Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 170558 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 1258 AM EST Mon Feb 17 2020 .SYNOPSIS... A cold front will slide across the Lower Great Lakes overnight with just a few light snow showers and flurries expected. High pressure will then push across our region Monday while bringing a period of fair weather that will last through Monday evening. Low pressure will then cross the Great Lakes later Monday night and Tuesday, bringing warmer temperatures with an initial mix of snow and rain changing to all rain, before colder air returns and leads to some limited lake snows southeast of the lakes Wednesday and Thursday. && .NEAR TERM /THROUGH TODAY/... Early this morning a cold front lies across the eastern Lake Ontario region and Lake Ontario...with scattered snow showers upon it. As the front passes snow, and behind it, some brief lake effect snow will develop. The p-type will merely be in the form of some snow showers owing to renewed moisture within the dendritic snow growth zone. Expect any accumulations to be under an inch and mainly confined to areas east and southeast of Lake Ontario...with the snow showers and flurries rapidly diminishing late tonight and early Monday morning with the departure of the front... and as the low level flow turns more northerly and directional shear rapidly increases. On Monday surface high pressure will build in rather quickly behind the front, with lingering lake effect clouds and flurries south of the lakes giving way to partly to mostly sunny skies in the afternoon. Daytime highs will range from the upper 30s across the western Southern Tier to the upper 20s across the North Country. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... Monday night, warm air advection will increase across the region, and as a result, low temperatures will occur early and warm through the night. This will result as southerly flow will increase as an area of high pressure tracks to the east of the region and as a developing area of low pressure tracks across the Great Lakes Monday night into Tuesday morning. Early low temperatures will be in the mid to upper 20s for most areas south of Lake Ontario, except for some low 30s in the Western SOuthern Tier, and low to mid teens for the North Country. The developing low will take shape and become better organized on Monday evening over the upper Mississippi Valley as a potent shortwave trough crosses the Northern Plains. POPs will increase after Midnight Monday night as the area of low pressure and cold front approach the area. Chance POPs will be in place a few hours after Midnight across the far western portion of the area, and continue to expand eastward through the early morning. Likely POPs or higher will expand across most of the area by the time of the morning commute. Most of the precipitation should be in the form of rain as warm air advection continues ahead of the system, but snow will be likely starting closer to daybreak east of Lake Ontario where temperatures will be a bit slower to warm. Tuesday, precipitation will be overspread across the entire area after daybreak on Tuesday with snow for areas across the North Country to start the day. Snow for areas of the higher terrain of the North Country will accumulate to around 2 to 4 inches before warm air advection changes most of the snow to rain. A few locations in the highest terrain of the North Country may stay as a mix on Tuesday and not change over to all rain. The best chance for accumulating snow will be the southern portion of the Tug Hill where upsloping southerly winds will enhance some of the snowfall. Higher terrain of the Western Southern Tier may start as snow before changing over to rain, with the potential for up to a slushy inch of snowfall accumulation. A low level jet over the area late Monday night into Tuesday morning will help enhance moisture transport and warm air advection, resulting in the best chance for widespread steady precipitation from around daybreak through around lunchtime. The low level jet will also provide the area with some gusty winds through the early afternoon. PWat values over the area will approach eight tenths of an inch on Tuesday morning. Pwat values this high are more normal for late in the Spring or early Fall. Steady precipitation will taper off through the afternoon as the cold front crosses the area. Cold air advection will start to cool temperatures, but highs will reach the low to mid 40s for areas south of Lake Ontario and the mid 30s to near 40 for the North Country. Behind the cold front, showers that remain will start to change back to a mix of rain/snow and eventually all snow as temperatures cool. Cold air advection will continue Tuesday night as another cold front crosses the region, reinforcing the cold air advection, this will cause 850H temperatures to drop to the -12C to -15C range by Wednesday morning. With the cold air advection and some synoptic moisture still available, a lake response will begin downwind of the lakes. As of right now, snow looks like it should be light through Tuesday night into early Wednesday morning before additional cold air advection and an approaching trough for later Wednesday. Temperatures on Tuesday night will be in the low to mid 20s, with a few locations east of Lake Ontario in the teens. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... A broad upper level longwave trough will span eastward from the Great Lakes to New England on Wednesday through Thursday. This will allow for the colder temperatures to remain in the area for a couple of days, with Thursday shaping up to be the coldest day. Along with this pattern, general WNW flow combined with increased lake instability shall produce a few rounds of lake effect snow showers east and southeast of the lakes. While the model guidances are hinting at a pattern conducive for lake effect snow, it is too early to pin point the exact details. As it appears currently, this pattern favors a better chance of producing accumulating snow for the lake snows off of Lake Ontario rather than Lake Erie. The best potential for these bands look to occur when there is a lake to lake connection from Lake Huron into Lake Ontario on Wednesday night through Thursday morning. Lake effect snows southeast of the lakes will continue through Thursday night, while diminishing during the morning hours on Friday as warm air is advected into the region by an area of broad high pressure. High pressure looks to remain overhead for the remainder of the weekend, resulting in a gradual warming trend with dry conditions. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... A weak cold front will dip across Lake Ontario early this 06Z TAF period, with just a few flurries of snow near KART and later KROC. This front will bring MVFR ceiling heights to much of the region by daybreak, and for the higher terrain of the Southern Tier, IFR ceiling heights are likely around sunrise and a few hours thereafter. High pressure will then cross the region today, with light winds and flight conditions returning to VFR. Winds will become southerly tonight, and breezy as a 50 knot LLJ develops overnight. With the boundary layer mixed, LLWS will be spotty. While the southerly winds continue the second half of tonight, a swath of precipitation (starting as snow across eastern TAF sites) will push into the region from the Ohio Valley with flight conditions deteriorating to MVFR (and IFR in snow). Outlook... Tuesday...MVFR/brief IFR with mixed rain and snow changing to rain, then ending. LLWS possible. Wednesday and Thursday...Mainly VFR...except for localized MVFR/IFR in limited lake snows southeast of the lakes. Friday...VFR. && .MARINE... While winds across Lake Ontario are starting to diminish...Small Craft Advisory-level waves will persist into the early overnight hours across far eastern portions of the lake. Winds and waves will then drop off further following the passage of a weak cold front overnight...though some choppy conditions will still persist. Behind the front high pressure will cross the Lower Great Lakes on Monday. Low pressure will then track across the central Great Lakes and southern Ontario province Monday night and Tuesday. Southerly winds will increase late Monday night and Tuesday, which may potentially require additional Small Craft headlines. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...Small Craft Advisory until 1 AM EST early this morning for LOZ044-045. && $$ SYNOPSIS...Apffel/JJR NEAR TERM...Apffel/JJR SHORT TERM...SW LONG TERM...EAJ AVIATION...Thomas MARINE...Apffel/JJR

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