-012-021- 509>514. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.