Week 3: March 15-21, 2023

Cold and Wet Week

A deep, persistent upper-level trough moved in and settled over the Midwest this week, which resulted in unseasonably cold temperatures paired with frequent precipitation (Figure 1). Michigan and northern Ohio were the only states that had near-normal temperatures this week. The remainder of the Midwest was well below normal, with the northwest and southern-most extents of the region experiencing the largest deviations (Figure 2). On average, Minnesota recorded the largest temperature departure of 10°F below normal. Maximum temperatures were also below normal, but were near or slightly above normal in Michigan and northern Ohio (Figure 3). Minimum temperature departures were at least 9°F below normal throughout much of the region this week (Figure 4). Only a small area in northern Michigan (including the Upper Peninsula) recorded near or above-normal minimum temperatures. Overall, 114 low minimum and 169 low maximum temperature records were broken or tied this week (Figure 5).

The upper-level low trapped moisture at the surface and resulted in multiple precipitation events this week. Although most everywhere received at or below-normal precipitation, scattered pockets received above-normal totals, and the far north received up to 300 percent of normal precipitation (Figure 6). Throughout the week, 53 precipitation records were broken or tied (Figure 7). Snowfall was scattered this week. Some areas, especially the far north, received well above-normal snowfall, while other pockets received none (Figure 8). This aligns with the snowfall records set or tied this week, as there were 29 scattered around the Midwest (Figure 9). Ontonagon County, Michigan (located in the UP), recorded the highest one-day maximum snowfall total this week with 15.4 inches on March 18th.

March 16-17

A strong cold front made its way into the Midwest in the morning on March 16th and brought mixed precipitation along with much colder temperatures. The system, which originated in the Great Plains, entered the Midwest around 8am EDT (Figure 10a, NCEI). Precipitation along the frontal boundary started off as rain, but then transitioned into mixed precipitation and eventually snow as the passing of the cold front caused temperatures to dip below freezing in the northern Midwest (Figure 10b, WPC). By the afternoon, the cold front was still stalled in the western Midwest, so precipitation ahead of the front was still rain (Figure 11a, WPC, 3/16 5pm EDT). Radar imagery in Figure 11b (NCEI, 3/16 5pm EDT) shows banded reflectivity in the north, indicating snowfall. Looking back at Figure 11a, high wind speeds were observed in Minnesota, and blowing snow led to very dangerous road conditions. The low continued to intensify as it moved over Lake Michigan and by the morning on the 17th, most of the Midwest observed near or below-freezing temperatures (Figure 12a, WPC, 3/17 8am EDT). Precipitation was mostly out of the area by 8:00 AM March 17 (Figure 12b, NCEI, 3/17 8am EDT). By the end of this event, the northern Midwest received up to 6 inches of snowfall (Figure 13).

March 18-19

Right after this strong cold front swept the Midwest, another frontal boundary set up and passed through, beginning on the morning of March 18th (Figure 14a, WPC, 3/18 8am EDT). Light snowfall was seen in Indiana and Michigan (Figure 14b, NCEI, 3/18 8am EDT). As Lake Michigan has observed warmer lake temperatures this winter, ice concentration has been well below normal (Figure 15, GLERL). Due to the warmer waters and the influx of cold air on March 18, lake effect snow was supported. This activity started in the late morning on March 18th and continued in the Lake Michigan region all day. Lake effect snow is manifested in radar imagery as bands of small, blue-green dots (Figure 16, NCEI, 3/18 2pm EDT), which provides a physical explanation for rapid fluctuations in snowfall intensity and wind speeds. High wind speeds combined with heavy snowfall rates, at times, caused whiteout conditions on Michigan roads, and led to a pileup involving upwards of 100 cars.

Streamflow Conditions

Streamflow conditions did not change all that much when compared to last week. Conditions in eastern Indiana, Ohio, and Kentucky worsened, while conditions in the rest of the Midwest returned to more normal values (Figure 17).