Area Forecast Discussion
Issued by NWS Buffalo, NY
Issued by NWS Buffalo, NY
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398 FXUS61 KBUF 220142 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 842 PM EST Thu Nov 21 2024 .SYNOPSIS... Strong low pressure will continue to spin over the Northeast US through Friday night, producing low elevation rain and high elevation wet snow across the region. The highest elevations will see locally moderate accumulations across the Southern Tier and Tug Hill Plateau, with no accumulation for lower elevations. A few leftover rain and wet snow showers will continue Saturday through early Sunday before mainly dry weather returns later Sunday. && .NEAR TERM /THROUGH FRIDAY/... Radar imagery showing widespread, synoptic scale precipitation from the Genesee Valley east across Central NY and the eastern Lake Ontario region. Most of this is rain, except for the highest elevations of the Tug Hill Plateau and Finger Lakes where wet snow is falling. Meanwhile across Western NY, an area of lake effect showers persists along the Lake Erie shore from Silver Creek southwest to Ripley in a light flow regime. Temperatures have dropped to the mid 30s within this band from evaporational cooling and latent cooling from melting, allowing some wet snow to mix in even along the Lake Erie shore. This will likely change back to rain overnight as northerly flow off the warm lake waters increases. A large and deep mid/upper level low over the upper Ohio Valley this evening will continue to move east to the Mid Atlantic by later Thursday. At the surface, the primary low over the western Great Lakes continues to weaken and give way to secondary cyclogenesis off the east coast. Tonight, the surface low off the coast of New Jersey will deepen and retrograde northwest into the Catskills, continuing widespread lower elevation rain and high terrain snow. Forecast thermal profiles will be ever-changing with time due to milder air from the east being pulled into the low, supporting a difficult higher terrain snow forecast. The coldest column temperatures are through the first half of tonight, and then start to warm slightly late tonight. While temperatures will cause a difficult precipitation type forecast, moisture will be plentiful due to moisture being advected in to the area from the Atlantic and support a large precipitation shield backing westward over the region tonight. This all being said, the lower elevation lake plains will stay almost all rain, with no snow accumulation and temperatures remaining in the upper 30s. Thermal profiles will support colder temperatures across higher elevations, with some minor accumulations showing up above about 1000-1200 feet, and moderate accumulations above 1500 feet across the Southern Tier, western Finger Lakes, and Tug Hill region. Expect slushy, wet totals of 3-7" for the highest terrain in these areas, while the valleys below see far less. Winter Weather Advisories have been issued for the ridges of Wyoming County, higher terrain of the western Southern Tier and Tug Hill tonight through Friday morning. The surface low will then move southward into eastern Pennsylvania Friday, causing dry air to filter into the forecast area and precipitation to begin to dwindle down from east to west during the afternoon. However, due to northwest winds supporting orographic lift and limited lake enhancement western New York, especially the western Southern Tier showers will continue. Temperatures will gradually warm both surface and aloft Friday as somewhat warmer Atlantic air is wrapped back west by the system, resulting in a change back to rain in most areas, even across higher terrain. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... P-type might become a bit of a challenge by Friday night as drier air begins to wrap in around the departing low. While precipitation will `likely` continue in the liquid form below 1000 feet, above that elevation there will be a transition gradually over to snow. That said...there is one caveat, as was mentioned drier air moving into the mid-levels may produce just drizzle. This is indicated in BUFKIT sounding profiles with a pronounced dry layer in the DGZ (-10 to -20 layer). Additionally...the airmass circulating in across the Lower Lakes is not all that cold, with 850T`s only down to -3C to -4C) aloft. Therefore...have limited snow accumulations to under an inch Friday night into Saturday morning across the S. Tier. The higher terrain of the Tug/Western Dacks it will be matter of how much precipitation lingers as the low pulls further away overnight. Even so...we are only looking at nuisance accumulations of an inch or less there too. As the low moves further out to sea Saturday it will then draw Atlantic moisture back eastward across the forecast area. A cool WNW flow (850H temps