Discussion on the Willmar Snowfall and some notes about the all-time Minnesota snowfall record.

This week's extraordinary snowfall in central Minnesota has led to questions concerning all-time 
snowfall extremes for the state of Minnesota. In response to these questions, we've reviewed the 
historical archives and wish to share our findings with you.

I'll begin by discussing this week's Willmar data. The National Weather Service cooperative 
observer in Willmar operates on a 24-hour observation cycle ending at 8:00 am. The snowfall 
total reported for the 24 hour period from 8:00 am on Monday, November 26 to 8:00 am on 
Tuesday, November 27 was 21.0 inches. This is the number that will appear in the official federal 
database. Although the observer made supplemental, informal observations mid-day on the 27th, 
the only 24-hour total that will be formally recognized for posterity is the 21-inch value. The 
snowfall total reported for the 24 hour period from 8:00 am on Tuesday, November 27 to 8:00 am 
on Wednesday, November 28 was 9.3 inches. Thus, the 48-hour total was 30.3 inches. I note that 
the observer (via the Weather Service) cites a storm total of 30.4 inches. It is unclear to me 
whether the additional 0.1 inch occurred prior to 8:00 am on the 26th or after 8:00 am on the 28th.

The 24-hour snowfall total of 21.0 inches and the storm total of 30.4 inches represent an 
astonishing amount of snow. However, these values were NOT Minnesota records, and in fact, 
the storm total is NOT a record for the city of Willmar. One record was broken ... the previous 24-
hour record for snowfall for Willmar was 18 inches, set March 16, 1917 and again November 30, 
1985. A multi-day storm total for November 29 - December 2, 1985 in Willmar reached 30.7, just 
nosing out this year's storm for the top spot in Willmar history. 

We have determined that the all-time 24-hour snowfall record for Minnesota is 36 inches, set on 
January 7, 1994 and reported by the National Weather Service cooperative observer at the Wolf 
Ridge Environmental Learning Center near Finland in Lake County. A storm total of 46.5 inches 
for the three day period, January 6 - January 8, 1994 is also a state of Minnesota record. The 
storm was a classic "North Shore" snow event, with northeast winds lifting water vapor from an 
ice-free Lake Superior and releasing this moisture up the slope of the "North Shore Ridge" where 
Wolf Ridge is located a few miles inland. Temperatures during the event were never higher than 
the low teen's and at times dropped below zero. Correspondingly, the water equivalent of the 
snow was quite light, totaling 1.57 inches in the 46.5 inches of snow (a ratio of approximately 30 
to 1). According to observer notes, the snow persisted for 60 consecutive hours.

The State Climatology Office previously acknowledged the Minnesota 24-hour snowfall record to 
be 28.0 inches set on April 5, 1933 at the Pigeon River Bridge near Grand Portage in Cook 
County. The single storm snowfall record was thought to be 36.9 inches set October 31 - 
December 3, 1991 at the Duluth International Airport.

In spite of the wealth of climate data available and our powerful computing resources, the 
verification of Minnesota's climate extremes can be a difficult and time-consuming process. On a 
national scale, the process became so challenging and contentious that NOAA formed a broad-
based "National Climate Extremes Committee", a group of individuals that meet to sanction new 
climate records for the United States. Our office will attempt to validate new Minnesota climate 
extremes when anomalies occur, but an accurate verification of the new records will seldom be 
available in real time. We will maintain the climate extremes section of our Web site 
(http://134.84.160.120/doc/historical/extremes.htm) to the extent that time and resources allow. 
By week's end, we will update the snowfall extremes as noted in this message.

Have a safe and healthy winter,

Greg