Long Arm of Winter Brings Lake Effect Snow to Midwest, Ice Risk to South

Strong winds and recurrent blasts of bitter cold continue to plague much of the central and eastern United States, with little change in sight into early next week. Like spokes on a wheel, upper-level waves are circulating around a large, powerful center of low pressure anchored near Hudson Bay. At the surface, each wave has been driving a huge zone of frigid high pressure into the U.S. heartland. On Wednesday, sea-level pressure readings broke all-time records at four state capitols and a number of other locations, including:

Bismarck, North Dakota: 1055.4 mb

Concordia, Kansas: 1055.1 mb

Grand Island, Nebraska: 1056.9 mb

Huron, South Dakota: 1056.0 mb

Lincoln, Nebraska: 1055.9 mb

Pierre, South Dakota: 1055.9 mb

Sioux Falls, South Dakota: 1054.5 mb

Sioux City, Iowa: 1055.2 mb

Topeka, Kansas: 1054.3 mb

[Preliminary data courtesy David Roth, NOAA]

The sea-level pressure in Mitchell, South Dakota, soared to a preliminary reading of 1056.8 mb. If confirmed, this will be a statewide record, according to state climatologist Dennis Todey.

Temperatures this week fell below 0°F across much of the upper Midwest, with dangerous wind chills well below zero. Tallahassee, Florida, dipped to 24°F on Thursday morning. However, considering the strength of the surface highs, daily record lows have been surprisingly scarce. In Vermont, Barre-Montpelier managed to plummet to a new daily record low of -20°F.


Figure 1. The GFS model's surface forecast for 00Z Saturday, issued at 00Z Friday, shows high pressure firmly in control across most of North America. Image credit: Levi Cowan, tropicaltidbits.com.

The dominance of surface high pressure across the nation has left little opportunity for major winter storms to develop. Even weaker systems have made the most of their limited moisture, though, with the help of jet-stream dynamics, biting winds, and bitter cold. Parts of the western Washington, D.C., metro area got socked with more snow than many forecasters expected on Tuesday--more than 4 inches in places. (Capital Weather Gang dubbed it "a 'clipper' that delivered.") The next spoke on our winter wheel rotated across the Midwest last night. Blizzard warnings were hoisted across southern Minnesota and northern Iowa, with winter storm warnings extending eastward into parts of Ohio. This morning's map is dominated by wind-chill advisories that stretch from Montana to Pennsylvania. On the southern fringes of the persistent high pressure, a winter weather advisory is in effect today across southern Mississippi for a potential mix of rain, snow, and freezing rain. A similar setup will play out across parts of southern Texas on Saturday, with freezing rain and sleet possible. In both cases, temperatures will be marginal and any accumulations should be on the light side. A somewhat greater risk of freezing rain could extend northeast through Arkansas later in the weekend.


Figure 2. Jeff Armstrong walks to work on Tuesday, January 6, in Rock Island, Illinois. The Quad Cities area woke up to 5 to 6 inches of fresh snow on Tuesday, with temperatures on Wednesday dipping to -12¯F and wind chills as low as -26¯F. Photo credit: AP Photo/The Dispatch, Todd Mizener.

Gearing up for the lake-effect machine
By far the most impressive precipitation this weekend can be expected downwind of the Great Lakes. Strong west-southwest winds and cold surface air will provide near-ideal conditions for an extended period of lake-effect snow downwind of Lake Erie and Lake Ontario. The region around Buffalo, New York--still reeling from as much as 88 inches in mid-November, is getting plastered once again. A CoCoRaHS cooperative observer in the Buffalo suburb of Kenmore reported 12.2 inches through 7 AM EST today. Up to five feet of snow could fall by Saturday in favored locations east of Lake Ontario, with up to three feet possible in far southwest New York, south of Buffalo and east of Lake Erie. The exact trajectory of the strong winds will determine where the heaviest snowbands set up. As the November storm demonstrated, snowfall totals in a lake-effect storm can vary hugely over just a few miles.

While it's the mega-lake-effect snowstorms that grab the headlines, residents of the lake-effect region of New York also experience many lighter snows that can gradually build up through a series of gray, cold midwinter days. Sometimes the snowpack gets partially or completely eroded by a round of rain, or simply by moist, mild air that facilitates melting. In his book "Lake Effect: Tales of Large Lakes, Arctic Winds, and Recurrent Snows" (Syracuse University Press, 2012), Mark Monmonier, a geography professor at Syracuse, waxes philosophical about his local winters: "For most of us, living with the 'lake-effect snow machine' is a small price for our pleasant summers, delightful autumns, and comparative freedom from devastating winds and floods."

I'll be back with a new post on Monday. Have a great weekend!

Bob Henson