Marine Weather and Tide Forecast for Clayton, NY

NEAR TERM /THROUGH TONIGHT/
Broad low pressure over the Upper Mississippi Valley will gradually consolidate while making its way to Lake Superior today...and in the process will push its attendant warm front into our region from the Ohio Valley
At the same time
a vigorous southern stream shortwave near the Arkansas-Missouri border as of this writing will eject northeastward across the Ohio Valley...with its attendant swath of deeper moisture and forcing catching up to and merging with the warm frontal zone. All of this will result in a nice swath of isentropic upglide/DCVA and deepening moisture spreading across our area from southwest to northeast between roughly 12z and 18z today...which in turn will result in a swath of light to moderate precipitation overspreading the area in a commensurate manner...with the ongoing steady warm advection regime supporting predominantly rain across our area. The only exception to this will be across far northern portions of the North Country...where somewhat colder air initially may support a brief period of snow or a rain/snow mix at the onset...before warm advection overwhelms the atmospheric column and drives a changeover to all rain within a few hours.

Model consensus continues to depict a solid third to a half inch of basin-average rainfall coming from this swath of rain...which will then thin out from southwest to northeast this afternoon and early this evening as forcing wanes and drier air overspreads the region aloft
This being said
copious amounts of low level moisture look to remain in place behind the departing rain shield...and should result in fairly widespread low clouds persisting across our region through the remainder of the period...along with some spotty leftover sprinkles and/or drizzle...and developing areas of fog across the higher terrain.

With respect to temperatures...highs today will range from the mid to upper 30s across the North Country (where a colder ENE low level flow will linger the longest) to around 50 along the Lake Erie shoreline of Chautauqua county...where diminishing rain and a developing southerly downslope flow will help to give readings a bit of an added boost this afternoon. Thanks to the milder airmass and widespread lower clouds...lows tonight will then range from the mid- upper 30s east of Lake Ontario to the upper 30s and lower 40s elsewhere...or some 10 to 15 degrees above normal for this point in December.

SHORT TERM /TUESDAY THROUGH WEDNESDAY/
A digging shortwave trough over the Upper Midwest/Plains will advances eastward on Tuesday. Surface low pressure is expected to develop across the Tennessee Valley region and track northeast across Ohio into western Pennsylvania by late Tuesday. Ahead of this system lingering low level moisture could support some patchy light rain or drizzle through the first half of the day.

A widespread area of precipitation is expected to blossom across the area during the afternoon and into Tuesday night, as forcing increases ahead of the approaching surface wave along a tightening thermal gradient ahead of an approaching cold front. Profiles are warm enough to support all rain through most, if not all of Tuesday night. Rainfall does not look overall heavy with basin averages staying below a third of an inch. Higher terrain east of the lakes could see a bit higher amounts as ensembles indicate a 50-65% chance of at least a half inch of rain. Given the manageable rainfall amounts and some snow melt, 00Z guidance (NAEFS/GEFS/HEFS) suggest only a few rivers and creeks going into action stage, with no real hydro concerns with this event.

Cold front eases across the region Wednesday as the surface wave lifts into New England. Cold advection behind the front likely resulting in snow mixing in with the rain across higher terrain, followed by a transition to all snow for the higher terrain east of Lake Erie by late Wednesday afternoon. Profiles suggesting that lower elevations likely stay all rain. The cold advection will also support a non-diurnal temperature trend with temperatures gradually falling off during the day.

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
...SIGNIFICANT LAKE EFFECT SNOW POSSIBLE WEDNESDAY NIGHT THROUGH EARLY FRIDAY...

The pattern will briefly amplify again across North America the second half of the week, with a ridge building over the Rockies and a strong downstream trough digging into the Great Lakes. This pattern amplification will be brief, with a zonal flow quickly developing by next weekend.

