Area Forecast Discussion
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806 FXUS61 KPBZ 102308 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 608 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/... No changes were needed for the eve update as a shortwave is sliding over the Great Lakes toward the base of the high- amplitude, Eastern North American trough. That disturbance will spread some light snow, and eventual snow showers with further approach and overnight passage. Accumulation will be minimal as broad ascent and mid level moisture on the van of the system is limited. In addition, model soundings indicate moisture and temperature profiles that are not favorable for snow growth in the cold flow in its wake. Overnight lows again will be slightly below average. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... After a dry and slightly warmer day, 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 increases ahead of an approaching shortwave. A couple inches looks 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 quickly increase and allow for a long duration of lake effect snow potential across the I-80 corridor beginning Tuesday through Wednesday. Overall, minimal change was made to the inherited forecast and the potential for heavy snow across northern counties remains, therefore, the winter storm watch remains in effect for Monday night through Wednesday. && .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 /00Z MONDAY THROUGH FRIDAY/... Condition deterioration to MVFR, with lcl IFR in -sn, 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. && $$

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