Midwest Weekly Highlights - March 22-31, 2005

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Last 10 Days of March a Period of "Firsts"

The last ten days of the month brought a variety of weather conditions to the Midwest, not unexpected for the month of March. A slow-moving low pressure system moving out of the southwestern U.S. March 22-23 brought the first significant precipitation of the month to the abnormally dry southern Midwest.  The first widespread mild weather of the spring, with temperatures reaching the mid 70s as far north as Michigan, came near the end of the month.  That was a prelude to the first severe weather outbreak of the season for the Midwest on March 30th.

Temperatures for March 22-31 averaged near average to above normal across most of the region (Figure 1).  A narrow band extending from west-central Missouri across central Illinois, central Indiana, and central Ohio experienced temperatures from 1F to 2F below normal, while north and south of this band temperatures were above normal.  The warmest region of the Midwest this period was much of Minnesota, where temperatures were 4F to 6F above normal.   This was the wettest period of the month, with above normal precipitation in the Ohio Valley (Figure 2).  There were pockets of near normal precipitation in Iowa, and Minnesota.  It continued very dry across most of Wisconsin and Michigan.


Storms Bring Rain South,  Snow North

On the morning of March 22 a developing low pressure system was located over western Oklahoma (Figure 3, Unisys).  Moisture from the Gulf of Mexico was steaming north ahead of the low, and a large shield of precipitation extended from Kansas eastward to Indiana and south to the Gulf Coast.  Precipitation continued to fall aver the next 24 hours as the low moved eastward to central Tennessee.  By the morning of March 23 cold air was being drawn southward by the storm circulation, and snow was falling across central Iowa and into northern Illinois.  Snowfall was generally around 2 inches (Figure 4), but there were some locations reporting 3 to 5 inches in central Iowa.  Boone County, IA reported 4 to 5 inches, while Audubon County reported 3 to 4 inches.  The heaviest precipitation with this weather system, 1.00 to 1.50 inches, fell over southeastern Missouri and southwestern Illinois (Figure 5). 

A second storm came in on the heels of the first on March 25, following almost the same path. More rain spread across the central Midwest, with some light snow across northern Illinois, southern Wisconsin, and southern Michigan.   Precipitation amounts were lighter, generally less than 0.75 inch, and the main band of precipitation was farther north than the previous storm (Figure 6).

A third low pressure system moved out of southern Texas on March 26, and by the morning of March 27 it was intensifying over northwestern Alabama (Figure 7).  This system brought more rain to the southeastern portions of the region, particularly southern Indiana, most of Ohio, and Kentucky. By the morning of March 28 the storm had moved only to west-central North Carolina, with rain still falling as far west as southern Indiana and western Kentucky  After several days of wet weather, flood warnings were issued for counties in western Indiana, eastern Ohio, and in Kentucky as 1.50 to 2.00 inches of rain caused flooding of small creeks and streams.  Numerous roads were reported flooded in the three states.  Daily rainfall records were set at a number of locations on March 28.  Cincinnati,OH reported 1.87 inches, breaking the old record of 1.07 inches in 1899.  Columbus, OH received 1.45 inches, breaking the old record of 1.05 inches in 1921.  Jackson, KY reported 1.14 inches of rain, breaking the old record of 1.12 inches in 1996.


Severe Thunderstorms Produce Waterspouts

In addition to the heavy rainfall, severe thunderstorms rolled across Kentucky.  In Calloway County, straight-line thunderstorm winds caused damage to an estimated 25 to 30 trailers in a RV trailer park.  The primary damage was from trees falling on the trailers, but some of the damage was due to carports and tool sheds hitting the trailers.  Two trailers were knocked off their foundations.  An emergency manager reported that one inch hail had accumulated four inches deep, and was still evident 40 minutes after the storm.  In Fort Heiman in Calloway County, located on Kentucky Lake, an 80 mph wind gust was recorded.  Three eyewitnesses reported three small short duration waterspouts on Kentucky Lake.  One of the waterspouts caused damage at a  resort, knocking two docks loose and lifting a third out of the water and smashing it into a nearby house.

Grip of Cold Weather Broken

On the morning of March 29 the eastern storm was moving off the mid-Atlantic coast, while in the northern plains another low was beginning to intensify.  A large fetch of strong southerly winds pulled warm air northward, and temperatures in the 60s and 70s spread over most of the region.  On March 30 temperatures in the mid 70s could be found as far north as southern Michigan, with some 80s across southern Missouri and Kentucky (Figure 8, Unisys).  This was the first week this month that temperatures across the region generally averaged above normal.


Hail, Hail, the Storms Are Here

March 30 dawned with much of the central Midwest under a moderate risk for severe weather by the Storm Prediction Center (Figure 9).   Increasing warmth, moisture, favorable wind profiles in the upper atmosphere, and a strong cold front all combined to raise the threat of severe storms.  Storms did break out during the late morning, and by early afternoon tornado and severe thunderstorm watches were in effect for parts of Iowa,  Missouri, and most of Illinois.  While tornadoes were possible, the atmospheric conditions especially favored large hail and damaging winds.  Storms intensified during the afternoon, with numerous reports of hail, some the size of baseballs (Figure 10).  The were 14 tornado reports - nine in Iowa, three in Minnesota, one in Illinois, and one in Wisconsin.  A severe thunderstorm watch was issued into Indiana during the evening, but the storms had started to weaken  and there were just a few scattered wind damage reports in Indiana and western Ohio.  As intense as many of the storms were, rainfall was was not particularly heavy because the storms were moving at speeds of 50-60 mph, minimizing the time of the storms over any one area.  Rainfall amounts were generally less than 0.75 inch, although a few locations in Iowa and Illinois received more than 1.25 inches.