Tornado Girl Posted January 12, 2011 Share Posted January 12, 2011 I've seen quite a few questions about LES. So, I thought I would add this about the ingredients need for LES 1 Sufficient temperature difference between the lake surface and overlying air 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 should be 15 °C to 25 °C cooler than the surface of the lake, and the dew point differential between the 850-millibar (mb) level and the surface must be at least 13 °C. In general, the greater the temperature difference between the cold air and the warm water, the heavier the snow showers will be 2 One of the most important aspects when considering intensity is Inversion heights Inversion heights < 3000 ft preclude heavy lake-effect snows Inversion heights > 7500 ft strongly support heavy lake-effect snows 3 Directional wind shear Small amounts of directional wind change with height (< 30 degrees) below the inversion favors horizontal roll convection Highly sheared environments (> 60 degrees) disrupt and diminish the efficiency of rolls, leading only to flurries 4 Orographic Lift Higher elevation can make a big difference. Higher elevations increase cooling and condensation of water vapor in the air. On average you can add 4-8 inches per 100 foot raise in elevation for annual totals 5 Wind speed is important too The wind speed determines how far inland and the horizontal spreading of lake-effect snow. If the winds are light the snow will be close to the to the shore. (1-10 miles). Whereas, Strong winds will blow the snow further inland ( more than 10 miles) Wind speed needs to be light enough across the lake in order to allow moisture convergence to occur.. If winds are too strong in the PBL, let's say over 50 mph, The moisture may not be able to evaporate enough to produce heavy lake effect snow. The best combination would be deep layer of arctic air moving between 10 and 40 miles per hour. Two examples of LES sounding for heavy snow Link to comment Share on other sites More sharing options...
lakeeffectkid383 Posted January 12, 2011 Share Posted January 12, 2011 I've seen quite a few questions about LES. So, I thought I would add this about the ingredients need for LES 1 Sufficient temperature difference between the lake surface and overlying air 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 should be 15 °C to 25 °C cooler than the surface of the lake, and the dew point differential between the 850-millibar (mb) level and the surface must be at least 13 °C. In general, the greater the temperature difference between the cold air and the warm water, the heavier the snow showers will be 2 One of the most important aspects when considering intensity is Inversion heights Inversion heights < 3000 ft preclude heavy lake-effect snows Inversion heights > 7500 ft strongly support heavy lake-effect snows 3 Directional wind shear Small amounts of directional wind change with height (< 30 degrees) below the inversion favors horizontal roll convection Highly sheared environments (> 60 degrees) disrupt and diminish the efficiency of rolls, leading only to flurries 4 Orographic Lift Higher elevation can make a big difference. Higher elevations increase cooling and condensation of water vapor in the air. On average you can add 4-8 inches per 100 foot raise in elevation 5 Wind speed is important too The wind speed determines how far inland and the horizontal spreading of lake-effect snow. If the winds are light the snow will be close to the to the shore. (1-10 miles). Whereas, Strong winds will blow the snow further inland ( more than 10 miles) Wind speed needs to be light enough across the lake in order to allow moisture convergence to occur.. If winds are too strong in the PBL, let's say over 50 mph, The moisture may not be able to evaporate enough to produce heavy lake effect snow. The best combination would be deep layer of arctic air moving between 10 and 40 miles per hour. Thats a little exaggerated at least here in WNY.It may be like that on the tug but if that was true here youd be talking about 4-8 inches in a place like West Seneca (800 ft) to 20-40 inches 5 miles away in some of the Boston Hills (1300 feet). Id say an average is 2-4 inches per 100 feet rather then 4-8. lol. Link to comment Share on other sites More sharing options...
Saggy Posted January 12, 2011 Share Posted January 12, 2011 Thats a little exaggerated at least here in WNY.It may be like that on the tug but if that was true here youd be talking about 4-8 inches in a place like West Seneca (800 ft) to 20-40 inches 5 miles away in some of the Boston Hills (1300 feet). Id say an average is 2-4 inches per 100 feet rather then 4-8. lol. I wouldn't doubt it is that high on the Tug. The increase you see in snow depth just driving a few miles can be amazing at times. Link to comment Share on other sites More sharing options...
baroclinic_instability Posted January 12, 2011 Share Posted January 12, 2011 4-8" per 100 feet may be a bit extreme on a climo basis, but you hit the point home correctly that elevation can make a big difference. One great example is the Gogebic region in Wisconsin south of Ashland (near Hurley, WI) where about 800 feet of uplift makes all the difference between flurries in Ashland and sometimes feet of snow in certain LES storms depending on the setup. The Wasatch Range in Utah on the eastern side of the Great Salt Lake is another great example. Link to comment Share on other sites More sharing options...
