Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 290625 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 125 AM EST Sat Feb 29 2020 .SYNOPSIS... A swath of moderately heavy snow will accompany the passage of a cold front early this morning...while accumulating lake snows will persist east of both lakes. A cold northwest flow will support additional snow showers today for all areas except the North Country. Significant day to day warming can then be expected for Sunday and Monday. && .NEAR TERM /THROUGH TODAY/... Currently as of 6Z, the Lake Ontario lake band is dropping across the counties just south of the lake. This is occuring as a trough drops south across the lake. Localized reductions in visibility will be possible in this band of snow as it moves south, but the band is weakening the farther inland it travels. Early this morning through today, vertically stacked low pressure over Quebec will slowly meander its way eastward to northern New England and the Canadian Maritimes. This feature will push a secondary cold front southward across our area early this morning...with a modified shot of sub-arctic air then following in its wake. The resulting cold cyclonic flow across our region will continue to maintain lake effect and lake enhanced snows across our region through today...with the activity generally sliding southward to areas southeast of the lakes and weakening over time as the initial westerly flow out ahead of the cold front turns more northwesterly and becomes a bit more sheared. The passage of the secondary cold front will also generate a round of more widespread light to briefly moderate snow early this morning...resulting in general additional inch or two of accumulation outside of the main lake effect areas. Off Lake Erie...ongoing lake snows east of the lake will continue to briefly ratchet up in intensity through this morning as the secondary cold front approaches and provides a boost in moisture and large-scale lift...though the presence of at least some directional shear should still help keep this more diffuse in nature. Expect this to peak through the early morning hours...before weakening and settling southward across the higher terrain through the remainder of the day as the flow turns more northwesterly and the fetch across the lake shortens. Expect additional accumulations across southern Erie and Wyoming counties and the western Southern Tier to range from 4 to 7 inches through early this morning and 2 to 3 inches on today...for which Lake Effect Snow Warnings remain in effect. Further north...the more immediate Buffalo southtowns and far southern sections of Genesee County could pick up an additional 1 to 3 inches before the activity settles back southward this morning...with total amounts in most areas likely to stay under advisory criteria. Meanwhile off Lake Ontario...a single intense band will quickly get shunted bodily southward by the advancing secondary cold front...with the band sinking across the entire south shore of the lake and bringing a brief burst of heavier snow to the Niagara- Northern Cayuga county corridor that could produce a quick few inches of accumulation. The strong single band will break apart...with the general west-northwesterly flow in the wake of the front and an increase in shear leading to a larger area of weaker...multibanded lake snows for the remainder of today. In terms of additional accumulations...Wayne/Northern Cayuga counties will likely see an additional 3-5" through the early morning...with an additional 2-3" then falling across the Wayne-Oswego County corridor today. For this reason...Lake Effect Snow Warnings and Winter Weather Advisories remain in effect for these areas as outlined below. Further west...far northeastern portions of Monroe county could also see localized lower-end advisory-criteria amounts...with the areal coverage of these currently appearing too low to warrant an additional headline. Outside of the lake snows and general snowfall mentioned above... today will feature a return to much lighter winds but also well below normal temperatures...with lows this morning dipping into the single digits across the North Country and the mid teens elsewhere...and highs today struggling to get much above the upper teens to mid 20s. && .SHORT TERM /TONIGHT THROUGH MONDAY NIGHT/... Lake effect snows will be in the process of weakening and winding down during this period. Lake Erie will see this occur first as equilibrium levels fall below 5K aided by a lowering subsidence inversion and warming mid-levels. Off lake Ontario, deeper moisture and upstream connections may keep lake snows going further into the night with some minor additional accumulations. Otherwise, there too lake snows will be in the process of weakening and by Sunday morning should all but wrap up shortly after sunrise. In terms of temperatures, lows will be found from the single digits east of Lake Ontario to the teens across the rest of the region by sunrise Sunday. Winter doesn`t stick around too long again with a rapid warming trend. A mid-level shortwave