This winter, so far, has been highlighted by mild temperatures, rare snow showers, scraggly snow banks, and brown patches of grass. Long-time outdoor sporting events that rely on the snow have been cancelled, postponed, or moved to different locations because of thin ice. The deepest snowpack recorded in the Twin Cities so far this winter was 4 inches on the morning of December 4th and it has consistently been below 2 inches for the last 6 weeks. As of the morning of January 31st, the Minneapolis-Saint Paul International Airport recorded only 1 inch of snow on the ground. Last winter, we woke up on the morning of January 31st with 5 inches of snow. Through the end of January, we’ve only received 14.9 inches of snow at the airport, compared with 60.4 inches last winter! However, the thin snow cover over Minnesota and northern Iowa still had a profound effect on temperatures over the last few days, even if it still did get into the 40s.
Highs over southern Iowa soared into the mid-60s, while much of Minnesota and northern Iowa were stuck in the 30s and 40s. In fact, while it was a warm 44 degrees in the Twin Cities and 42 in Mason City, IA on Monday afternoon, the mercury soared to 61 degrees in Ames, IA, just 90 miles south of Mason City. The most significant aspect of the large temperature difference between Minnesota and southern Iowa was the fact that no fronts (cold front, warm front, etc.) were present anywhere within the region. These temperature differences lined up exactly with the distribution of snow cover over the region. Mason City reported 7 inches of snow on the ground on Monday morning, while Ames was completely snow free only 90 miles away. Because of the persistent snow cover in northern Iowa and Minnesota, most of the energy from the sun went into warming up the snowpack (up to freezing so it can melt) and melting snow, rather than warming the ground and the air. As a result, temperatures were mired in the 40s rather than soaring into the 60s throughout much of the region. The warm air mass that moved into the area from the southern half of the country was also cooled as it passed over the snowpack, dropping its temperature about 20 degrees. Such large temperature differences are common in the region during the spring, when warm air masses from the southern U.S. move into the region and distinct boundaries in the snow pack exist.