Extreme Cold/Wind Chill — Mille Lacs, Minnesota

2021-02-14 · Mille Lacs, Minnesota

Event narrative

Several sources of weather sensors provided wind chill values during this prolonged cold snap. The lowest wind chill value of -43F occurred near Milaca at 0500 LST.

Wider weather episode

During the first week of February, an Arctic air mass moved southward across the Upper Midwest and continued through the middle of the month. The core of the cold air remained centered across south-central Canada before slowly weakening and moving off to the east after the weekend of February 13th and 14th. Several days of well below normal temperatures, combined with subtle wind speeds, generated periods of wind chill values below -35F. Before the weekend of February 13th/14th, there was a period around the 7th/8th where wind chill values averaged near -35F around Benson, Willmar, and Alexandria. The bulk of the lowest wind chills, when combined with temperatures dropping to around -20F to -30F, were Saturday night through Sunday morning, February 13th/14th. The strongest wind speeds occurred in the southwest where the pressure gradient was highest. Wind speeds in this area averaged 10 to 20 mph Sunday morning with wind chills near -45F to -50F as temperatures fell to -20F. Other areas of west-central to south-central Minnesota had similar wind chill values which averaged between -35F and -45F. Farther to the east, where wind speeds were not as strong, but temperatures fell to near -20F Sunday morning, so wind chill values averaged between -35F to -40F, especially early Sunday morning as the sun rose and mixing in the boundary layer allowed for higher wind speeds near the surface.

A secondary surge of low wind chill values occurred late Sunday and into Monday morning February 15th, especially across west-central Wisconsin where wind speeds were slightly higher based on the tighter pressure gradient. Actual temperatures were much lower and winds were lighter. However, even a slight 5 to 8 mph wind speed caused wind chill values to drop below -35F for several hours.

Wind chill values were obtained from ASOS, AWOS, MnDOT, and other private weather wind sensors throughout central and southern Minnesota.

The following are some of the lowest wind chill values during the height of the cold snap:

-50F at Glenwood, Minnesota.

-50F at Morris, Minnesota.

-49F at Alexandria, Minnesota.

-47F at Benson, Minnesota.

-47F at Clara City, Minnesota.

-47F at Sauk Centre, Minnesota.

Source: NOAA Storm Events Database, event_id 932917. Narrative written by the NWS forecast office that issued the report.