Area Forecast Discussion
Issued by NWS Buffalo, NY

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000 FXUS61 KBUF 190221 AFDBUF Area Forecast Discussion National Weather Service Buffalo NY 921 PM EST Thu Jan 18 2018 .SYNOPSIS... The cold weather and areas of lake snows from the past several days will give way to a pronounced warming trend...one that will begin on Friday. High pressure settling off the coast of the Carolinas will pump progressively milder air into our region during the course of the weekend so that temperatures will finally push into the 40s. && .NEAR TERM /THROUGH FRIDAY/...
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As we move through tonight...a rather well-defined shortwave will weaken while quickly rippling eastward across our region. The brief boost in moisture and lift provided by this passing feature will bring some short-lived scattered snow showers to areas from roughly about the New York State Thruway northward. As for the lake snows...warm advection has already shut down the snow off Lake Erie and has seriously weakened the snows to the east of Lake Ontario. While the very weak lake snows near the Tug Hill should flare back up for a few hours towards daybreak as a result of the passing shortwave...the winter weather advisory has been discontinued as additional snowfall should only be an inch or two. On Friday...heights will rebound across our region in the wake of the shortwave...and this in concert with continued steady low level warm air advection will help to steadily wear down the Lake Ontario lake snows...with these producing another inch or so of accumulation before finally disintegrating into some leftover scattered snow showers. Otherwise the day will be largely dry with morning clouds giving way to some partial sunshine south of Lake Ontario...with the aforementioned warm air advection also helping to boost temperatures back into the lower to mid 30s in most places...and possibly even to the upper 30s across interior portions of the Genesee Valley.
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&& .SHORT TERM /FRIDAY NIGHT THROUGH MONDAY NIGHT/... Friday evening there may still be a few light lake effect snow showers east of Lake Ontario. These will quickly end during the evening as inversion heights drop below 4K feet and low level moisture is stripped away as a warm front moves northeast across the area. Otherwise it will be dry Friday night, with more in the way of clouds near the Canadian border in closer proximity to the retreating warm front, and more clearing near the PA state line. It will become quite windy again with a tight pressure gradient and a 50+ knot low level jet crossing the area. An inversion and poor low level lapse rates will not allow for full mixing, but nonetheless expect gusts in the 35-40 mph range overnight. Expect lows of around 30 on the lake plains of Western NY, and mid to upper 20s elsewhere. These lows will occur during the evening, with mixing and warm advection forcing slowly rising temperatures overnight. On Saturday the warm frontal boundary will sag back to the south across Lake Ontario and the eastern Lake Ontario region as a weak backdoor cold front. Convergence and frontogenesis will be very weak, but there may be just enough when combined with lake moisture and upslope flow to produce some very light precip east of Lake Ontario. The cloud bearing layer may be too warm to support ice nuclei, so if precip materializes it may be in the form of drizzle or freezing drizzle. For the rest of the region, expect dry conditions with low clouds increasing as low level moisture increases. It will remain quite windy, with gusts of 35-40 mph in the morning slowly coming down through the day as the low level jet core moves off to the east. Expect highs within a few degrees of 40 in most areas, with mid to upper 30s for the North Country. Saturday night will be dry with a weak surface ridge in place across the eastern Great Lakes. Expect a good deal of cloud cover with NAM and GFS BUFKIT soundings showing a rather extensive layer of low level moisture in place, which is a common occurrence during a mid winter warm-up with warm air crossing cold, snow covered ground. The majority of the day Sunday will be dry and cloudy with a few exceptions. A warm frontal segment will sharpen across the Saint Lawrence Valley, and this may bring some light snow or rain to the North Country where colder temperatures hang on. Another warm frontal segment may bring rain showers to Western NY by late in the day. Highs will again be within a few degrees of 40 in most areas, with mid 30s for the North Country. Monday and Monday night a more significant trough will advance into the central Great Lakes. Warm advection and moisture transport will increase across our region Monday, which may support a few showers from time to time. A cold front will then cross the region late Monday or Monday night, with the ECMWF a little slower on timing than GFS based guidance. A plume of deep moisture ahead of the front combined with increasing ascent will produce periods of rain. Monday will likely be the warmest day of the stretch, with at least mid to upper 40s likely in Western NY. The combination of rain, and increased snowmelt from higher temperatures and dewpoints may bring some flood concern by later Monday and Monday night. This warm-up is not as dramatic as last weekend, and rain amounts are also likely to be lower given the fast passage of the cold front. Nonetheless, there may be some potential for ice jam flooding by late Monday and Monday night. && .LONG TERM /TUESDAY THROUGH THURSDAY/... Tuesday into Wednesday, colder air will rush back into the region with a blustery southwest to west wind behind the cold front. This will bring a return to more typical mid-winter temperatures for mid- week along with lake effect snow within wraparound moisture and lowering 850mb temps. Will have to keep an eye on how the ice cover on Lake Erie evolves over the early week warmup, as it will have an impact on the magnitude of whatever lake effect snows develops in Western NY. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/...
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An upper level disturbance will quickly cross the region from west to east tonight. This will bring some brief scattered snow showers to areas from roughly KBUF-KROC-KSYR northward...while also helping to maintain some weakening lake snows east of Lake Ontario. Expect flight conditions to range from MVFR in the lake snows east of Lake Ontario (including around KART) to predominantly VFR elsewhere. On Friday...lingering lake snows east of Lake Ontario will disintegrate into some scattered light snow showers...with MVFR conditions otherwise prevailing there. Meanwhile south of Lake Ontario...fairly widespread MVFR cigs in the morning will gradually give way to VFR conditions from south to north as drier air begins spreading into the region. Outlook... Friday night...Mainly VFR. Saturday through Sunday...Widespread MVFR ceilings redeveloping on Saturday...then persisting through Saturday night and Sunday. Monday and Monday night...VFR/MVFR with rain showers developing. Tuesday...MVFR/IFR with rain showers changing to snow showers before ending...then areas of lake effect snow also developing east of the lakes Tuesday night. Wednesday...VFR/MVFR with a chance of snow showers.
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&& .MARINE... A persistent pressure gradient will maintain brisk west- southwesterly flow across the lakes into the upcoming weekend, and small craft advisories remain in place into Saturday. High pressure nosing across the region will relax the winds Sunday before winds freshen once again on Monday ahead of a strong low pressure system tracking out of the central Plains. && .BUF WATCHES/WARNINGS/ADVISORIES...
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NY...None. MARINE...Small Craft Advisory until 10 PM EST Saturday for LEZ040-041. Small Craft Advisory until 4 AM EST Sunday for LOZ042>045.
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&& $$ SYNOPSIS...JJR/RSH NEAR TERM...JJR/RSH SHORT TERM...HITCHCOCK LONG TERM...CHURCH AVIATION...JJR/RSH MARINE...WOOD

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