Another significant lake effect snow event is likely east of Lake Erie and Lake Ontario starting Wednesday night and lasting through early Friday. While the overall pattern is supportive, there remains plenty of uncertainty with the details of the forecast, including band placement, intensity, and timing. There is still uncertainty with how the preceding synoptic system will track and deepen Wednesday and Wednesday night, and this will influence the behavior of the early stages of the lake effect snow event.

This airmass is a little colder than last week, with 850MB temps bottoming out around -16C. This will support strong instability with lake induced equilibrium levels around 15K feet and a favorably deep dendritic crystal growth zone within the cloud bearing layer. CIPS analogs suggest a high likelihood of significant accumulations east of Lake Erie and Lake Ontario during this period, as do comparisons to locally generated analog research. This event will be notably shorter in duration than our first two events of the year, lasting about 2 days total.

Off Lake Erie, expect accumulating lake effect snow east of the lake. It is far too early for the more precise details of band location, but there is some suggestion that the band may at least be close to Buffalo at times, especially later Wednesday night and Thursday. Off Lake Ontario, expect accumulating lake effect snow east of the lake, including the Tug Hill Plateau and surrounding lower elevations, possibly including Watertown at times. It will still be several more days until more precise location and intensity details can be forecast with any degree of accuracy.

Thursday will be the coldest day of December so far, with highs in the mid 20s for lower elevations and around 20 for higher terrain.
Wind chills will be down in the single digits at times.

Lake effect snow will weaken and end Friday east or northeast of the lakes. High pressure will then build over the eastern Great Lakes and New England briefly later Friday and Friday night, before moving off the east coast next weekend. Warm advection will quickly begin in the wake of the departing high, allowing for a steady warming trend over the weekend. The 12Z operational model runs would suggest mainly dry weather over the weekend, but spread in ensemble guidance suggests greater uncertainty in precipitation potential within the emerging warm advection pattern. With this in mind, kept chance pops for some light rain/snow showers next weekend.

AVIATION /09Z MONDAY THROUGH FRIDAY/
Broad low pressure over the Upper Mississippi Valley will gradually consolidate while making its way to Lake Superior today...and in the process will push its attendant warm front into our region from the Ohio Valley. This will result in a swath of widespread light to moderate rain and an attendant deterioration to IFR/MVFR flight conditions overspreading our region this morning through early this afternoon.

The rain will then tend to taper off to some scattered leftover sprinkles and/or areas of drizzle later this afternoon and this evening...however with copious low level moisture remaining in place flight conditions will likely remain locked in the IFR to lower-end MVFR ranges
These will be worst across the higher terrain
where areas of fog will likely develop tonight.

Outlook...
Tuesday...Areas of MVFR, with rain developing late.
Tuesday night and Wednesday.. MVFR/IFR with rain changing to wet snow from west to east.
Wednesday night and Thursday...VFR/MVFR with a chance of snow showers...and heavier lake effect snow/LIFR likely east of the lakes.
Friday...IFR in weakening bands of lake effect snow northeast of the Lakes, otherwise VFR.

MARINE
On Lake Ontario an increasing easterly flow will develop out ahead of an approaching warm front today...and will bring a period of advisory-level conditions to the nearshore waters west of Rochester this morning into early this afternoon. Winds will turn offshore and weaken...thereby bringing improving conditions later this afternoon and early this evening.

Meanwhile on Lake Erie...light to modest southerlies will veer to southwesterly and increase to moderate levels for a brief period this afternoon...however winds and waves are expected to remain below advisory criteria.

Otherwise...the Lower Great Lakes will likely be free of advisory- level conditions until later Wednesday or Wednesday evening...when a westerly flow of colder air will strengthen across the region. This will likely bring a period of SCA-worthy conditions that will last into Friday.

BUF WATCHES/WARNINGS/ADVISORIES
NY...None.
MARINE...Small Craft Advisory until 7 PM EST this evening for LOZ042.
Small Craft Advisory until 4 PM EST this afternoon for LOZ043.