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Published November 23, 2010
Southwest Snowpack(updated 11/18/10)
Data Source(s): National Water and Climate Center, Western Regional Climate Center
Where snow has fallen in the high country it has melted. As of November 18, the snowpack conditions in Arizona and New Mexico were exhibiting less-than-average snow water equivalent (SWE) in most basins, according to the Natural Resources Conservation Service’s (NRCS) snow telemetry (SNOTEL) monitoring stations (Figure 8). The average SWE for Arizona is approximately 20 percent of the 1971–2000 average. The San Francisco River Basin reports the lowest SWE values in the state, with approximately 5 percent of average.
In New Mexico, most basins have reported less than 42 percent of average. SWE in the Mimbres River Basin, however, is more than 600 percent of average because 0.3 inches of SWE have fallen; the historical average is only 0.1 inches.
The Rocky Mountain states to the north, which supply most of the water in the Colorado River and Rio Grande, have experienced near-average early winter snowfall. The NOAA–Climate Prediction Center’s winter outlook for December–February shows a greater chance for above-average temperatures and below-average precipitation for many parts of Arizona, New Mexico, Utah, and Colorado through the winter and early spring. These forecasts are based on the current moderate to strong La Niña event. These events tend to bring drier and warmer-than-average conditions to the region.
Snowpack telemetry (SNOTEL) sites are automated stations that measure snowpack depth, temperature, precipitation, soil moisture content, and soil saturation. A parameter called snow water content (SWC) or snow water equivalent (SWE) is calculated from this information. SWC 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 SWC than light, powdery snow.
This figure shows the SWC 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 SWC measurements made by the Natural Resource Conservation Service.
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, Managing Editor, CLIMAS Associate Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Dollin, CLIMAS Publications Assistant
- Dave Dubious, New Mexico State Climatologist
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
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