December 8-14, 2008
Midwest Weekly Highlights - December 8-14, 2008
Storms Slam the Midwest
An active and cold weather pattern continued across the Midwest during the second week of December. Two major weather systems affected the region this week causing widespread precipitation while temperatures swung from frigid to unseasonably warm and back again.
December 9-10 Storm
The first system crossed the Midwest on December 9-10 as a surface low pressure tracked from Colorado, in to northeast Missouri on December 9 before lifting to the northeast on December 10 (Figure 1). The storm brought as much as 5 inches of snow to much of central Wisconsin and northern Lower Michigan on December 9 (Figure 2). Further to the south, mixed precipitation and cold rain fell over much of Iowa, Illinois, and Missouri. By December 10, the system lifted to the northeast, dragging a cold front across much of the region. As cold air filtered in to the region, precipitation transitioned from rain to snow across eastern Iowa, western Illinois and northern Missouri. The passage of this front brought much needed rains to areas of Kentucky, Indiana, and Ohio that have experienced drought conditions (Figure 3). As much as 3 inches of rain fell across portions of south-central Kentucky.
December 14 Storm
Weather conditions were generally quiet across the region until December 14, when another low pressure tracked from Colorado northeast in to Iowa. To the north and west of this system, arctic cold and blizzard conditions prevailed. Portions of Minnesota saw as much as a foot of snow, while considerable blowing and drifting of snow led to the closure of Interstate 94 in northwest Minnesota (Figure 4). To the south and east unseasonably warm air rushed in to parts of eastern Iowa, Illinois, Missouri and Indiana. While high temperatures north of the cold front struggled to reach 10°F, areas to the south of the front saw highs ranging from 40°F to 60°F (Figure 5). A high of 57°F on December 14 tied the record set in 1921 in Logan, IA (Harrison County). The stark contrast between the cold and warm air masses was evident as temperatures dropped as much as 45°F in the 24 hours following the passage of the cold front across Minnesota.
Weekly Summary
Overall, precipitation across the Midwest was generally above normal (Figure 6). Areas of extreme western Minnesota saw as much as 500% of normal precipitation, while drought-stricken areas of southeast Kentucky saw as much as 300% of normal precipitation, bringing some relief to the area. The remainder of the region generally saw at least 50% of normal precipitation, although areas of extreme southwest Iowa and northwest Missouri only received about 10% of normal precipitation. The December 9 Midwest U.S. Drought Monitor continued to show extreme (D3) drought conditions in southern Kentucky and severe (D2) drought conditions across central Wisconsin (Figure 7).
Temperatures across the region this week were generally below normal (Figure 8). The coldest conditions were found across Minnesota, Wisconsin, and Michigan where temperatures were 4°F to as much as 10°F below normal. Large parts of central and southern Illinois and most of Missouri saw near normal temperatures, while central and western Missouri were slightly warmer than normal.
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