Flash Floods in Missouri
A large area of southern Missouri received precipitation that was more than 600% of normal during the first week of August (Figure 1). Weekly totals in this region ranged from 4" to over 10" of rainfall (Figure 2). In Richland, MO (part of Camden, Laclede, and Pulaski counties), a preliminary local storm indicated that rainfall totals from the morning of the 5th to the morning of the 7th was an astonishing 17". Another impressive total was from a CoCoRaHS observer in Fort Leonard Wood, MO (Texas County), who reported 10.37" on the morning of August 6th (24-hour observation), 8.52" of which came within only 7 hours between midnight and the 7am observeration. As a result of this heavy precipitation, flash flooding was a major issue in southern Missouri, prompting evacuations, several flood-related injuries, extensive road closures, and several water rescues. Unfortunately, there has been at least two flash flood fatalities confirmed in Waynesville, MO (Pulaski County) and Pineville, MO (McDonald County).
Outside southern Missouri, below normal precipitation was widespread across much of the Midwest, with the largest negative departures stretching in a band from Iowa to northern Kentucky, where little to no precipitation was received throughout the week. Several daily precipitation records were set, including some that were also monthly and all-time precipitation records.
Widespread Below Normal Temperatures
The last three years, August has kicked off with above normal temperatures, so having widespread below normal temperatures the first week of August this year (Figure 3) was a nice change to the typical oppressive August heat. Northern Minnesota had the largest temperatures departures of 8°F to 10°F below normal. As a result of the cooler temperatures, there were several daily temperature records broken, all of which were record lows.
There were several severe weather reports throughout the region during the week, including hail, wind and some tornado reports as well (Figure 4). The most active day was August 6th, when a line of severe thunderstorms moved across the upper Midwest, bringing large hail to Minnesota and hail, very strong winds, and tornadoes to Wisconsin. Altogether, there were three tornado reports on the 6th in Wisconsin, two of which indicated that the tornado was embedded in a large area of straight-line winds. The tornadoes occurred in London (Waupaca County), Appleton (Outagamie County), and Kaukauna (Brown County) in Wisconsin. Severe weather reports were scattered across the region on all other days of the week, with the exception of August 3rd, which had no reports.
The August 6th release of the US Drought Monitor shows that just over 4% of the region is now in moderate drought, which is roughly a 2% increase from last week (Figure 5). The areas designated as moderate drought include portions of northwest Missouri, western Iowa, and northern Minnesota. Even though Missouri received heavy rains this week, much of this precipitation did not fall over the areas designated as moderate drought unfortunately. In fact, some of the drought areas in Missouri received little to no precipitation throughout the week (only 0-10% of normal), most likely worsening the drought conditions in these regions.
Growing Season Update
According to the USDA August 5th Crop Progress Report, corn silking is right on par with the 5-year average in many Midwest states, but many states are showing the corn dough stage to be slightly behind the 5-year average. Fortunately, a majority of the corn and soybean crop in the region is in fair, good, or excellent condition. The cooler than normal temperatures so far this summer have resulted in a slower accumulation of growing degree days than normal across much of the Midwest, especially in the west (Figure 6). If the trend of below normal temperatures continues, there could be an increased risk of freeze damage this fall.
In southwest Michigan, the harvest of peaches and blueberries is moving along, according to the Michigan State Extension regional report from August 6th. However, the report also notes that growers should also be aware that the cooler temperatures are ideal for certain pests, like the spotted winged drosophila, which is a pest of most berry crops, cherries, grapes, and other tree fruits.
The Missouri Climate Center also contributed to this report.