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Published May 23, 2012
Southwest Snowpack(data through 5/17/12)
Data Source(s): National Water and Climate Center, Western Regional Climate Center
Below-average precipitation and warmer-than-average temperatures across most of the Southwest after December caused the water contained in snowpacks, or snow water equivalent (SWE), to be persistently below average. Streamflow forecasts, which partly reflect the amount of past precipitation, were similarly below average for most of the winter.
Currently, snowpacks in Arizona have completely melted, while all but a few SNOTEL monitoring sites that measure SWE in New Mexico are reporting no snow (Figure 8). Some of the sites in both states completely melted about four weeks earlier than average. The only basin in Arizona, New Mexico, Colorado, Wyoming, and Utah with near-average snowpacks is the Cimarron watershed in New Mexico. However, the Natural Resources Conservation Service (NRCS), which administers the SNOTEL sites, cautions that the data in this basin may not be accurate. The Cimarron watershed was one of only two basins in both Arizona and New Mexico to receive more than 100 percent of average precipitation between October 1 and May 17.
In the Upper Colorado River and Rio Grande basins, no watersheds had more than 90 percent of average precipitation between October 1 and May 17; most basins received less than 80 percent. Consequently, all monitoring stations in Colorado, Utah, and Wyoming currently report well below-average SWE and streamflow forecasts for both the Colorado River and Rio Grande are well below average (see Streamflow Forecast).
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.
The CLIMAS Web site contains official and non-official forecasts, as well as other information. While we make every effort to verify this information, please understand that we do not warrant the accuracy of any of these materials.... Read full disclaimer