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INTERMOUNTAIN WEST CLIMATE SUMMARY, JANUARY 2008 Intermountain West Snowpack data through 12/31/07 January 1 snowpack conditions are below average for most of the Intermountain West Region, with the exception of several southern basins in Colorado and Utah (Figure 5). In water year 2008, there was above average snowfall in October in Colorado and northern Utah, but this melted out during a warm Novem- ber. Then, early December brought several large storms to the southern mountains in both Utah and Colorado, which are the only areas in the region with above average snowpack now. In Colorado, the southern basins of the San Juan, Rio Grande, and Arkansas Rivers have sub-basins with above 150% of average SWE. Utah's highest SWE is in the Sevier River basin at 115% of average. In contrast to these basins, northern Colorado, north- ern Utah and most of Wyoming are below average. Wyoming's North Platte River basin is above average, but the rest of the state ranges from 58- 102% of average SWE. This pattern of above average snowfall in the south and below average snowfall in the north is opposite of typical La Nina years. The teleconnection between La Nina and below average snowfall in southern Utah is especially strong, but this year is proving to be different from past La Ninas. For more information about the current status of La Nina, see page 16. Notes Snow water equivalent (SWE) or snow water content (SWC) refers to the depth of water that would result by melting the snowpack at the measurement site. Snowpack telemetry (SNOTEL) sites are automated stations operated by NRCS that measure snowpack. In addition, SWE is measured manually at other locations called snow courses. SWE is determined by mea- suring the weight of snow on a "pillow" (like a very large bathroom scale) at the SNOTEL site. Knowing the size of the pillow and the density of water, SWE is then calculated from the weight mea- surement. Given two snow samples of the same depth, heavy, wet snow will yield a greater SWE than light, powdery snow. SWE is important in predicting runoff and streamflow. Figure 5 shows the SWE based on SNOTEL and snow course sites in the Intermountain West states, compared to the 1971- 2000 average values. The number of SNOTEL or snow course sites varies by basin. Basins with no SNOTEL sites or incomplete data are designated in white on the map. To see the locations of individual SNOTEL sites, see each state's water availability page. > 150 % 131 - 150 111 - 130 91 - 110 Figure 5. Snow water equivalent (SWE) as a percent of average for available monitoring sites in the Intermountain West as of January 1, 2008 (NRCS). 71 - 90 51 - 70 <50 Incomplete Data On the Web · For graphs like this and snowpack graphs of other parts of the western U.S., visit: http://www.wcc.nrcs.usda.gov/snowcourse/snow_map.html. · For snow course and SNOTEL data updated daily, please visit one of the following sites: River basin data of SWE and precipitation: http:// www.wrcc.dri.edu/snotelanom/snotelbasin. · Individual station data of SWE and precipitation for SNOTEL and snow course sites: http://www.wcc.nrcs.usda.gov/snowcourse/snow_rpt. html or http://www.wcc.nrcs.usda.gov/snotel/ . · Graphic representations of SWE and precipitation at individual SNOTEL sites: http://www.wcc.nrcs.usda.gov/snow/snotel-data.html. RECENT CONDITIONS I 8