Midwest Weekly Highlights - April 24-30, 2005

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Colder, Wetter Pattern Brings April to an End

Three weeks of warmer than normal weather for the Midwest was knocked back on its heels by much colder weather the last week of the month.  A change in the jet stream pattern over the United States funneled much colder air into the nation's midsection (Figure 1), cold enough to fuel a major snowstorm over parts of the region at the beginning of the period.  Temperatures this week ranged from 6F to 12F below normal (Figure 2), with the coldest weather in the western portions of the region. Several systems moved through the Midwest this week, but the southern storm track restricted precipitation to the southern half of the region for the most part. Although the dry areas of the northern  Midwest did receive some beneficial precipitation, conditions there remain relatively dry.  The precipitation pattern was indicative of the southern storm track (Figure 3), with precipitation from 100 to 300 percent of normal for the week east of a line from from southeastern Missouri to eastern Indiana through central lower Michigan.  There were only scattered light showers in the northwestern half of the region and precipitation was generally less than 50 percent of normal there.  The north-central Great Lakes region has been much drier than normal the past two months, and this is reflected in the Abnormally Dry designation on the latest U.S. Drought Monitor (Figure 4).  There was some improvement in eastern Michigan as a result of the heavy, wet snow early in this period.


If April Showers Bring May Flowers, What Does April Snow Bring?

On Sunday morning, April 24, an intense low pressure system was centered over western New York and dominating the weather from the Mississippi river to the Atlantic coast (Figure 5).  Snow had begun falling over eastern Michigan and northern Ohio on the 23rd, but it did not start accumulating until late on the 23rd through the morning of April 24th. The snow reached accumulations of more than a foot in northeastern lower Michigan (Figure 6, NWS), and many locations set new daily snowfall records for April 24.  High winds combined with the heavy, wet snow brought down large tree limbs and power lines in the "thumb" of lower Michigan, and drifts were reported as high as three to four feet.  The winds and snow combined to make travel nearly impossible in this area. Due to the warm ground temperatures, air temperatures at or slightly above freezing,  and the melting and settling of the heavy snow the actual depth of snow on the ground generally was lower than the maximum accumulation.  Snow also accumulated one to two inches in northern Indiana and northwestern Ohio, and measurable snow fell as far south as Cinncinatti.  The largest amounts of snowfall, however were found in the lake-effect belt south of Cleveland, where more than two feet of snow piled up in the Broadview Heights/North Royalton area.  Cleveland received 1.6 inches of snow, bringing its April total to a record 19.0 inches.  The previous record was 14.3 inches set in 1943.  The seasonal total in Cleveland is 117.9 inches, and 2004-2005 is now the snowiest season on record.

       Selected Storm Snowfall Amounts                                        Record Daily Snowfall for April 24

Location	Amount (inches)		Location	New Record	Previous Record
White Lake, MI (NWS	14.6		Flint, MI	4.3	2.7 in 1890
Yale, MI	14.1		Alpena, MI	3.5	1.1 in 1971
Capac, MI	14.0		Detroit, MI	3.1	0.5 in 1967
Lum, MI	12.5		Columbus, OH	3.0	0.0
Highland, MI	12.0		Dayton, OH	0.4	0.1 in 1995
Richmond, MI	11.3		Cincinnati, OH	0.3	0.0
Brown City, MI	11.0		Jackson, KY	1.2	0.0
Deckerville, MI	10.0
Sandusky, MI	9.0
Clio, MI	8.5
Kimball, MI	8.0
Broadview Heights, OH	25.3
Thompson, OH	21.8
Hambden Township, OH	21.1
Solon, OH	19.8
Chardon Township, OH	17.5

In the wake of the storm frigid air spilled into the eastern U.S. as far south as the Gulf of Mexico, producing record cold weather in some areas.  Jackson, KY set a record low of 32F on April 24, breaking the old record of 35F set in 1996.  Record minimum high temperatures were set at Jackson, KY with 45F (old record 46F in 1995) and in London, KY with 48F (old record 52F in 1954). The low temperature of 33F at Louisville tied the record for April 24, last reached in 1927.


The Refrigerator Door Is Left Open

Even as the storm over the northeastern U.S. weakened and moved eastward, another system was organizing in the Central Plains.  This system moved through the Midwest on April 26 accompanied by mostly light showers, and it pushed to the east coast by April 27.  A series of upper level disturbances then rotated around the massive upper low centered just south of Hudson Bay (Figure 7), maintaining a steady flow of cold air to the Midwest.  Numerous scattered showers developed in the unstable cold air during the afternoon and evening hours, and some of these were accompanied by small hail at times.  Over the northern Midwest some of the precipitation fell as snow.  On April 27 Marquette, MI Received 2.1 inches of snow, a new record for the date.  A number of locations in Michigan received a trace to a few tenths of snow on April 27 and April 28.

This low dominated the weather over the eastern two thirds of the U.S. through the end of the month.  The last of the disturbances rotating around the low was reflected in a low over the southern plains on April 28, which then moved east on April 29.  Most of the rain with this was limited to the southern half of the region.  North of the low pressure center rainfall was generally light, less than 0.25 inch. However, east of the low heavy rain fell south of the Ohio River through Kentucky, with a number of locations exceeding 3.00 inches of rain (Figure 8) and resulting in flash flooding.  On April 29 Jackson, KY received 1.79 inches of rain, a new record for that date (old record 0.93 in 1994).  A second record was set on April 30 when Jackson received 1.59 inches of rain (old record 1.05 in 1998). For the period from 6:00 a.m. on April 29 to 6:00 am.m on April 30, Jackson received 3.13 inches of rain, the greatest 24-hour rainfall in the month of April.  London. KY also set a new daily rainfall record on April 30 of 1.56 inches, breaking the old record of 0.99 inches in 1998.


Record Cold Marks the End of April

Clearing skies and colder air behind the storm moving through the Ohio Valley allowed temperatures to drop into the low and mid 30s as far south as southwestern Missouri on the morning of April 30 (Figure 9, Unisys).  Joplin, MO set a record low of 34F, breaking the old record of 36F set in 1996.  Kansas City, MO International Airport dropped to 31F, tying a record set in 1903.