September 17-23, 2008
Midwest Weekly Highlights - September 17-23, 2008
Warm, Quiet Weather, but Ike Effects Linger
An upper level ridge of high pressure dominated Midwest weather this week, keeping most areas dry and the weather seasonably warm. However, portions of Indiana, Ohio, Illinois, and Kentucky were still dealing with the aftermath of the September 14 passage of the remnants of Hurricane Ike.
Temperatures this week were above normal across most of the region, ranging from 6 °F to 10 °F above normal from northern Illinois to western Minnesota (Figure 1). The coolest area was from southern Missouri into southern Illinois, where temperatures were near normal. Low temperatures this week were generally from the upper 40s to the low 60s. Highs were the mid to upper 70s in the northern Midwest to the low to mid 80s south although by the end of the period highs were in the low 80s as far north as northern Wisconsin. On September 23 LaCrosse, WI recorded its eighth consecutive 80°F day, the longest late-season string in 100 years.
There was scattered precipitation in the Midwest this week, but most was concentrated in southern and western portions of Missouri and in southern Illinois (Figure 2). Showers and thunderstorms, some with heavy rain, developed in association with a weak upper level low (Figure 3) that moved through the southern Midwest on September 20-21. Dry areas of Minnesota received some rain on September 22-23 as a line showers and thunderstorms extending south into western Missouri developed ahead of a cold front. There was some expansion of Moderate (D1) drought in Minnesota and Wisconsin on the September 23 U.S. Drought Monitor, but the biggest change was in Kentucky (Figure 4). Moderate (D1) drought is indicated in all but a narrow area along the Ohio River, and Severe (D2) drought is now being depicted in the south-central portion of the Kentucky.
There were only a few instances of severe weather this period. There were isolated reports of severe weather on September 19-20 in Missouri, Illinois, and Indiana. There were a number of reports of severe weather, mostly hail, in southwestern Iowa and northeastern Minnesota on September 23 from a line of thunderstorms ahead of a weakening cold front.
A Slow Return to Normal
Flooding gradually subsided and power was restored to most customers as the week progressed. Power outages caused by Ike's passage through the Midwest were extensive. On September 19 there were still an estimated 550,000 customers without power in Ohio, and on September 23 several thousand customers in central and northern Ohio were still waiting for power to be restored. In Kentucky, power had been restored to all but 2,700 customers out of more than 1.2 million without power immediately after the storm.
The winds also damaged crops in Ohio and Kentucky. In Ohio, wind damage was most severe in fields with drought-stressed corn with weak stalks, and late-planted corn with shallow, limited root systems. Estimated harvest losses could range from 1 to 5 percent per field to as high as 40 percent to 50 percent. Damage to soybean fields was reported in Kentucky, in addition to the corn and tobacco damage reported last week.
Flooding continued on the Kankakee River in northwestern Indiana and eastern Illinois (Figure 5), on the Illinois River (Figure 6), and on the Mississippi River south of the confluence of the Illinois and Mississippi as the floodwaters from last week's heavy rain moved downstream (Figure 7). On the Illinois River, the river stage crested at 31.0 feet in Henry, IL on September 19 and was the third highest crest ever recorded. The river stage at Peoria crested at 27.0 feet on September 19, the sixth highest on record. For both locations this was the highest crest recorded since March 22-23, 1982. At the end of this week there was still minor flooding on some rivers in southwestern Michigan, while the Kalamazoo and Grand Rivers had declined below flood stage and continued to fall.
SDH