Marine Weather and Tide Forecast for Mentor, OH

NEAR TERM /THROUGH WEDNESDAY NIGHT/
930 PM Update...
Some changes to the POPs as we are in a bit of a lake effect snow lull, awaiting the next batch of low level moisture coming in from the northwest. POPs in the lake effect areas ramp up again by morning. Cold overnight.

Previous Discussion...
Headlines remain unchanged with this update. The most impactful period of the near term appears to be through this afternoon and evening as an intense offshore lake effect snow band shifts south, impacting the primary snowbelt generally east of Cleveland, including the I-90 corridor.

Recent water vapor satellite imagery depicts a shortwave rounding the base of an upper-level trough across the Lower Great Lakes this afternoon which has resulted in widespread light to moderate snow.
An ongoing intense lake-effect snow band across western NY will begin to sag south towards the lakeshore area of Northeast Ohio and Northwest Pennsylvania through this afternoon. Difficult travel conditions, particularly along the I-90 corridor, are expected as this band moves south over the next several hours, with high confidence in snowfall rates of 1 to 2 inches per hour. Elsewhere, light to moderate snow will gradually decrease in coverage, becoming more "showery", evident by the arrival of upstream dry air across eastern MI and southern Ontario.

A cold air mass, characterized by 850 mb temperatures falling to around -17 degrees C, will arrive later this evening and overnight, with boundary layer flow becoming WNW. Dry air and boundary layer shear will initially limit lake effect snow coverage this evening, though anticipate an increase in moisture and a decrease in shear to allow for lake effect snow to become better organized by Wednesday morning across the primary snowbelt east of Cleveland. Snow will gradually decrease from west to east Wednesday evening and overnight as a ridge of high pressure begins to build east across the Ohio Valley.

For the most part, wind chill temperatures will remain in the single digits during the day, and at or just below zero in the overnight to early morning hours.

SHORT TERM /THURSDAY THROUGH FRIDAY/
Another potent upper level trough will dive south out of Canada on Thursday, crossing the Great Lakes Region. Surface low pressure will be located near James Bay with a trough extending south across the Great Lakes Region. Isentropic ascent fueled by 30-40 knots will develop ahead of the trough and lead to widespread light snow across the area on Thursday. We should see sufficient deep moisture and lift through early afternoon before the flow veers to west northwest behind the trough and we transition to more of a lake enhanced scenario. The airmass will not be cold enough for pure lake effect behind the system on Thursday night but enhancement is likely while moisture lingers to nearly 700mb with shallow lift developing downwind of the lakes. Favored upslope flow areas will be more likely to snow heading into Thursday evening. Overall snow amounts will tend to be 1-2 inches on Thursday, with slightly lower amounts along the I-75 corridor and locally higher amounts across the snowbelt where snow will linger into Thursday night. Temperatures on Thursday will be in the mid to upper 20s so snow should stick on untreated surfaces, dropping into the lower 20s Thursday night.

The trough exits quickly to the east with ridging both at the surface and aloft on Friday. Partial clearing is expected along with temperatures making a push into the 30s. Southwest flow will increase through the day and be brisk with gusts to 20-25 mph so the real feel for temperatures will still be closer to 20.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
Active weather continues into the long term with another round of precipitation on Friday night and Saturday, followed by very cold air to start next week. A southern stream wave will move out of the southern plains Friday night before being absorbed into an expansive trough surging south out of Canada. Temperatures cool into the upper 20s to low 30s with some help from evaporational cooling as precipitation arrives. It looks like boundary layer will be on the fringe of rain/snow, partly transitioning to rain in NW Ohio for a few hours on Saturday. Farther east temperatures may be just cool enough to be snow at times and perhaps see some very light accumulations over the higher terrain. Trended lows down a degree or so given the widespread precipitation.

A cold front arrives Saturday night with a secondary push of arctic air arriving Sunday night into Monday. This will likely be the coldest air of the season as long range models have come into good agreement with 850mb temperatures of -24 to -26C over the region on Monday. This cold air looks to come around the Great Lakes from the Upper Midwest. Temperatures continue to trend downward for the Monday and Tuesday time frame with wind chills that may drop into the -10 to -20 degree range on Monday night. There is still time for the forecast to change but confidence is increasing in very cold conditions to start next week. Cold Weather Advisories may be needed for some areas. Stay tuned to later forecast updates.

AVIATION /00Z Wednesday THROUGH Sunday/
Light snow is gradually exiting the area, although it will still take a few hours over in the eastern terminals of NE OH/NW PA.
As snow does exit and lake effect wanes later this evening, ceilings come up to VFR for a period of time overnight, but expect the return of MVFR ceilings towards daybreak Wednesday with more low level moisture heading in from the northwest. Some light snow returns as well for terminals downwind of the lake.
Gradual improvement in the flight conditions through the day on Wednesday as high pressure builds in from the south and slowly scours out the low level moisture that had moved back into the area.

Outlook...Non-VFR in lake effect snow will continue through Wednesday night across portions of Northeast Ohio and Northwest Pennsylvania. Non-VFR will return in widespread snow from a clipper system late Thursday through Friday. Non-VFR likely to return in widespread rain and snow Saturday into Sunday.

MARINE
Unsettled conditions will continue on Lake Erie with Small Craft Advisories in effect east of Vermilion. Advisories have not been issued west of Vermilion due to the ice coverage in the nearshore waters. Some movement of the ice is likely as winds remain elevated on the lake. Patchy freezing spray is also possible but temperatures have been marginal enough to not expect heavy accretions at this time.

Winds on Lake Erie will shift to northwesterly tonight as a trough pushes south of the lake. High waves of 4 to 7 feet will move into the nearshore waters with onshore flow. Winds back to southwesterly on Wednesday as high pressure builds into the Ohio Valley. This will allow for some improvement in conditions for the waters off of Lorain and Cuyahoga Counties as larger waves shift offshore through the day on Wednesday. Farther east Small Craft Advisories have been extended into Friday as winds and waves remain high. Another trough is forecast to cross Lake Erie on Thursday with increasing wind conditions on Wednesday night. Small Craft Advisories may be needed again for the nearshore waters in the Central basin with marginal wind and wave conditions at times through mid-week. By Friday we do see winds shift to southerly with higher waves moving into the open waters. A break in advisories is possible although winds will remain in the 15-20 knot range so still expect choppy conditions.

Arctic air spreads into the region from Sunday night into Tuesday.
Freezing spray along with expanding ice coverage on Lake Erie is likely.

CLE WATCHES/WARNINGS/ADVISORIES
OH...Winter Weather Advisory until 4 PM EST Wednesday for OHZ012- 014-089.
Winter Weather Advisory until 10 AM EST Wednesday for OHZ013.
PA...Winter Weather Advisory until 4 PM EST Wednesday for PAZ003.
Lake Effect Snow Warning until 1 AM EST Thursday for PAZ001- 002.
MARINE...Small Craft Advisory until 7 AM EST Wednesday for LEZ145-146.
Small Craft Advisory until 10 AM EST Friday for LEZ147>149.