Midwest Weekly Highlights - August 15-21, 2008

More Cool, Dry Weather

This was the second week of generally cool, dry weather across the Midwest. High pressure anchored over the region kept rainfall to a minimum, although rain increased from Missouri into Illinois at the end of the period as a surface trough of low pressure moved through the northern Gulf States. Precipitation this week was less than 25 percent of normal across most of the region (Figure 1). Rainfall was 50 to as much as 200 percent of normal from central to southern Missouri as a result of the late week system. The continuation of dry weather in the Midwest brought some marked changes to the August 19 U.S. Drought Monitor (Figure 2). Moderate (D1) drought continued in central Minnesota, but was also indicated in a small area of north-central Minnesota. In addition, dryness is now being indicated in parts of Missouri, Wisconsin, Michigan and Ohio. The most significant change was in Kentucky, where Moderate Drought expanded into the southeastern tier of counties.

Temperatures this week reflected the position of the northeast to southwest ridge of high pressure across the Midwest (Figure 3). Temperatures across the southwestern portions of the region were much below normal this week, while temperatures across Minnesota and Wisconsin were near to above normal. Temperatures ranged from 8°F below normal in southwestern Missouri to 4°F above normal in northwestern Minnesota (Figure 4). High temperatures this week were generally in the 70s to 80s, with highs more consistently in the 80s to as high as 90°F in western Minnesota. Lows were generally in the 50s to low 60s. A low temperature record of 56°F was set on August 18 in Vichy-Rolla, MO. The previous record was 57°F set in 1992.
 

Rain Spreads North and East

The only significant rain this week began to spread north and east from the southern Plains as a trough of low pressure extending from Texas to Arkansas drifted east on August 20. Showers and scattered thunderstorms moved through southern Missouri and then into Illinois. Amounts were generally less then one inch, although isolated 3 to 4 inch amounts were reported in southern and central Missouri.

There were only two reports of severe weather in the Midwest the entire week. Thunderstorm winds caused damage in Saginaw, MI (Saginaw County) on August 17, and thunderstorm winds caused tree damage in Toledo, OH (Lucas County) on August 18.

SDH