Avalanche Forecast
Regions: Cascades - West.
Expect quiet weather overnight, before another round of snowfall during the day Wednesday creates dangerous avalanche conditions by the afternoon. Fresh storm slabs will be easy to trigger in terrain 35 degrees and steeper at upper elevations. Be especially leery of wind loaded areas and convex slopes.
Discussion
Storms since Sunday favored the northern portion of the zone, where you may find up to 2ft of new snow above 4000ft. The new snow is likely well bonded to a firm crust formed late last week, but mid storm layers are reactive and need time to heal. Observers in adjacent zones reported a handful of natural and triggered storm slab avalanches Monday and Tuesday. Avalanches were small (D1) and shallow and occurred in northerly, wind loaded, upper elevation terrain on steep convex slopes. With brief periods of filtered sunshine, rollerballs and pinwheels were observed on steep solar aspects.
Snowpack Discussion
Update: January 24th 2020Â (The regional synopsis is updated every Thursday @ 6 pm)
During the afternoon of January 23, 2020 one person was buried and killed by an avalanche that released from the roof of a home north of Blewett Pass near Highway 97. The elevation was approximately 1,700ft above sea level. She was found underneath 4 to 5ft of debris. She was discovered and excavated some time after the accident, where CPR was performed. Additional emergency response arrived within 15 minutes, but they were unable to revive her.
Our deepest condolences go out to the family and friends of the victim.
January to Remember
A parade of storms since the New Year began brought relentless precipitation, and impressive snowpack growth throughout the region. Areas along the west slopes of the Cascades have rarely gone more than 24-48hrs without precipitation. In the past three weeks, the Volcanoes and Passes received 20-28in of water equivalent, translating into incredible snowfall totals - Mt. Baker Ski Area reported 240in of new snow since January 1. The majority of NWAC weather station sites are reporting snow depths well over 120% of normal for this time of year. Ongoing precipitation and fluctuating snow levels have maintained elevated avalanche danger throughout the month, with avalanche warnings issued for nearly all forecast zones on 4 separate days (January 6, 7, 12, 23). Â
Snow depth imagery for the Northwest Region on January 23, 2020. Many areas in the Cascades and Olympics show well over 100 inches of snow on the ground. Image courtesy of NOHRSC Regional Snow Analysis.Â
Location
January 1-23 Precipitation (Water Equivalent)
Hurricane Ridge
14.79â
Mt Baker Ski Area
28.65â
Harts Pass
11.2â
Stevens Pass
20.26â
Leavenworth
4.01â
Snoqualmie Pass
25.43â
Paradise, Mt Rainier
24.13â
Mt Hood Meadows
22.34â
Table 1: Precipitation totals for select weather stations January 1-23, 2020. Huge numbers at Baker, Rainier, Hood, and the Passes and there is still another week left this month.
MLK Weekend and a Pattern of Rain on Dry Snow
After a prolonged cold period with arctic air and lowland snow, MLK weekend brought unseasonably warm temperatures and a rapid thaw. High snow levels and rain caused wet avalanche activity throughout the region January 18-19. A few very large natural avalanches occurred at upper elevations where all precipitation fell as snow. A cooling trend followed, creating a pronounced crust that is now buried in almost all forecast zones. Cold, dry snow January 21-22 was followed by a rapid warm-up and the most significant rain on snow event yet, causing avalanche warnings on January 23 for 5 of our 10 forecast zones.
The crown of a very large avalanche around 10,000ft on the Newton Headwall of Mt Hood which likely occurred during the storm late last week. 01/19/20 Photo: Kevin Kayl
The buried MLK crust is widespread throughout the region and a prominent marker in the snowpack. Crystal Backcountry 01/20/20 Photo Jeremy Allyn
One More Week To Go
January isnât over yet, and the long term forecast continues to show an active and wet weather pattern for the Northwest. The low-snow, drought-like conditions of the early season seem like a distant memory at this point. Weâve certainly made up for lost time in 2020, and this already impressive month looks to end with a bang.
Avalanche Problems
Storm Slabs
Steady snowfall above 3500ft during the day Wednesday will likely form fresh storm slabs and thicken existing slabs from the past few days. Avalanches will become easier to trigger by the afternoon as new snow accumulates. In upper elevation areas where the wind drifts the snow deeper, avalanches could be larger. Carefully assess new and recent storm snow layers as you travel. Look for recent avalanches, shooting cracks, and collapses. Hand-shear tests and small slope tests could give you the best idea of how the snow may respond to a trigger. Seek out supported and lower angled terrain to avoid the problem. Steer around large convex slopes 35 degrees and steeper, especially those with obvious signs of wind loaded snow. Keep wet loose avalanches in mind as you may encounter wet unconsolidated surface snow, or witness rain on snow at lower elevations.
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1