Area Forecast Discussion
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000 FXUS61 KPBZ 110419 AAC AFDPBZ Area Forecast Discussion...UPDATED National Weather Service Pittsburgh PA 1119 PM EST Sun Dec 10 2017 .SYNOPSIS... Cold temperatures and periodic snow chances can be expected for the coming week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
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No substantive changes needed overnight, although the gradient in PoPs has been sharpened to focus higher PoPs across the I-80 corridor. Any light snow showers in this vicinity should amount to no more than a light dusting, although most areas are not likely to see any meaningful accumulation. Previous discussion follows... A shortwave trough is moving sewd from the Great Lakes into the upper Ohio Valley Region as it digs toward the base of the entrenched ern CONUS trough. That disturbance may spawn some light snow, and some eventual snow showers with overnight passage. Accumulation will be minimal as broad ascent and mid- level moisture with the system are very limited. In addition, model soundings indicate moisture, wind and temperature profiles remain unfavorable for snow growth in the cold flow in its wake. Overnight minima will be slightly below average.
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After a dry and slightly warmer Mon, the longwave trough that has persisted over the northeast will deepen as a strong jet core enters the backside of the trough. Light snow will develop Monday night as moisture and lift increase ahead of an approaching shortwave. A couple inches look likely across northern zones closer to the surface low by daybreak...with lesser amounts farther south. A second wave will quickly follow on Tuesday...reinforcing the longwave trough and shifting the trough axis east. This will set up strong cold air advection as flow aloft turns to the northwest. Lapse rates and inversion heights will increase quickly and allow for a long duration of lake-effect snow potential across the I-80 corridor beginning Tuesday through Wednesday. Overall, minimal changes were made to the inherited forecast and the potential for heavy snow across northern counties remains, therefore, the Winter Storm Watch remains in effect for Mon night through Wed.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... An upstream shortwave is projected to back flow to the west on Wednesday night, thus ending lake enhanced snow, before the reinforcing front spawns more snow showers on Thursday, and initiates more cold for Friday. Thereafter, another upstream trough is projected to flatten flow and moderate temperature briefly back toward the averages before cold frontral passage drops them again for the start of the new week. && .AVIATION /04Z MONDAY THROUGH FRIDAY/... Condition deterioration to MVFR, with lcl IFR in shsn, is expected as a shortwave crosses the region tonight. Confidence in that IFR visibility potential is relatively low given the lack of progged moisture and lift with this system. Southwest wind will briefly veer westerly before shifting back to the SW tomorrow in advance of a more potent system, progged for Mon night. .Outlook... Widespread restrictions will come with low pressure forecast for Monday night/Tuesday with restrictions continuing through midweek. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...Winter Storm Watch from Monday evening through Wednesday afternoon for PAZ007>009-015-016. WV...None. && $$ Update...Kramar is the U.S. government's official web portal to all federal, state and local government web resources and services.