Everything you need to know about lake-effect snow
It's a term weather-watchers will hear meteorologists talking about quite often come late fall and through winter. But what exactly is it and how far can it reach?
You've seen it in the news, lake-effect snow slamming cities along the Great Lakes. But what exactly is lake-effect snow?
Lake-effect snow. It's a term weather-watchers will hear meteorologists talk about quite often come late fall and through winter. But what exactly is lake-effect snow, and how far-reaching can this phenomenon be?
One of the biggest lake-effect snowfall events on record hammered areas near Buffalo, New York, with 5 feet of snow in a span of two days back in November 2014.
The lake-effect event in 2014 unfolded during the evening hours on Monday, Nov. 17, 2014, as a narrow, shifting band moved off Lake Erie. However, the 15- to 20-mile-wide band of intense snow eventually settled just south of the City of Buffalo and parked there into Tuesday night, Nov. 18, before dissolving as it shifted northward early on Wednesday, Nov. 19.
The bulk of the snow from the lake-effect band was described as being a wall of snow when viewed from a short distance away and deposited 3 feet of snow in the first 12 hours and went on to bring 65 inches to South Cheektowaga, New York, a suburb about 10 miles east of Buffalo. Indeed, dashcam footage shot during that storm showed intense snowfall and whiteout conditions rivaling any blizzard.
Brian Cintron walks in his snow-bound south Buffalo neighborhood on Thursday, Nov. 20, 2014, in Buffalo, N.Y. A blast of lake-effect snow pounded Buffalo for a third day piling more misery on a city already buried by an epic, deadly snowfall. (AP Photo/Mike Groll, File)
Just north of Cheektowaga, however, the snow totals were far from the 5-foot mark.
Meteorologists at the National Weather Service office in Buffalo described snow total disparity in the November 2014 snow event, saying, "Over 5 feet of snow fell over areas just east of the City of Buffalo, with mere inches a few miles to the north."
As if 60 inches of snow wasn't enough, a second round of lake-effect snow targeted roughly the same area that was hit the hardest from Nov. 19-20 and deposited another 1-4 feet, bringing the combined snowfall from both events to as high as 7 feet in some of the hardest-hit locations.
More than a dozen people were killed, thousands of motorists were trapped in vehicles during the November 2014 events, falling trees triggered power outages and hundreds of roofs and structures collapsed under the tremendous weight of the snow, according to the NWS office in Buffalo.
The western New York lake-effect event is one of the most extreme cases of lake-effect snow on record, but there are typically dozens of lesser lake-effect snow events that occur across the Great Lakes region during a typical cold-weather season.
This image of a band of lake-effect snow was captured on Tuesday, April 9, 2019, looking south from the city of Buffalo, New York. (NOAA)
One key factor needed for lake-effect snow, not surprisingly, is a large body of water, which is why much of the discussion around lake-effect snow -- and some of the most astonishing lake-effect snow events -- centers on the Great Lakes region.
The majority of lake-effect snow events tend to occur during the late autumn to the first part of the winter when the waters of the Great Lakes are still unfrozen and warm relative to the colder air flowing across the region from Canada.
There is a mathematical threshold in temperature between the air and lake waters for lake-effect snow to occur.
"Meteorologists look for a temperature difference of 23 degrees Fahrenheit or greater between the lake water and the air approximately 5,000 feet above the surface of the lakes," according to AccuWeather Senior Snow Warning Meteorologist Brian Wimer.
"The greater the temperature difference between the lake and the air above, the heavier the lake-effect snow will be," Wimer explained.
When the temperature difference needed for lake-effect snow is present but when the air is well above freezing, there can still be a lake-effect weather event, but precipitation that falls will be rain instead of snow. This is sometimes the case during the first outbreaks of chilly air of the autumn season.
Lake-effect snow tends to organize in narrow bands, where snow falls beneath the clouds. The bands tend to vary in width but can extend for dozens and even hundreds of miles.
Often, in between the bands of snow, during the daylight, the sun can be shining brightly, while only a few miles away, under a band of lake-effect snow, it can seem like a widespread blizzard with snow piling up at a rapid pace.
Lake-effect snow events, like most other weather phenomena, vary in intensity and duration. Some lake-effect snow events may last only a few hours. Sometimes, they can go on for days.
Depending on the length and duration, lake-effect events can deposit an inch or two of snow or unload several feet of snow. Within the more extreme bands of lake-effect snow, thunder and lightning can occur, and the visibility can drop to near zero. Winds can be quite strong and gusty, resulting in blizzard conditions, which, by definition, require sustained wind or frequent gusts to 35 miles per hour or greater and considerable falling snow or blowing snow (or both) that reduces visibility to less than one-quarter of a mile for at least three hours.
