Colorado Snowpack Approaches Seasonal Peak

Denver, CO – April 8^th, 2025 – As of April 1st Colorado’s snow water equivalent (SWE) is at 85 percent of median, compared to 112 percent on this date last year. Statewide monthly precipitation for March reached 105 percent, while water year to date (WYTD) is at 92 percent of median. March brought increased storm activity, bolstering precipitation and snowpack values, especially across western, northern and central basins. The southern half of the state remains below average, reflecting the extended period of below average precipitation from December through February. However, 30-day precipitation totals through March show improvements. The Gunnison, Arkansas, Upper Rio Grande (URG) and combined San Miguel-Dolores-Animas-San Juan (SMDASJ) basins each record above to near average precipitation for the month, with values reaching 108, 77, 86 and 117 percent, respectively. Even with the recent increase in March precipitation, snowpack remains below median in the Gunnison, Arkansas, Upper Rio Grande and combined SMDASJ basins which are at 81, 74, 56 and 63 percent of median, respectively. 

Throughout the final week of March, all basins in the state experienced snowmelt, most notably in the southern half of the state where accelerated melt occurred at many sites. In the Upper Rio Grande basin snowmelt is particularly pronounced with several sites showing both lower than average peak SWE and faster than normal melt rates. Statewide median peak SWE typically occurs April 8^th, although actual timing varies basin to basin. The Headwaters of the Rio Grande sub-basin are days away from peak with the median date around April 11^th. Following a storm over the first weekend of April the Headwaters of the Rio Grande sub-basin records a modest boost in SWE, now holding 73 percent of median and ranking in the 17^th percentile.

Colorado’s northern river basins all have near to above median snowpack ranging from 93 to 103 percent. As of April 1^st, the South Platte is at 98 percent of median snowpack, the Laramie and North Platte at 103 percent, Colorado Headwaters is at 96 percent and the Yampa-White-Little Snake at 93 percent. Each of these basins have reached approximately 84 to 91 percent of median peak SWE, with room to grow before their median peak dates in mid to late April. 

While April has the potential to deliver meaningful snowpack accumulation, it’s worth noting that many sites in southern basins have likely already passed their seasonal peak. Median peak SWE dates in these basins range from April 2^nd to April 8^th. To date, the Arkansas, URG and SMDASJ reached their highest SWE around March 23-24. Current SWE as a percent of median ranges from 47 to 71 percent in southern basins. These values reflect a notably below average snowpack and while not all sites are record breaking, there are some sites among the lowest on record or near record at several locations. Of the 198 SNOTEL and snow course sites in Colorado, 40 sites (20% percent) currently fall within the lowest 15^th percentile for their respective period of records. “These values reflect how far off some sites are from their typical accumulation and highlight the larger picture of below normal snowpack in the southern basins,” says Nagam Gill, NRCS hydrologist. SNOTEL records in this group span 9 to 47 years, while manual snow course surveys extend from 42 to 88 years of data. 

Statewide reservoir storage is at 92 percent of median and 58 percent of total capacity. While this is slightly below last year’s 100 percent of median at this time, most major reservoir across the state observe near 30 year medians. Dillon Reservoir is at 97 percent of median and 80 percent capacity and Lake Granby holds 101 percent of median at 58 percent capacity. Pueblo Reservoir is at 109 percent of median and 71 percent of capacity. The streamflow forecast at Pueblo Reservoir Inflow project 370,000 acre-feet for the April – September period or 94 percent of median and has stayed consistent from last months projections. Blue Mesa is at 96 percent of median and 60 percent of capacity. Notably below average is McPhee Reservoir at 76 percent of median and 56 percent of capacity. 

April 1 volumetric streamflow forecasts reflect snowpack and precipitation conditions across Colorado at 86 percent of median. Forecasts are near to above average for northern basins and below to much below average for the southern half of the state. Statewide, 40 percent of forecast points are at 75 or less of median and 27 percent of those points fall in the lower 25^th percentile. Navajo Reservoir Inflow forecasts a 325 kaf median departure from the period of record (POR) median. McPhee Reservoir Inflow is at 64 percent of median with a 91 kaf departure. Forecast volumes in the Colorado Headwaters, Yampa-White-Little Snake, Laramie and North Platte, and South Platte are at 96, 95, 102 and 93 percent of median seasonal streamflow volumes, respectively. In contrast, the Gunnison, Arkansas, URG and combined SMDASJ basins are forecast at 86, 87, 63 and 60 percent of median, respectively. These outlooks reflect the considerable differences in peak SWE and melt out trends already underway in the southern portion of the state. Compared to March 1 outlooks, forecast volumes decline by roughly 12 to 15 percentage points in the URG and SMDASJ basins, driven by accelerated snowmelt during late March. The variability of forecasted volumes means that relying solely on the 50% exceedance forecast may not fully capture the uncertainty in future weather. A critical consideration when reviewing these forecasts is the full suite of exceedance probabilities.

Colorado’s Snowpack and Reservoir Storage as of April 1^st, 2025

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

* *For more detailed information about January mountain snowpack refer to the April 1st, 2025 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.