Despite Calm Pattern, Snowpack Near Average For Pacific Northwest

On Friday, my brother and I traveled up to Stevens Pass and had an amazing time skiing in the sunshine. Conditions were a little icy to begin, but after 11am or so, the south-facing slopes on the backside of the mountain softened up a bit and we were treated to some amazing spring-like skiing. It was my first time to Stevens in at least a decade and I couldn’t remember much about the mountain, but the mountain certainly exceeded my expectations in terrain and beauty. The summit featured panoramic views of Mt. Stuart and Glacier Peak, and it was really fun to ski past the massive Chief Joseph-Monroe 500kv transmission line while zooming down the “Orion” run, which is owned by the Bonneville Power Administration and is one of the principal power lines connecting the eastern and western halves of the state. The image below, taken on 4/10/2010 by Flickr user kpaekilo1, shows skiers maneuvering around these high-voltage transmission lines.

But as wonderful as the skiing was in the sun-bathed southern slopes, it was godawful in any of the shaded spots, which were covered in a thick layer of ice. And skiing between the trees was an even worse experience, with mottled textures of ice dotted with occasional pine needles, twigs, and sap drippings from the conifers above. All of the trees within the resort were bare of snow, and I didn’t even see a dusting of white covering the trees high in the distance from the panorama spanning the summit. Simply stated – the scenery was more reminiscent of late March than mid February.

Of course, none of this was any surprise. After an exceptionally snowy first week of January that resulted in Governor Inslee issuing a State of Emergency for major flooding west and extraordinary snowfall over and east of the Cascades, the rest of January and much of February have been dominated by persistent ridging just off the West Coast. This has sent nearly all of our storms north into British Columbia/Alaska and has brought well-above-average temperatures and blazing sunshine to the mountains while the lowlands have been shrouded in inversions and smog. With warm temps and so little new snow in the mountains, I imagined that we would currently have below-average snowpack throughout the state at both low and high elevations.

But as the image below shows, most of the snowpack across the West is near or just slightly below-average. The Western slopes of the Washington Cascades are near-average, and near-average snowfall extends from the Blue Mountains through much of the Rocky Mountain System, including the Snake River Plain and Colorado Plateau. Snowpack is approximately 80% of average for the Eastern Rockies and much of Southern/Eastern Oregon, but these numbers aren’t awful by any means.

Additionally, this snowpack does NOT have a typical La Nina distribution. The “classic” La Nina pattern has above-average snowfall for the Pacific Northwest due to cool troughing but below-average snowfall for the Sierras and Southern Rockies due to persistent ridging sending all storms to the north. Much of December and early January did indeed have a La Nina pattern with troughing over the Pacific Northwest, but there was one major caveat: this trough extended further south than usual and were thus able to deliver cool, moist air to locations normally left high and dry during La Nina patterns.

When we look at snowpack graphs over the 2021-2022 winter, we can see the reason for the surprisingly high snowfall – the rapid snowbuild earlier this year. Stevens Pass has had essentially the same snowpack for the past 30 days. But for the entirety of December, it underwent a period of sustained growth as cool storms repeatedly battered the Pacific Northwest, and this growth culminated in a meteoric rise during the first week of January as extremely wet Pacific storms overrode the bitter arctic air in place from late December’s arctic blast.

When we look at other stations throughout the west, we find a similar pattern for the year. “Bateman” is located in northern New Mexico at an elevation of 9,300 feet, yet it had the same general pattern as Stevens. Snowpack got off to a slow start, but the second half of December and first week of January were very snowy as trough that unloaded the arctic air into the Pacific Northwest progressed all the way to Southern California and the Four Corners region. And just like the Pacific Northwest, they’ve had very little activity since early January, though a nice dump of powder last week surely made for some happy skiers at nearby Taos ski resort.

La Nina Update and Snowpack Forecast

A moderate La Nina is still in effect for the tropical Pacific, but it peaked in mid-December and is expected to continue weakening through the spring before transitioning to ENSO-Neutral between May & July. Sea-surface-temperatures off our coast are still cooler-than-average, but they are not as cool as they were back in December and early January due to the persistent ridging we’ve seen, which prevents storms from mixing colder, deeper water up to the surface.

Unfortunately, the next week is expected to be drier-than-average for the Pacific Northwest, and unlike this weekend, we won’t have bluebird skies and above-average temperatures to accompany our dry conditions. Some models hint at a slight uptick in precipitation by the beginning of the following week, but the pattern still looks relatively benign through the following week.

However, skiers shouldn’t give up hope yet. There is often a “lull” between the observed La Nina conditions over the equatorial Pacific and the pattern over the Pacific Northwest, and La Nina springs can still have wetter and cooler-than-average conditions for the Pacific Northwest. Not all La Ninas have cool/wet springs; in fact, the 2021 La Nina had one of the driest springs on record. But during the 21st century, the coolest and wettest springs – and the most prolonged ski seasons – have all occurred during La Nina years.

The Climate Prediction Center shows a classic La Nina pattern persisting through the spring, with approximately a 45% chance of below-average temperatures and 40% chance of above-average precipitation for the Pacific NW from Feb-Apr. The CPC still has a 25% chance of warmer and drier-than-average weather, so while a warm/dry solution isn’t as heavily favored as a cool/wet one, it is still well within the range of possibilities.

Enjoy the tranquil weather this week, and let’s hope for a return to cool, wet, and snowy weather in March!