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Published March 21, 2012
Southwest Snowpack(data through 3/15/12)
Data Source(s): National Water and Climate Center, Western Regional Climate Center
Below-average precipitation across most of the region in the last month caused snowpacks to decrease in Arizona and New Mexico. In Arizona, the amount of water contained in snowpacks, or snow water equivalent (SWE), measured by snow telemetry (SNOTEL) stations was less than 50 percent of average in all but one river basin as of March 15 (Figure 8). The central Mogollon Rim and the Verde River Basin measured only 15 and 20 percent of average, respectively. The San Francisco Peaks had the highest SWE, at 81 percent of average—down 14 percent from one month before. A recent storm beginning on March 18 and not reflected in the SWE values reported here will help boost snowpacks in Arizona but likely will not push values above average in many places.
In New Mexico, seven of the 11 river basins reported in Figure 8 had well below-average snowpacks. The San Francisco and the Gila river basins, located in the southwest corner of the state, measured 50 percent of average. The Zuni/Bluewater River Basin in central New Mexico was the only basin with above-average SWE, measuring 121 percent of average. Northern areas benefited from a few storms in February, but high winds increased sublimation, especially at lower elevations. Sublimation is the transformation of snow to water vapor, which reduces snowpacks.
Colorado and Utah also have below-average SWE, with all but one basin reporting below-average snowpacks. Snowpacks may melt earlier than average this year, as the NOAA-Climate Prediction Center (CPC) forecasts above-average spring temperatures. There is still ample time for spring storms to blanket the mountains in snow, although forecasts call for equal chances for above-, below,- or near-average precipitation.Notes:
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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