Nature Note – Low-level Jets

Strong winds in the lower atmosphere often develop in late autumn along Lake Champlain. These events, called low-level jets, can occur when a high pressure system over the Atlantic Ocean creates southerly winds which become channelized and accelerated by the north-south orientation of the Champlain Valley. They can happen at any time of the year, but are most common between late summer and early winter when the difference in temperature between the water and the air above is greatest. The greater the difference in temperature between the warm lake water and cooler air above it, the greater the potential to mix stronger winds aloft down to the surface of the lake.

As ice begins to form, the temperature differential is dampened. Wind speeds during low-level jet events typically reach 25 to 40 miles per hour, strong enough for the Weather Service to issue wind advisories. Low-level jets are most likely to occur at night and tend to be pushed against the eastern wall of the Champlain Valley. For more information about this lake-influenced weather phenomenon check out the National Weather Services explanation in their October 2008 Champlain Weather Chronicle.