It's been a chilly start to November to say the very least! Through the first 13 days of the month, we're running a full 3° below the long-term normals, and we're an astounding 4.5° colder than last year's pace!
What's to blame? We can look to a number of factors, but one of the easiest identifiers is the amount of snow cover already present at this early point of the season! The daily reading from NOAA's National Operational Hydrological Remote Sensing Center (NOHRSC) reveals that nearly ONE THIRD of the country has snow on the ground on November 13 (31% to be exact)!
Much of that snow cover is to our Northwest, which has been a dominant source region for our air so far early this month. In a nutshell, air has incredible difficulty heating over snow cover, due to the snow's high reflective properties... That gives these Canadian air masses, of which we've had several thus far, an added punch!
Hence, it should come as no great surprise that we've had just 3 out of November's first 13 days register above normal temperatures!
On the contrary, exactly one year ago, just 10.7% of the nation was snow covered, and that was largely over the intermountain west! Notice the lack of snow cover in Minnesota, the Dakotas, and Eastern Montana. When incoming Canadian air travels over that much bare ground, it moderates significantly before reaching our area.
By comparison, the coldest high temperature of November, 2011's opening 13 days was 41°. November, 2012 has had 3 of its first 13 days with temperatures 41° or colder, including Monday's teeth chattering 34°!