WNYLakeEffect Posted January 12, 2011 Share Posted January 12, 2011 Thats a little exaggerated at least here in WNY.It may be like that on the tug but if that was true here youd be talking about 4-8 inches in a place like West Seneca (800 ft) to 20-40 inches 5 miles away in some of the Boston Hills (1300 feet). Id say an average is 2-4 inches per 100 feet rather then 4-8. lol. It's a lot different on the Chautauqua Ridge. The COOP 2 miles SSE of Westfield probably averaged 80" or so (I haven't completely averaged it yet, it actually might be less). Over the past 5 winters (not long, but it gives you an idea), the COOP at Mayville averaged 230.5". They're about 5 miles and 600 feet apart. That's 30"/mile or 25"/100 feet. I've seen no reason to doubt either COOPs accuracy, considering the Fredonia and Sherman sites. From my house (120" a year) to Mayville, it's about 14 miles away and 150 feet different. So, along Chautauqua Lake, it's 7.9"/mile and 73.3"/100 feet, and that's not at lake level (1308 feet). 8 or 9 miles east of me, the Jamestown COOP only averages just under 100". Perrysburg has averaged 223.2" over the past 7 winters, but Gowanda, 3.5mi and 600-800 feet away, probably averages 120" or less (records from Gowanda are a wreck). The perfect display of this gradient was November 2008. A few days before T-Giving, there was over a foot of snow on the ground at my house, 2 feet from Sinclairville to Cassadaga, but nothing just 4 or 5 miles down the Chautauqua Ridge. Snow was falling on the top of the Ridge, but it was rain at the bottom. Link to comment Share on other sites More sharing options...
Tornado Girl Posted January 12, 2011 Author Share Posted January 12, 2011 Thats a little exaggerated at least here in WNY.It may be like that on the tug but if that was true here youd be talking about 4-8 inches in a place like West Seneca (800 ft) to 20-40 inches 5 miles away in some of the Boston Hills (1300 feet). Id say an average is 2-4 inches per 100 feet rather then 4-8. lol. I know that formula works for the most part For several areas around 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 western and upstate New York; for the Great Salt Lake, the Wasatch Range; for Atlantic Canada, the Long Range Mountains in Newfoundland and the Cape Breton Highlands in Nova Scotia; and for the Alaska panhandle, the Coast Mountains. I read somewhere but I can't remember where that It is estimated that annual snowfall increases by 65 cm per 100-meter elevation gain leeward of the Great Lakes. Link to comment Share on other sites More sharing options...
Wx4cast Posted February 6, 2011 Share Posted February 6, 2011 Thats a little exaggerated at least here in WNY.It may be like that on the tug but if that was true here youd be talking about 4-8 inches in a place like West Seneca (800 ft) to 20-40 inches 5 miles away in some of the Boston Hills (1300 feet). Id say an average is 2-4 inches per 100 feet rather then 4-8. lol. I know that formula works for the most part For several areas around 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 western and upstate New York; for the Great Salt Lake, the Wasatch Range; for Atlantic Canada, the Long Range Mountains in Newfoundland and the Cape Breton Highlands in Nova Scotia; and for the Alaska panhandle, the Coast Mountains. I read somewhere but I can't remember where that It is estimated that annual snowfall increases by 65 cm per 100-meter elevation gain leeward of the Great Lakes. This has been on my mind for a while and I finally found the sources to backup TG's post. In an article titled Lake Effect storms by PJ Sousounis on page 1105 (the second page of the article), the author states " terrain can enhance individual snowstorm totals by about 5cm for every 100 meters of rise." In Niziol's et. al article in the March 1995 issue of Weather and Forecasting (Volume10) on page 62-63: " Orography can make a very significant contribution to snowfall. For example, Muller (1966) noted a 12-20 cm (5-8 in.) increase in annual snowfall per 330-m (100 feet) increase in elevation to the lee of the lakes." Link to comment Share on other sites More sharing options...
Wx4cast Posted February 9, 2011 Share Posted February 9, 2011 Here are some interesting reads on Lake Effect: Lake Effect Storms Operational Forecasting of LES in NYS Lake Effect Snow paper by Niziol & others. Here's another interesting read, too: Lake effect and lake enhanced snow in the Champlain Valley of VT Link to comment Share on other sites More sharing options...
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