Snow Drought Current Conditions and Impacts in the West

The big story at the moment is the abundance of snow, not the lack of snow, across a large swath of the West. An almost continuous barrage of atmospheric rivers, beginning in the last few days of December, have made landfall in central and northern California, spreading copious amounts of precipitation (including mountain snowfall) in the Sierra Nevada, Great Basin, and parts of the Upper Colorado River Basin. These storms have been largely beneficial for drought improvements, but excessive rainfall has caused major flooding in parts of California. Snow water equivalent (SWE) is currently at 200% to over 300% of normal for much of this region, with record high SWE for this time of year at a number of SNOTEL sites in the Sierra Nevada. Even more encouraging is that many locations, especially at higher elevations, have already exceeded water year peak SWE values that typically occur from mid-March to mid-April. One example is Mammoth Pass, California, in the eastern Sierra Nevada, which currently has 37.4 inches of SWE, 314% of median for the date, and 104% of median water year peak. 

All that said, there is still a small spatial extent of snow drought in isolated regions. The Sangre De Cristo Mountains, straddling the New Mexico–Colorado border, is one of those regions. SWE at most SNOTEL sites in the Sangre De Cristo Mountains is in the range of about 40%–70% of normal. This area has been in the southeast of the storm track with minor impacts but not nearly the amounts of snow that have fallen further north and west. The snowpack in southeastern Arizona and southwestern New Mexico in the Gila Mountains has improved substantially since mid-December. The northern Rockies is another region to keep an eye on, with many locations at slightly below normal SWE (75%–90%) and a number of locations in northern Idaho, western Montana, and northern Wyoming in the 15th–30th percentile.

In Alaska, where observations are limited, most SNOTEL sites indicate that SWE is near normal to above normal, with very limited snow drought. An interesting pattern that set up in early December brought heavy snowfall to the Anchorage area but much less snow a short distance to the southeast around Turnagain Pass. SWE at the Anchorage Hillside SNOTEL site is currently 157% of normal SWE, whereas SWE at Mt. Aleyska, less than 50 miles away, is at just 71% of normal SWE. Snowpack is also below normal along the south side of the Alaska Range with very little snowfall since mid-December.

Stations with SWE Below the 30th Percentile

Snow Water Equivalent Percent of Water Year Peak

Daily SWE at Mammoth Pass, California

* Quantifying snow drought values is an ongoing research effort. Here we have used the 30th percentile as a starting point based on partner expertise and research. Get more information on the current definition of snow drought here. 

For More Information, Please Contact:

Daniel McEvoy
Western Regional Climate Center
Daniel.McEvoy@dri.edu

Amanda Sheffield
NOAA/NIDIS California-Nevada Regional Drought Information Coordinator
Amanda.Sheffield@noaa.gov

Britt Parker
NOAA/NIDIS Pacific Northwest Regional Drought Information Coordinator
Britt.Parker@noaa.gov