Before and after satellite images show how little snow is left in the western US

By Meteorologist Dakota Smith, CNN

(CNN) — A record warm March has melted an already abysmal snowpack across the western United States, with impacts clearly visible in satellite imagery. It’s setting the stage for an especially concerning summer season for a region critically dependent on mountain snow.

Snowpack in the western US typically reaches its highest level by late March or early April, but instead it’s at record lows, meaning a host of potential impacts, including greater wildfire risk and less water availability to river basins come summer. That includes the Colorado River Basin, which has been mired in water scarcity issues for years.

The great melt-off started two weeks ago alongside an unprecedented heat wave that peaked with the country’s warmest March temperature on record. It’s still pumping out record-breaking temperatures 10 days later.

One of the West’s driest and warmest winters on record meant snowpack was already at record lows even before the climate change-fueled heat dome arrived.

Then it did, and as temperatures soared to as high as 30 degrees above normal, snowpack plummeted in the Colorado Rockies.

Typically, snowpack in the Colorado Rockies peaks in early April, but the persistent heat means this peak likely happened a month earlier than normal in the first week of March.

Even with some snow in the forecast next week, the already low snow levels and lingering warmth will make it incredibly difficult for the Rockies to see any real snowpack improvement.

In California, snow water equivalent, a measurement that monitors health of snowpack, dropped to 22% of average over the last month as record heat significantly diminished statewide snowpack.

California’s snowpack has also likely peaked about a month earlier than normal. Snow cover, the percentage of land area covered in snow, in the Sierra Nevada has dramatically decreased from 52% on March 1 to 21% on March 24.

Snow water equivalent is at its lowest on record across both the Lower and Upper Colorado River Basins. These basins feed the Colorado River, which provides water to over 35 million people, industries and crops across seven states.

As summer begins, rivers and people alike may begin to feel the impact of low snowpack as mountains become snowless and stop providing water earlier than normal.

The loss could deepen the West’s long drought and exacerbate the already contentious water negotiations along the Colorado River. If the hot and dry conditions persist, it could strain water supplies for homes, agriculture and power generation across the region.

Low snowpack in the Colorado River Basin is likely to become a more frequent issue as planet-warming pollution increases the likelihood, duration, and severity of heat waves. Climate scientists at World Weather Attribution published an analysis that found the ongoing heat wave would be “virtually impossible for this time of year” in a world without human-caused global warming.

Climate change is also shifting seasonal timing in ways that will worsen future snowpack trends. Winter is the fastest-warming season across much of the US, which will likely mean lower overall snowpack, earlier peaks and a worsening outlook for the Colorado River in the years to come.

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