March 22-31, 2023
Week 4: March 22-31, 2023
Overview
A very active week in the Midwest closed out the month of March. A broad trough was set up over the region for much of the week, with a disturbance at the end of the week which brought intense, widespread severe weather. Looking at the week as a whole, average temperatures were slightly below normal in the south and below normal in the north; far western Minnesota recorded temperatures up to 22°F below normal (Figure 1). Both maximum and minimum temperatures followed this same pattern, with a diagonal axis of near-normal temperatures (Figure 2, Figure 3). Overall, 25 high and 80 low temperature records were broken or tied this week (Figure 4a, Figure 4b). The following sections will elaborate more on the details of precipitation this week, but overall, southwest-northeast oriented swath extending from Missouri to Ohio and Michigan received at least 200% of normal precipitation (Figure 5). However, much of the northwest, excluding a few pockets, had below-normal totals. There were 261 precipitation records broken or tied this week, many of which occurred in the Ohio River Valley Region (Figure 6). Snow was only observed this week in the northern Midwest, with above-normal totals scattered across the northwestern half of the region (Figure 7*). Most of the 85 snowfall records broken or tied this week occurred around the Illinois-Wisconsin border (Figure 8*).
March 23rd-25th Severe Weather
There was seldom a day this week where the Midwest did not see any precipitation. The most extensive system occurred along a frontal boundary that set up in the southern Midwest overnight on March 23rd into the 24th. This is the same system that caused deadly tornadoes and severe weather in Mississippi and Alabama. Figure 9a shows the surface map from 11pm EDT on March 23rd, and Figure 9b shows radar imagery from the same time. This system lingered in the area all day on March 24th before reorienting and shifting northward overnight. Cold surface temperatures resulted in heavy snow all day for the northern Midwest before the system moved out of the area on the evening of the 25th. There were numerous high wind reports in Missouri, Illinois, Kentucky, and Ohio from this system; the highest wind gust was 72 mph in Ashtabula County, Ohio. Hail of up to 1.25 inches in diameter was observed in Missouri and Illinois. Dade County, Wisconsin, reported the highest one-day maximum from this event with 12.1 inches of snow.
March 31st Severe Weather
A potent low pressure system began to develop over the Plains, then continued to intensify as it entered the Midwest in the morning on March 31st (Figure 10, 3/31 8am EDT). Thanks to very strong jet cores, plenty of warm, moist air was pumped into this system from the Gulf of Mexico. The unseasonable moisture combined with excessive instability and wind shear created a conducive environment for tornado formation and strong straight-line winds. The northern Midwest remained on the cold side of the low and received heavy, wet snow accompanied with blizzard conditions overnight on the 31st. Due to the widespread nature of this event, surveys are still ongoing, meaning that preliminary damage ratings and storm reports may change. All the following information is as of April 4th; the National Weather Service’s storm summary pages are being promptly updated with any new information.
Northern Snow
The main activity with this system started to ramp up in the afternoon on the 31st. While supercells developed in Iowa, scattered storms developed in the northern Midwest as well. Since temperatures were near or below freezing in central Minnesota and northern Wisconsin, some mixed precipitation and slushy snow was observed along with thunder, lightning, hail, and gusty winds. During the evening, temperatures in Minnesota and parts of Wisconsin dropped below freezing and the low continued to travel eastward, which resulted in blizzard conditions. Blizzard warnings blanketed southern Minnesota and western Wisconsin, with winter storm warnings in place in surrounding areas. High winds coupled with heavy, wet snow caused downed trees and power lines, and left thousands without power (Minnesota Department of Natural Resources Climate Journal). The warmer colors and banding in radar imagery from 2am EDT on April 1st indicate the heavy nature of this snow from southern Minnesota through the Upper Peninsula (Figure 11). Snow moved out in the late morning on April 1st as the low traveled eastward and weakened. Parts of northern Wisconsin and the UP received upwards of 20 inches of snow (Figure 12). After this event, the Minneapolis-St. Paul Airport sat at its third snowiest winter since 1884. The following National Weather Service offices’ tweets summarize snowfall totals from this event:
Tornado Outbreak
After an initial round of scattered storms throughout the area on the morning of March 31st, discrete supercells began popping up in Missouri in the early afternoon ahead of a cold front, as indicated by surface analysis (Figure 13a, 3/31 2pm EDT, WPC) and radar imagery (Figure 13b, 3/31 2pm EDT, NCEI). As these supercells intensified, they formed into a quasi-linear convective system (QLCS) and brought large hail and strong winds to the western Midwest. By 5pm EDT, tornadoes were forming along the leading edge of the QLCS. The strongest tornado from this event was observed around this time; this tornado developed in Wapello County (southeastern Iowa) and travelled over 40 miles northeast through Keouk and Washington Counties (Figure 14, NWS Quad Cities). It was rated an EF4 with maximum wind speeds of 170 mph; houses, farmsteads, vehicles, and trees were completely destroyed, and 3 injuries were reported.
As the QLCS continually intensified and became more organized, two linear segments could be observed- one moved through northern Illinois and the other moved through central Illinois into Indiana (Figure 15, 3/31 8pm EDT, NCEI). The more northern segment caused tornadoes with up to an EF2 rating and straight-line winds up to 90 mph in the Chicago metro area. Dupage County, Illinois, reported wind speeds of 85mph around 9pm EDT. The more southern line expanded into southern Illinois and moved into Indiana around 10pm EDT (Figure 16, NCEI). Numerous strong tornadoes were reported along the leading edge of this line. The longest tracking tornado in this area traveled 28 miles from Robinson, Illinois to Sullivan County, Indiana (Figure 17, NWS Central Illinois). This tornado was rated an EF3 by the National Weather Service office in Central Illinois, however NWS Indianapolis’ EF3 rating is still preliminary. Numerous structures were completely destroyed due to 155 mph peak winds, and unfortunately, there were three fatalities and eight injuries. Widespread damage can be seen in this drone footage . Another deadly tornado occurred near McCormick’s Creek State Park (southwest of Indianapolis) and is preliminarily rated EF3. This tornado traveled 4.01 miles and had a peak wind speed of 138 mph. Homes and buildings in the area were destroyed or damaged and, sadly, two fatalities occurred in the park along with two injuries.
This system continued to travel east and brought hail, high winds, and some weak tornadoes to Ohio and Kentucky before weakening and moving out of the Midwest around 4am EDT on April 1st. All severe reports from this week can be seen in Figure 18. The following National Weather Service offices put together storm summaries for this event with more details about the tornadoes, the environment, and include photos.
Streamflow Update
Heavy precipitation in the Ohio River Valley throughout the week caused streamflow conditions to be well above normal (Figure 19). The only area in the Midwest with below normal streamflow conditions was central Iowa.
*Disclaimer: Much of the snowfall from the March 31st winter storm are included in April 1st maps given the timing of observations. To learn more about National Weather Service COOP measurement times, read this Understanding Measurement Times article.