Snow Drought Current Conditions and Impacts in the West

Snow drought conditions remain over much of the Southwest U.S., Sierra Nevada, and Rocky Mountains with nearly one-third of SNOTEL stations below the 30th percentile snow water equivalent (SWE). Since the last update in early February, snowpack has improved in parts of Oregon, Utah, Colorado, and Wyoming. However, SWE deficits were quite large prior to these improvements with snow drought persisting in some areas even with the added snowpack. For example, February brought a series of cooler, wet storms that relieved warm snow drought concerns over some of Oregon. However, the southwest and southeast regions of the state remain below normal for snow accumulation and most likely will not achieve historic peak snowpack this season. Utah also received beneficial snow from a major storm cycle in mid-February but not enough to reach normal snowpack conditions.

The greatest area of snow drought expansion and degradation has been in the Sierra Nevada. No large storms (for Sierra Nevada standards) have occurred since the strong atmospheric river in late January. Some weak-to-moderate storms occurred in February and early March but not enough to keep up with climatology, leaving most Sierra Nevada stations below the 30th percentile SWE. Conditions degrade from north-to-south with a number of locations in the Southern Sierra below the 10th percentile SWE.

A major storm occurred March 12-14, bringing heavy snow and substantial SWE increases to the Front Range, Colorado, eastern Wyoming, and north slope of the Uinta Mountains in northeast Utah. The Denver airport received 27.1 inches of snow in two days, making it the fourth biggest snowstorm on record. These particular locations recovered from snow drought thanks to this storm. The South Platte River Basin, which drains the Front Range snowpack, gained 1.8 inches of SWE (when averaged over all SNOTELs in the basin) between March 13-16 and was at 100% of median on March 16. 

Precipitation totals west of the Front Range, including the headwaters of the Colorado River, were beneficial, but much lower than on the east side. For the same period, March 12-14, the Colorado Headwaters River Basin (a sub-basin of the Upper Colorado), which feeds into water supply for much of the Southwest U.S., gained only 0.8 inches of SWE and was at 89% of median on March 16. A few pockets of heavy snowfall included the Verde River catchment in central Arizona and the Mountains of eastern Utah. For most locations in the west, however, this storm provided just enough to keep up with the seasonal average, and many individual stations within the Colorado Headwaters Basin remain below 30th percentile SWE.

Most of Alaska remains free of snow drought with the exception of the Koyukuk River Basin in north-central Alaska that drains part of the south slope of the Brooks Range. Several of the March 1 snow courses in this basin with 40-50 years of record reported SWE below the 15th percentile. At the Disaster Creek snow course, with 50 years of observations, two inches of SWE were recorded at the 6th percentile (63% of median). Further south, some isolated snow courses in the Susitna and Copper River Basins are reporting SWE below the 30th percentile. 

Snow Water Equivalent (SWE) Values in the West: 30th Percentile or Lower

Accumulated Snow Water Equivalent in the South Platte River Basin and Colorado Headwaters

*Quantifying snow drought values is an ongoing research effort. Here we have used the 30th percentile as a starting point based on partner expertise. 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 and Missouri River Basin Regional Drought Information Coordinator
Britt.Parker@noaa.gov