Midwest Weekly Highlights - December 8-14, 2009

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Cold and Snowy

A major winter storm brought heavy snow to the northwestern portions of the Midwest this week, and further reinforced the cold air over the central U.S.

Temperatures were well below normal this week, ranging from 20 °F below normal in northwestern Minnesota to near normal in eastern Ohio (Figure 1). Departures of 6°F below normal or more were found over the deep snow cover (Figure 2) from Iowa to Michigan and northward. Record minimum and low maximum temperatures were set this week in the snow-covered areas.

Precipitation was 200 to 400 percent of normal across much of the region (Figure 3). The exceptions were northwestern Minnesota where precipitation was less than 25 percent of normal for the week, and in southwestern Missouri. Snowfall was 6 inches or more in a broad band from Iowa through Michigan (Figure 4). The December 8 U.S. Drought Monitor continued to depict Moderate to Severe drought over northern Wisconsin (Figure 5). The heavy snow this week occurred after the Drought Monitor was issued, and any changes because of the precipitation will be reflected in next week's Drought Monitor.
 

Major Winter Storm

An intensifying storm system was centered over western Colorado on the morning of December 8 (Figure 6). An extensive shield of precipitation extended from the low with snow already occurring as far east as Iowa that morning. A variety of winter watches, warnings, and advisories blanketed an area from Colorado through the central Midwest (Figure 7). As the low moved east and then northeast, snow continued to spread across the northern Midwest whipped as winds gusted to 50 mph or more around the intensifying cyclone. By late afternoon on December 8 blizzard warnings were in effect for eastern Nebraska, the entire state of Iowa, southern Minnesota, northern Missouri, and much of the southern half of Wisconsin (Figure 8). On the morning of December 9 the intense storm was centered over northern Illinois (Figure 9). The the storm's circulation affected the eastern half of the U.S. andblizzard warnings remained in effect for large portions of the Midwest (Figure 10). High wind warnings and advisories were in effect for much of the central and eastern U.S. south of the snow area.
 

Snow Buries Iowa, Wisconsin, Michigan

Snow from this storm fell over a large portion of the Midwest, but the heaviest snow fell along and north of the path of the low pressure center. Snow accumulated six inches or more across Iowa, extreme northwestern Missouri, southern Minnesota, most of Wisconsin, northwestern Illinois, the Michigan Upper Peninsula and northern lower Michigan (Figure 11). More than a foot of snow fell from central Iowa across southern Wisconsin and into Michigan, with lake-enhanced snowfall of 29.5 inches reported in Ironwood, MI (Gogebic County). The statewide average snowfall in Iowa was 10.2 inches, the highest single-storm statewide average since the snowstorm of January 2-4, 1971, when snowfall averaged 10.5 inches. The snow disrupted travel in Iowa, but timely warnings by the National Weather Service and the timing of the storm minimized impacts. The worst snow and wind conditions did not begin until the evening of December 8 after most people were home. Schools were closed early and classes were canceled in Des Moines (Polk County) on December 9 and 10. Preliminary reports attributed several deaths to the storm in Iowa. One person died of a heart attack while shoveling snow.  Another died of exposure after apparently falling from exhaustion while walking through deep snow.   The National Guard was placed on alert but at last count only 13 motorists had to be rescued. There were scattered power outages due to the wind an cold.

The storm caused massive travel problems in Wisconsin. Interstate travel was snarled when as many as 12 semi-trailer trucks became stuck on the ramps where Interstates I-39, I-90, and I-94 intersect in Madison (Dane County). Wisconsin Governor Jim Doyle closed all state government offices and the University of Wisconsin campuses on December 9. Students on the Madison campus organized a snowball fight in which 3,000 students reportedly took part on December 10. An estimated 26,000 customers of We Energies in southeastern Wisconsin lost power during the storm, along with another 12,000 customers of Wisconsin Public Service near Lake Michigan and Green Bay in northeastern Wisconsin. The heavy, wet snow along with high winds caused extensive tree damage in southern Wisconsin, especially to evergreens. There were reports of trees being uprooted by the combination of the weight of the snow and high winds. The storm also halted the remaining corn harvest in Wisconsin. About 25 percent of the corn remained to be harvested when the storm hit. Normally there is only about 5 percent remaining to be harvested this late in the season.

Highest Snowfall Totals in Each State

Amount (in)	Location	Type	County	State
29.5	Ironwood	NWS Coop	Gogebic	MI
20.4	Washburn 5.1 WNW	CoCoRaHS	Bayfield	WI
17.6	Gilbert 0.2 W	CoCoRaHS	Story	IA
17.6	Orangeville 2.8 NW	CoCoRaHS	Stephenson	IL
15.1	Preston	NWS Coop	Fillmore	MN
12.0	Fairfax	NWS Coop	Atchison	MO

A number of locations in the Midwest set all-time daily snowfall records during this storm.
 

High Winds Pound The Region

Outside of the areas receiving heavy snow, winds generated by this massive storm the affected the remainder of the Midwest and in fact much of the eastern half of the country. Winds gusted in excess of 50 to 60 mph across a large portion of the Midwest (Figure 12). There were extensive power outages in southeastern Michigan, where as many as 70,000 customers of DTE Energy lost power. At least 30,000 customers of Duke Energy in the Cincinnati Tri-State area were without power on December 9 as broken tree limbs crashed onto power lines, and scattered outages were reported further north in the Dayton area The winds delayed travel at many airports across the Midwest where snow had not already caused delays.

Heavy rain on December 8 and high winds in Kentucky on December 9 resulted in three fatalities. One man drowned in a flooded creek in Metcalfe County. A pregnant woman and her unborn child were killed when she was hit by a tree split by the wind in Pulaski County. Another woman died in Harlan County when her vehicle hydroplaned, left the road and hit a tree. An estimated 7,000 customers of Kentucky Utilities lost power from the winds.

Uneventful End to Week

High pressure settled over the Midwest in the aftermath of this major winter storm and the weather the remainder of the week was generally quiet. Temperatures moderated toward the end of the period as the high moved to the east coast and southerly winds developed across the Midwest. Showers and some thundershowers developed across the southern half of Illinois and Indiana late on December 12 as the warmer air returned northward, and rainfall amounts exceed one inch in some locations. Further to the north, the precipitation fell as scattered light freezing rain and drizzle until temperatures rose above freezing.

Temperatures rose above normal on December 14 in the southeastern half of the region ahead of an advancing cold front. The front swept though most of the region by the end of the day, returning most of the region to seasonable conditions.

SDH