Midwest Weekly Highlights - February 8-14, 2008

Another Active Week

Weather systems continued to cross through the Midwest this week, bringing periods of precipitation to parts of the region. However, central portions of the Midwest, hit hard by winter storms the first week of the month enjoyed a respite from stormy weather.

Temperatures were much below normal this week across the northwestern half of the region but just above normal in the far southeast (Figure 1). Average daily temperatures ranged from 10°F to 14°F below normal northern Missouri and northern Illinois northwest through Minnesota. Temperatures ranged from 8°F below normal in central Illinois to 2°F above normal in southeastern Kentucky.

The central Midwest saw little precipitation this week, which was welcome after last week's torrential rains. Precipitation was above normal across northern Iowa, Minnesota, Wisconsin, and, most of Michigan (Figure 2). A second area of higher than normal precipitation extended from southern Missouri eastward along the Ohio River and northeastward through Ohio. Snowfall was well above normal across the northern half of the region and from south-central Missouri through the Ohio Valley (Figure 3). There was little change in the February 12 U.S. Drought Monitor from last week, with small pockets of drought in Minnesota, Wisconsin, and in southeastern Kentucky (Figure 4).
 

Arctic Outbreak and Lake-Effect Snow

On February 9 the leading edge of an Arctic air mass pushed southeastward into the Dakotas and took aim on the Midwest. By the morning of February 10 the Arctic front had pushed through the entire Midwest, producing frigid temperatures along with dangerous wind chills (Figure 5). Low temperatures on February 10 were between -10°F and -21°F from Minnesota south to northern Iowa and across Wisconsin (Figure 6). The difference in pressure between the strong Arctic high and and intense low over Ontario produced strong northwest winds across the region on the 9th and 10th, with the strongest winds from northern Iowa and southeast Minnesota across Wisconsin and Michigan. Winds were sustained from 15 to 30 mph, and gusting to 45 mph and higher. These winds combined with temperatures in the single digits produced wind chill temperatures from -25°F to -40°F. The winds whipped up falling snow and snow on the ground, producing treacherous travel conditions over much of the affected area. After an initial period of snow ahead of the cold front, heavy lake-effect snow fell over the western Michigan shore of Lake Michigan (Figure 7). By early morning on February 10 lake-effect snow bands were well-developed over southern Michigan. Heavy snow and the high winds produced near-whiteout conditions with visibilities reduced to zero in many areas close to the lake. The lake-effect snow continued through most of the day on February 10. The strong winds made snowfall difficult to measure, but generally 3 to 4 inches accumulated and an estimated 6 to 8 inches of snow fell at locations in Ottawa and Van Buren Counties.
 

Freezing Rain, Sleet, and Snow in Southern Midwest

On the morning of February 11 the Arctic boundary had reached the Gulf Coast, and another low pressure system was developing over the central Rockies (Figure 8). This low dove south along the front into Oklahoma and then turned eastward. Warm, moist air overrunning the shallow Arctic ahead of the low resulted in a long band of wintry precipitation which extended from the Missouri Ozarks through southern Illinois and into western Kentucky. For southern Missouri this was the third major ice storm in the past 13 months. Ice accumulated to one inch across the Ozarks, with locally higher amounts (Figure 9). Further to the east in the St. Louis area most of the precipitation fell as sleet, with as much as 5 inches in some eastern counties. From southeastern Missouri across southern Illinois, western Kentucky, and southwestern Indiana ice accumulated from 0.75 to 1.00 inch, and then was followed by 1 to 4 inches of sleet and snow. On February 14 power was still out in some areas affected by the storm.
 

...and Back to the North

On February 13 a storm that came ashore in the Pacific northwest was making its way across the northern Rockies and into the Dakotas (Figure 10). This storm laid down a quick 1 to 4 inches of snow across southern Minnesota and west-central Wisconsin from late on February 13 through early February 14. During the day on February 14, heavier snow fell along the leading edge of the next surge of Arctic air. This resulted in more substantial snow from north-central Iowa across southern Wisconsin and into Michigan (Figure 11). Ten inches to more than a foot of snow fell in parts of southern Wisconsin (Montello (Marquette County), 13.0"; DeSoto, WI (Crawford County), 12.3"). Three to four inches accumulated across Michigan, but 9 inches of snow fell in Ludington, MI (Mason County). This latest storm added enough snow to set a new all-time seasonal snowfall record for Madison, WI. As of February 14 the Dane County Regional Airport in Madison had recorded 80.2 inches of snow, breaking the old seasonal snowfall record of 76.1 inches of snow in 1978-1979. More snow will likely be added to that record before this season is over.
 

Flooding Continues

At the end of the week moderate flooding was still occurring as a result of the precipitation and snow melt the first week of February on the lower Illinois River, the Wabash River (Illinois/Indiana), and the Kankakee River and Tippecanoe Rivers in Indiana.

SDH