May 11-17, 2004
Midwest Weekly Highlights - May 11-17, 2004
Active Weather Pattern Across the Midwest
A strong low pressure system and attendant cold
front moving through the Midwest this week brought rain and even some
snow to the region. This resulted in much-needed precipitation in
Minnesota and the upper Midwest.
Precipitation the week of May 11-17 was much above normal in many parts
of the region (Figure 1).
The only areas to receive below normal rainfall were northwestern Iowa,
a band from south central Iowa through central Missouri, and an area
from southeastern Indiana through northwestern Kentucky and the
southern half of Ohio. Temperatures reflected the mean position
of the front during the week, with large depatures below normal in the
northwestern half of the Midwest and above normal in the southeast (Figure 2). Average
daily temperatures were 12 to 14F below normal in northwestern
Minnesota, and 6 to 8F above normal in southeastern Ohio.
Snow in May
On the morning of May 11 a cold stretched from a low in southeastern
Montana through Iowa and northern Illinois, Indiana, and Ohio (Figure 3, Unisys).
Over the next 24 hours the low moved eastnortheastward, and as it did
so it pulled very warm air northward ahead of the low. By late on
May 11 the front bisected Minnesota.. A record high of 89F was
set in Redwood Falls, MN on May 11, while on the north side of the
front high temperatures struggled to reach 40F. Snow and sleet
were reported in northwestern Minnesota, with significant snowfall
accumulations from North Dakota northward into Manitoba, Canada.
Thunderstorms later brought 2 to 5 inches of rain to northwestern
Minnesota as the main cold front plowed through the upper
Midwest. By the morning of May 13 very cold air had settled in
over the upper Midwest. On May 14 several record lows were
set Minnesota with temperatures in the 30s as far south as southern
Iowa.
Severe Weather Almost Each Day
There were reports of severe weather on almost every day during the
period. On May 11 severe thunderstorms produed 1.00 inch hail and
high winds downed trees, power lines, some billboards and a traffic
signal in Farmington in St. Francois County, MO. On May 12 severe
thunderstorms developed across northern Illinois, causing urban and
flash flooding. Scattered severe storms containing hail were also
reported in Missouri, Minnesota, and Wisconsin. Northeastern
Illinois was hit again on May 13 as severe storms struck the Chicago
metropolitan area during rush hour. The storms resulted in heavy
rains producing urban and flash flooding across several counties, and
there were some reports of minor wind damage Storms in central
Illinois produced an estimated 2 to 4 inches of rain and caused
flooding in Shelby and Christian counties. By May 14 the severe
weather had shifted east into Indiana and Michigan in the warm air
ahead of the front. There were four reported tornado touchdowns
in central Michigan Saginaw,
Clinton, and Sanilac Counties. An apartment complex
was damaged near Shields, MI (Saginaw County), and one silo destroyed
and two others damaged near Maple Rapids, MI (Clinton County).
The Midwest enjoyed a brief respite from the active weather pattern on
May 15 as high pressure took control of the weather. By May 16
the high was moving off to the east and another cold front was moving
through the Northern Plains. Thunderstorms developed as far east
as southwestern Minnesota, and a few of these reached severe levels
producing minor wind damage. On the morning of May 17 the cold
front had reached northwestern Iowa, and a warm front extended from the
low in Wisconsin down into Illinois and then eastward across northern
Ohio (Figure 4). These
boundaries provided the focus for more severe weather from Iowa through southern
Wisconsin, and from southern lower Michigan through
most of Ohio (Figure 5,
SPC). There were several reports of large hail in Iowa, with baseball
size hail (2.75") reported in Madison County, IA.