The peak in mountain snowpack (the amount of water stored in the snow) is typically in early April in Colorado’s southern mountains, and later in April in the north. Looking at the conditions right now, we’ve almost certainly passed the peak for this year. And the numbers don’t look good, especially in the southern part of the state.

To recap how we got here, the snow season got off to a huge start in November, then came one of the driest winters on record in the mountains. March was a little more active, but was also quite warm.

As of April 13, the mountains that feed water into the southern river basins had less than half of the usual snowpack they would usually have on that date. The numbers aren’t as bad in the northern mountains, with 80-90% of average snowpack. But keep in mind that in the northern basins, the average is still going *up* in mid-April, but the snow this year is already starting to decline. So with warm, sunny days and no new snow falling, these numbers are also going to get smaller as April goes on. From the perspective of “snow drought” and water supply for the coming summer, this is not what you want the snowpack map to look like in mid-April.

Since we’re almost certainly past the peak, we can also see how this year’s peak stacks up compared to past years. In many locations, these numbers make the picture look even worse. This map shows the percentile rank of the peak snow water equivalent (SWE) compared to all past years at each SNOTEL station, focusing on southern Colorado and northern New Mexico. On this map, if you see 50 it means it’s right in the middle of the historical distribution; 100 means the highest on record, and 0 the lowest. Through the San Juan and Sangre de Cristo mountains, many stations are below the 10th percentile, and several had their lowest or 2nd-lowest peak snowpack since they were installed (most were established in the late 1970s or early 80s).

For example, at the Upper San Juan SNOTEL station near Wolf Creek Pass, it’s the 2nd-lowest peak SWE since the station was established in 1979, worse than even 2018 (which was a terrible drought and wildfire year in southwestern Colorado), though still ahead of the historic 2002 drought year. With record-warm conditions in recent days and sunny conditions that increase sublimation, what snowpack remains is going to continue declining rapidly.

In the northern parts of the San Juan mountains, the snowpack numbers aren’t quite as bleak, but overall it is shaping up to be a very poor year for streamflow and water supply in southwest Colorado (and throughout the southwest US). The water supply forecasts from the Colorado Basin River Forecast Center bear this out. The predicted river flows for April through July (when the vast majority of the annual flow occurs) are not so bad in the headwaters of the Colorado River in Colorado, where the projection is for 80-100% of average water supply. But in the southwestern Colorado rivers like the Animas, San Juan, and Dolores, flows will be much lower than average, and Lake Powell is expected to see less than 70% of its average inflow. Lake Powell levels aren’t quite at the historic lows from a few years ago, but the lake is still far lower than its historical average and will likely see further declines this year with poor inflows and continued high demand for water.

And the situation on the Rio Grande River may be even worse. As shown above, the snowpack in the Upper Rio Grande basin in Colorado is at less than half of average, and in New Mexico it’s even worse. Upper Rio Grande streamflow forecasts from NRCS are generally 50-70% of average, and farther downstream in New Mexico there may only be a quarter of the usual water. I attended the Rio Grande State of the Basin symposium in Alamosa a couple weeks ago, and the mood among the water-savvy crowd was noticeably downbeat about the situation for the months to come.

Where does this fit in to recent trends?

The poor mountain snowpack and early melt-out this year align with the trends in Colorado’s southern mountains over the last 40+ years. We’ve analyzed the trends at the SNOTEL stations that have data back to at least 1979, for both the peak SWE and the date of the peak SWE. If you see opaque circles on the maps below, there is a statistically significant trend over this time period; if the circles are transparent the trend is not significant. In Colorado’s northern mountains, trends over the last 45 years are fairly modest overall, with some mixed signals. But in the southern mountains, the data make a very clear statement: snowpack is declining, and the peak is happening earlier. At many of the stations in the San Juan and Sangre de Cristo mountains, the peak SWE has declined by 3-5% per decade, and the peak has shifted 2-4 weeks earlier. (When this year’s poor snowpack gets incorporated, these trends might look even steeper.) A combination of factors are responsible for these trends, including that the 1980s were unusually wet, so the recent declines look even worse; rising temperatures globally and especially in the interior west, and increases in dust-on-snow that reduces the ability of snow to reflect sunlight. Heat waves in April, like the one we’ve experienced in recent days, don’t help the situation either, as discussed in this paper about a similar heatwave in April 2021. You might recall that we had one last year too.

The overall downward trend doesn’t mean we can’t still get years with big snowpack — some of the same locations that are near record lows this year were near record *highs* in 2019 and 2023. But the bad years are outnumbering the good ones over time.

Could there be a “Miracle May” to improve the situation like what happened in 2015? In western US weather and climate, anything is possible! But it does not appear to be very likely. Although La Niña conditions that have been in place through the winter are waning, the NOAA Climate Prediction Center outlook shows high confidence for continued drier-than-average conditions through the spring and early summer. It would be nice if we could find some better news about drought and water in Colorado to share, but right now unfortunately there isn’t much good news to find.