FXUS61 KBUF 040541 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1241 AM EST Wed Dec 4 2024 .SYNOPSIS... Lake effect snow continues across areas southeast of Lake Erie and Ontario late this evening with some additional accumulation, but intensity of the snow has been considerably lower than over the weekend. Lake effect snow bands will move north overnight through early Wednesday, bringing a quick burst of snow and minor accumulations to areas east and northeast of Lake Erie and Lake Ontario. Low pressure will then pass just north of the area Wednesday night through Thursday, with very gusty winds, periods of snow, blowing snow, and possibly a few snow squalls. The greatest accumulations will be east of Lake Erie and Lake Ontario as lake enhancement develops. && .NEAR TERM /THROUGH TODAY/... The main concern through Wednesday morning will be the last of this very long duration lake effect snow event. The intensity of snowfall is not nearly as high as over the weekend, but still enough to have some impact. Lake induced equilibrium levels will continue to run 12- 14K feet through this evening, before falling rapidly Wednesday morning as warm advection aloft increases and inversion heights lower. Backing of boundary layer flow to the southwest tonight behind a weak mid-level trough passage has begun carrying lake effect northward. Off Lake Erie... Lake effect snow has spread across much of the Southern Tier this evening, but has been slowly shifting northward as the low-level winds continue to back to the southwest. Latest GOES imagery shows high clouds associated with a weak mid-level trough passage that has aided in the the development of 850mb southwesterly flow and eventual shift northward of snowbands through the Buffalo area. Latest radar imagery as of 10 PM EST shows a few snow showers reaching the Southtowns currently and eventually lifting north through the city after midnight and headed towards Wednesday morning eventually ending up in Niagara County and weakening before daybreak. Snowfall rates may still be moderate, but the rapid northward shift of the band will likely limit accumulations to 1-3" overnight. The snow will mostly be over by the start of the morning drive. Off Lake Ontario... A band of snow has reorganized over the lake this evening, extending into Oswego County. As this trough continues to pass to the east, expecting a similar response east of Lake Ontario with snowfall lifting northward towards the Watertown area after midnight. with backing boundary layer flow. Expect 2-4" overnight through Wednesday morning as the band moves north across the area. There may be some impact to the morning drive in Jefferson County. Wednesday, any lingering lake effect across Niagara County off Lake Erie, and northern Jefferson County off Lake Ontario, will weaken and mostly end through the morning hours as ongoing warm advection continues to lower inversion heights. Our attention then turns briefly back to the synoptic scale. Low pressure will track just north of the upper Lakes, with a broad warm advection pattern supporting a chance of some occasional light snow Wednesday. Accumulation in most areas will be minimal from this. East of Lake Ontario, increasing southwesterly upslope flow may produce a few inches in the afternoon across the Tug Hill Plateau. More on this event in the short term section below. && .SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/... ...IMPACTFUL WINTER STORM LIKELY WEDNESDAY NIGHT THROUGH THURSDAY NIGHT... Low pressure will track across southern Ontario province Wednesday night before moving across northern Maine on Thursday and then strengthening to 973mb as it enters the Canadian Maritimes Thursday night. This system will produce a hybrid snow event, with some synoptic scale snow along with some lake effect and upslope enhanced snow. Strong winds Wednesday night through Thursday night will increase the impacts and cause areas of blowing snow. An associated cold front will move across the area from west to east late Wednesday night. This will produce an period of snow for all areas, which may briefly be mixed with rain across some lower elevations at its onset. Strong westerly winds will start immediately following the frontal passage. 850 mb winds increase to 50 knots which will support widespread wind gusts to 40 mph with gusts to 50 mph downwind of the lakeshores and across higher terrain. Following the frontal passage, the mid level trough and 850mb temps to -12C will support lake effect snow. Unlike our last event, the strong westerly flow will not support banding, and moisture will somewhat depend on upstream lakes and will be enhanced by orographic lift. Adjusted snowfall forecast accordingly, favoring higher resolution guidance during this phase. Since the strong westerly flow will push lake/orographic snows into Allegany County have added that to the winter storm watch. The steadiest snows will be Wednesday night and Thursday, and then will become more localized Thursday night. Storm totals are likely to run in the 8 to 16 inch range across higher terrain east of the lakes, with considerably less along I-90 which is near the lakeshore. Lower elevations will get much less, averaging 3 to 6 inches. This will include the risk for snow squalls (heavy snow and gusty winds) during the day on Thursday, as the upper level trough moves through. Despite the lower snow amounts, this storm will be very impactful because of the strong winds which