Cold Start to the Week with Warmer Temperatures Following

Looking at the first week of February as a whole, mean temperatures were generally below normal in the northern Midwest, while the opposite was true for the southern Midwest (Figure 1). Much of the east had near-normal mean temperatures. Only the far northern Midwest had maximum temperatures that were below normal; the rest of the region, especially northern Missouri and southern Iowa, had above-normal maximum temperatures (Figure 2). On the other hand, minimum temperatures were below normal in much of the Midwest this week, with some small pockets of above or near-normal temperatures (Figure 3). Overall, this week, there were 45 high maximum and 10 high minimum temperature records broken or tied, most of which occurred in the southwest part of the region (Figure 4).

An extremely cold, Arctic airmass dipped into the northern United States early this week before making its way out east. Figure 5a shows the area of anomalously cold low-level temperatures (blues/purples) start to clip the northern Midwest in the afternoon (1pm EST) of February 2nd. As this airmass traversed eastward, it trended further away from normal temperatures, as shown in Figure 5b (1pm EST, February 3rd). Cold, low-level temperatures resulted in below-normal temperatures at the surface for the first half of the week, especially in the north (Figure 6). While temperatures in the northern Midwest were frigid, Mount Washington in New Hampshire experienced record temperatures, wind chills and wind speeds on February 3rd. This is due to a phenomenon known as tropopause fold, where stratospheric air briefly pokes into the troposphere, bringing arctic temperatures and high wind speeds. Cold, low-level temperatures are typically associated with mid and upper-level troughs. In Figure 7a (7am EST, February 4th), an upper-level ridge followed the upper-level trough that was over New England at this point. This trough remained over the Midwest for about 24 hours, then another moved through overnight on February 5th (Figure 7b, 7pm EST). Associated anomalously high upper-level heights stayed in the area for the remainder of the week (Figure 7c, 7pm EST, February 7th). These patterns are typically associated with warm, clear weather, which occurred in the second half of the week (Figure 8). The temperature in Kansas City reached 70°F on February 6th, which tied the current record.

Extraordinarily Dry Conditions for Most

The first week of February was incredibly dry for the Midwest; most of the region received no precipitation, and the areas that did trended well below normal (Figure 9). The farthest northern and southern extents of the Midwest received upwards of 0.75 inches of precipitation (Figure 10). Dade County, Missouri, recorded the most precipitation this week, with a total of 1.44 inches. Most stations in the Midwest ranked this week as or tied for the driest first week of February on record (Figure 11).

Snowfall accumulations were also sparse; only a small area in Michigan’s Upper Peninsula recorded near normal snowfall accumulations (Figure 12). This area received up to 13.5 inches of snow, which was recorded in Chippewa County, Michigan (in the UP) (Figure 13). Most of the snowfall occurred in the first half of the week, when the upper-level trough/arctic airmass clipped the northern Midwest (Figure 14).

River levels were lower than they were last week throughout the Midwest, but this was not necessarily a negative for rivers that were previously at above-normal levels (Figure 15).

Drought Update

Minimal change in the US Drought Monitor was noted in the western Midwest. A slight expansion of Moderate Drought occurred in central Missouri. In Indiana, parts of the Abnormally Dry (D0) conditions were removed as well as a 1- category improvement to the Moderate Drought (D1) in eastern Indiana/western Ohio.