At the beginning of January, 42 percent of the contiguous U.S., including much of the West and the Rocky Mountains extending into New England, was blanketed in snow. By the 11th, warmer temperatures encroached upon the lower elevations of the western U.S. as well as the High Plains and erroded the snow cover to approximately 28 percent. Two mid-month storm systems swept down from Canada and brought new snowfall across a wide swath of the U.S. from Kansas to Pennsylvania and into the Northeast. According to NOAA's National Snow Analysis, on January 22nd, 51.3 percent of the contiguous U.S. had snow on the ground — the peak for the month. An Arctic air outbreak at the end of January brought near-record to record cold temperatures to parts of the Midwest accompanied by dangerously cold wind chills. With large sections of the Great Lakes still ice free, significant lake effect snowfall occurred across portions of the Great Lakes. By the end of January, 40 percent of the Lower 48 states was covered in snow.
U.S. January Snow Cover Extent Anomalies
Source: Rutgers Global Snow Lab
According to NOAA data analyzed by the Rutgers Global Snow Lab, the monthly snow cover across the contiguous U.S. was 1.41 million square miles, 45,600 square miles above the 1981-2010 average. This was the 24th largest January snow cover extent in the 53-year satellite record. Above-average snow cover was observed across the Rocky Mountains, High Plains, Ohio Valley and into the Northeast. Below-average snow cover was observed for much of the central and southern Plains.
February 1 Snow Water Equivalent
Melting of winter and spring mountain snowpack provides a crucial summer water source across much of the western United States. The total annual water budget for agriculture and human use in the mountainous West is highly dependent on the amount of snow melt that will occur in spring and is proportional to the amount of snow on the ground, which can be approximated by a measure of the snow water equivalent. On February 1st, below-average snow water equivalent, in many instances between 25 and 50 percent of normal, was observed across the Cascade Range in Oregon and Washington. Other areas with less than average snow water equivalent occurred across the Bitterroots and southern Rocky Mountains. Above-average snow water equivalent was observed along the Sierra Nevada range and central Rocky Mountains with some locations in Utah and Colorado reporting greater than 200 percent of normal snow water equivalent. Near- average snow water equivalent was observed across portions of northern California, Utah and central Montana and eastern Wyoming.
27 Jan NOAA-20 satellite view of "cloud streets"
over the Great Lakes. Source: NOAA
At the end of January, a significant Arctic airmass plunged into the High Plains and Great Lakes states bringing dangerously cold temperatures and wind chills. With significant portions of the Great Lakes ice-free, the cold air moved over the relatively "warm" lake water, causing the air to rise and condense. As a result, cumulus clouds form in bands parallel to the prevailing wind direction and begin to precipitate, or drop snow, on the downwind shores of the lakes. Large differences between the air and water temperatures in combination with a long fetch of ice-free lake surface can produce more intense snowfall. Grand Rapids, MI reported more than 14 inches of snow while Buffalo, NY reported 21 inches associated with this cold air outbreak induced lake effect snow.