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Published March 24, 2011
Southwest Snowpack(updated 3/17/11)
Data Source(s): National Water and Climate Center, Western Regional Climate Center
Snowpack levels continued to drop over the past month as very little precipitation fell across most of Arizona and New Mexico. The current La Niña event drew winter storms northward into the Upper Colorado River Basin states of Utah, Colorado, and Wyoming. As of March 17, nearly all Snow Telemetry (SNOTEL) stations in Arizona and New Mexico measured below-average to well below-average snow water equivalent (SWE) (Figure 8). SWE in the central Mogollon Rim area was the lowest in Arizona, measuring only 15 percent of average. The Verde River Basin measured the highest SWE in the state, with only 53 percent of average. In New Mexico, the San Miguel, Dolores, Animas, and San Juan river basins in the northern part of the state had near-average levels measuring 92 percent of average SWE. The snowpack in the southern portion of the state fared worse, with the Mimbres, San Francisco, and Gila river basins containing only 8, 23, and 28 percent of average SWE, respectively. While many river basins in the region measured near-record levels of snowpack during the winter months of 2010, this winter was almost completely opposite.
Forecasts show a weakening La Niña pattern but still call for elevated chances of below-average precipitation for the spring months. As a result, streamflow forecasts anticipate below-average to well below-average runoff from most basins in the Southwest, except those with headwaters in the Rocky Mountains to the north of Arizona and New Mexico where precipitation has been higher this winter.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 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
- 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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