NOAA's National Centers for Environmental Information
At the beginning of November, snow cover in the U.S. was confined to the high terrain of the Rockies and Cascades, as well as portions of the northern Plains states. On November 1st, 7.1 percent of the contiguous U.S. had snow cover according to the National Operational Hydrologic Remote Sensing Center. Snow storms affecting the Pacific Northwest and Central Rockies increased the snow cover extent across the country to a maximum areal coverage of 18.6 percent on November 16th. By the end of the month, 11.2 percent of the U.S. was under snow cover. The month as a whole had snow extents significantly below average across the contiguous U.S. The average snow extent was 197,684 square miles (512,000 square km) below the long term mean, ranking November 2009 as having the 6th lowest snow extent since the satellite record began in 1965. In contrast, October 2009 was the snowiest October on record for the contiguous U.S.
The two satellite-derived images above show the daily snow cover across North America (left map) and the Northern Hemisphere (right map) throughout November 2009.
Arctic sea ice reached a record low extent for the first half of November according to the National Snow and Ice Data Center. The previous November smallest minimum extent occurred in 2007. The record was due to high pressure being anchored near the pole during October, leading to warm surface temperatures slowing the rate of freezing and anomalously strong winds breaking up existing ice. The small ice extent will have implications next summer when ice thickness will be lower, allowing the seasonal ice melt to occur faster. By the end of November, the sea ice extent had grown to a larger extent than the same period in 2007.
Heavy snowfall affected portions of northern China on November 11th and 12th. According to the Chinese Central Meteorological Observatory, the northern and central provinces of Hebei, Shanxi, Shaanxi, Shandong and Henan observed their heaviest snowfall since record keeping began in 1949. Most of the snow fell west of Beijing, but the country’s capital city accumulated about 1 inch of snow.
On November 14th through 15th, portions of Colorado experienced a significant autumn snowstorm. Accumulations ranged from 3 to 15 inches (8 to 38 cm) across northern and central Colorado, with the heaviest amounts west of Denver. Lighter snowfall amounts were reported across southern Wyoming, southwestern Nebraska, and western Kansas.