December Conundrumby Mark Lahtinen
December 18, 2012
Coming into this winter (I guess we’re not actually there yet , are we) it looked like we might be in for a repeat of last year in the Twin Cities with the dry late summer and fall, drought and 16 consecutive warmer than average months (until October). The historical record (120 years) has only had back-to-back approximately 30 inch or less seasonal snowfalls 3 times so it is about a one in 40 year occurrence. The years were 1917-18 and 1918-19 (30.8”, 25.4”), 1929-30 and 1930-31 (27.5”, 14.2”) and the last time was in 1957-58 to 1958-59 (21.2”, 19.1”). Are we overdue?
In addition, a little over a month ago Minnesota was the dry bulls-eye on the Dec-Jan-Feb climate prediction precipitation map. That has since changed and Minnesota is now the cold bulls-eye on the temperature prediction map with equal chances for precipitation.
Whump! Then we got the official 10.5 inches of snow a little over a week ago. Ten inches of snow in December (the Dec. average is 8.9 inches) should be a game changer. The 40 plus years with 10 inches or more of snow in December have had an average of about 91 days for the natural snow ski season which is 3 weeks longer than the historical average of 70 days or 10 weeks. Yahoo! In addition, 17 of 25 of the 100 plus ski-day seasons have happened in winters where the December snow was 10 inches or more – 16 of the 17 since 1950. The range of ski days in 10 inch December winters is 40 (1912-13) to 132 (the top in 1950-51). Even the one 50 F high we had on December 3 shouldn’t matter. If there is a 50 F day in the last half of December it matters more, as you would expect.
The average natural snow ski season start in 10 inch snow Decembers is about the 2nd or 3rd of December so we were about a week behind on December 9 this year.
All should be good, right?
Fly in the ointment. None of the previous 40 plus 10 inch Decembers was a top warm December so we’re entering new territory. We are currently running about 8 F above normal for December although that will be falling soon as the weather cools later this week. Top warm Decembers have an average natural snow ski season of 42 days or about 60% of normal and about 34 inches of snow instead of about 50 inches in an average winter. The ski season start is about January 6th although it is quite variable as there are starts and stops as the snow may melt and come and go.
The snow depth has gone from 9 inches on December 10 to 1 inch on December 16 at the National Weather office in Chanhassen where the data for the Twin Cities climate site is collected. This is a stop to the natural snow ski season in that area. There is more snow to the north and, again, thank goodness for snowmaking.
The 10.5 inch snowfall we had was the third largest single December snowfall on record. Curious though is that the 10 Decembers with the largest snowfall events have a slightly shorter following ski season by about 10 days (don’t know why but it’s probably not significant).
One of the weather blogs says there is no significant snowfall for the Twin Cities for the next two weeks but there may be plowable snow just after Christmas. It does sound like colder weather is coming though.
Where do we go from here? I don’t know ... but I hope it is skiing on more than just the man-made snow.