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Published January 24, 2012
Southwest Snowpack(updated 1/16/12)
Data Source(s): National Water and Climate Center, Western Regional Climate Center
A string of storms in early to mid-December brought substantial snow to portions of the Southwest, especially in central and southern Arizona and New Mexico. One month ago, nearly all of the basins reported above-average snowpacks. Since the beginning of 2012, however, storms have been few and far between, causing the amount of water contained in snowpacks, or snow water equivalent (SWE), to decline. As of January 16, SWE measured by snow telemetry (SNOTEL) stations ranged from 74 percent of average in the Verde River Basin to 110 percent of average in both the Upper Salt and Upper Gila river basins (Figure 8). SWE in New Mexico had a larger range, from 62 percent of average in the Animas River Basin to 177 percent in the Mimbres River Basin.
December storms that dropped copious precipitation on the Southwest did not pack the same punch in Colorado, Wyoming, and Utah—states that supply most of the water to the Colorado River and Rio Grande—as much. In addition, dry conditions have reigned in these regions and in the Southwest during the last few weeks. As a result, SWE values were predominantly below average across the Upper Colorado River Basin as of January 16. For example, SWE in all of the basins in Colorado measured less than 83 percent of average, and some stations in Utah reported values as low as 37 percent of average, with 10 of 14 basins reporting less than 60 percent of average. These conditions are contributing to below-average spring streamflow forecasts for the Colorado River.
Seasonal precipitation and temperature outlooks issued by the NOAA-Climate Prediction Center (CPC) show increased chances for above-average temperatures and below-average precipitation across Arizona and New Mexico (see Figures 9 and 10). These forecasts reflect expected impacts of the current weak to moderate La Niña event.
Snowpack telemetry (SNOTEL) sites are automated stations that measure snowpack depth, temperature, precipitation, soil moisture content, and soil saturation. A parameter called snow water equivalent (SWE) is calculated from this information. SWE refers to the depth of water that would result by melting the snowpack at the SNOTEL site and is important in estimating runoff and streamflow. It depends mainly on the density of the snow. Given two snow samples of the same depth, heavy, wet snow will yield a greater SWE than light, powdery snow.
This figure shows the SWE for selected river basins, based on SNOTEL sites in or near the basins, compared to the 1971–2000 average values. The number of SNOTEL sites varies by basin. Basins with more than one site are represented as an average of the sites. Individual sites do not always report data due to lack of snow or instrument error. CLIMAS generates this figure using daily SWE measurements made by the Natural Resources Conservation Service.
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Dan Ferguson, CLIMAS Program Director
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, CLIMAS Associate Staff Scientist
- Gigi Owen, CLIMAS Assistant Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Swetish, CLIMAS Publications Assistant
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
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