Midwest Weekly Highlights - November 24-30, 2008

---

More Cold Dry, Weather

It was another cold, dry week across most of the Midwest. During the first half of the period, there was lake-effect snow in Ohio and in lower Michigan, and additional lake-effect snow in northern areas late in the week along with a more substantial weather system in the central Midwest.

The week started out with below-normal temperatures across most of the region, but the weather began to warm as high pressure northwesterly winds abated and warmer air edged into the region from the west. The exception was over the eastern half of Ohio, which remained under the influence of a strong and slow-moving low pressure system over southern Ontario. Much of eastern Ohio remained under a shield of clouds through November 26, and northwesterly winds blowing across Lake Erie resulted in persistent lake-effect snow. Temperatures this week were normal to above west of the Mississippi River, and ranged from 4°F above normal in western Minnesota to about 1°F below normal in eastern Missouri (Figure 1). East of the Mississippi River, temperatures ranged from 1°F below normal in western Illinois to 7°F below normal in southeastern Ohio.

Almost all the precipitation this week was lake-effect snow until the end of the period, when a storm in the central Midwest produced snow from Missouri through Indiana (Figure 2). Except around the lakes and southeast of the Ohio River, precipitation was generally less than 50 percent of normal (Figure 3). There was little change in Midwest drought status on the November 25 U.S. Drought Monitor (Figure 4), with some Severe Drought in central Wisconsin to the southern U. P. of Michigan, and Severe to Extreme Drought in southeastern Kentucky.
 

Nice Start to Long Holiday Weekend

The weather on Thanksgiving Day was sunny and milder across the southern half of the Midwest. A blanket of clouds covered an area from northeast Minnesota through Wisconsin and Michigan, and a few snow flurries occurred in central and northern Wisconsin (Figure 5). More lake-effect snow occurred from northern Minnesota into northern lower Michigan as surface winds turned into the northwest and carried moisture off of the Great Lakes. Snowfall amounts were generally 2.0 to 4.0 inches, with the highest amounts in the the Michigan U. P.
 

First Winter Storm for Central Midwest

On November 29 a large trough of low pressure aloft was moving out of the Rockies and into the Plains (Figure 6). As this trough rotated into the Midwest, surface low pressure began to organize in the lower Mississippi Valley. The surface low moved slowly northward as the upper low closed off over Illinois (Figure 7). An area of snow developed from western Missouri and Iowa into central Indiana. By the morning of November 30, 2.0 to more than 4.0 inches of new snow was on the ground in these areas (Figure 8). The deepest snow at the end of the week was in the Michigan U. P. and the northern half of lower Michigan (Figure 9). Additional snow, heavy at times, fell during the day from northern Illinois and Indiana to eastern Wisconsin and eastward through lower Michigan, hampering travelers returning from the long holiday weekend.

SDH