March 18-24, 2008
Midwest Weekly Highlights - March 18-24, 2008
Cold and Very Wet
After a period of relatively calm weather the middle week of the month, storms returned to the Midwest this week pounding the region with heavy snow in the north and torrential rain in the south.
There were two distinct areas of much above normal precipitation this week. The first was from western Minnesota through southern Wisconsin and into southern lower Michigan (Figure 1), largely from the snow storm on Easter weekend. The second was a broader band of precipitation from Missouri through southern Illinois, Indiana, most of Ohio. Precipitation in this area was generally 200 percent of normal, but reached from 700 percent of normal from the Missouri Ozarks into southwestern Illinois. Western Iowa and the northern portions of Wisconsin and lower Michigan were dry this week, with precipitation only 25 to 50 percent of normal. The only area of Moderate (D1) drought remaining in the Midwest on the March 18 Drought Monitor was small area in west-central Minnesota.
Snowfall this week was heavy across the southern two-thirds of Minnesota and Wisconsin, extreme northern Illinois, southern Michigan, and northern Indiana and Ohio (Figure 2). At the end of this week four or more inches of snow still covered the ground across much of Minnesota, Wisconsin, and western lower Michigan (Figure 3).
Average daily temperatures this week were below normal across most of the region, with the exception of much of Iowa, where temperatures were near to slightly above normal (Figure 4). Temperatures were 7°F to 8°F below normal across the Michigan U.P., where snow was still one to three feet deep.
Midwest Flooding
An intensifying wave of low pressure developed on March 17 in the Texas panhandle and headed to the lower Midwest. This system tapped into abundant Gulf moisture and combined with a strong upper level jet and a warm, unstable atmosphere to produce extremely heavy rain from southwestern Missouri eastward into southern Indiana over the next three days. The first area affected wa southwestern Missouri, which received most of the heavy rain on March 17 and early on March 18 (Figure 5, NWS). Much of the region received four to six inches of rain, with isolated areas of 10 inches or more. By the morning of March 18 the surface low pressure system was located near St. Louis, MO, and heavy rain was falling from the central Ozarks into southern Illinois and Indiana (Figure 6).
Torrential rains from March 17-20 triggered widespread flooding with an area from southeastern Missouri into southwestern Illinois receiving more than 12 inches over the from March 18-20 (Figure 7). The National Weather Service cooperative observer located in Cape Girardeau, MO reported 13.84 inches for the 48-hour period from the morning of March 18 to the morning of March 20, with the Cape Girardeau Regional Airport reporting 11.49 inches for just the 18th alone.
This weather system produced flooding from Texas through the Ohio Valley (Figure 8). Many locations set rainfall records on March 18 for the wettest March day and the all-time wettest day on record. Many of the smaller streams and rivers across Missouri, Illinois Indiana, and Ohio experienced the worst flooding, while the the Mississippi, Missouri, and Ohio Rivers experienced saw only moderate flooding and were more protected by their levee systems. At least 17 deaths were linked to the flooding and severe weather and thousands of people have been displaced from their homes. Dozens of state and local roads throughout southeast Missouri and southern Illinois were closed due to high water.
In Cape Girardeau, MO the Mississippi River reached a crest of over 41 feet, short of the 48 foot crest in 1993 but still among the highest river stage recorded there. On March 24 the crest was 41.04 feet, 9.04 feet above flood stage. This was the highest water level there since 2002 and the 8th highest crest on record. Preliminary measurements indicate that 17.83 inches of rain fell at Cape Girardeau in March 2008. This breaks the previous all-time monthly record at Cape Girardeau of 16.89 inches, set in May of 1973, and as well as the March record rainfall of 11.89 inches sent in 1977. Only eight months ago Cape Girardeau recorded its all-time driest month on record, when only 0.01 inch fell in August.
On March 19 President Bush declared 70 Missouri counties and the City of St. Louis federal disaster areas, clearing the way for federal disaster aid to help state and local recovery efforts (Figure 9).
Heavy Snow Across Central Midwest
As the southern storm exited the Midwest on March 20, winter storm watches and warnings were posted in an area stretching from southern Minnesota to northwestern Ohio (Figure 10) in anticipation of another storm forecast move through the central Midwest. By the morning of March 21, Good Friday, heavy snow was falling from Minnesota into Illinois. The timing of this storm was especially bad as it occurred on the Good Friday travel day of the Easter weekend. The storm hampered travel even before it began to fall. Hours before the snow was expected to start, 127 flights out of Chicago's O'Hare International Airport were cancelled. The snow was particularly heavy in western Minnesota, where up to 15 inches of snow accumulated (Figure 11). In the wake of the storm a swath of 5 to 10 inches of snow, with some locally higher amounts, was on the ground from western Minnesota to southeastern Wisconsin, extreme northeastern Illinois, southern Michigan, and northern Ohio (Figure 12). More than 450 flights were cancelled at Chicago's O'Hare airport and numerous others delayed. Flights were also cancelled at Milwaukee's Mitchell International Airport and Detroit's Metropolitan Airport. Milwaukee, WI received 11.5 inches of snow from this storm (Figure 13), which brought the seasonal snowfall total to 96.9 inches, the second highest total behind 109.8 inches set in the winter of 1885-1886. An additional 1.1 inches of snow on Easter weekend bumped Milwaukee's seasonal snowfall to 98.0 inches.
MCP/SDH