Temperature

Temperatures averaged slightly above normal across southern parts of the region (Figure 1). Temperatures were near or slightly below normal across the Upper Midwest. The largest anomalies were in western Kentucky and the Missouri Bootheel, where temperatures averaged at most 6°F above normal for the week.

Minimum temperatures followed the same pattern as average temperatures, with minimum temperatures generally most above normal in Kentucky and southeastern Missouri, usually by 4-7°F (Figure 2). Elsewhere, minimum temperatures were near to slightly below normal in isolated pockets of the Upper Midwest. In Waverly, Ohio, a minimum temperature of 55°F or greater was observed for three consecutive days, April 19-21, which marked the warmest stretch of minimum temperatures in April in Waverly since 2013. At the same station in Waverly, a minimum temperature of 67°F was observed on April 19, which was the single warmest minimum temperature in April since 2014 and tied for the third warmest minimum temperature on record in April since 1893.

Maximum temperatures were slightly more anomalous, with parts of the region reaching as much as 8°F above normal for the week (Figure 3). This included southwestern Minnesota, as well as southern reaches of the region. Michigan’s UP and northern Wisconsin accounted for most of the region’s below normal temperatures, where maximum temperatures averaged up to 6°F below normal for the week.

Precipitation/April 20th Heavy Rains & Flooding/Drought

Precipitation varied across the region, with the Ohio Valley generally receiving less than 50 percent of normal precipitation while places along and in the Mississippi River Valley received well over 200 percent of normal precipitation (Figure 4). Two systems came through bringing separate bouts of precipitation throughout the week. The first one brought nearly 2 inches of rain to southern Missouri, with lesser totals of roughly 1 inch through southern Minnesota, western Wisconsin and the northern Lower Peninsula of Michigan. The second system arrived on April 20, and again parts of Missouri received heavy rainfall, this time totaling upwards of 3 inches. At a station in Butler, Missouri, 6.13 inches of precipitation was recorded for the 7-day period ending April 21, which tied the record for the 6th wettest April week on record. Several rivers in central and southern Missouri rose to minor and moderate flood stage after the second storm system on April 20.

There was also some severe weather associated with these systems, with 376 storm reports this week (Figure 5). While the vast majority were hail and straight-line wind reports—122 and 190, respectively—there were also 13 tornado reports and 36 large hail reports. Most of the tornado reports occurred with the first storm of the week in southwestern Iowa on April 17, and they were intermittent and weak. In northern Iowa, tennis ball size hail was reported on social media from an observer in Plymouth, and baseball size hail was reported just north of Waverly.

Drought was somewhat improved due to increasingly wet conditions across the region. While D2 (severe drought) remained unchanged, D1 (moderate drought) was completely removed across Missouri (Figure 6). D0 (abnormally dry) saw significant improvement across Iowa and Missouri.