This time last year, Missouri was under a blanket of white snow. What a difference a year makes.
"We had more than 20 inches of snow by the end of January last year, but this year we've only had 3-4 inches so far, with Kansas City and Springfield receiving an inch or less," says Pat Guinan, climatologist with the University of Missouri Extension Commercial Agriculture Program. "December and January both averaged 4-6 degrees above normal and it looks like these seasonably mild temperatures are going to persist through the first week of February."
The winter of 2010-2011 ranked as one of the snowiest on record, but a difference in Arctic winds reversed fortunes for the beginning of the 2011-2012 winter season.
Both years encountered the impact of La Niña, colder-than-normal sea surface temperatures in the equatorial Pacific that affect weather trends, and of the Arctic Oscillation, a phenomenon of atmospheric pressure changes in the Arctic. Last winter, a negative phase of the Arctic Oscillation pushed the cold polar jet stream to the south. This year, a positive phase of Arctic Oscillation kept the polar jet stream from dipping into the eastern two-thirds of the U.S., letting Canadians keep their cold winters to themselves.
"In the positive phase, we have very few incursions of Arctic air into the United States, and that's why we've seen very persistent mild conditions through December and January," Guinan says. "The largest departure from normal temperatures has been in the northern Plains, where they've run 8-10 degrees above normal, but here in the Midwest we've seen 4-6 degrees higher."
These higher temperatures have been a benefit to some. Cattle farmers are enjoying temperatures that allow for easier winter calving. Crop farmers were working well into December completing fall tillage.
"Here in Missouri, November and December were fairly wet but January was a little bit dryer," Guinan says. "With these wetter and mild conditions we saw hardly any frost line, with soil temperatures that mostly remained above freezing. When you have no frost line and rainfall occurs, that's going to soak right into the soil profile."
The outlook for February looks to break away from the dryness of January, but remain warmer.
"It does look more active with respect to precipitation, with a significant system impacting the state with 1-2 inches of rain soon," Guinan says.
Right now, he adds, Missourians should be thankful they do not live in Alaska
"Fairbanks has had its fifth-coldest January on record, and some of the western interior areas of Alaska – Nome, for example – have experienced their coldest January ever," Guinan says. "Southern parts of Alaska are now experiencing more blizzard warnings as we start the month of February."
Find Missouri climate information through the Missouri Climate Center at http://climate.missouri.edu.