We spend a lot of time thinking about snow in our mountains, because Colorado is a headwaters state, and the water stored in that snowpack ends up serving ecosystems, farms, and millions of people not just in Colorado but in all directions. As we progress toward the end of February, the overall picture of Colorado’s mountain snowpack comes into much clearer focus. As of February 20th, the snow water equivalent (SWE) in Colorado’s mountains, as measured at SNOTEL stations, was 97% of the median value for this day, compared to the 1991-2020 period. The northern mountains were a little bit above average (for example, the Yampa-White basin was at 104% of average), and the southern mountains a bit below (88% of median for the mountain areas feeding the Rio Grande river).

Snow Water Equivalent percent of the 1991-2020 median at Colorado SNOTEL stations, including values aggregated over the major river basins. Obtained from the USDA NRCS Interactive Map.

The state of the snowpack at this point in the winter can be characterized as pretty ok. Certainly much better than some of the drought years over recent decades, but also nowhere near the huge snows that fell last year across Colorado. (At this time last year, we were sitting at about 120% of average statewide.)

The snow accumulation season started quite slow: most locations were lagging well behind the average snowpack, with a few sites near record lows, in early January. But then a major storm cycle in mid-January gave a huge boost to the snowpack, bringing it back within shouting distance of the average. February has been a more typical month in the mountains, with a steady string of storms, some hitting the northern ranges and others benefiting the south. That brings us to the decent position we’re in now: not amazing, but not too bad either.

Time series of snow water equivalent for the state of Colorado. Water year 2024 (the current year) is shown by the black line, with the 1991-2020 median in the green line, the median peak shown by the “x”, and the historical range shown by the color shading. From the USDA NRCS Colorado Snow Survey.

How much do the current conditions tell us about where we’ll end up?

It turns out that for the statewide average, the snowpack value on February 20th correlates very strongly with the eventual peak, as shown in the graph below. (The correlation coefficient is 0.85, for those familiar with that metric.) In past years when the snowpack was similar in late February to where it is this year, the eventual peak tended to be a little below average. Only one year when the February snowpack was similar to this year did the seasonal peak end up well above average (1998…more on that in a second.) There’s still about a month and a half until the typical peak (a little less in the south, more in the north), meaning there’s still time for things to change. In a typical year, a whole lot of snow falls between late February and mid-April! But it’s also uncommon for a huge change in the overall seasonal picture after this time in the winter.

Comparison of Colorado statewide SWE on February 20 (on the horizontal axis) with the water year peak SWE (on the vertical axis), in inches. The median peak is shown by the dashed line at 17″. This year’s value is shown by the hashmark on the horizontal axis, with question marks indicating where this year could potentially end up. A few past years are highlighted. The correlation between the February 20 and peak values is 0.85. Data from 1987-2024, obtained from USDA NRCS.

So, what should we expect for the rest of the winter and spring? Although snowpack is just a bit below average, the water supply forecasts for the Upper Colorado River Basin look even lower. The Colorado Basin River Forecast Center’s mid-February update projected that April-July streamflow into Blue Mesa Reservoir along the Gunnison River will be 88% of average. For this reservoir—Colorado’s largest—that would be a decent outcome. However, the projected flow into Lake Powell is only 77% of average. Lake Powell rose above its historic lows after the big snows last year, but is still far below average levels (let alone being filled.)

There are a couple of wild cards to consider. One is that we remain in El Niño conditions, which tends to increase the odds of a wet and snowy spring (see Figure 2.12 here). Recall the reference above to 1998, when snowpack that was just ok in February ended up well above average by late April. That was a strong El Niño similar to this year. The CPC monthly outlook for March does tilt toward wetter-than-average conditions, so that is a possible reason for hope.

NOAA Climate Prediction Center monthly outlook for precipitation in March 2024. From https://www.cpc.ncep.noaa.gov

On the flip side, the long-term trend toward warm springs and earlier melts in the mountains continues as the climate warms, which could alter the eventual water supply as well. As pointed out in this post, the biggest reason for errors in streamflow forecasts is the fact that we don’t know what’s going to happen with the weather over the next couple months! So, while history and these outlooks give some useful hints, as usual we will just need to wait and see what happens.

By Russ Schumacher

I have served as Colorado State Climatologist and Director of the Colorado Climate Center since 2017. I am a professor of atmospheric science at Colorado State University, with research and teaching interests that include extreme precipitation, weather prediction, the climatology of precipitation, and Colorado’s weather and climate.