Temperatures Below Normal in the West; Above Normal in the East

To close out the month, average temperature departures in the Midwest were divided by a predominantly north/south oriented line of near normal temperatures; in the west, temperatures ranged from 1-8°F below normal, and in the east, temperatures ranged from 1-9°F above normal (Figure 1). Statewide, Iowa and Ohio had the largest temperature deviations of 4.6°F below normal and 4.8°F above normal, respectively. Both maximum (Figure 2) and minimum (Figure 3) temperature departures followed roughly the same pattern. An area of anomalously low upper-level heights, associated with a deep trough over the Plains, caused cooler air in the western Midwest, while anomalously high upper-level heights were present in the east and prevented the cooler air from moving through the rest of the region (cool and warm colors, respectively, in Figure 4). The area between these two air masses lines up well with the previously mentioned line of near normal temperatures.

Snowstorm Barrels Through Midwest

Precipitation this week was near normal throughout the Midwest with localized areas of both above and below normal accumulations; some pockets received up to 200 percent of normal precipitation, while others received as low as 25 percent (Figure 5). Parts of the southern Midwest received up to 2.5 inches of liquid precipitation accumulation this week (Figure 6).

The main event in the last week of January was a weather system that moved through the area overnight on January 24 and throughout the day on January 25. This system brought heavy, wet snow and mixed precipitation to much of the Midwest, and caused a severe weather outbreak in the southern US. As shown in Figure 7a, a deep, upper-level trough associated with low surface pressure was situated over the central United States on the afternoon of the 24th. Figure 7b shows this trough moving over the Midwest 24 hours later, when effects from the system were most intense. Movement of this system can be seen in the following sequence of radar images from 12:00 AM (Figure 8a), 7:00 AM (Figure 8b), 12:00 PM (Figure 8c), and 7:00 PM (Figure 8d) on the 25th (all times in EST). As the day went on, the system weakened and began to move over the Great Lakes, and only isolated patches of snowfall remained going into the evening. The highest snowfall totals from this system were centered around the Great Lakes and southern Missouri, but totals throughout the region ranged from 1-10 inches of snow (Figure 9). Elkhart County, Indiana, won the title of highest one-day maximum snowfall when 11.6 inches of snow was recorded on January 25. Despite the heavy snowfall rates and high totals recorded, many Midwesterners saw little, if any, additional accumulation from the later part of this system. While the atmosphere was still moist enough for precipitation to reach the surface, surface temperatures in the path of the system were at or above freezing at 1:00 PM CST, causing most additional snowfall to melt almost immediately after reaching the ground (Figure 10). This storm affected road conditions and caused reduced visibility, causing pileups on highways; one in southern Wisconsin included more than 80 vehicles.

Overall, this week, areas in the core of this system received above normal snowfall (125-750 percent) while the outer boundaries were below normal (Figure 11). Additional snowfall that occurred this week can be seen in Figure 12, where the northeastern Midwest recorded 5-15 inches. 154 snowfall records were broken or tied this week (Figure 13).

Drought and Streamflow Improvements

River levels this week were as close to normal as they have been in quite a while. Areas in Ohio and Illinois where levels were well above normal last week improved to being just slightly above normal, and rivers in Missouri, Illinois, and Indiana that were below normal last week have improved as well (Figure 14). Additionally, 3.6 percent of area in the Abnormally Dry (D0) category has been removed when compared to the January 24th US Drought Monitor, most of which occurred in areas of Missouri, Illinois, Indiana, and Ohio (Figure 15).