231 FXUS61 KBUF 090838 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 338 AM EST Sat Feb 9 2019 .SYNOPSIS... Cold westerly flow across the lakes will continue to generate localized lake effect snow across the western Southern Tier and southeast of Lake Ontario this morning before ending by afternoon. Lake effect snow will re-develop southeast of Lake Ontario tonight with additional local accumulations. Outside of lake effect areas it will be mainly dry and cold through tonight. A weak front will bring some widespread light snow late Sunday and Sunday night with minor accumulations. && .NEAR TERM /THROUGH TONIGHT/... Lake effect snow will continue to be the main concern through the near term period. Lake induced equilibrium levels are still running at 8-9K feet early this morning, but will drop to around 6K feet from late morning through tonight as the cold airmass becomes more shallow. Despite the low inversion height, conditions beneath the inversion will still be favorable for a lake response with a fairly deep layer of dendritic crystal growth through the cloud bearing layer. Off Lake Erie... Multiple bands of relatively weak lake effect snow showers will continue into early this morning. The wind yesterday presumably opened up some of the ice on the lake, allowing for a better lake response. Furthermore, there is still sensible heat flux even through thin ice cover, just not latent heat flux. A surface ridge will build northward across the lake this morning, with associated increased shear, dry air, and lowering inversion heights bringing an end to the lake effect. Until then, expect additional accumulations of around an inch in the persistent bands through early to mid morning, along with blowing and drifting snow. Off Lake Ontario... The cellular structure of snow showers at the southeast end of the lake is indicative of shear at the moment. The disorganized nature of the band of snow is limiting accumulations right now. IR satellite imagery showing a convergence band from Lakes Superior and Huron sitting just north of Lake Ontario at 07Z. This feature is forecast to move southward through early morning as boundary layer flow veers, and will merge with the Lake Ontario band. The added convergence from this upstream connection should allow the band to intensify again for a few hours across central and southern Oswego County for one last gasp of higher snowfall rates. The veering boundary layer flow will then carry the band farther south and west across Northern Cayuga and eastern Wayne counties through mid morning before weakening by midday. The snow may end altogether for a few hours this afternoon as dry air and subsidence take hold across Lake Ontario following the trough passage. Farther west, the western end of the Lake Ontario band with upstream help from Lake Huron will continue to produce light snow across Niagara, Orleans, and northwest Monroe counties through early morning. A band of snow may drift south across the rest of the Rochester area for a few hours mid morning as boundary layer flow becomes more northwest. As far as additional accumulations go, after 4AM expect another 3-5 inches across southern Oswego, Northern Cayuga, and northeast Wayne counties with the greatest amounts in southern Oswego. An inch or so will fall from western Wayne County westward across Rochester to Orleans and Niagara counties. Blowing and drifting will continue through the morning hours. Latest mesoscale model guidance continues to suggest the Lake Ontario band will make a comeback this evening. Strong surface high pressure will pass by just south of the lake tonight from PA to the Mid Atlantic states. Anticyclonic westerly flow on the northern edge of the high will interact cooperatively with a developing land breeze along the south shore of the lake, allowing a single band to re-develop by early to mid evening over the lake. Latest high-res guidance suggests the eastern end of this band will come onshore across Oswego and Northern Cayuga counties, producing local accumulating snow. These types of bands often drop their heaviest snow right near the shoreline given the strong land breeze forcing, and can have notoriously high snow-water ratios. That said, in the weak flow environment there is always a good deal of uncertainty as to whether the heavy snow will fall over the lake or just onshore. Given this uncertainty, have not raised any additional headlines yet, but did increase POPS and snow amounts to 3-6 inches in a small area from Fair Haven to Oswego for tonight. If the heavier portion of the band stays offshore, amounts will be lower. On the flip side, if the heaviest portion of the band extends to the shoreline for an extended period of time, warning criteria amounts are within the realm of possibility. Outside of lake effect areas, expect a mix of clouds and sun today and partly cloudy skies tonight. Temperatures have returned to below normal for now. Highs today will be in the low to mid 20s at lower elevations and teens across higher terrain. Lows tonight will be in the low to mid teens on the lake plains, with some single digits across the interior Southern Tier and east of Lake Ontario. && .