Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 282049 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 449 PM EDT Wed Oct 28 2020 .SYNOPSIS... High pressure will support a brief period of dry weather tonight into early Thursday morning. A storm system will then pass well to our south Thursday and Thursday night. This storm will produce another round of widespread rain, especially along and south of the Thruway. The rain will mix with some wet snow later Thursday night and Friday morning, with minor accumulations possible across the higher terrain of the Southern Tier. Strong high pressure will bring a return to dry weather Friday night and Saturday. && .NEAR TERM /THROUGH THURSDAY NIGHT/... A weak bubble of high pressure will remain over Ohio and PA tonight, and this will provide a brief break of dry weather for most of our region. Any temporary clearing through the first half of tonight will be short lived as clouds stream northward again ahead of the next system. Still cannot rule out a few isolated light rain/wet snow showers east of Lake Ontario overnight as lingering shallow lake instability interacts with a weak passing trough. Lows will drop into the upper 30s to lower 40s in most locations, with mid 30s for the North Country. Thursday and Thursday night...the remnants of Zeta will quickly become extra-tropical and become involved with a mid-latitude frontal zone. The remnant surface low of Zeta will race from just south of the Ohio Valley Thursday morning to off the Jersey Shore by late Thursday evening. Meanwhile the baroclinic frontal zone north of Zeta and its associated frontogenesis, deformation, and strong upper level jet dynamics will force a large shield of stratiform precipitation to the north of the track of Zeta. A mid level trough and associated DPVA will cross the eastern Great Lakes Thursday evening, with the added forcing marking the time of most widespread precipitation across our area. Looking at the details, the entire region should still be dry at daybreak Thursday. Rain will then overspread the Southern Tier by mid to late morning, then spreading north to near the NYS Thruway corridor during the afternoon. The northern edge of the precipitation shield will likely have a very sharp cutoff given the low level dry air being fed into the region by increasing northeast flow from strengthening high pressure to our north. The most widespread precipitation will occur Thursday evening with an added boost of forcing from the passing mid level trough, and also due to an increase in lake enhancement from northeast flow off Lake Ontario as cold air begins to deepen and lake induced equilibrium levels rise. The synoptic precipitation will then taper off from northwest to southeast late Thursday night as the system moves well offshore of southern New England. Precipitation type will be all rain through early Thursday evening. Colder air surface and aloft will feed into NY during the latter stages of the event, allowing the rain to mix with, and change to wet snow. The changeover will likely occur first across the higher terrain by late Thursday evening, then progress to lower elevations by late Thursday night. Multi-model, multi-run consensus still suggests minor accumulations will be highly elevation dependent, with 1-2 inches expected across the higher terrain of Cattaraugus and Allegany counties and possibly the Bristol Hills, with a coating to an inch on the hills in surrounding counties. Farther north on the lake plains, there may be a few wet snowflakes in the air late Thursday night, but no accumulation is expected. Friday all of the widespread synoptic scale precipitation will have exited by daybreak. Cold northwest flow will still support scattered lake effect snow showers through midday south of Lake Ontario and Lake Erie, possibly mixed with some rain close to the lakes. This may produce an additional light coating in a few spots over the hills. High pressure will build towards the eastern Great Lakes later in the afternoon, with rapidly lowering inversion heights bringing an end to the brief, weak lake response. Friday will be very cold, with highs only in the upper 30s on the lake plains and low to mid 30s for higher terrain. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... An area of surface high pressure spanning across the Great Lakes Friday night will continue to push east into the eastern Great Lakes and eventually New England Sunday. With the high pressure overhead of the region Friday night, dry conditions are expected. While directly under the center of surface high pressure Friday night, calm winds along with mostly clear skies will promote ample radiational cooling causing Friday night to be the coldest night thus far this season. Lows Friday will drop down into 20s across the Lake Plains to upper teens along the higher terrain. Dry chilly conditions continue Saturday and into Saturday night as the area of surface high pressure continues to slide eastward into New England and eventually exits the east coast. Temperatures Saturday night will be warmer than Friday night as a tightening pressure gradient from the next incoming system will cause winds to freshen, and thus dampen the radiational cooling effect. As alluded to previously, the next upper level trough and associated surface features(low and cold front) is progged to cross the Great Lakes Saturday night through Sunday. As such, the upper level trough should sharpen late Sunday which will put the arrival and passage of the surface cold front Sunday afternoon. That said, expect increasing cloud cover and rain shower chances throughout the day on Sunday. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... Strong cold air advection will follow the passage of the cold front Sunday night. This will mark a couple day stretch in the beginning of next week of below normal temperatures as temperatures at 850mb drop to around -12C. The cool air combined with west-northwest flow and wrap around moisture from the system prior in the weekend will result in a period of lake effect rain and snow showers southeast of both lakes Sunday night and Monday. A wave of low pressure and mid-level trough will pass across Canada Monday afternoon and Tuesday. With this, a fresh batch of cold air should arrive late Monday into Tuesday which will produce a few more lake effect rain and snow showers east and southeast of the lakes. Any leftover precip should come to an end by Tuesday afternoon and mark a period of dry weather as a broad area of high pressure builds over southeastern CONUS and nudges into the area. Warm air advection with an increasing south-southwest flow Tuesday will help raise temperatures back to near normal for Tuesday night and Wednesday. && .AVIATION /21Z WEDNESDAY THROUGH MONDAY/... While MVFR cigs will linger across the Southern Tier til about nightfall...general VFR weather will be found throughout the region tonight. The VFR conditions may be accompanied by some nuisance showers east of Lake Ontario. Low pressure will then pass well south of the area Thursday. A large shield of rain to the north of the low will overspread the Southern Tier in the morning, then develop northward to near the south shore of Lake Ontario by late afternoon. VSBY will deteriorate to MVFR in the steadier rain. CIGS will also deteriorate through the day Thursday, with widespread MVFR at lower elevations and IFR higher terrain in the afternoon. Outlook... Thursday night...MVFR/IFR with rain, mixing with or changing to wet snow. Friday...MVFR/IFR with wet snow or rain showers tapering off in the morning, improving to VFR/MVFR. Saturday...VFR. Sunday...VFR/MVFR with a chance of showers. Sunday night and Monday...MVFR/IFR possible in lake effect rain and snow showers southeast of the lakes. && .MARINE... High pressure will build south of the area this afternoon and evening, allowing west to southwest winds to freshen. This will support a round of Small Craft Advisory conditions on both Lake Erie and Lake Ontario through this evening. Winds will then diminish later tonight. Low pressure will move from the Ohio Valley to off the northern Mid Atlantic Thursday through early Friday. A period of stronger northeast winds will develop on the eastern Great Lakes as a tight pressure gradient develops between this low and high pressure building into Ontario and Quebec. This will bring another round of Small Craft Advisory conditions staring Thursday afternoon and lasting through Friday morning on both lakes. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 11 PM EDT this evening for LEZ020- 040-041. Small Craft Advisory until 5 AM EDT Thursday for LOZ043>045. Small Craft Advisory until midnight EDT tonight for LOZ042. && $$ SYNOPSIS...Hitchcock/RSH NEAR TERM...Hitchcock/RSH SHORT TERM...EAJ LONG TERM...EAJ/PP AVIATION...Hitchcock/RSH MARINE...Hitchcock

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