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SLZ022 Saint Lawrence River From Cape Vincent To Saint Regis 948 Am Est Tue Dec 5 2023
This afternoon..East winds less than 10 knots. Cloudy.
Tonight..Northeast winds 5 to 10 knots. Mostly cloudy.
Wednesday..Northeast winds 10 knots or less becoming northwest. Mostly Sunny.
Wednesday night..Northwest winds less than 10 knots. Mainly clear.
Thursday..South winds 10 knots or less becoming southeast. A chance of snow showers.
Friday..Southeast winds 5 to 10 knots becoming south. Mostly cloudy.
Saturday..South winds 5 to 15 knots. A chance of rain Saturday night.

SLZ005
No data

FXUS61 KBUF 052330 AFDBUF

Area Forecast Discussion National Weather Service Buffalo NY 630 PM EST Tue Dec 5 2023

SYNOPSIS
Low pressure tracking across the Ohio Valley will bring some light snow from Western NY to the Genesee Valley and Finger Lakes tonight with minor accumulations. There will be some lingering lake enhanced snow Wednesday south of the lakes with spotty additional minor accumulations in the morning. A frontal boundary will then bring another chance for light snow Wednesday night into Thursday. A significant warming trend will then develop late in the week.

NEAR TERM /THROUGH WEDNESDAY/
A mid level trough crossing the eastern Great Lakes this evening will continue to support a period of large scale ascent. The weak surface low associated with the trough will move from the Ohio Valley this evening to the Mid Atlantic overnight. A broad/weak area of isentropic upglide, deformation, and frontogenesis north of the low track will continue to support widespread, weak ascent across Western and Central NY through the rest of the evening.

Radar imagery shows widespread light snow across all of Western NY, the Genesee Valley, and western Finger Lakes early this evening. All of this is light, but still enough to result in widespread measurable precipitation through the evening hours. The widespread light snow will fade away late evening or early overnight as forcing weakens with the exit of the mid level trough. Some modest lake effect/enhanced snow showers will continue overnight in weak northerly flow, mainly from near or just east of Rochester over to western Oswego County and southward into the Finger Lakes off Lake Ontario, and across the Chautauqua Ridge off Lake Ontario. Snow accumulation tonight will be light, generally an inch or less in most areas. The higher terrain of the western Southern Tier will see 1-2".

Wednesday, with the trough still moving through and then out of the region, lingering snow showers will continue especially in the morning. Lake effect will cause light snow showers to linger through most of the day southeast of the lakes to some extent. Increased ridging and drier air that will briefly move into the region ahead of the next weak system that is approaching from the west will start to cut down on any lake response that lingers through the morning.
The best chance for lingering lake snows into the later portion of the afternoon will be areas down wind of the best lake fetch off of the southeast portion of Lake Ontario. Snow amounts of around a half inch or so can be expected south of Buffalo, and up to an inch is possible for areas south of Lake Ontario across the higher terrain closer to the Finger Lakes. A cool day expected with highs in the low to upper 20s east of Lake Ontario, and in the upper 20s to mid 30s for areas south of Lake Ontario.

SHORT TERM /WEDNESDAY NIGHT THROUGH SATURDAY NIGHT/
Last remnants of N-NW flow lake effect will end on Wednesday evening due to increasing warm air advection aloft and subsidence as ridge crosses. Warm air advection is occurring ahead of clipper system dropping across northern Ontario and the upper Great Lakes. Late Wednesday night, swath of light snow tied to this forcing will arrive over western NY spreading as far as the Finger Lakes by daybreak on Thursday. Moisture is limited with this system and the shortwave is shearing out over time. Net result, a high pop, low QPF setup. Most spots see less than 1" of snow late Wednesday night into midday Thursday. The snow will fall during the morning commute and with temperatures still below freezing, could be some slippery spots on untreated and less traveled roads. Light snow tapers in the afternoon to some rain/snow or even just rain showers as the low- levels warm enough.

Thursday night into Friday will be fairly quiet as warm front lifts northeast of the area. May see some lingering strato cu but still looks breezy and warm with highs into the upper 40s or even lower 50s. Friday night into Saturday, attention will become focused on sharp shortwave trough digging into the southern Plains. This system will lift across the Tennessee valley while phasing with shortwave trough digging in from south central Canada by Sunday morning. Warm air advection ahead of the system will continue to boost temps well above normal with highs on Saturday well into the 50s for all but the eastern Lake Ontario region. Trend for any rain Saturday and even for most of Saturday night is slower, but did retain higher pops later Saturday night as the complex phasing trough and associated sfc low heads north across the lower Great Lakes.

LONG TERM /SUNDAY THROUGH TUESDAY/
Into Sunday, deepening low likely down below 980mb, in addition to a 1.5 PV anomaly that passes across our region Sunday night will make for strong winds. In general models and ensembles favor the deepening low tracking northwest of western NY before shifting into Quebec later Sunday night/Monday. There are differences in how quick to the east the low progresses. Rain, slowly pushing eastward on Sunday will become more showery Sunday and Sunday night with the passage of a cold front. Slight instability ahead of the front could even lead to a few lightning strikes across WNY before the cold front passage. Strong southerly flow ahead of the cold front that supports the mild temperatures could even approach advisory thresholds for wind gusts before winds veer with the passing cold front later Sunday and Sunday night. At this time winds will likely become stronger with cold air advection aloft, tightening surface pressure gradient a lingering LLJ near 50 knots. Local guidance points to limited high wind or advisory wind event.

Colder air pushing in behind the cold front Sunday night and Monday will begin to form bands of lake effect rain/snow. At this time a fair amount of wind shear, the rapid loss of synoptic moisture with the deformation band lifting northward into Canada and approach of surface high pressure will negatively impact any lake effect bands of precipitation to close out this period.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
A weak clipper system will continue to generate widespread light snow through the first half of tonight across Western NY, the Genesee Valley, and western Finger Lakes with 1-2SM VSBY and MVFR CIGS. This includes KBUF, KROC, KIAG, and KJHW through 03Z-05Z.
Overnight, the widespread snow will fade away as the clipper departs.

Some modest lake enhanced snow showers will continue south of the lakes overnight through Wednesday morning. Off Lake Erie, this will mostly focus over the Chautauqua Ridge including KJHW at times. Off Lake Ontario, most of the lake effect snow showers will be from near or just east of KROC over to KFZY and then south into the Finger Lakes. Outside of lake effect areas, fairly widespread MVFR CIGS will continue overnight through much of Wednesday. The lake effect snow showers will gradually diminish Wednesday afternoon.

Outlook...

Thursday...VFR/MVFR. Light snow likely in the morning, then a chance of rain and snow showers.

Friday...VFR/MVFR. A small chance of rain and snow showers.

Saturday...Mainly VFR.

Sunday...VFR/MVFR. Breezy. Rain changing to rain/snow showers late.

MARINE
Light and variable winds will generally start to increase through the afternoon out of the north. Northerly winds will increase late tonight into Wednesday when low pressure passes by to the south, however winds/waves should remain below small craft criteria. Winds will briefly increase on Thursday as a shortwave trough passes over the area. Winds on Lake Erie, will approach Small Craft Advisory levels.

BUF WATCHES/WARNINGS/ADVISORIES
NY...None.
MARINE...None.

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