Week 2: April 8-14, 2023

Warm Week for the Midwest!

The entire United States experienced beautiful, summer-like weather during the second week of April. High pressure, typically associated with warm temperatures and clear conditions, was present across the entire county (Figure 1, 4/11 2pm EDT, WPC), and was influenced by upper-level ridging (Figure 2, 4/11 2pm EDT, Alicia Bentley). While these figures were from just one date this week, they were representative of the surface and upper-level conditions observed throughout the whole week. The entire Midwest recorded well above-normal temperatures, but southern Minnesota and northern Iowa experienced temperatures up to 19°F above normal (Figure 3). The most notable anomalies were observed in the maximum temperatures this week; the same area experienced average maximum temperatures of up to 25°F above normal (Figure 4)! The areas where minimum temperatures were most above normal shifted slightly north to expand from northwestern Iowa through southern Minnesota and western Wisconsin, to northwestern Michigan (Figure 5). As a whole, Wisconsin’s average weekly temperature was 15.8°F above normal.

Not to anyone’s surprise, numerous high temperature records were broken throughout the Midwest. Figure 6a shows that 420 high maximum and 197 high minimum daily temperature records were broken or tied this week. Figure 6b indicates many stations ranked this as the warmest second week of April ever recorded. Stations in both Lansing, MI, and Minneapolis-St. Paul, MN, recorded temperatures above 80°F for four days straight, which has never happened in the first half of April (4/1-4/16). The high temperature in Sioux City, IA, on April 12th was 92°F, which clocked in as a tie for the 6th highest temperature recorded at that station in April since 1896. Another April record was almost broken at Green Bay International Airport when a high temperature of 86°F was recorded on April 12th; this was a tie for the 4th warmest maximum temperature at this station in April since 1886. Additionally, Youngstown-Warren Regional Airport in Ohio recorded a high temperature of 86°F on April 14th, which was the 4th highest temperature at that station in April since 1897.

Limited Precipitation

As expected with high pressure, minimal precipitation was observed this week. The most notable precipitation was a short-lived snow system that developed in north/central Wisconsin overnight on April 7th and tracked through northern Michigan in the early hours of April 8th before dissipating in the early afternoon. The highest snowfall totals from this event were seen in northeastern Wisconsin, bordering the Upper Peninsula, and measured to be up to 3.5 inches (Figure 7). Aside from this event, no major precipitation systems were observed this week; some light, scattered precipitation occurred primarily on April 10th and April 14th, but accumulations were low (Figure 8). Almost all stations throughout the Midwest tied for the driest second week of April on record (Figure 9).

Streamflows did not change much when compared to the previous week. Values in Minnesota and northern Wisconsin shifted to above normal, as increased temperatures caused a rapid onset of snowmelt (Figure 10). The most change occurred in the southern Midwest as streamflows became closer to normal or below normal, especially in Kentucky, Missouri, and Iowa.