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SLZ022 Saint Lawrence River From Cape Vincent To Saint Regis 328 Am Est Thu Dec 7 2023
Today..South winds 10 knots or less becoming east. A chance of snow late this morning. A chance of snow showers this afternoon.
Tonight..Northeast winds less than 10 knots. A chance of snow showers through the early overnight.
Friday..East winds 10 knots or less. Mostly cloudy in the morning, then becoming partly Sunny.
Friday night..East winds 10 knots or less. Mostly cloudy.
Saturday..Southeast winds 5 to 15 knots becoming south. Rain likely Saturday night.
Sunday..South winds 15 to 20 knots becoming west. Rain during the day, then snow and rain Sunday night.
Monday..West winds 15 to 20 knots becoming southwest 10 to 15 knots. Snow showers during the day, then a chance of snow showers Monday night.

SLZ005
No data

FXUS61 KBUF 071930 AFDBUF

Area Forecast Discussion National Weather Service Buffalo NY 230 PM EST Thu Dec 7 2023

SYNOPSIS
A warm front stalled over central New York will produce some additional light snow across the eastern Lake Ontario region through this evening. Notably milder air will overspread the region to end the week with temperatures climbing into the 50s by Saturday afternoon. A low pressure system will bring moderate to heavy rain across the area Saturday night into Sunday. Rain will change over to snow Sunday night.

NEAR TERM /THROUGH FRIDAY/
A mid-level warm front has stalled out from the eastern Lake Ontario region into central NY this afternoon. The previously narrow band of light to moderate snow associated with this front has since diminished into a broader area of light snow as its eastward progression slowed, with cloudy albeit drier weather back across WNY as cloud tops are below the DGZ. Some limited lake enhancement has developed east/northeast of Lake Erie as 850H temps are marginally cold enough and the flow aligns down the long axis of the lake, though the increasing WAA regime has already greatly diminished the strength of this band. Surface temps in the wake of the front are elevation dependent though still largely above freezing, supporting a mix of mostly light rain and snow. While the accumulating snows have longed since ended across WNY, some nuisance accumulations (generally under an inch) are possible east of Lake Ontario through this evening as the boundary shifts east and additional lake enhancement develops.

The stronger warm air advection will kick in from the west late this evening and persist overnight tonight as high pressure ridging builds over the central Great Lakes and a low pressure system moves across the northern Plains. This will effectively squash the last of the lingering lake response off Lake Erie, though it will likely persist for longer off Lake Ontario. Increased low-level forcing and moisture below the DGZ with surface temps at or below freezing in close proximity to the lingering boundary support a slight chance for some freezing drizzle for a few hours overnight, mainly after midnight across portions of eastern Oswego and southern Lewis counties. Temperatures should hold steady in the low to mid 30s overnight back across the rest of WNY.

The stalled boundary will finally shove off to the east Friday as the axis of a mid-level ridge moves over the region. High pressure subsidence will ensure a dry day with some clearing from the west in the late morning, though additional clouds will likely move back in later in the afternoon. Light southerly flow and WAA will boost high temperatures some 10 degrees warmer compared to those seen today, potentially even surpassing the 50 degree mark along the Lake Erie shoreline and in the typical warm spots in the Genesee Valley.

SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/
Mid level ridge axis centered across New York Friday night will slide east into New England Saturday. This will support an elongated surface high across the East Coast. Overall, with the building heights and subsidence from the high will promote a dry night along with a fairly dry day Saturday. Temperatures will continue to be on the warmer side with lows Friday night ranging in the upper 30s across the areas east of Lake Ontario to the low to mid 40s elsewhere. The warm spell will continue into Saturday as southerly flow will aid in some downsloping and support temperatures to warm up into the upper 40s across the Tug Hill region and in the low to mid 50s elsewhere.

Meanwhile, a deep trough will advance from the central United States and support a surface low and cold front to push across the central Great Lakes and Ohio Valley late Saturday and Saturday night. As the front approached the western doorstep of western New York, chances for rain showers will increase, with the best timing of the heavier precipitation arriving around daybreak Sunday. This all being said, the combination of the trough and the aforementioned surface high pressure on the Eastern Seaboard will funnel in moisture to the frontal zone not only from the Gulf of Mexico but also the Atlantic Ocean. Overall this will support moderate rain to fall late Saturday night. Otherwise, the warm mild temperatures will continue Saturday night with lows in the low to mid 40s region wide.

LONG TERM /SUNDAY THROUGH THURSDAY/
Active weather still in store Sunday into Monday with moderate to heavy rain on Sunday changing to several inches of wet snow Sunday night into early Monday from west to east.

