Midwest Weekly Highlights - March 25-31, 2009
A Roaring End to March
The month of March roared out like a lion in contrast to the relatively quiet third week. Several major storm systems moved through the Midwest producing weather ranging from snow to severe thunderstorms.
Temperatures this week were near to slightly above normal in the southeast half of the region, and below to much below normal in the northwestern half (Figure 1). The temperature gradient was most pronounced in the northwest half, with temperature departures ranging from 0°F to 1°F below normal in southeastern Illinois to 12°F below normal in northwestern Minnesota.
Precipitation this week was much heavier than normal in the northern two-thirds of Minnesota, from Missouri through northwestern Illinois and into southern Wisconsin, and from eastern Kentucky through extreme southeastern Ohio (Figure 2). An area of much below normal precipitation, only 10 to 50 percent of normal, separated the heavy precipitation areas in the western Midwest. The distinct areas of heavy precipitation reflected the tracks of the storms that moved through the Midwest during the week as the heaviest precipitation tended to occur along and north of the storm tracks (Figure 3).
There was a further retreat in the southern extent of the snow cover in the northeastern Midwest this week, but the two major storms added to the snow cover in Minnesota. Several inches of snow covered the ground as far south as Missouri and up to 8 inches of snow was on the ground in central and northern Illinois on March 29 (Figure 4), but sunny skies, warming temperatures, and bright March sunshine ate away at the snow quickly. At the end of the week the southern snow was all but gone, and four or more inches of snow still covered the ground over the northern two thirds of Minnesota Minnesota and the Michigan U. P. (Figure 5).
The heaviest precipitation this week missed the driest areas of Wisconsin and southeastern Minnesota, but did fall in the parts of Kentucky and Ohio that had been starting to show dryness. The March 31 U.S. Drought Monitor, however, indicated little change in the status of drought this week in the Midwest ( Figure 6).
The March of March Storms
Rain continued across Indiana and Ohio March 25-26 as the large storm that affected the Midwest starting on March 22. Rainfall amounts ranged from 0.30 to 0.75 inch, except for eastern and southeastern Ohio where amounts exceed 1.00 to 1.25 inches.
There was only a short break before the next major storm began affecting the Midwest. This storm took shape over the Southern Plains (Figure 7), and then moved east and then northeast. Ahead of this system, showers and thunderstorms were widespread from Missouri eastward on March 28. Severe storms occurred over southern Indiana and western Kentucky. Two tornadoes touched down in western Kentucky, including a tornado rated EF3 in eastern Union and southeastern Henderson Counties. This tornado struck the town of Corydon, KY (Henderson County), destroying six homes, caused major damage to 10 others and minor damage to 60. There were two injuries reported as a result of the storm. Additional information on the tornado, including damage photos and a map of the storm tracks can be seen at the NWS Paducah, KY web site.
On the cold side of the storm, winter weather returned and winter weather advisories, warnings, and watches were posted over a broad swath of the central Midwest (Figure 8). Heavy, wet snow fell from western Missouri northeastward through southeastern Iowa, central and northern Illinois, southern Wisconsin, and Michigan (Figure 9). The heaviest snow amount, 7 to 8 inches, fell in far northeastern Illinois, where winds off of Lake Michigan enhanced the snowfall. Heavy snow was accompanied by thunder and lightning near St. Louis, MO and Peoria, IL, and an area from Peoria south to Springfield, IL received from 4 to 7 inches of snow. Skies cleared rapidly behind the storm on March 29, and temperatures above freezing and late march sunshine melted away the lighter amounts of snow during the day (Figure 10). On March 30 snow cover was limited to areas which received the heaviest amounts of snow, and on March 31 another day of milder weather took care of the rest of the snow (Figure 11).
Even as this storm was departing the region, another storm was winding up over the Central Plains. This was another intense system as the upper level low became closed off from the general flow. For the second time in just a week blizzard warnings were posted for the Dakotas and western Minnesota (Figure 12), with winter storm warnings and winter weather advisories across the rest of Minnesota and northern Wisconsin. This was a slow-moving system, and warnings were continued through March 31 as the low slowly made its way northward though Minnesota (Figure 13). two-day snowfall totals ranged generally from 6 to 12 inches in a band across central Minnesota, but parts of far western Minnesota received more than 24 inches of snow (Figure 14). Cook and Lake counties piled up 14 to 16 inches of snow. With this storm and as of the morning of April 1, 124.2 inches of snow had fallen at International Falls, MN (Koochiching County) for the 2008-2009 season, breaking the old record of 116.0 inches set in 1995-1996.
As this latest storm continued to spin over northern Minnesota late on March 31, yet another low pressure system was organizing over the northern Rockies and taking aim on the Midwest.
Spring Flooding Continues
The Red River along the border of Minnesota and North Dakota was still about 20 feet above flood stage at Fargo at the end of the week, but on a steady decline. Although there was heavy snow this week, the cold weather kept the snow from melting and most of the precipitation that fell in the area was not running off into the river. However, there was still significant overland flooding and there were large areas of water that had frozen. The situation was complicated by significant ice jams on some Minnesota and North Dakota tributaries to the Red River. Flood warnings remained in effect at the end of the week for much of the Red River Valley in Minnesota and eastern North Dakota.
Moderate to major flooding was occurring on the lower Illinois River, and minor flooding on the Mississippi River from the Clarksville, MO Lock and Dam to Cape Girardeau. For a complete overview of river observations, visit the NWS Advanced Hydrologic Prediction Service web site.