NOAA's National Centers for Environmental Information
During December, above-average temperatures were observed across the Southwest and parts of the Rockies, Great Plains, and Southeast while below-average temperatures were observed in the Midwest and Northeast. Below-average precipitation was observed for a large portion of the Lower 48, particularly the West, Central Plains, Midwest and parts of the Northeast. Above-average precipitation was observed in the Northern Rockies and Lower Mississippi Valley. The warm and dry conditions in much of the West limited snow totals for many locations, except for the Northwest and Northern Rockies where numerous Pacific storms brought heavy precipitation and mountain snow. Several winter storms also impacted the Midwest with a mid-December winter storm impacting parts of the South, bringing snow from the Southern Texas to the Maine. According to NOAA's National Snow Analysis, on December 1st, 9.2 percent of the contiguous U.S. had snow on the ground — the highest elevations in the West, parts of the Upper Midwest and far northern New England. The monthly snow cover peaked on December 25th with 49.0 percent of the nation having snow on the ground. The month ended with 41.9 percent of the Lower 48 snow covered — the Northwest, Northern Rockies, Northern and Central Plains, Midwest and the Northeast.
According to NOAA data analyzed by the Rutgers Global Snow Lab,the monthly snow cover across the contiguous U.S. was 1.06 million square miles, 120,000 square miles below the 1981-2010 average. This was the 20th smallest December snow cover extent in the 52-year satellite record and smallest since 2014. Above-average snow cover was observed for the Midwest, Northeast, Northern Rockies and parts of the Southeast. Below-average snow cover was observed in the Southwest, Central and Southern Rockies and the Great Plains.
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. As a result of several strong Pacific storms slamming into the Northwest during December, on January 1st, near- to above-average snowpack was observed in the northern Cascades with above-average snowpack totals for the Northern Rockies. Some locations in Idaho, Montana and Wyoming had mountain snowpack more than 180 percent of normal for the date. Most other locations across the West had very low snowpack totals with less than 25 percent of normal snowpack for the southern Cascades, the Great Basin, Southern Rockies and Sierra Nevada Mountains. Near-normal snowpack was observed in the Central Rockies. In Alaska, below-average snowpack was observed in southern parts of the state with near- and above-average snowpack across central Alaska.
Significant Events
On December 8th–10th, a slow moving low and associated cold front brought heavy snowfall from areas of southern Texas to the Northeast. Heavy snow was observed in parts of the Southeast with over 10 inches of snow reported in parts of Alabama, Georgia and the Carolinas. The heaviest snow totals, reaching 18 inches in some locations were reported in western North Carolina. Further to the south and west, more than six inches of snow was reported in Texas, Louisiana, Mississippi and Tennessee. In the Northeast, snow total were generally in the six-to-ten inch range. Heavy snowfall across the South of this magnitude is unusual, but not unpreceded. The snow totals in southern Texas were not record-breaking, but did rank among the 10 highest for Corpus Christi, Victoria, and Laredo. Numerous impacts resulted from the storm including cancelled flights, closed roads and closed schools.