The Watertown metro area, northern Tug Hill Plateau and sparsely-populated portions of the northwestern Adirondacks received several feet as powerful lake-effect snows did not balk — for nearly three days.

The Tri-Lakes region was on the outer periphery of the snow, receiving between 4 and 6 inches around Saranac Lake and Lake Placid with western portions of the local area closer to the more intense lake-effect snows receiving more. A report indicated that 9.5 inches of snow had fallen in Tupper Lake as of 7 a.m. Monday, according to the National Weather Service’s Burlington, Vermont Office, which serves Franklin, Essex, St. Lawrence and Clinton counties.

With the lake-effect snow winding down Sunday night and Monday, several northern Tug Hill Plateau locations in Jefferson and Lewis counties reported storm totals in excess of 5 feet as of press time Monday afternoon.

Copenhagen, a village located about 13 miles southeast of Watertown, was the apparent bullseye for weekend snows. A spotter reported 65.9 inches to the National Weather Service’s Buffalo office, which serves the Tug Hill region, as of 11 a.m. Monday. Nearby Barnes Corners reported 65.5 inches as of 7 a.m. Monday. A report from Fort Drum noted 63 inches of snowfall accumulation as of 11 a.m. Monday. Montague, about 20 miles southeast of Watertown reported 60 inches as of 9 a.m. Monday.

The Abominable Snowman was spotted on Broadway in downtown Saranac Lake on Monday. (Enterprise photo — Grace McIntyre)

Even for the Tug Hill — which routinely boasts eye-popping snowfall accumulations — the weekend event was significant, according to Steve Welch, a meteorologist at the National Weather Service’s Buffalo office.

“Not every (lake-effect snow) event off of Lake Ontario is going to produce 5 feet, but 2 to 3 feet is pretty frequent for the Tug Hill throughout the winter,” he said. “We tend to get these 5 feet events once every year or two.”

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Elevation enhancement

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Snow surrounds a partially-frozen Lake Flower in Saranac Lake on Monday. (Enterprise photo — Grace McIntyre)

Welch explained that local topography is key to understanding the mammoth lake-effect snowfall accumulations that frequently impact the Tug Hill Plateau.

“When you have a wind flow that’s hitting that higher elevation, that air rises, which compresses the moisture in that layer of the atmosphere,” he said. “That usually causes increased precipitation to fall versus areas of lower elevation nearby.”

As the air rises, it becomes cooler, and cold air is able to hold less moisture than warm air. The atmosphere can be thought of as squeezing a wet rag. The cooling of the air is akin to applying more pressure to the rag: both result in more moisture being pushed out and — in the case of the atmosphere — falling to the ground as frozen or liquid precipitation.

The Tug Hill Plateau presents a textbook example of this phenomenon, known as “upsloping.” Lake Ontario’s surface elevation is 243 feet while the Tug Hill — whose center is only about 20 miles from Lake Ontario’s shore — rises to about 2,100 feet. This elevation gain over a relatively short distance usually produces higher snowfall totals for elevated locations during the same storm as areas a similar distance away from Lake Ontario, but without the added elevation, receive.

Upsloping is not unique to lake-effect snows or the Tug Hill Plateau. Welch mentioned the mountainous terrain of western North Carolina and eastern Tennessee contributed to excessive rainfall totals in those regions from Tropical Storm Helene this summer. Locally, upsloping resulted in partially excessive and devastating rainfall totals from Tropical Storm Irene in 2011.

Snow surrounds a partially-frozen Lake Flower in Saranac Lake on Monday. (Enterprise photo — Grace McIntyre)

“Any higher terrain that a weather feature interacts with will have higher precipitation on that side of the terrain (where the air is rising),” he said.

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Lake-e-fluff

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Those who have spent significant time in or around snow know that its consistency can vary significantly. Some storms produce wet slushy snow while other snowfall is light and fluffy.

There are a multitude of atmospheric factors that interact with each other to determine the snowfall’s consistency for any given storm. The essence of the equation revolves around the “snow-to-liquid ratio.” This is determined by dividing the amount of snow measured by the amount of liquid water that would exist if that snow were to theoretically be melted.

