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Published February 22, 2012
Southwest Snowpack(updated 2/17/12)
Data Source(s): National Water and Climate Center, Western Regional Climate Center
At least five storms in December dumped copious snow in the higher elevations of Arizona and New Mexico, building above-average snowpacks. Wet conditions were somewhat unexpected given the presence of a La Niña event. However, warm and dry weather prevailed in January, causing substantial declines in the water contained in snowpacks, or snow water equivalent (SWE). Arizona and New Mexico saw their ninth and 19th warmest January since 1894, respectively, and precipitation was less than 50 percent of average across most of both states. Similarly dry conditions persisted in the first two weeks of February.
As of February 16, SWE measured by snow telemetry (SNOTEL) stations in Arizona ranged from well below average to slightly below average (Figure 8). The Verde River Basin had the lowest SWE, measuring 54 percent of average, while the San Francisco Peaks had the highest, at 97 percent of average. As a whole, SWE in Arizona measured 57 percent of average. In New Mexico, five of the 11 basins reported in Figure 8 have above-average SWE. The highest values are in the Mimbres River Basin in the southwest corner of the state, where SWE is 119 percent of average. The San Francisco River Basin, also in the southwest corner of New Mexico, had the lowest SWE, with an average of 73 percent. Since mid-November, most of Colorado, Wyoming, and Utah also have had less than 70 percent of average precipitation, and all but three basins in these states report below-average SWE.
Dry and warm conditions since the end of December likely will continue. The seasonal precipitation and temperature outlooks issued by the NOAA-Climate Prediction Center (CPC) show increased chances for below-average precipitation and above average-temperatures for most of the Southwest (see Figures 9 and 10).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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