April 8-14, 2008
Midwest Weekly Highlights - April 8-14, 2008
No Rest for the Wet and Weary
The march of storms across the Midwest continued unabated into the second week of April. Precipitation this week was much above normal across all but the extreme eastern portions of the region (Figure 1). Southwestern Missouri received more than three times the normal weekly precipitation, as did eastern Wisconsin and the Michigan Upper Peninsula. Much of the precipitation in the northern Midwest fell as snow, and snowfall from Minnesota across northern Wisconsin was five to seven times normal (Figure 2). At the end of this week deep snow covered much of central and northeastern Minnesota, northern Wisconsin, and the Michigan UP (Figure 3). The abundant precipitation has further improved the somewhat dry conditions in the northern Midwest, and for the first time since the second week of May 2005, there is no D1 (Moderate) drought depicted in the Midwest on the U.S. Drought Monitor (Figure 4).
This was a much colder than normal week west of the Mississippi River, and normal to above normal in the eastern portion of the region. Average daily temperatures ranged from 8°F to 10°F below normal in western Missouri and Iowa to 2°F to 4°F above normal across much of eastern Ohio and Kentucky (Figure 5).
Storm #1
At dawn on April 8 a wave of low pressure was located over the southwestern corner of Missouri, with rain spreading northward into Iowa (Figure 6). A flash flood watch was in effect for most of Missouri into west-central Illinois (Figure 7). As the low moved northeastward, one band of heavy precipitation pushed farther north into northwestern Missouri and central Iowa, while a second area moved through the Ozarks (Figure 8). By the morning of April 9 the strong low pressure system was located over northern lower Michigan. In it's wake one to three inches of rain fell from western Missouri northeast into southeastern Iowa, and three to five inches of snow accumulated over northeastern Wisconsin and the western half of the Michigan UP. Thunderstorms spun up two tornadoes in Michigan and produced some minor wind damage in Illinois.
Deja Vu
On the morning of April 10 the Great Lakes low had moved to central Quebec and another storm, stronger than the first, was already intensifying in central Oklahoma (Figure 9) and taking aim on the entire Midwest. Flash flood watches extended from Missouri through Illinois and into northern Indiana and western Kentucky. Winter storm watches, warnings, and advisories extended across Minnesota and northern Wisconsin (Figure 10). High wind warnings and advisories were in effect for much of Iowa. By midday a band of heavy precipitation extended from Nebraska through southern Minnesota, Wisconsin, Michigan, and into Ohio (Figure 11).
Over the next two days this storm moved slowly northward, producing a smorgasbord of spring and winter weather across the region. In the warm air east and south of the main low, thunderstorms developed in the unstable atmosphere. Strong winds through the atmosphere contributed to the development of supercell thunderstorms, a number of which spawned tornadoes. The greatest concentration of severe storms occurred in a band from near Kansas City, MO to central Iowa. There were 26 tornado reports in the Midwest on April 10, the majority of these in Iowa. Tornadoes also touched down in Missouri and in extreme western Illinois. Fortunately, most of the tornadoes were weak and caused minor structural damage and downed trees and power lines. The most severe damage was in Van Buren County, IA, where a tornado rated EF2 touched down near Lebanon, IA and produced significant damage to the second floor of a retail establishment
The strong low pressure system moved only to northern Iowa by the morning of April 11 (Figure 12), and continued to affect most of the region. Out ahead of the cold front trailing from the low, severe thunderstorms erupted across Michigan, Ohio, and Kentucky. At least two tornadoes touched down in Kentucky, resulting in at least three injuries. Baseball-sized hail (2.75") was reported near Albany, KY (Clinton County) in the storm that produced one of the tornadoes. There were numerous reports of hail in Michigan, with golf ball-sized hail (1.75") in De Witt, MI (Clinton County).
Heavy snow with blizzard conditions affected Minnesota and Wisconsin. Snow accumulated 6 to more than 14 inches in northeastern Minnesota, northern Wisconsin, and the Michigan UP (Figure 13), with 16.9 inches reported near Askov, MN (Pine County). Winds gusting in excess of 40 mph toppled trees and power lines from northeastern Minnesota into northern Wisconsin. Duluth International Airport recorded a wind gust of 62 mph, with a few other locations reporting gusts over 50 mph.
Finally...
The large upper level trough associated with the low over the Midwest slowly departed the Midwest on April 12-13. A trace of snow was reported at number of locations in the central Midwest on the morning of April 13, including St. Louis and Chicago. Cold, unstable air associated with the trough kept skies cloudy over the southern half of the Midwest on April 13 (Figure 14). Springfield, MO tied the record low maximum temperature of 42°F, first set on April 13, 1957. Clearing skies overnight allowed temperatures to plummet on the morning of April 14. A low of 11°F at Rhinelander, WI, tied the record first set in 1940. A low temperature of 28°F in Joplin, MO tied the record first reached in 1950.
At the end of this week a number of rivers and streams in throughout the Midwest were continuing to experience minor to moderate flooding as a result of the heavy precipitation, and in some cases, snowmelt (Figure 15). Most stations south of Rock Island, IL on the Mississippi River were experiencing minor to moderate flooding. In Rock County, WI major flooding was expected as the Rock river continued to rise south of Lake Koshkonong.
SDH