After a beautiful week of warm weather with temperatures in the 60s and 70s, Mother Nature could pull a Cher and “turn back time” in the Midwest this weekend. There’s a good chance that spring will “do a 180” back to winter, dropping temperatures like a rock and dumping snow along the way. It probably won’t be the storm of the century with hustle and bustle screeching to a halt, but the storm could make for some sloppy travel.
All indications show a compact, fairly powerful low pressure system and cold front heading out of South Dakota late Friday night (April 26, 2019), making a bee-line for parts of the Midwest on Saturday. The storm will likely spread snow from west to east across the following areas from morning through the evening – eastern South Dakota, southern Minnesota, northeastern Iowa, southern Wisconsin and northern Illinois. The snow will fade in these areas after midnight Saturday night as it moves into southern Michigan.
The storm will contain plenty of energy and moisture. Temperatures at the ground and aloft will be warm enough for precipitation to begin as rain early Saturday. Meteorologists at the National Weather Service (NWS) expect cold, Canadian air to keep temperatures in the 30s across the region – around 30 degrees below normal for late April – but should stay at or just above freezing, marginally cold enough to support snowfall. The heavy precipitation is expected to cool the mid-atmosphere enough to overcome the relatively warmer surface, quickly changing the rain to heavy, wet snow. This process is called “dynamic cooling.”
Where To Be On The Look-Out
The NWS issued Winter Storm Watches for many of the areas previously mentioned, and may add more. Snow totals as high as six inches are possible along and south of the I-90 corridor (south of Minneapolis-St. Paul), with localized accumulations of eight to nine inches. Snowfall rates could reach one to two inches per hour with wind gusts of 35 mph, leading to blowing snow and reduced visibility.
Some of the Minnesota cities in the potential snow path are Marshall, Mankato and Rochester; in Iowa it’s along a path from Mason City to Dubuque; in Wisconsin it’s La Crosse, Prairie du Chien, Madison and Milwaukee; in Illinois it’s the far northern Chicago suburbs.
Late season snow storms aren’t unprecedented in these parts of the Midwest. In early May 2013, many Minnesotans and Wisconsonites got quite a storm that set all-time monthly records for these states, with several places receiving 12 to 18 inches. Compared to this, Saturday’s storm may only cause minor travel problems, along with new memories of a spring snowstorm that people can talk about in church on Sunday or at the water cooler on Monday.
Although there’s a high level of confidence among forecasters regarding the outcome of the storm, everything depends on its precise track, which could shift at the last minute, sometimes within just a few hours of striking. Also, it can be tricky for computer models to determine precipitation type and snow amounts this time of the year since spring hasn’t fully settled into the Midwest. The models are not gospel, but meteorologists use them for guidance when forecasting.