Lake Effect Snow

Hi it's Rebecca again, I've been mentioning lake effect snow lately; so I thought I would post an blog entry about it. I'm sure some of you living outside of the snowbells are curious about what it is. This blog entry will give you a broad overview of what lake effect snow is, how it forms, and where it can occur. As well as the difference between a lake effect snow storm and a synoptic scale snow storm.

Before I get into lake effect snow amounts I want to give you a broad overview of the Tug Hill Plateau. Nestled in the ‘North Country between Lake Ontario and the Adirondacks, Tug Hill is a region of unbroken northern hardwood forests and pristine wetlands drained by a vast network of coldwater streams. The Tug Hill region is located in four Upstate New York counties: Jefferson, Lewis, Oneida, and Oswego. The top of the plateau is relatively flat compared to other areas in New York State.  The most outstanding characteristic of the Tug Hill region is its undeveloped state. There are some small, scattered hamlets and villages along the outer edges of the region, but the core area is heavily forested and relatively unpopulated. In spite of the region being sparsely populated (for some strange reason), a few  places like Boonville, Barnes Corners, Redfield, and Montague occasionally make the news during the winter. Many old timers up here think Tug Hill got its name sometime  around the 18th and 19th centuries. in this time span the term "tugging" was use to describe  areas that were reached by horses or oxen pulling a wagon up a long road to get to a high area.  H.E. Krueger in an article "The Lesser Wilderness - Tug Hill" he claims the Tug Hill was named by two early settlers, Isaac Perry and a Mr. Buell when traveling up the hill west of Turin The Tug Hill covers an area of 2,100 square miles with an elevation from about 350 feet on the west to over 2,000 feet in the east. The area because of its location on the east-end of Lake Ontario, along with the combination of winter winds blowing over almost 200 miles of Lake Ontario waters, and the 2,000-foot rise of Tug Hill creates these heavy lake snows. These storms are responsible for the majority of the over 200 inches of snow the Tug receives annually, turning the region into a winter wonderland. The heavy snowfall is one of Tug Hill’s greatest recreational assets.

            Several towns in the region hold impressive records. An out of the way place called Hooker (near Barnes Corners) recorded 466.9” of snow in the winter of 1976-77. The monthly record for snow accumulation belongs to Bennet Bridges and is 192” in January 1978. The official record for a one day snowfall in NY State belongs to Montague NY. The hamlet had 77” of snow in 24 hours on the 11th/12th of January 1997. Montague also holds the single storm record for snowfall in NY with 95” from January 10th-14th in 1997.  Not to be outdone, Redfield received 141 inches during the 12 day lake effect event of February, 2007. Well that tells you a little bit about this fascinating area...now on to lake effect snow.

Just what is Lake Effect Snow?

Lake effect snow, also called snow squalls, results from cold, arctic air traveling over a relatively warm body of water. The cold, dry air picks up the water moisture and deposits it, in the form of snow, over land areas in- lee of the warmer water. In the case of the Northeast lake effect snows can occur around Lakes Ontario and Erie and to a lesser extent around Lake Champlain and the Sound off of Long Island.  After the passage of a cold front the relatively warm waters of the Great Lakes often create convective instability in an otherwise stable, arctic continental airmass. Therefore, while areas in eastern New York and the rest of New England are clearing up after a recent cold front or storms passage, The Great Lakes communities hold their breath waiting for the lake effect snow machine to awaken. Lake-enhanced snow is different from lake-effect as it is part of an already present system.

How does Lake Effect Snow form?

The first two ingredients

These come under the heading of temperature contrast. The temperature between the lake surface and overlying air promotes "convective instability" that provides the basic energy source for lake effect snow. Ideally, the ambient air temperature at 850mb should be at least 13°C cooler than the surface water temp. Heat and moisture from the warm lakes rises into the "modified" arctic air where it then cools and condenses into snow clouds.   The intensity of the lake effect snowfall also depends upon how far the wind moved over the  lake surface (the fetch) . The longer the fetch, the more moisture the air can obtain and more snow it can form. One reason that mid-lake bands are so impressive is that the fetch is maximized. In the case of Lake Ontario the band can be 150 miles or longer. Major storms rarely develop unless the fetch is at least 50 miles. If the lake has a lot of ice cover; the band intensity is greatly reduced. This is because the ice cuts down on evaporation. Therefore the fetch can't pick up much moisture. This is the reason Lake Erie normally only has lake effect snow during the early winter. Lake Erie is the most likely of the Great Lakes to freeze because it is by far the shallowest. whereas, Lake Ontario is the least likely due to its vast depth and southern location compared to the upper Great lakes.  

