Area Forecast Discussion
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000 FXUS61 KPBZ 182108 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 408 PM EST Sat Nov 18 2017 .SYNOPSIS...
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A strong cold front will cross tonight bringing strong winds and a changeover to snow showers by early Sunday morning.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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Bulk of heaviest rain will continue to shift northward, with a bit off a lull expected until the front approaches tonight. We should still see temperatures rapidly warm in advance of the front, which may offer up just enough instability for a rumble of thunder so we will keep this in the forecast through the early eve. Will maintain the flood watch as is for now, until precip with the front crosses. Boundary is rather progressive so overall concerns for flooding are minimal at this point. Still expecting a period of strong winds with the front as it crosses and behind with as lapse rates steepen. While pressure rises are rather impressive, this will be just along the frontal boundary, which may lead to the need for a special weather statement, but not long enough to hoist an advisory as none of the other model guidance, bufkit soundings etc, suggest widespread and prolonged advisory-level conditions. Will leave the current wind advisory for the terrain as is, as conditions will linger there. Changeover to snow is expected overnight as cold air returns to the region. Warm and saturated ground will limit accumulation at first, with rather low snow ratios but this should improve as the core of the coldest air approaches later Sunday.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
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Northwesterly flow will continue scattered snow showers and keep temperatures in the 30s through the day. Highest PoPs remain the snow belt north of I-80 and in the mountains of PA/WV/MD where lake enhancement/upslope is anticipated. Still thinking 2-4 is reasonable, though some higher amounts may be possible. Best window for accumulating snow in the terrain looks to be as the second shortwave dives through the trough tomorrow afternoon, deepening the saturation layer through the snow growth zone, but this only lasts for a short period of time. With this in mind, have opted not to issue a winter weather advisory at this time. Snow showers will continue through Sunday night with the passage of this second shortwave and northwest flow. Building ridge of high pressure and backing flow should end chances for showers by Monday morning, with dry conditions expected through Tuesday. Some warming is is expected under an upper ridge, which should get us closer to seasonal values by Tuesday.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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Minimal change was needed in the extended. The majority of the week will be dry with seasonal temperatures outside of a weak wave progged to pass to the north midweek. Have kept slight chances in for locations north of I80 on Wednesday. Next system is progged for late in the period, with broad troughing in place. Model guidance differs, so opted to stay near a blend of guidance.
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&& .AVIATION /21Z SATURDAY THROUGH THURSDAY/...
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Any improvement above MVFR will be brief this evening as the warm sector of low pressure digging toward the Southern Great Lakes traverses the area. Expect redeterioration to IFR with rain and then snow as the systems cold front crosses in the predawn of Sunday. The strong pressure gradient of this system will continue to support llvl wind shear and gusts of 30 to 40 kts with the frontal passage tonight. MVFR stratocu will linger in the cold flow behind the front on Sunday, in addition to local IFR in snow showers, especially at FKL and DUJ. .Outlook... The next chance for restrictions is expected with a late Tuesday cold front.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...Wind Advisory from 7 PM this evening to 10 AM EST Sunday for MDZ001. OH...Flood Watch until midnight EST tonight for OHZ039>041-048>050. PA...Flood Watch until 3 AM EST Sunday for PAZ007>009-013>016- 020>023-029-073-074. Wind Advisory from 7 PM this evening to 10 AM EST Sunday for PAZ074-076. WV...Flood Watch until midnight EST tonight for WVZ001-002. Wind Advisory from 7 PM this evening to 10 AM EST Sunday for WVZ510>514.
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