From The Washington Post (Becky Bollinger):
…the snow season usually starts in October in the Rocky Mountains. By the end of November, snow depth on the Cascades, Sierra Nevada, and eastward to the interior Rockies typically ranges from 2 inches at lower elevations to over 20 inches on the highest elevations.
So what have we seen this year? Unfortunately, not much.
The lackluster snowpack is particularly worrisome amid widespread drought in the region — 94 percent of the West is experiencing drought, and many lakes and reservoirs are at historically low levels. A healthy snowpack this winter could help replenish water levels during the spring melt season -— but if snowpack is limited, deficits will grow.
Warm and dry conditions this fall have led to significant snowfall deficits across the western United States. November was warmer than average, and precipitation was below average everywhere except Washington state, which had a string of storms that caused major flooding.
The National Weather Service reported high elevation snowfall lagging behind by 10 to 20 inches last month…
Every basin in the west is below normal, ranging from as little as 2 percent of normal on the Lower Colorado in Arizona to 81 percent of normal for the Upper Columbia in Washington.
There’s still time
It’s a pretty bleak picture for the start of winter. The bad news is that early season snowpack is an important contribution to the peak snowpack. The good news is that 1) we’ve got a lot of time left, and 2) we can still make up these deficits…
One factor that can affect the region’s winter precipitation is the current La Niña, which is likely to continue through the winter and into the spring. While it’s not always a perfect relationship, we tend to see above-average snowfall in the northwest and below-average snowfall in the southwest during La Niña winters.
If this pans out, the Pacific Northwest and northern Rockies are more likely to get average peak snowpack, but the southern basins would more likely peak below average.
One other challenge to contend with is the temperature outlook. The Climate Prediction Center’s seasonal outlook calls for a greater chance of above-average temperatures for Utah, Colorado and to the south. Above-average temperatures for the lower elevation areas would increase the likelihood of melting, and could also result in earlier and lower peak snowpack. The Pacific Northwest is expected to see below-average temperatures…
With the La Niña and temperature forecasts, the odds are better for Washington, Oregon, Idaho and Montana to have a decent winter, even after a poor start. Northern California, the Great Basin, Wyoming, and the northern reaches of Utah and Colorado could also recover. The areas that are likely to be in the worst shape in the spring would be the central and southern mountains of Utah and Colorado and the rest of the Southwest.
It’s still early enough in the season for things to turn around, however, so let’s all hope for some holiday magic in the form of snowflakes!
Becky Bolinger is the assistant state climatologist for Colorado and a research scientist at Colorado State University.