The wind speed determines how far inland and the horizontal spreading of lake-effect snow. With relatively light winds, the snow maximum will be closer to the shore. Strong winds tend to blow the snow further inland and produce a snow maximum which is more than 10 miles inland. The heaviest snows rarely occur right at shoreline. Wind speed needs to be light enough across the lake in-order for moisture convergence to occur. The moisture content of the air depends on the previous dewpoint of the air moving over the lake and the moisture acquired through evaporation over the lake. If winds are too strong ( over 50 miles per hour), enough moisture may not be able to evaporate to produce heavy lake effect snow. The best combination is cold arctic air moving between 10 and 40 miles per hour.

The third ingredient

Forecasting lake effect snow can be a huge challenge. Therefore knowing the wind direction is vidal. Wind direction is measured in degrees, as on a compass where 360 degrees is north, 90 degrees is east, 180 degrees is south, and 270 degrees is west. Since Lake Ontario is elongated west-east, and since the Tug Hill is on the eastern end of the lake. Winds with a 270 flow will often bring in a single extremely intense snow band that dumps huge amount of snow. Sometimes the Capital District will be affected by snow off of Ontario this usually occurs when winds 30 to 40 mph set up on a 280-290 flow.

The forth ingredient       This is the topography around the lake.  Elevation plays a major role in lake effect snow production  ( this is called orographic lift ).  This occurs when the wind comes over the flat, nearly frictionless (somewhat ice covered) Great Lakes and then plows into the shore and over the land. This creates friction as well as lift when it hits the land and elevation change. When the air is lifted, you get clouds and eventually lake effect snow showers. For the Great Lakes this would include locations such as the Keewenaw Peninsula of Michigan, the Bruce Peninsula in southern Ontario, the Tug Hill and Allegheny Plateaus of upstate New York; It is estimated that annual snowfall increases by 65 cm (25 1/2 inches) per 100-meter  (slightly more than 328 feet) in elevation gain leeward of the Great Lakes.

 There are other factors as well. Some of these are wind shear, thermal convergence, and  frictional convergence. I will not go into these. However, if you want to know about them. Drop me  an Email and I would be happy to answer any questions you may have.

Where can it Occur?

The lake effect I've been discussing has been on the Great Lakes. However,  these types of snowstorms can occur anywhere cold air moves over a fairly large area of relatively warmer water during the winter.

Below are a few maps that show some of these places.

                                                                   Pictures courtesy of NWS Buffalo

The  difference between a synoptic scale snow storm and a lake effect storm

The main difference between a lake effect snow and a synoptic scale snow storm, is that lake effect snow storms are not low pressure system storms. Instead it is cold, dry air  moving over the  Lakes that brings the snow. Another major difference is a winter storm may last a few hours to a day or so with on and off snow, Where-as a lake effect snow storm will often produce snow continuously for 48 hours or longer in a particular area. Lake effect snows can precipitate as much as 76 inches  of light-density snow in 24 hours with snowfall rates as high as 6 to 8 inches per hour. In fact in 2007 a lake snow band lasted over 10 days; when it was over anywhere from 100 to 141 inches had fallen. The good news was that the band meandered around a lot during that time. Imagine what the snow amounts would have been if the band had more or less stayed in one place.

                        Here are a few pictures of the Tug Hill. To give you an idea what it looks like.

The Winteridge near Lowville run by the Northrup family

There is always a wind on the Tug. So wind skiing can be a lot of fun

One of the windmills outside of Lowville.

A good way to get around in winter

Well that's about it. I hope you enjoyed reading this post. Again I will be happy to answer any questions you may have.

Rebecca