Click here to go to the Western Water Assessment climate dashboard. Here’s an excerpt:
Highlights
May was wetter than average across most of Colorado, adding to the above-average snowpacks in many basins. Drier than average conditions were experienced in most of Wyoming and northern Utah.
The spring runoff, in line with previous forecasts, has been above average to much above average in nearly all of Wyoming, and in northern, central, and southeastern Colorado. Below to much-below-average runoff has been observed in southwestern and south-central Colorado, southwestern Utah, and most of the eastern Great Basin.
Many gages in Colorado and Wyoming have seen record-high or near-record-high daily flows in the past three weeks, with minor to moderate flooding in some areas.
With the above-average spring runoff in the northern two-thirds of the region, reservoirs are regaining storage depleted by the last two years of dry conditions.
Atmospheric and oceanic conditions are still pointing to the very likely emergence of an El Niño event by fall. Sea-surface temperatures have continued to warm in the equatorial Pacific…
May Precipitation and Temperatures, and Current Drought
May was wetter than average across Colorado (except the southeastern quarter), southern Utah, and far southeastern Wyoming Western US Seasonal Precipitation. The month was drier than average in northern Utah and nearly all of Wyoming, though only relatively small areas saw less than 50% of average precipitation.
May temperatures Western US Seasonal Precipitation were up 3°F to cooler than average in most of Colorado, eastern Utah, and eastern Wyoming, and up to 4°F warmer than the monthly average, in the remainder of Wyoming and Utah.
The latest US Drought Monitor US Drought Monitor, representing conditions as of June 10, shows slightly less drought for the region compared to early May. Drought conditions improved in eastern and southwestern Colorado, while worsening in a smaller area of south-central Colorado. The proportion of the region in D2 or worse drought: Utah unchanged at 22%, Colorado at 17%, down from 19%, and Wyoming unchanged at zero.
Current Snowpack
Early June is typically well past the peak accumulation at even the highest-elevation SNOTEL sites, and many sites have normally melted out by this date. Thus, the numerical percent-of-median-SWE values on the Current Basin Snowpack Map Western US Seasonal Precipitation should be treated with caution. That said, the prevalence of dark blue colors (>150% of median) on the map in Colorado, Wyoming, and far northern Utah does indicate an unusually large and persistent late-season snowpack in those basins. The basins in southwestern Colorado and southern Utah that were lagging behind seasonal normals throughout the spring have completely melted out and are not shown on the map.
According to the Colorado Dust-on-Snow Program (CODOS), no more dust events have occurred since May 13, leaving the seasonal total at eight events. The latest CODOS update noted that consolidated dust layers from events D3–D8 were exposed at the snow surface during field surveys done from June 2–4 at CODOS sites at Grand Mesa, Hoosier Pass, Loveland Pass (Grizzly Peak), Berthoud Pass, Willow Creek Pass, Rabbit Ears Pass, and McClure Pass, as well as Independence Pass. With the exposed dust, snow-surface albedo (reflectivity) is unusually low, and melt rates will be above-average through the remainder of the season, leading to a steeper-than-average declining limb of the annual hydrograph.