will cause areas of blowing snow. This will not only apply to the new snows, but also to the snow which has already fallen in our last event. It also will not be as localized as our last event, with at least some snow and wind to cope with across the entire region. Impacts will diminish Friday as winds drop off with gusts 20 to 25 mph. Lake effect snows will continue during the day, but with limited moisture lake effect will depend on moisture connections from upstream lakes. As a result snow will be more localized, but will still have some impacts. Winds will shift to the southwest Friday night, with whatever is left of the bands moving east/northeast of the lakes. This will perhaps bring a little more snow to the Buffalo metro area, although snow intensity and amounts will be limited. && .LONG TERM /FRIDAY THROUGH TUESDAY/... It will be cold enough aloft to support some lingering lake effect snow on Saturday. With the flow shifting to the southwest, snows will move across the Niagara Frontier and Jefferson County, but the moving band will only produce minor accumulations. Lake snows will taper off Saturday night as warmer air aloft moves in. Warmer Sunday and mainly dry with highs reaching into the 40s across lower elevations. Model consensus tracks low pressure to our north and west Monday and Tuesday, which would result in a mainly, if not all rain event. Sill some spread in model guidance, so depending on its track and strength there's some risk for mixed precipitation at the onset Sunday night and Monday, but mainly across higher terrain and the North Country. Otherwise it will be a fairly soaking rainfall with ballpark rainfall amounts in the half inch to an inch. This combined with snow melt will cause rises on creeks and rivers, but limited rainfall amounts and recent dry weather support MMEFS ensembles which show only a low risk (less than 20 percent) for flooding. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... Bands of lake effect snow off both lakes will move rapidly northward through the wee hours of the morning as boundary layer flow quickly backs to the SSW. IFR/IFR conditions will be found within these bands of snow, with mainly VFR elsewhere. Off Lake Erie, the band of snow will move through KBUF from about 06Z to 08Z, KIAG from 07Z-10Z, then move farther north and west and weaken by daybreak. The eastern end of the band may bring a few light snow showers to KROC as well before daybreak. Off Lake Ontario, the band will move through KART with off and on snow from 06Z through about 11Z before moving farther north and weakening shortly after daybreak. It will become quite windy today northeast of Lake Erie, with gusts of 30-35 knots at KBUF and KIAG, and 15-25 knots elsewhere. Our attention then turns to snow associated with low pressure passing north of the region. Expect areas of mainly light snow to develop this afternoon, first east of Lake Ontario and then later afternoon across Western NY with areas of MVFR/IFR developing. The snow will become more widespread tonight, and a strong cold front will also move from west to east across the region, producing a few quick bursts of moderate to heavy snow or snow squalls. Lake effect snow will also begin to develop late tonight east of Lake Erie and Lake Ontario, embedded within the general snowfall. It will continue to be quite windy tonight, with areas of blowing snow developing. Outlook... Thursday...Areas of MVFR/IFR in snow showers. Heavier lake effect snow east of the lakes with local LIFR. Very windy with blowing snow. Friday...VFR/MVFR with scattered snow showers. Localized IFR in lingering lake effect snow showers southeast of the lakes. Saturday...VFR/MVFR with a chance of snow showers. Sunday...Mainly VFR. && .MARINE... Northwest winds will continue to produce choppy conditions on Lake Erie and Lake Ontario into the evening, but winds and waves will generally stay below Small Craft Advisory criteria. Winds will start to increase out of the southwest on the lakes later in the evening from west to east as the pressure gradient increases over the region with an area of low pressure approaching from the northwest and a sfc high to the south. This will prompt the need for Small Craft Advisories which will then transition to Gale Warnings that are in effect for times listed below. Moderately strong low pressure will then pass just north of the lakes later Wednesday through early Thursday before a secondary coastal low deepens over the Canadian Maritimes Thursday night. This will cause the Gale conditions on Lake Erie Wednesday through Thursday, and Lake Ontario early Thursday through Thursday night. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...Winter Storm Watch from this afternoon through late Thursday night for NYZ006>008. Winter Storm Watch from this evening through late Thursday night for NYZ012-019>021-085. MARINE...Small Craft Advisory from 4 AM early this morning to 1 AM EST Friday for LEZ020. Small Craft Advisory until 7 AM EST this morning for LEZ040-041. Gale Warning from 7 AM this morning to 7 PM EST Thursday for LEZ040-041. Small Craft Advisory from 4 AM early this morning to 1 AM EST Friday for LOZ030. Small Craft Advisory from 4 AM early this morning to 4 AM EST Thursday for LOZ042>045. Gale Warning from 4 AM Thursday to 1 AM EST Friday for LOZ042>045-062>065. && $$ SYNOPSIS...Hitchcock NEAR TERM...Brothers/Hitchcock/SW SHORT TERM...Apffel LONG TERM...Apffel AVIATION...Hitchcock MARINE...Hitchcock/SW