What is Snow Drought?
Snow drought is defined as period of abnormally low snowpack for the time of year, reflecting either below-normal cold-season precipitation (dry snow drought) or a lack of snow accumulation despite near-normal precipitation (warm snow drought), caused by warm temperatures and precipitation falling as rain rather than snow or unusually early snowmelt. (AMS Glossary of Meteorology)
Current situation and impacts in the West
May 10, 2018:
Early May is well into the snowmelt season in the Western US. Cold late season storms can bring snowfall, but tend to slow the melt process rather than build the snowpack. Currently, snowpack remains well below normal in southern Oregon, California, southern Idaho, Utah, southern Colorado, and northern New Mexico. Many sites in these regions are at less than 25% of normal, and many lower elevation sites have already melted out with no snowpack remaining. A sharp contrast is found to the north in Washington and the northern Rockies where most sites have well above normal snowpack. In Central Alaska snowpack is above normal while most sites in the Kenai Peninsula and Chugach Mountains in the southern part of the state are below normal. [Next update scheduled for May 24, 2018]
USDA Natural Resources Conservation Service (NRCS) percent of 1981-2010 median snow water equivalent (SWE) over the western U.S. (left/top) and Alaska (right/bottom) for May 7, 2018. Only stations with at least 20-years of data are shown. For an interactive version of this map, including percent of period of station record median SWE, please visit NRCS
SNOTEL basin-wide average SWE time series for the San Miguel, Dolores, Animas and San Juan River basins in southwest Colorado. Black line is this year, lighter red line is the average, and darker red line is the median. The region peaked in late March at 52% of normal peak SWE, and is currently at only 15% of normal SWE for this date.
SNOw Data Assimilation System (SNODAS) percent of average (2004-2018) snow water equivalent (SWE) for May 6, 2018. Image made using Climate Engine. Please note the shorter historical period of this dataset compared to the station data above.