Marine Weather and Tide Forecast for Hamburg, NY

KEY MESSAGES
1) Modest lake effect snow develops and also turns colder behind a passing cold front tonight.

2) Lake effect snowbands intensify Sunday night and continue through Wednesday with potential significant accumulations, blowing and drifting snow.

3) Arctic airmass over the region will bring frigid temperatures and the potential for dangerous wind chills next week.

DISCUSSION
KEY MESSAGE 1...Modest lake effect snow develops tonight and turns colder behind the cold front.

CAA behind this strong cold front will send H850 T's down -15C to - 18C over the region by Sunday. This will lead to the development of a weak lake effect response northeast of Lake Erie and east-northeast of Lake Ontario through Sunday. The limiting factor through Sunday will be the 'lack' of deep synoptic moisture until Sunday evening into Monday. Therefore, lake snows will largely remain light with snowfall rates generally well under 1" per hour off both lakes
That said
a southwest flow and the full fetch of the lake Erie will help to squeeze out possibly 1-3" through Sunday afternoon to include the Southtowns, Buffalo Metro area, and Northtowns
Off Lake Ontario
expect 2 to 4" with isolated higher amounts northeast (Watertown area) and east of the lake through Sunday afternoon
After that
synoptic moisture will increase Sunday evening with intensifying lake snows.

KEY MESSAGE 2...Lake effect snowbands intensify Sunday night and continue through Wednesday with potential significant accumulations, blowing and drifting snow.

A series of cold fronts early next week will deliver another round of lake effect snow to our region.

On a southwest flow initial lake snows Sunday and into Sunday evening will likely be light with still a fair amount of dry air in the mid levels. By late Sunday night in associated with a northern branch shortwave trough, deeper moisture will arrive across the eastern Great Lakes region, which will intensify bands of lake effect snow off both Lakes.

Initial pattern is favorable for a heavy band of lake effect snow on a southwest flow...with a sub 500 dm 500 hPa closed low over southern Hudson Bay, with a trough axis southward across the western Great Lakes.

Strong convergence, with deeper colder air along with the increase in ambient moisture will allow for a heavy band of lake effect snow to begin across Grand Island and Niagara and western Orleans County Sunday night...and several hours later, through the Saint Lawrence valley. Snow intensities will increase upwards to 2 inches per hour by early Monday morning, before an arctic front pushes the snowbands southward. Lake bands will linger enough ahead of the arctic front Sunday night and Monday morning to allow for warning criteria snow.

By Monday afternoon and through Tuesday a more westerly flow will orient lake effect snowbands across the traditional snowbelts east of both lakes during this long duration snow event. Upstream lake connections are favorable which could lead to significant snow accumulations this period east of the Lakes. Snowfall rates two inches per hour east of Lake Erie, though with upstream lake connections, and the lake band oriented along the long fetch of Lake Ontario, snowfall rates could briefly reach 4 inches per hour on the Tug Hill Monday night through Tuesday night.

An arctic front plowing southward across our region with strong cold air advection, combined with a 40 to 45 knot LLJ will bring strong gusty winds with gusts upwards to 40 to 50 mph. This will bring blowing and drifting snow and with the dry characteristic to the snow visibilities will become white out at times, especially within the heart of the lake snows. Have elected to issue winter storm warnings to account for both the lake effect snow accumulations as well as the blowing snow creating white out conditions, with the strongest gusts expected Monday afternoon through Monday night along and behind the arctic front.

Supporting the lake snows will be 850 hPa temperatures dropping to - 20 to -24C which will create more than enough instability over the still open lake waters...while lake induced equilibrium levels upward towards 10K feet allow for plenty of vertical growth to the lake snowbands.

By Tuesday afternoon the lake snows may begin to lift northward back towards Buffalo and Watertown as a subtle shortwave trough in the mean flow ripples through our region. While this trough will bring light widespread snow, it will also bring back additional ambient moisture to maintain lake snowbands. However, increased wind shear ahead of the trough may disrupt lake snows to broader, weaker bands of snow. By Wednesday ahead of a surface low winds will back to southerly breaking apart lake snowbands while they lift northward.
Additional light snow will be possible later Wednesday as this surface low draws closer to our region.

KEY MESSAGE 3...Arctic airmass over the region will bring frigid temperatures and the potential for dangerous wind chills next week.

An arctic airmass will drop across our region Monday, with the arrival from north to south behind an arctic front. Temperatures Monday night will lower towards zero inland and...to the single digits near the Lakes. With a still breezy westerly flow apparent temperatures will drop into the negative teens to as low as 20 below Monday night across the eastern Great Lakes region. The ensemble guidance of GFS/ECMWF continues to highlight SW NYS as the area most likely to feel sub -15F wind chills. These wind chill values will only improve to zero to 10 below Tuesday and Tuesday night...owing to wind flow a bit lighter.

AVIATION /00Z SUNDAY THROUGH THURSDAY/
Modest lake effect snow will develop tonight behind a departing cold front as cold air begins to deepen again over the eastern Great Lakes. Limited synoptic scale moisture will keep lake effect snow on the light side tonight through Sunday. This evening, some very light snow will continue to cross most of the area with mainly MVFR conditions. A few pockets of lake enhancement northeast of Lake Ontario will bring periods of IFR to KART. Most of the limited lake effect snow will then drift just south of KART overnight.

Sunday, some limited lake effect snow will develop before daybreak northeast of Lake Erie near KBUF with local IFR. This band should drift north towards KIAG through the morning and then mostly dissipate in the afternoon. Off Lake Ontario, limited lake effect snow and local IFR will continue mainly just south of KART through the day. VFR will prevail outside of lake effect areas.

Outlook...

Monday...Windy with bands of lake effect snow and attendant IFR/LIFR conditions northeast of the lakes intensifying and shifting southward to areas east of the lakes
Otherwise
MVFR/VFR with brief IFR/MVFR possible in passing snow showers.

Monday night through Tuesday...Heavy lake effect snow possible east of Lake Erie and Lake Ontario with IFR/LIFR in bands. MVFR/brief IFR outside of lake effect areas within snow showers.

Wednesday...Snow showers increase in coverage areawide with cold front. IFR or below at times.

Thursday...Lake effect snow east and northeast of the lakes with IFR/LIFR conditions. MVFR/brief IFR outside of lake effect areas within snow showers

MARINE
A prolonged period of elevated winds and waves will continue on Lake Erie and Lake Ontario through much of next week.

A low pressure system will pass to our north with a cold front crossing the region by this evening. Winds will once again pick up behind this cold front with Small Craft Advisory conditions on both lakes tonight...with such conditions expected to remain in place through Sunday.

The passage of an arctic cold front Monday will potentially bring gales on both Lakes late Monday through early Tuesday along with areas of heavy freezing spray.

BUF WATCHES/WARNINGS/ADVISORIES
NY...Winter Storm Warning from 1 PM Sunday to 4 PM EST Wednesday for NYZ001-002-010-011.
Winter Weather Advisory until 1 AM EST Sunday for NYZ006>008.
Winter Storm Warning from 7 AM Sunday to 4 PM EST Wednesday for NYZ006>008.
Winter Storm Warning from 7 AM Monday to 4 PM EST Wednesday for NYZ012-019-020-085.
MARINE...Small Craft Advisory until 6 AM EST Monday for LEZ040-041.
Gale Watch from Monday morning through Tuesday morning for LEZ040-041.
Small Craft Advisory until 7 AM EST Monday for LOZ042.
Gale Watch from Monday morning through late Tuesday night for LOZ042>045-062>065.
Small Craft Advisory until 7 AM EST Monday for LOZ043>045.