After much uncertainty the last few days, models and ensembles are more or less on board with farther east track to wavy frontal boundary and waves of low pressure moving along it Sunday into Monday morning. Latest GFS did trend a bit west on Sunday night with the heavier QPF/snow, but also is an outlier now compared to its ensembles and other guidance/ensembles. This eastern shift occurs as shortwave trough digging across the lower Mississippi Valley on Sunday swings across the northeast by Monday, but never quite phases with northern branch shortwave trough crossing northern Ontario and the upper Great Lakes. It was only when these two branches phased did we see a strong low passing to the west of here on Sunday that was advertised in the models earlier this week. That is not there now in guidance or ensembles though. Upshot is winds for our forecast area are not looking to be as strong either Sunday with the southerlies ahead of the system or with the west-northwest winds in the cold air behind the system. Heaviest rain on Sunday in the warm sector will occur where strongest moisture advection of abnormally high PWATs well over the 90th percentile occurs ahead of the front (eastern Finger Lakes northward to the eastern Lake Ontario region).
By late Sunday night, areas on the Tug Hill may see over 2 inches of liquid boosted by upslope flow. Farther west though, the gradient of QPF will be sharper with Genesee Valley/Finger Lakes near an inch while most of western NY sees 0.5 to 0.75 inch of liquid before the rain turns to snow. This heavy rain could cause some issues as model ensembles for river forecast points indicate a low, but non-zero chance some rivers especially in the Black River basin could rise to action stage with the rain and melting snow. This will have be to be monitored as we progress into the weekend.

As the next wave of low pressure lifts by on Sunday night, good agreement that switch from rain to snow occurs as early as dusk Sunday evening for higher terrain of southwest NYS, then eventually through the evening for the rest of western NY with most locations to snow by midnight. Quick change on to the east the rest of the night. All areas will see ptype of snow by daybreak on Monday. Only exception may be right along the Lake Ontario shoreline over far se portion of the lake with ra/sn mix. It is certainly possible winter headlines may eventually be needed for the change to wet snow Sunday night into Monday, with highest chances of that from Southern Tier to the Finger Lakes and probably more so for the higher terrain east of Lake Ontario. In these spots, models and ensemble probability data suggest several inches of wet/sloppy snow could occur and it is here there is also higher signal for widespread moderate impacts on the latest Probabilistic Winter Storm Severity Index (Prob WSSI).
Now even though lower elevations may not much as snow from this event compared to higher terrain (so long as the eastern trend holds), the commute on Monday morning looks difficult for all areas as rain changes to up to a few inches of slushy snow and temps will be at or just below freezing.

Steady system snow exits fairly quickly on Monday. Though there will be some scattered leftover lake effect snow, at this point it appears to be light as it will be held down by limited deep moisture and less low-level cyclonic flow as ridge slips in quickly late Monday into Monday night. Forecast soundings across the lakes Monday look quite mixed with inverted-V profile which usually is not that great for much lake effect. Does look like a seasonally cool day with a blustery NW wind.

Rest of long term looks changeable. Modest warm up on Tuesday with gusty WSW winds will be followed by cool down on Wednesday as a fairly sharp cold front drops across. Highest pops near the lakes for now but maybe a touch of light snow for all areas on Wednesday if this front ends up having a bit more punch than shown right now.
Another round of warm air advection starts up on Thursday.

AVIATION /20Z THURSDAY THROUGH TUESDAY/
Variable flight conditions found across the terminals this afternoon as a mid-level warm front is stalled from the eastern Lake Ontario region to central NY. A mix of MVFR/IFR conditions with light snow showers are found in closer proximity to and east of the front (KFZY/KART) with some minor lake enhancement developing east of the lake. Drier to the west of the front with mainly MVFR cigs, with pockets of VFR across far western NY (KBUF/KIAG) and local IFR across the higher terrain of the Southern Tier. These conditions are generally expected to persist through this evening with gradually subsiding winds.

Precipitation coverage will greatly diminish overnight tonight, though lake enhancement may persist east of Lake Ontario until the pre-dawn hours early Friday morning. There is low confidence in the possibility of freezing drizzle near the stalled boundary after midnight across portions of the North Country, mainly east of KFZY and south of KART.

Conditions will improve to widespread VFR Friday morning with clearing skies outside of the North Country, where VFR/MVFR cloud cover may linger.

Outlook...
Friday night and Saturday...Mainly VFR.
Sunday...VFR/MVFR. Breezy. Rain changing to rain/snow showers late.
Monday...MVFR. Breezy with a chance of snow showers.
Tuesday...Mainly VFR.

MARINE
Elevated winds behind a warm front that lifted north of the lakes will continue choppy, low-end SCA conditions on Lake Erie through early this evening. Winds not quite as strong on Lake Ontario and are generally directed offshore.

Winds will subside overnight tonight as surface high pressure builds across and then east of the lakes. Offshore south/southeasterly winds will increase some on Friday, though remain below SCA criteria through much of Saturday.

BUF WATCHES/WARNINGS/ADVISORIES
NY...None.
MARINE...Small Craft Advisory until 7 PM EST this evening for LEZ040- 041.

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