Midwest Weekly Highlights - March 22-31, 2011
Out Like a Lion
After an uneventful first three weeks, March came to a close with a return to wintry weather across much of the Midwest with much colder than normal weather and spring snow storms.
Temperatures were well below normal the last ten days of the month. Temperature departures ranged from 3°F to 4°F from southern Missouri through Kentucky, to 9°F to 12°F below normal from Minnesota eastward through Michigan and northern Ohio (Figure 1). There were many temperature records set during the last ten days of the month. From March 22nd through March 24th most of these were record high maximum and minimum temperatures. Record low temperatures prevailed the remainder of the period, and these occurred primarily over snow-covered areas of Minnesota, Wisconsin, and Michigan.
Most of the Midwest was much drier than normal as the month of March drew to a close (Figure 2). The exception was central and southern Minnesota, Wisconsin, and Michigan, where precipitation was 150 to 200 percent of normal largely due to a major snow storm at the start of this period. Snowfall was much above normal in this same area, and also across central Missouri, southern Illinois, and southern Indiana (Figure 3). Precipitation in the central Midwest continued to alleviate somewhat dry conditions in southern areas, but persistent dry weather in the northern Lower Michigan, the Upper Peninsula, and the Arrowhead of Minnesota resulted in the depiction of Moderate Drought on the March 29 U.S. Drought Monitor (Figure 4).
The additional snow in the upper Midwest this period did not give encouragement to those facing the impending spring flooding. There was at least four inches of snow on the ground in much of Minnesota, the northern two-thirds of Wisconsin, and lower Michigan (Figure 5), with as much as 20 inches on the ground in northwestern Minnesota. That snow had a water content from two to eight inches (Figure 6). Despite the snow, there was some good news. There was little additional precipitation in the form of rain, and temperatures were cold enough to prevent rapid snow melt. Nevertheless, river stages are high in the upper Midwest and some flooding is occurring (Figure 7). Snow melt and April rainfall will be the major concerns over the next several weeks.
A Stormy Start South
The last ten days of March began with a major storm system affecting much of the region, producing everything from tornadoes to heavy snow. The surface weather map on the morning of March 22nd was typically March. A strong high pressure system was centered over Hudson's Bay in Canada and extending south into the Great Lakes, while a strong low pressure system was organizing in the Central Plains (Figure 8) with a frontal boundary separated the air masses. High temperatures were in the 70s and 80s in the southern Midwest on March 22nd, and in the 20s and 30s in the northern Midwest (Figure 9). Strong southerly winds helped fuel thunderstorms just ahead of the cold front in Missouri and Iowa, while further to the east the strong winds and low humidity fanned brush fires in Jefferson, Franklin, and Washington Counties in Missouri. The fires burned more than 200 acres and and destroyed one home.
By early afternoon a tornado watch had been issued for eastern Nebraska and Kansas to western Iowa and Missouri (Figure 10). Later in the afternoon at least two tornadoes touched down in Iowa and one in eastern Nebraska (Figure 11). There were numerous reports of hail 1.0 to 1.75 inch in diameter across the watch area.
The severe thunderstorms continued on March 23rd as the low pressure system and trailing cold front moved through Illinois (Figure 12). There were numerous reports of hail and damaging thunderstorm winds across the southern half of Indiana, central and southern Ohio, and much of Kentucky (Figure 13). Golf ball-size hail (1.75 inches) was common. There were reports of 2.00 inch hail in Indiana and Kentucky, with one report of 2.50 inch hail near London, KY (Laurel County) in the early evening hours of March 23rd. Thunderstorm winds resulted in downed trees, power lines, and damage to buildings. There were two fatalities from the storms in Ohio. A young boy was killed when a tree fell on a tent he was in at a Boy Scout camp at the Shawnee State Forest near Friendship, OH (Scioto County). A woman also was killed by a falling tree at a campground in the same state forest.
Winter Hangs On North
While severe thunderstorms were occurring south of the frontal boundary, heavy snow fell in a wide band from the Dakotas across Minnesota, much of Wisconsin, and southern lower Michigan. Snowfall over the period from March 22-24 was generally four to ten inches (Figure 14). The heaviest snow accumulated in eastern Wisconsin, where more than 15 inches fell, accompanied by thunder and lightning at times on the night of March 22nd. The heavy, wet snow resulted in power outages as trees snapped under the weight of the snow. Winds gusting to between 25 and 30 mph resulted in low visibilities and hazardous driving conditions. Many locations in Minnesota, Wisconsin and Michigan set daily snowfall records. Two locations in Minnesota and one in Wisconsin set all-time daily snowfall records during this storm. In Michigan, the snow was preceded by a period of light freezing rain which resulted in a number of traffic accidents, one with a fatality. The roof on a church in Grand Blanc Township (Genesee County) collapsed under the weight of snow and ice. The building was unoccupied at the time.
More Snow Ushers Out March
High pressure settled in over the Midwest following the March 22-24 storm, bringing cold weather back to the entire Midwest. A wave of low pressure that developed on the front stalled in the southern U.S. (Figure 15) caused snow to fall from western Iowa through central Missouri into Illinois March 25-26. Three to four inches of snow fell in southwestern Iowa and northwestern Missouri by the early morning hours of March 25 (Figure 16). There was a lull in the snow during the day on March 25th, but it picked up again in the evening and by the morning of March 26th heavy snow was falling across eastern Missouri and southwestern Illinois. By the time the snow ended three to more than five inches of snow was on the ground (Figure 17, Figure 18).
Although high pressure dominated the Midwest the last several days of March, upper level disturbances produced some precipitation. One to three inches of snow fell in southern Iowa on March 28-29, and in northeastern Ohio on March 30th (Figure 19).