December 2005 Saint Cloud Weather Summary

Cloudy Last Week of December Makes a Warm Month out of a Cold One

Despite having three weeks of below normal temperatures, December 2005 became the eighth warmer than normal December in the past 9 years. The average temperature of 18.0°F was 3.6°F above normal. December 2005 was on pace to join December 2000 as the only colder than normal Decembers since 1997. During December 1-21, the average temperature was only 11.8°F, averaging 4.1°F below normal. During this three week period, there were 14 days with a high below 20 degrees (which would be normal for January) and 8 days with a low of zero or below. The cold weather was largely the result of the snow cover from the post-Thanksgiving storm and a persistent northwest steering wind pattern that steered the coldest air in North America over the United States to the east of the Rockies.

However, the pattern changed drastically on December 22. For the last 10 days of December, the average temperature was 31.1°F, 20.5°F above normal. After the morning of December 22, the temperature never fell below 24°F and was no lower than 28°F during December 23-30. The warm weather was associated with persistent low clouds and occasionally dense fog. In fact, there was zero sunshine during the last 8 full days of December. This is the longest sunless streak Saint Cloud has experienced since the 15 consecutive sunless days in late December 1991 into January 1992.

What produced the drastic change? The cold air got used up by being dragged into middle latitudes. Then, the steering winds shifted to a west-to-east flow pattern, locking up any new cold air in far northern Canada. However, as snow melt began, that moisture got trapped near the ground, producing the low clouds and fog. Since there was snow cover throughout central Minnesota and South Dakota, there was no way for a south wind to bring drier air into Minnesota, so the clouds and very warm low temperatures remained.

Two major snowstorms (December 13-15 and December 29-30) during December pushed the total snowfall to 15.1 inches. That December snowfall was 7.3 inches above normal and ties December 1996 as the 9th highest December snowfall in 106 years of records. In fact, a glance at the 10 snowiest Decembers show the two most recent winterlike Decembers: December 1996 which had 16.2 inches of snow and December 2000 (3rd coldest December on record). All other Decembers since 1996 have been warmer than normal. In addition, this was the first December since 2000 during which a snow cover was sustained all month. The 11 inches of snow cover reported on the 16th was the deepest December snow cover since December 30, 2000 and the deepest snow cover of any month since February 13, 2004.

The December 2005 melted precipitation totalled 1.01 inches, 0.31 inch above normal. All but 0.05 inch of the precipitation was in the form of snow during the month.

Will Saint Cloud be able to break out of the mild and gloomy weather pattern? There are some signs that the steering winds will shift to the northwest by later this week, allowing somewhat colder air, but also drier air into central Minnesota. Until then, we wait under the clouds.