December 15-21, 2008
Midwest Weekly Highlights - December 15-21, 2008
More Storms, More Snow and Ice
A major winter storm plowed across the center of the Midwest on December 18 and 19, and active weather continued December 20 and 21, with snowfall on December 20 and blizzard conditions caused by wind-whipped snow on December 21. These storms dropped heavy snow across Minnesota and Wisconsin, while areas to the south saw sleet and freezing rain. Due to these systems, precipitation this week was as much as 500% to 700% of normal across parts of western Iowa, while most of the region saw at least 100% of normal precipitation (Figure 1). The driest parts of the region were in southern Kentucky and southwest Missouri where only 50% of normal precipitation was found. The December 16 Midwest Drought Monitor showed improvement across eastern Kentucky, which emerged from Extreme (D3) drought for the first time since early October, 2008 (Figure 2). There was no real improvement in drought conditions across Wisconsin, which continued to see Severe (D2) drought.
Temperatures varied greatly across the region (Figure 3). The western two-thirds of the region saw below to much below normal temperatures, with parts of Minnesota and Wisconsin as much as 15°F below normal. This especially cold air was ushered in by an arctic cold front which crossed much of the region on December 15 and caused temperatures to plummet by as much as 40 degrees in 24 hours (Figure 4). In contrast, parts of southeastern Ohio and Kentucky experienced above normal temperatures.
December 18-19 Storm
A deep low pressure moved from the Four Corners region of the to near St. Louis on December 19, bringing snow, sleet, and freezing rain to much of the Midwest (Figure 5). While a surface warm front extended from southern Illinois east in to Indiana, warm air was also being carried aloft over arctic surface air across parts of central and northern Illinois and central Indiana, setting up a classical freezing rain scenario. Ice storm warnings were posted across much of southern Iowa, northern Missouri and central Illinois (Figure 6). Precipitation falling in to this cold surface air mass froze on contact, creating a wide area of freezing rain with ice accumulations ranging from 0.2 inches to over 0.75 inches over central Illinois (Figure 7). Ameren utilities reported thousands of customers without power across central Illinois (Figure 8). Further to the east in Indiana conditions were also extremely treacherous. More than 100,000 Indiana utilities customers were reported without power across the state due to the ice, and 70,000 were still without power on Sunday, December 21. Areas of northeast Indiana reported as much as 0.5 inches of ice. Further north, a swath of northern Iowa and southern Wisconsin reported up to 7 inches of snow with the storm (Figure 9). Snowfall rates of 1.5 inches per hour at the height of the storm caused travel difficulties across southern Wisconsin.
December 20-21 Storm
Another powerful storm brought snowfall to Minnesota, Wisconsin, and Michigan on December 20 and 21 (Figure 10). Most of Minnesota and Wisconsin saw around 6 inches of snow, while parts of Michigan received as much as 10 inches of snow due to lake effect enhancement (Figure 11). However, the biggest hazard caused by the storm was winds of 15 to 30 miles per hour as the cold front passed. These winds created dangerous wind chills of -30°F across much of Minnesota, Wisconsin, Iowa and Illinois. These winds also whipped freshly fallen snow in to ground blizzard conditions across Illinois and Indiana where Blizzard Warnings were issued on December 21. Interstates 74 and 80 were closed in Illinois, and Interstate 80 was closed in eastern Iowa as snow drifts closed traffic lanes and snow plows were reported stuck in drifts. Blizzard conditions in Indiana led to one fatality in a 100 car pileup on Interstate 94.
AB