still around -2C/-3C) with the increase in moisture will lead to a reinvigorated lake response causing showers to expand across much of the area. The main lake enhanced/upslope areas east and southeast of the lakes will see the most activity, though the warmer daytime temps will `likely` support rain as the dominant p- type for all locales. Temps cooling overnight Saturday night may support some wet snow across the higher terrain areas. Sunday....a mid-level shortwave dropping southeast through the region is advertised to bring a brief shot of colder air (850H temps -4 to -8C) to the region. This will likely be just enough to maintain at least a chance for showers (rain/wet snow higher terrain) east/southeast of the lakes through the day. However, drier air again filtering into the region should limit the lake effect potential despite the injection of colder air. Sunday night...continued drier air working into the region and then warming mid-levels will slowly bring about an end to any lake induced showers by Monday morning. && .LONG TERM /MONDAY THROUGH THURSDAY/... Surface high pressure will briefly ridge across the region Monday morning, resulting in mainly fair and warm weather for the day. After this, a mid level trough digging across the upper Great Lakes will lead to surface low pressure developing and tracking across the eastern Great Lakes Monday night into Tuesday. This will bring a shot of widespread rain showers with modest rainfall amounts around a quarter inch. It will also become windy and cooler Tuesday in the wake of the passing surface low. Consensus 850mb temperatures drop down to around -8C by late Tuesday night, with a fairly moist cyclonic flow aloft. This will support some lake effect precipitation, with it cold enough for some of this to be snow. Westerly winds will direct most of the lake effect and upslope enhanced precipitation across the typical snow belts east of the lakes Tuesday night and Wednesday. Accumulating snows are likely, with advisory level amounts (greater than 4 inches) possible but far from a certainty. Due to the marginally cold air mass, greater accumulations would be more likely across higher terrain such as the Chautauqua Ridge and Tug Hill. A more zonal flow aloft develops by Thursday, with some models developing a wave of low pressure and tracking it to our south. This possible system in addition to lingering lake effect may produce some rain or snow showers. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... An expansive and strong upper level low will move from the upper Ohio Valley towards the Mid Atlantic tonight through Friday. A surface low over the western Great Lakes will continue to weaken and give way to a strong east coast low, which will make a loop back into southeast NY and eastern PA before moving out to sea Friday night. This system will produce widespread lower elevation rain and high elevation wet snow tonight through the first half of Friday, before the widespread precipitation tapers off from east to west later Friday afternoon and night. VSBY will be VFR to MVFR in areas of rain, and IFR in snow tonight through Friday. CIGS will deteriorate this evening as the low levels saturate, with widespread IFR CIGS later tonight through all of Friday in cyclonic northerly flow. It will become quite windy later tonight and Friday, especially over and near the lakeshores where gusts may approach 30 knots. Outlook... Saturday...VFR/MVFR with a few rain and wet snow showers. Sunday...VFR/MVFR with a chance of a rain or snow shower. Monday...VFR/MVFR with a chance of rain. Tuesday...MVFR with rain and snow showers possible. && .MARINE... A surface low will rapidly deepen off the east coast tonight, then make a cyclonic loop back into southeast NY and eastern PA late tonight through Friday before moving back out to sea Friday night. North winds will increase over Lake Ontario and Lake Erie as this system deepens and moves closer, with higher end Small Craft Advisory conditions on both lakes overnight through Friday before winds diminish Friday night as the system moves back out to sea. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...Winter Weather Advisory until noon EST Friday for NYZ008-012- 019>021. MARINE...Small Craft Advisory from 7 AM to 7 PM EST Friday for LEZ020. Small Craft Advisory until 1 AM EST Saturday for LEZ040. Small Craft Advisory until 7 PM EST Friday for LEZ041. Small Craft Advisory until 7 PM EST Friday for LOZ043- 044. Small Craft Advisory from 4 AM to 7 PM EST Friday for LOZ030. Small Craft Advisory until 10 PM EST Friday for LOZ042. Small Craft Advisory until 4 PM EST Friday for LOZ045. Small Craft Advisory from 4 AM to 4 PM EST Friday for SLZ022-024. && $$ SYNOPSIS...Hitchcock NEAR TERM...EAJ/Hitchcock SHORT TERM...AR LONG TERM...Apffel AVIATION...Hitchcock MARINE...EAJ/Hitchcock