For example, a 12:1 ratio — which is considered average consistency — translates to a foot of snow melting down to an inch of liquid water. Higher ratios — those in excess of 15:1 — tend to produce fluffy snow while lower ratios — those below 10:1 — tend to produce dense, wet snow.

The ratio is primarily driven by air temperature in the area of the atmosphere that meteorologists call the dendritic growth zone — or where snow forms. Air temperatures between 0 and 14 degrees Fahrenheit constitute the ideal range for high snow-to-liquid ratios. Air temperatures that are below freezing but outside of that range — either between 14 and 32 or below 0 degrees Fahrenheit tend to produce smaller snowflakes that — when they accumulate — pack together tighter, resulting in denser snow and lower ratios. Snowflakes that form within that range tend to expand more. When they fall, they take up more space and trap air between other flakes, resulting in snow with a consistency resembling cotton candy.

The atmospheric setups that lead to lake-effect snow over the Great Lakes usually support higher ratios, according to Welch. He attributes much of that to where the air comes from.

Welch explained that unlike nor’easters — which tend to originate over the southeastern U.S. — lake effect snow is driven by air masses that originate closer to the Arctic. By the time the air reaches the Great Lakes, it tends to be in or close to the temperature range for large dendrite growth, resulting in fluffy flakes that trap air and lead to higher liquid-to-snow ratios.

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Community collaboration

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The National Weather Service encourages the public to report snowfall totals at their locations during winter storms. They rely heavily on the reports to get a better sense of how much snow fell in specific portions of their forecast area, which can otherwise be difficult to ascertain, especially across large rural forecast areas, such as northern New York.

“It definitely helps us to draw that picture in the forecast area of just how much snow fell,” Welch said. “With lake-effect, it can be such a tight gradient where literally a few miles means the difference of going from no snow to a foot of snow or more, so (the reports) really help to get the highest density of information that we can.”

Obtaining an accurate snowfall reading can be tricky. Meteorologists recommend using a smooth board on a level surface. Measuring directly on the grass may result in an uneven or slightly inflated snowfall total, as blades of grass can create small air pockets at the base and prop up the snow layer.

The board should be painted white or otherwise light in color to avoid excess heating from solar radiation, which could potentially melt some of the snow before measurement, decreasing the report’s accuracy. Snow should also be cleared off from the board after each measurement is recorded.

To get a total in an extended-duration storm, each of those recorded intervals should be added together — rather than taking one big measurement at the end of the storm, by which point the snow that fell earlier may have compressed, resulting in a lower and less accurate measurement.

Location is key. Meteorologists recommend placing the board at least 20 feet away from structures, which could impact the way snow falls if there is a breeze. If drifting occurs, meteorologists recommend taking several measurements in the area and calculating the average.

They compare the submitted data to their predictions leading up to the event, which can help them to make better-informed forecasts going forward. Anyone can submit a report — for snowfall, as well as a variety of other weather phenomena throughout the year — to the National Weather Service office that serves their area.

Reports from Franklin, Essex, Clinton and St. Lawrence counties can be made at weather.gov/btv/stormreport. Reports originating in Warren, Hamilton and Herkimer counties can be made at weather.gov/aly/reportWx.

While anyone can submit a report, the National Weather Service also offers free classes to the public that teach how to become a trained spotter, which can help people submit more accurate reports. More information about training can be found at weather.gov/btv/skywarn.

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Looking ahead

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The Tri-Lakes region has more chances for snowfall this week as below-average temperatures are expected to remain anchored across the eastern U.S. through the end of the week.

“It’s an active pattern in general,” Welch said.

While accumulations will be nothing near what the Tug Hill saw over the last weekend, early forecasts show the possibility of 3 to 5 inches of snow for Tri-Lakes communities Wednesday night and Thursday, according to the National Weather Service’s Burlington, Vermont office.

Their forecast notes that additional light accumulations are possible over the weekend — although it is too early to say how much — before temperatures are expected to moderate for the beginning of next week.