Western Below-Normal Temperatures; Near-Normal in the East

Average temperatures this week were below normal in the western Midwest and near normal in most of the eastern Midwest (Figure 1). Michigan, and a very small part of northeastern Wisconsin, were the only areas that had above-normal temperatures this week. Statewide, Iowa recorded the largest temperature deviation of 5.7°F below normal. The mean temperature in O’Brien County, Iowa was 9°F this week, which was 13.4°F below normal. Maximum temperatures remained below or at normal, with the largest departures in the northwest (Figure 2). There was a west/east divide in minimum temperatures, with below-normal temperatures in the west, above-normal in the east, and near-normal in the central Midwest (Figure 3). On December 21, most stations in the northwest portion of the region recorded mean temperatures in the top ten coldest on record for that date (Figure 4).

Above-Normal Northern Precipitation

This week, much of the northern Midwest received between 175-750 percent of normal precipitation, while below normal precipitation was recorded throughout the southern and eastern Midwest (Figure 5). Some pockets of the south received at or slightly above-normal precipitation. Jackson County, Wisconsin, received 2.73 inches of precipitation this week (2.41 inches above normal) with 2.31 inches recorded on December 15th, making that the highest one day maximum in the Midwest this week. Multiple stations in the northwest Midwest set or tied records for the wettest third week of December on record, while stations in the south (mostly Missouri) set records for being the driest third week of December on record (Figure 6). Streamflow conditions throughout much of the Midwest improved, and some flows in Illinois and Wisconsin exceeded the 90th percentile (Figure 7).

99 Daily Snowfall Records

Much of Minnesota and Wisconsin received up to 750 percent of normal snowfall this week, and northern Iowa and western Michigan received up to 300 percent of normal snowfall (Figure 8). The rest of the Midwest received less than normal snowfall, if any. The heaviest snow was seen in northern Minnesota and Wisconsin, where up to and over 25 inches of snow was measured (Figure 9). Lake County, Minnesota, received 28.4 inches of snow, which was 23.1 inches above normal, and set the one day maximum in the Midwest this week of 19 inches on December 15. Measurements from NWS Duluth indicate that this snow storm was the 8th largest to occur in a 48-hour period. There were 99 daily snowfall records that were broken or tied this week, most of which were in Minnesota and Wisconsin (Figure 10). Other records were scattered throughout the Midwest in Iowa, Michigan, and Ohio.

Drought Monitor Update

Drought conditions have continued to improve, with a 6.18 percent reduction of land in drought from last week (Figure 11). Compared to last week, there was one class degradation in Indiana and Ohio, and one class improvement in all states besides Michigan.