Bands of lake-effect snow often produce very heavy snow, sometimes at the rate of 2-4 inches per hour, but sometimes even at a heavier pace, as was the case with the November 2014 event. The snowfall rate during that infamous event approached a jaw-dropping 6 inches per hour at times. At that rate, snow removal crews cannot keep up, and travel grinds to a halt.
"If the wind direction does not change for an extended period of time, very heavy snowfall totals measured in feet, instead of inches, can result," Wimer said.
"In some cases, these bands can be very narrow, such as 5-10 miles wide. In other cases, when the wind direction shifts, the bands produce more widespread snow, but totals at particular locations are typically not as high," Wimer explained.
Another factor that can affect the amount of and intensity of lake-effect snow bands has to do with a factor known as "fetch," a term meteorologists use to describe the distance that winds blow across a lake in the same direction. The longer the fetch of air blowing across a lake or even across multiple lakes is, the more intense the bands of lake-effect snow can be.
"For example, a west-to-east wind across the length of Lake Ontario results in cold air passing over a longer expanse of water than a wind blowing from north to south across Lake Ontario," Wimer said.
In the first case, a city such as Watertown, New York, or a region of northern New York state known as the Tughill Plateau, is in a prime location to be hammered with feet of snow. Meanwhile, several inches of snow may fall in the zone between Rochester and Syracuse, New York.
"The bigger lake-effect events in Cleveland and northeastern Ohio often occur when a band of snow first develops off Lake Huron then crosses Lake Erie and picks up a second round of moisture," Wimer added.
Tom Kitson of Ayr, Ont., with companions Dug and Champ, waits for a friend outside a convenience store on Thursday, Nov. 20, 2014, in West Seneca, N.Y. (AP Photo/Mike Groll)
Even though prevailing winds in the wintertime are from the northwest across the Great Lakes region, occasionally cold winds can blow from the southwest or the northeast and bring snow to different areas. In the case of southwest winds off Lake Erie, lake-effect snow can clobber Buffalo, the Niagara Peninsula or the towns south and east of Buffalo, as was the case in November 2014. Meanwhile, northeast winds coming off of Lake Michigan have delivered lake-effect snow to Chicago on occasion during the late fall and winter.
As cold air pushes down from Canada, lake-effect snow from the Great Lakes often starts developing off Lake Superior and can begin depositing snow on the southern shores of northern Wisconsin and the Upper Peninsula of Michigan. As the cold air advances, lake-effect snow emerging from lakes Michigan, Huron, Erie and Ontario usually will join in.
Common areas of the United States for lake-effect snow, also known as the snowbelts, are western and northern New York state, northwestern Pennsylvania, northeastern Ohio, northwestern Indiana, the western shore of the Lower Peninsula of Michigan and part of northeastern Wisconsin and much of the Upper Peninsula of Michigan.
And the phenomenon can be far-reaching.
Lake-effect snow sometimes falls more than 100 miles downwind of the Great Lakes. The mountains of New York state, western, central and northern Pennsylvania, the West Virginia mountains and western Maryland can all get a visit from lake-effect snow.
There are usually a few events during the winter in which lake-effect snow reaches all the way to the mountains of Tennessee and North Carolina. In rare cases, bands of lake-effect snow can extend hundreds of miles from lakes Superior or Huron through the Appalachians and even to parts of the mid-Atlantic and southwestern New England coasts.
The visibility was near zero in Adams Center, New York, during a lake-effect snow band on Feb. 28, 2020. (AccuWeather/Dexter Henry)
There is a misconception about lake-effect snow not being able to develop once the Great Lakes become frozen over or become clogged with a lot of ice. It is not uncommon for Lake Erie to almost completely freeze over during the coldest winters. But, when this happens, lake-effect snow can still develop.
"Since the surface of the frozen lake is much smoother than the land adjacent to the lake, the air tends to pile up on the lee shore," Wimer said, referring to the downwind side of a lake, "and results in clouds and some lake-effect snow. But," he added, "since there is less moisture available, lake-effect snowfall is drastically reduced in this case."
Lake-effect snow can also fall during the latter part of the winter and spring. These events tend to be less extreme than those of the late autumn and early winter as there is not as much of a difference in temperature between the lake water and the atmosphere above.
But, in mild winters, such as that during 2019-2020, lake waters may remain warmer than average and could set the stage for late-season lake-effect events.
During an intense late-February lake-effect snow event, Carthage, New York, picked up 50 inches of snow from Feb. 27-28, 2020.
Most long-term residents around the Great Lakes or commercial truck drivers are familiar with the trouble lake-effect snow can cause. In locations farther away, the familiarity of this reoccurring phenomenon tends to diminish. But, as was the case in the November 2014 event, even those familiar with lake-effect snow can underestimate the severity of an event despite advanced alerts and warnings from meteorologists.
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