January 3, 2013
Highlights
- December was generally wetter than average west of the Continental Divide, but mostly drier than average to the east
- Snowpack conditions improved in December but remain below-average across Colorado and in parts of Wyoming; snowpacks are near- or above-average in Utah and most of Wyoming
- The NOAA CPC climate outlooks now show a slight dry "tilt" for winter and early spring precipitation for the southern half of our region
December Precipitation and Temperatures, and Current Drought
December was wetter overall in our region than November and October, with most mountain regions seeing above-average precipitation for the month, including western and central Colorado, western Wyoming, and far northern Utah. There were also large areas with drier-than-average conditions, especially eastern Wyoming and most of eastern Colorado. Despite the December gains in many areas, the HPRCC Water Year Precipitation map shows that after the first quarter of the 2013 water year, nearly all of the region is drier than average, with some areas like southeastern Colorado seeing less than 50% of average October–December precipitation. December was cooler than average over most of the region, with the wetter areas generally seeing the below-average temperatures, and the drier parts of Wyoming and Utah being warmer than average. The latest US Drought Monitor, representing conditions as of January 1, shows a modest reduction in the area of severe (D2) and extreme (D3) drought conditions since late November, but the vast majority of the region is still classified in severe (D2) or worse drought: Colorado, 95%; Wyoming, 86%, and Utah, 66%.
Current Snowpack and Streamflows
As reported in the December 21 briefing, snowpacks across Colorado saw large gains in December. Even so, the NRCS Current Basin Snowpack map shows that Colorado—and southeastern and north-central Wyoming—still lag well behind average conditions for early January. In the rest of Wyoming and in Utah, snowpacks kept pace with normal accumulations during December and are near-average or slightly above average. The January 1 basinwide snowpack for the Upper Colorado River above Lake Powell was 86% of average, up sharply from 60% of average on December 1.
In the maps of current streamflows in the three states, note that most gages are now ice-affected and not reporting, as is normal for this time of year. The gages that are reporting are mostly showing normal (green) streamflows, below-normal (yellow), or much-below normal (brown) flows for the date, with very few in the above-normal categories. The Colorado River near Cisco, UT gage, was in the 13th percentile, at 76% of the median flow for December 2.
Seasonal Climate and Drought Forecasts
As reported in the December 21 briefing, the latest monthly and seasonal Climate Outlooks released on December 20 by NOAA CPC are now showing a slight tilt towards drier-than-average conditions for the winter and early spring in the southern portion of our region. The IRI's mid-December ENSO Prediction Plume shows a strong model consensus that ENSO-neutral conditions will continue through next spring, and only a slight chance of an El Niño or La Niña event emerging in that time frame. The CPC Climate Outlooks continue to show enhanced odds for above-normal temperatures for the winter and early spring season, consistent with the long-term trend towards warmer conditions. The latest CPC Seasonal Drought Outlook released January 3 once again projects that the drought conditions across our region will persist, through at least March 2013.