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... Sunday, high pressure will begin over our region and gradually fade to the southeast. While this feature will bring a quiet day for most there will be lingering lake effect snow to the southeast of Lake Ontario. Lake Induced Equilibrium levels will remain around 4K feet through the day and a shallow band of snow will start over Oswego county, and lift northward before fading across Jefferson County. A weak synoptic boundary layer wind will create minimal convergence in the lower levels, with greatest lift right near the shoreline of the warmer and open water of Lake Ontario. An additional inch or two of fluffy snow is possible close to the shoreline Sunday morning. The next synoptic snows will arrive late Sunday and through the night as a fast moving upper level shortwave passes and a weak surface trough dips across the region in response to the fleeting surface high. The quick moving and sheared out shortwave will yield minor snow accumulations of a coating to an inch for most, and perhaps a inch or two closer to the state line. Monday morning colder air will drop southward across Lake Ontario and behind this shortwave. It will become just cool enough for some streamers of lake effect flurries and light snow to form...initially over the lake on a land breeze...and then pushed inland across the northern Niagara Frontier on a northeast flow. Otherwise Monday will be quiet with Canadian high pressure nosing southward across our region. This will spread sunshine across our northern zones, though clouds may linger near the state line, and begin to increase Monday night ahead of our next storm system. Our next storm system is currently seen on Water Vapor imagery over the Northwest Pacific shoreline. The closed upper level low will dip southward along the California shoreline this weekend, and then advance across the Rockies and Plains early next week. This negatively tilted upper level long wave trough will deepen a surface low that will again cut through the central Great Lakes. Tuesday will start on the cold side with advancing precipitation starting as all snow late Monday night and Tuesday morning. A primary low will pass through the Great Lakes Tuesday and Tuesday night, moderating temperatures to above freezing for most of the area. This will change the snow/possible wintry mix over to plain rain later Tuesday and Tuesday night for much of WNY. A secondary lee side low will form off the Delmarva Peninsula Tuesday night and as this low deepens, the primary surface low to the north of Lake Ontario will begin to weaken. This will limit the northward push of milder air such that precipitation across the North Country Tuesday and Tuesday night may remain as all snow. Here is where confidence is high enough that there will be potential for significant synoptic snows and will add this to the HWO. Cold air will wrap back across our region later Tuesday night changing precipitation back to all snow for the entire region. However moisture will be limited and additional snowfall along the cold front will be minor. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... Zonal flow to start this period will become more amplified as another closed upper level low forms across the central Plains. Within moist cyclonic flow aloft there will likely be snow showers across the region Wednesday and Wednesday night, favored to the east of the Great Lakes where temperatures become cold enough to support lake effect snow in addition to orographic lift snow showers. Thursday high pressure will pass across the region, with fair weather and a mix of clouds and sunshine. A southerly wind Thursday night will likely bring warming temperatures through the night. A mild flow will be found on Friday across our region to the east of a digging upper level low. This low will spread rain/snow showers across our region Friday. It is within the realm of possibilities that we may even reach into the lower 50s Friday across the Lake Plain. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... Lake effect snow will continue east of the lakes through this morning. East of Lake Erie, multiple bands of lake effect snow will continue to produce areas of IFR VSBY and MVFR CIGS through 14Z today, including KJHW. This lake snow will then come to an end later this morning as high pressure begins to build over the lake. East of Lake Ontario, lake effect snow will continue mainly across Oswego County through early morning near KFZY, with additional bands of snow along the south shore of the lake all the way west to Niagara County producing areas of IFR VSBY and MVFR CIGS. Most of the steadier snow will stay just north of KROC through 12Z, although a few hours of IFR is possible mid morning as flow becomes more northwest. The northwest flow lake effect will weaken by midday today with most of the IFR coming to an end. Outside of lake effect areas VFR will prevail. Tonight VFR will prevail in most areas. The Lake Ontario lake effect will make a comeback at the southeast corner of the lake with local IFR developing in Northern Cayuga and Oswego counties. Outlook... Sunday...VFR. Sunday night...Areas of IFR in light snow. Monday...MVFR with a chance of light snow showers early, otherwise VFR. Monday night...Deteriorating to IFR late with snow developing. Tuesday...Areas of IFR with snow changing to rain. Wednesday...Areas of IFR with snow likely. && .MARINE... A tight pressure gradient in the wake of strong low pressure moving off the Labrador coast will continue to produce gales on Lake Ontario into this morning. WNW winds will then steadily diminish this afternoon and tonight as high pressure builds from the Ohio Valley to the Mid Atlantic states. Small Craft advisory conditions will gradually end from west to east later today and tonight. The nearby high pressure will then bring a period of light winds late tonight through Sunday. ENE winds will then increase ahead of low pressure moving into the western Great Lakes. This will bring a round of Small Craft Advisory conditions from later Monday through Tuesday and beyond. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...Winter Storm Warning until 1 PM EST this afternoon for NYZ006. Winter Weather Advisory until 1 PM EST this afternoon for NYZ004-005. MARINE...Small Craft Advisory until 10 AM EST this morning for LEZ020- 040-041. Small Craft Advisory until 10 AM EST this morning for LOZ030. Gale Warning until 10 AM EST this morning for LOZ043-044- 063-064. Gale Warning until 7 AM EST this morning for LOZ042-045- 062-065. && $$ SYNOPSIS...Hitchcock NEAR TERM...Hitchcock SHORT TERM...Thomas LONG TERM...Thomas AVIATION...Hitchcock MARINE...Hitchcock