Early Accumulation in Southern Basins, Sustained Development in Northern Colorado

Denver, CO – January 10th, 2025 – Statewide snow water equivalent (SWE) is 105 percent of the 1991-2020 median as of January 7^th. For context, SWE at this time last year was 76 percent of median, reflecting very different early season conditions. A notable storm during the first week of January 2025 delivered higher amounts of snowfall to northern basins. SNOTEL site Tower recorded impressive gains, with a SWE increase of 6.3 inches. Statewide, streamflow forecasts at the 50 percent exceedance probability are 99 percent of median. Water year to date precipitation as of January 1st is above normal at 108 percent of median and dropped to 105 percent of median on January 7^th.  

Early season storms brought snowfall to southern basins, leading to above average accumulation by mid-November. The combined San Miguel-Dolores-Animas-San Juan (SMDASJ) reached 171 percent of median by mid-November before tapering to 87 percent of median following several dry weeks. Despite recent dry weeks, late season monsoonal precipitation improved soil moisture levels, enhancing the basin’s overall runoff efficiency. At the start of the 2025 water year, soil moisture levels in southern basins ranged from 90 percent to 130 percent of median.  The Upper Rio Grande also had a strong early season start and peaked at 203 percent of median snowpack in November and is now at 82 percent of median. The Arkansas basin is currently at 103 percent of median, maintaining above normal snowpack levels through December.  

Between October and early November, statewide precipitation reached 110 percent of median, with southern basins benefitting most from consistent storms. During this period, basins like the SMDASJ and Upper Rio Grande were well above normal at 186 and 168 percent of median, respectively. In contrast, the South Platte and Laramie-North Platte basins received 55 and 65 percent of October median precipitation, respectively. November precipitation continued a varied trend highlighting a boost in eastern basins such as the South Platte at 167 percent of median and the Arkansas at 209 percent of median. Although December conditions remained dry for most basins, with statewide 30-day precipitation at 74 percent of median on January 1st, northern regions received relatively higher precipitation. For this 30-day period on January 1st the South Platte is at 100 percent of median, the Laramie-North Platte at 103 percent and the Yampa-White-Little Snake at 95 percent of median.  

Streamflow forecasts range from 82 percent in the Laramie-North Platte to 107 percent in the Arkansas basin at the 50 percent exceedance probability. While many forecasts remain near or slightly below median, the range of exceedance probabilities illustrates varying levels of uncertainty across basins. “January forecasts also have the widest range of exceedance probabilities, given that there is still much snow accumulation season to come, so as always we encourage you to consider the full suite of exceedance probabilities in addition to the 50%,” noted Karl Wetlaufer, NRCS forecast hydrologist, emphasizing the importance of monitoring future conditions. Another good reminder to consider the full suite of exceedance forecasts rather than focusing solely on median values when interpreting potential outcomes. 

As of January 2025, reservoir storage across Colorado stands at 93 percent of median statewide, a slight decline from the same time last year but not drastically lower. Reservoir levels reflect carryover from last season, with many basins showing relatively stable conditions. The Arkansas and Upper Rio Grande basins, report 114 and 124 percent of median storage, respectively, highlighting increased storage compared to the previous year. Conversely, the Gunnison and SMDASJ basins report below median storage. “Reservoir levels at this time of year are more of a baseline rather than a predictor, as they depend on upcoming snowmelt contributions during spring runoff,” notes Nagam Gill, NRCS hydrologist. 

* San Miguel-Dolores-Animas-San Juan River basin 

* *For more detailed information about January mountain snowpack refer to the  January 1st Colorado Water Supply Outlook Report. For the most up to date information about Colorado snowpack and water supply related information, refer to the Colorado Snow Survey website.