Image credit: NOAA/National Weather Service
A large and highly anticipated winter storm lasting almost 48 hours, from Tuesday February 21 into Thursday February 23, 2023, produced 12 to 20 inches of snow and left large snow drifts across southern and central Minnesota. The storm was quite large and intense, but in fact was less intense than had been feared.
Timing
The storm began with a wave of light to moderate snow from Tuesday night into Wednesday morning, as the leading edge of an expanding low-pressure system in the eastern Rockies moved into the region, interacted with cold air already in place, and generated enough lift to produce precipitation. The snow fell into generally light winds, leaving totals of 3-5 inches across the southern two-thirds of the state by morning. A few areas in far southern Minnesota received six inches of snow during this time.
The snow continued on and off across a narrow strip of southern Minnesota during Wednesday, but in many areas, the snow stopped completely for several hours, and in a few areas, the sun came out. Meanwhile, the same low-pressure system was strengthening and moving towards the region.
A much more intense phase of snow and wind developed later in the day Wednesday and lasted into Thursday. During this period, snow came in three waves across southern and central Minnesota, each of increasing intensity. The first lasted from mid-afternoon Wednesday until mid-evening, and generally produced 1-3 inches of snow. After a brief pause, the next wave blossomed over central Minnesota around 10 PM and produced 2-5 inches of snow. After another brief pause, the final wave worked northward in the pre-dawn hours, reaching peak intensity around sunrise, but then lingered in a weaker state for several hours, producing an additional 3-7 inches of snow accumulation. Many communities received 10 inches or more in the overnight hours alone.
Accumulations and impacts
Snowfall totals for the entire event reached or exceeded 12 inches over a large area, roughly covering the southern 40% of Minnesota, and occupying over 30 thousand square miles. Totals well in excess of a foot were common throughout this area. Some higher totals reported to the National Weather Services included 20-21 inches near and to the northwest of Marshall, near Taunton; 19-20 inches in Apple Valley; 18 inches in North Mankato; 17.5 inches in Prior Lake; 17.1 inches in Savage; and 17 inches in Canby, and Cambridge. Snowfall totals of 15 inches or more were common, and were distributed evenly around southern Minnesota. The Twin Cities (MSP) airport received 13.4 inches of snow, making it the second-largest February snowstorm on record, and #23 on the list of top snowfalls in the Twin Cities.
Strong winds that began on Wednesday blew through the night, creating large snowdrifts, especially in open areas. Some roads in southwestern Minnesota were closed, and in anticipation of the storm, Governor Tim Walz had declared a peacetime emergency and placed the National Guard on standby to provide rescue operations, and many schools and institutions closed or went to remote/online formats.
Geographic extent
The storm not only produced intense snow, but also had massive geographic reach. It's not unusual for storm systems to travel thousands of miles, leaving long and wide precipitation swaths. What is unusual is for precipitation to cover the Rockies, the Plains, the Upper Midwest, the Great Lakes, lower Ontario, and New England-- simultaneously. Indeed, on Wednesday and Wednesday night, nearly continuous bands of precipitation stretched from Montana and Wyoming through Maine, and into the Atlantic Ocean, covering 2000+ miles and four time zones. The low pressure center responsible for the winter weather was not particularly strong, but its circulation and warm front were able to gain extraordinary west-to-east extent, which is one reason the storm lasted so long and covered so much territory.
Recent trend towards more February storms like this?
This was a large snowstorm for southern Minnesota, and especially for the month of February. It was only the second February storm in the Twin Cities to make the top-25 list for total snowfall. Historically, February was a seasonal low point for major winter storms, but this event is part of a sharp trend in recent decades towards more February snow, driven by larger February storms. Incidentally, another large, 48-hour February snowstorm hit central and northeastern Minnesota almost exactly one year earlier.
Extraordinary forecast lead-time
Image credit: NOAA/National Weather Service, Twin Cities/Chanhassen
In many ways, this event was also a marvel of modern weather forecasting. Meteorologists are habitually plagued by uncertainty, but in this case were able to pinpoint the areas of greatest potential impact with high confidence several days in advance. Although forecast snowfall amounts were revised downward as the event unfolded, the areas that received a foot of snow or more closely matched the areas that forecasters had highlighted as early Friday (February 17), when the heaviest snows were still over 120 hours away.
The numerical forecast models that meteorologists use exhibited an uncanny level of agreement about the storm's intensity, and which areas would be hit the hardest. That agreement existed not just between the many different models, but also with each new model run. This strong agreement led to a very high level of forecaster confidence, which enabled meteorologists to alert the public much earlier and with much more precision than is typical with winter storms.
Additionally, for several days, the storm looked like it would produce even more snow and contain more winds than it did, which would have made it a record-breaking event at many locations and one of the great winter storms in history. The long forecast lead-time combined with its potentially historic magnitude created high public awareness, and this storm is likely the most anticipated winter storm in the history of Minnesota. No other storm was watched so closely by so many people for so many days prior to its arrival.
February 24, 2023