NOAA's National Centers for Environmental Information
During February, below-to-much-below-average temperatures were observed from the Great Lakes to the West Coast. This, in combination with above-to-much-above average precipitation across the region, resulted in above-average snowfall. Most of the precipitation which fell across the Ohio and Tennessee Valleys was in the form of rainfall as temperatures in this region were generally above-to-much-above average for the month. According to NOAA's National Snow Analysis, the minimum amount of snow cover across the contiguous U.S. occurred on February 3rd and 4th with 33.7 percent — across the higher elevations of the western mountains, across the northern and central Plains and into the Great Lakes and the Northeast. An active storm pattern brought the snow cover to 58.8 percent on the 21st, the monthly peak. By the end of the month, 43.7 percent of the U.S. had snow on the ground — from the western mountains and Pacific Northwest to the northern and central Plains and Great Lakes and into the Northeast.
According to NOAA data analyzed by the Rutgers Global Snow Lab, the monthly snow cover across the contiguous U.S. was 1.63 million square miles, 432,800 square miles above the 1981-2010 average. This was the 4th largest February snow cover extent in the 53-year satellite record and largest since 2010. Above-average snow cover was observed across the Pacific Northwest, the Great Basin, the central and northern Plains, and the Southwest. Below-average snow cover was observed across parts of the mid-Atlantic region.
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 was observed along the Cascades, into the Bitterroot Mountains, and in parts of the Southwest. Near-to-above-average snow water equivalent was observed along the Sierras, the Great Basin, and central Rockies. During the course of the month, most of the region received an abundance of snowfall. By the end of February, snow water equivalent values of 125% to 200% of median could be found across most of the region. Below average values were observed across the northern Cascades as well as the northern Bitterroots.
Snow cover across the western U.S. in 2019 is noticeably greater than what was observed a year ago at this time. The image on the left compares snow cover across the Sierra Nevada range in California during February 2018 and February 2019. It can be seen in the NOAA visible satellite image that only the highest elevations had snow cover in February 2018. This is in contrast to the right panel, which depicts snow across the entire range and surrounding region. Some mountain resorts received more than 33 feet of snow this winter. Also notice how green the San Joaquin Valley is in 2019 as compared with the more parched 2018 image. Much of this early 2019 precipitation can be attributed to a series of atmospheric rivers which slammed into the West Coast during February. Snow cover in early 2019 shows promise for managing water resources as we move into spring and summer since much of the western U.S. annual water budget comes from this important natural resource.