Western US snowpack shows steep loss in satellite images

A record-warm March and an intense heat wave melted much of the western United States' mountain snowpack, leaving many basins at or near record lows and visible in before-and-after satellite images.

A record-warm March and an intense heat wave have melted much of the western United States' mountain snowpack, and the change is visible in before-and-after satellite images. Snowpack normally peaks in late March or early April, but this season many ranges appear to have peaked about a month earlier before rapid melt. California and the Colorado River Basin show especially low measurements, and researchers cited an attribution study linking the heat wave to human-caused warming. Observed details: - The reporting describes a heat wave that began about two weeks earlier and pushed temperatures as much as 30 degrees above normal, which drove rapid snowmelt in the Colorado Rockies. - California's snow water equivalent dropped to 22% of average over the last month, and Sierra Nevada snow cover declined from 52% on March 1 to 21% by March 24. - Snow water equivalent is reported as the lowest on record across both the Lower and Upper Colorado River Basins; those basins feed the Colorado River, which supplies water to over 35 million people across seven states. - The article notes some snow is in short-range forecasts, but the already low baseline levels and lingering warmth make significant snowpack recovery difficult in the near term. Summary: The rapid loss of mountain snow reduces the seasonal reservoir that typically supports rivers, reservoirs and agriculture into summer, and it can increase seasonal wildfire risk. The reporting notes this could deepen the region's drought and affect water management for the Colorado River. Undetermined at this time.