Area Forecast Discussion
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000 FXUS61 KPBZ 200515 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1215 AM EST Fri Jan 20 2017 .SYNOPSIS...
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Rain will return to the region today as the next upper level system moves through. The mild pattern will continue through the weekend.
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&& .NEAR TERM /THROUGH TODAY/...
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For the overnight period, have continued with previous forecast of slowing down the onset of rain. First, it will take some time to moisten the lower layers of the atmosphere as the air is very dry from the surface up to around 10kft. Second, most of the good upper level support is streaming northwestward toward the main upper low, which will reach the northern plain/upper midwest by dawn. And lastly, the oncoming moisture/precipitation will encounter a rather strong ridge, which will begrudgingly drift eastward as dawn approaches. Temperatures have been updated with a blend of hires guidance. A tilted and elongated trough will swing through the area this morning. The associated surface warm front will swing through in the same direction just ahead of the aforementioned upper level system. Once the lower atmosphere saturates, showers will overspread the area from southwest to northeast. Western locales will see rain first, shortly before dawn, with the northeastern counties of my forecast area holding off until mid-morning. The showers will sweep through the area rather quickly, with the backedge reaching the northeast by late afternoon. Temperatures will average well above normal today.
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&& .SHORT TERM /TONIGHT THROUGH SUNDAY/...
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With upper level heights rising quickly this evening and the atmosphere drying out, have continued with the previous thinking of keeping Friday night and Saturday dry. The next strong upper level system begins to take shape over the Tennessee Valley Sunday morning. Moisture will once again begin to stream northward on the eastern side of the developing 500mb low. At the surface, low pressure will rapidly develop over OK Sunday morning and move rapidly toward the east coast, reaching the Mid- Atlantic region Sunday afternoon. Have kept the highest PoPs Sunday during the afternoon hours, in conjunction with movement of the southern stream low. Temperatures both Saturday and Sunday will be well above normal with Saturday providing the warmest temperatures.
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&& .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
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There is still much uncertainty pertaining to the forecast Monday and Tuesday, as even the ensembles are trying to come to an agreement on the speed and path of the Mid-Atlantic/Coastal low. Have shied away from the operational NAM solution, as it remains an outlier when compared to ensemble data. It does appear that precipitation will overspread the area Monday into early Tuesday. It also looks like some colder air will be pulled into the area on Monday still many questions as to how much and where. Coastal low should move out to sea sometime Monday night or Tuesday morning. The next system is expected to bring precipitation back to the area on Wednesday. The superblend will be used for the long term. Temperatures through the extended will be above normal.
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&& .AVIATION /05Z FRIDAY THROUGH TUESDAY/...
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General VFR across ports with patchy MVFR fog will deteriorate to MVFR in light rain and CIGs from 10-14Z across ports southwest to northeast, as a negatively tilted shortwave lifts across the region. A 5 to 7 hour period of IFR in rain and cigs is expected with the shortwave passage into late afternoon, followed by slow improvement later Friday night. Winds will be under 10 KTs through Friday, being southeast overnight, becoming southwest Friday. .OUTLOOK... Restrictions are likely Saturday night into Monday with slow moving low pressure.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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