A recent snowstorm that blew through the Mountain West was a welcome sight for states facing extreme drought. But across the southern half of the region, it may not have been as beneficial as it looks.
That’s because the storm came with a cold snap, and snow that forms in that extremely cold air doesn’t hold as much moisture.
“As temperatures get very, very cold, we tend to see precipitation in the form of snow that holds less moisture to the same given depth,” said Jordy Hendrikx, who directs the snow and avalanche lab at Montana State University.
Hendrikx said as a simple rule of thumb, every 10 inches of snow melts down to about 1 inch of water. If that snow forms in more extreme colds, though (like -20 degrees fahrenheit) it can produce half that much.
That translates to less runoff when it melts. Or rather, if it melts before it’s kicked up by the wind and faces sublimation.
“That’s where you go from solid snow, back into the vapor phase,” he said. “So we sort of lose it back into the atmosphere.”
Still, every bit of moisture helps in the weeks and months leading into spring. In places like Utah, Nevada, Colorado and New Mexico, the entire state is in a drought.
“Much of the Southwest has been in an extended drought. Here in New Mexico, we’ve seen extreme conditions for years,” said Mary Carlson, a spokesperson for the Bureau of Reclamation in Albuquerque.
Carlson said the mountains that feed the Rio Grande River have seen some good weeks recently, but they still need plenty more moisture.
“We definitely are eager to receive any snow that we can receive at this point,” she said.
Even the soil moisture levels there are low, Carlson said, which means some water will get soaked up before it can even runoff into the valleys in the spring.
“These next couple months are key,” she said. “The snow that falls late in the winter, early in the spring can really make or break a water year.”
However, there are still snow types to consider. If heavier snow now falls on this lighter snow, that sets our region up for even more avalanches. And it’s already been a deadly year.
This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Boise State Public Radio in Idaho, KUNR in Nevada, the O'Connor Center for the Rocky Mountain West in Montana, KUNC in Colorado, KUNM in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting.
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