Week 2: March 8-14, 2023

Overview

After a “false spring” swept through much of the Midwest over the past few weeks, winter weather returned for the second week of March. Below-normal and near-normal temperatures were observed throughout the Midwest, with a handful of slightly above-normal pockets in Wisconsin and Michigan (Figure 1). Statewide, Missouri’s average temperatures were 4.4°F below normal. Maximum temperatures were below normal everywhere, with the largest departures (up to 13°F below normal) seen in Missouri and Iowa (Figure 2). On the other hand, minimum temperatures were above or near normal for all Midwestern states, besides far western and far northeastern Minnesota where below-normal temperatures were recorded (Figure 3).

Persistent, upper-level ridging was present for the first half of this week, leading to a relatively calm week in terms of severe weather. An intense clipper system moved into the northern Midwest on March 11th, causing most of the observed precipitation this week. Above-normal totals were recorded in the west and in southern Michigan, but Minnesota’s and Wisconsin’s precipitation were most above normal (Figure 4). Snowfall this week was contained to the northern Midwest, but the areas that received snow saw well above-normal totals; parts of Minnesota, Iowa, Wisconsin, Illinois, and Michigan received up to 750 percent of normal totals (Figure 5). Over 160 snowfall records were broken or tied this week (Figure 6).

Heavy Precipitation in the South

A stalled frontal boundary located in Texas overnight on March 7th caused 1-inch hail producing storms. Although the Midwest did not see any severe weather, heavy rain lingered in Missouri through the early morning hours on March 8th. Parts of this swath received upwards of 1 inch of rainfall (Figure 7).

Intense Clipper System

Starting on March 10th, troughing at the 500mb level was dominant over the Midwest (Figure 8). This pattern persisted for the reminder of the week, which was a good indicator of the cold, wet weather that occurred. A low-pressure center developed in the Alberta/Saskatchewan area and moved southeast through the northern Rockies before entering Minnesota around midnight on March 11th. Figure 9a, the surface analysis from 2am EDT on March 11th, shows the low and associated frontal boundary still located in the Northern Rockies, while Figure 9b, radar imagery from the same time, shows precipitation out ahead of the low. As the day progressed, the system continued to develop and extended southward, and by 8pm EDT, much of the western Midwest was receiving or had received precipitation (Figure 10a). At this point, southern temperatures were a bit too warm to support snowfall. As the main system moved out of Minnesota, the surface low moved into western Minnesota which initiated more snowfall along the frontal boundary (Figure 10b, 3/12, 8pm EDT). This low stalled over Minnesota throughout the day on March 12th, which caused lighter bands of snow to stick around, adding to the already high accumulations. Overnight, temperatures everywhere except Missouri, southern Illinois and Indiana, and Kentucky dropped below freezing which supported the transition of precipitation into freezing rain and eventually snow (Figure 11a, Figure 11b, 3/12 5am EDT). Heavier snowfall tapered off early in the morning on March 13th for the region, but the passing cold front fired up even more scattered, light snow showers in the eastern Midwest, especially surrounding Lake Michigan. This activity stuck around until the evening on March 14th.

From the entirety of this system, most of Minnesota and Wisconsin received at least 5 inches of snow, and the most intense section of this band dropped up to 12.5 inches (Figure 12). A bullseye in central Iowa also received higher snowfall totals of up to 7.5 inches. Lake County, Minnesota, had the highest one-day maximum snowfall total when 13.8 inches were received on March 12th. From the Minnesota Department of Natural Resources, similarly oriented clipper systems typically move fast and do not produce high accumulations. This storm, however, stalled over the region as it continued to ingest moisture from the south which led to increased snowfall totals. Snow from this storm has made this winter the 8th snowiest on record for the Minneapolis-St. Paul Airport.

River and Drought Update

Minimal precipitation in most of the Midwest resulted in a return to normal streamflow conditions for most rivers (Figure 13). Conditions along the Illinois/Indiana border and surrounding Lake Michigan were still above normal, but conditions throughout Kentucky, Ohio, and parts of Iowa were below normal. The clipper system brought some relief to Minnesota’s drought, as Abnormally Dry (D0) conditions and areas of Moderate Drought (D1) were decreased in the southern part of the state (Figure 14).