tracking across the Canadian Prairies will push a warm front into and across the region on Sunday. Warm advection processes and H850T climbing to 0C/-3C across the region will result in high temperatures pushing near to a little above normal. As the warm front crosses the region there will also be a chance for some light showers. Otherwise, Look for highs in the upper 30s to lower 40s across the Genesee Valley and far Western NY. East of Lake Ontario, where the warm front won`t have quite made it through highs will be a bit cooler and in the upper 20s to near 30F. Sunday night, warm frontal boundary extending back into the Ohio and mid Mississippi valley will provide the avenue for a weak low to track along overnight. Deep moisture transport aided by a +45 knot LLJ and DPVA will lead to increasing chances of precipitation as we head into Monday. While the main p-type looks like rain, there maybe a brief period of mix precipitation before it transitions to all liquid on Monday. Precipitation amounts will generally be light and less than a quarter of an inch across area basins. In terms of temperatures, low temperatures will range from the teens to low 20s east of Lake Ontario into the 30s across the Finger Lakes and Western NY sunrise Monday. Highs on Monday, look for temperatures to climb into the 40s areawide. Monday night, the first wave exits the area and a weakening cold front approaches the region from the northwest. There will be a brief lull in the precipitation overnight before a series of weak waves ripple by to our south. This will bring additional chance of precipitation on Tuesday. Otherwise, lows overnight will be found in the mid to upper 30s across the region. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Multiple shortwave disturbances and attendant waves of low pressure rippling through the deep west to southwesterly large-scale flow will continue to potentially bring frequent chances for rain Tuesday into Thursday. This in combination with snowmelt from warmer temperatures and the subsequent rainfall could pose an elevated risk of flooding. The last in the series of surface waves looks to cross our region sometime between Wednesday and Wednesday night with a shot of colder air (but nothing unusually cold for early March) then following for Thursday. This would knock temperatures back closer to average for the tail end of the period while also possibly allowing a little wet snow to mix in on the backside of the system with any lingering rain showers. While the large scale pattern is in general agreement, there is considerable difference with the small scale feature which could potentially impact our region. The GFS shows a fast moving clipper system Thursday night-Friday with accumulating snows across Western NY. Meanwhile, the ECMWF plunges this little clipper system well to our south. It then merges it with a low exiting off the coast. This solution would have little if any impact on our region. For now, have kept low end chance POPs for the tail end of the week. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... A cold front will continue to push south across the region tonight...and this will generate a swath of moderately heavy snow that will translate into IFR to LIFR conditions for all of western New York. With the front and associated lake effect pressing south of the eastern Lake Ontario region, expect marked improvement to VFR overnight at KART. On Saturday...Continued general MVFR (with IFR at times at KJHW) can be expected southeast of the lakes in numerous snow showers and areas of lighter lake effect snow...while the North Country should experience a mix of MVFR to lower-end VFR conditions. Outlook... Saturday night and Sunday...Improvement to VFR with lingering lake effect snow showers southeast of the lakes coming to an end. Sunday night...MVFR/VFR with scattered rain and snow showers. Monday through Wednesday...MVFR/VFR with scattered to numerous rain showers. && .MARINE... Slowly departing deep low pressure over Quebec will maintain rather brisk westerly to west-northwesterly winds across the Lower Great Lakes through this evening...for which Small Craft Advisories are in effect as outlined below. Calmer conditions will then return later tonight and Sunday as high pressure builds directly across the region. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...Lake Effect Snow Warning until 4 AM EST early this morning for NYZ006>008. Winter Weather Advisory until 1 PM EST this afternoon for NYZ004-005. Lake Effect Snow Warning until 10 AM EST this morning for NYZ012-019-020-085. Winter Weather Advisory until 10 AM EST this morning for NYZ021. MARINE...Small Craft Advisory until 4 AM EST Sunday for LEZ040-041. Small Craft Advisory until 4 AM EST early this morning for LEZ020. Small Craft Advisory until 4 AM EST Sunday for LOZ043- 044. Small Craft Advisory until 1 AM EST Sunday for LOZ042-045. && $$ SYNOPSIS...RSH/SW NEAR TERM...JJR/SW SHORT TERM...AR LONG TERM...AR/JJR AVIATION...JLA/JJR/RSH MARINE...JJR/SW

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