June 17-23, 2005
Midwest Weekly Highlights - June 17-23, 2005
Cool, Dry Start....Hot,
Humid End
A strong upper level trough of low pressure covering the eastern United
States brought a cool and dry start to this period (Figure 1). The mean
position of the trough was reflected
in the
temperature departure pattern for the period (Figure 2).
Temperatures ranged from 3oF
to 4oF
below normal across the southeastern
half of the region, and were as warm as 8oF
above normal in northwestern
Minnesota. With the strong northwesterly flow aloft and dry
air
near the surface, there was little opportunity for rain except in
Minnesota, near the transition from the trough to the strong
ridge over the central U.S (Figure 3). Rainfall for June
is
much
below normal over most of the central Midwest (Figure 4),
and the
continuing dry weather was reflected in this week's U.S. Drought
Monitor (Figure 5). Areas of moderate
drought have
expanded, and a portion of north central Illinois and southeastern
Missouri
have been classified as in severe drought.
Severe
Storms Slam Minnesota
The period started on a quiet note as a large surface high
pressure system dominated the Midwest. Daytime temperature
were in the 70s and 80s, with
dew points in 50s making for very comfortable conditions. On June 19 a
cold front was pushing into the upper Midwest from the northern plains,
and on June 20 was firing off severe thunderstorms from the Dakotas
across central and
southern Minnesota, western Wisconsin, and north central Iowa (Figure 6). During
the day the storms were concentrated
in central Minnesota and western Wisconsin (Figure 7). By evening the
line of storms had moved into Iowa, where there were numerous reports
of
wind damage. There was considerable urban and flash flooding
in
the counties in the Minneapolis-St. Paul, MN metropolitan area,
disrupting morning rush hour traffic. One ham radio spotter
reported that 0.80 inches of rain fell in just 15 minutes. In
addition to torrential rain, there were numerous reports of 0.75 to
1.00 inch hail and downed tree limbs and power lines. Several
funnel clouds were reported near Alexandria, MN during the morning, and
two unconfirmed tornadoes were reported in western Minnesota during the
evening. One tornado briefly touched down in Emmet
County, IA
late on June 20.
The cold front that followed these storms pushed south through the
remainder of the Midwest without any precipitation, and two days of
dry, pleasant weather followed. On the afternoon of June 22
the
pool of drier air over the Midwest was readily discernible on the
visible satellite image as a cloud free area, with the edge of the
clouds marking the front (Figure 8, RAP).
Storms
Hit Michigan UP, and Minnesota Again
A cluster of
thunderstorms developed in response to an
upper air disturbance cutting through the northern Great Lakes
during the early morning hours of June 23 (Figure 9).
The thunderstorms moved southeast through the Michigan Upper Peninsula,
dropping an estimated two to three inches of rain. Flash flood warnings were
issued for Isle Royale National Park in Keweenaw
County, MI. Two
waterspouts were observed on Lake Michigan, each lasting less than a
minute. Another waterspout was observed just
southeast of
the Pointe
Aux Barques lighthouse on Lake
Huron (near Point
Hope in Huron County).
Late in the day, severe thunderstorm watches and a tornado watch were
posted from the Dakotas across Minnesota and into northern
Wisconsin. One tornado was reported in northwestern
Minnesota, but wind damage and some hail were the common reports..
Hot,
Humid Weather Edges Into
the Region
Strong southwest winds stetting up on the back side of the retreating
high pressure system brought hot, humid conditions to the northwestern
portion of the region on June 23. Temperatures soared into
the
mid and upper 90s in Iowa and Minnesota, and reached the low to mid 90s
across much of Wisconsin (Figure 10, Unisys).
Scores of locations in Minnesota set new high minimum temperatures
records on June 23. Minneapolis and St. Cloud, MN and Eau Claire, WI
all set new record high minimum temperatures, and St. Cloud also set a
new record high. The minimum temperature in Minneapolis was 80oF,
smashing the old record of 74oF
set in 1910 and 1911. Eau Claire has a minimum temperature of
73oF,
breaking the old record of 72oF
in 1901. St. Cloud started the day with a minimum temperature
of 76F, breaking the old record of 70oF
set in 1984. The temperature reached a maximum of 98oF
during the afternoon, breaking the old record of 97oF
set in 1911. La Crosse, WI also set a new record high of 98oF,
breaking the record of 97oF
set in 1995.