Avalanche Forecast
Issued: Jan 26th, 2020 10:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
NWAC,
Northwest Avalanche Center
The likelihood of triggering an avalanche will increase throughout the day as snow accumulates temperatures rise. Be wary of lee slopes where wind transported snow will deposit and form slabs. Avoid slopes steeper than 35 degrees where you see signs of wind transported snow.
Summary
Discussion
Less snow than expected fell on Sunday and cooling temperatures stabilized the snowpack. Another round of snow will fall on Monday with slowly warming temperatures. Conditions will remain generally stable, but the wind will transport new snow and form fresh wind slabs on lee slopes especially in the afternoon when the heaviest precipitation is expected.
As temperatures rise, so does the likelihood of triggering an avalanche. The warming may be enough to create the possibility of loose wet avalanches at the lower elevations. Look for signs of warming in the afternoon, such as rollerballs of snow, tree dripping water or snow falling off branches. When you see these signs you will be able to trigger loose wet avalanches on steep slopes. Use caution around steep slopes, especially near creeks, cliffs, and other terrain traps.
Snowpack Discussion
Update: January 24th 2020 (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).
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.
Location
January 1-23 Precipitation (Water Equivalent)
Hurricane Ridge
14.79”
Mt Baker Ski Area
28.65”
Harts Pass
11.2”
Stevens Pass
20.26”
Leavenworth
4.01”
Snoqualmie Pass
25.43”
Paradise, Mt Rainier
24.13”
Mt Hood Meadows
22.34”
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 isn’t 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. We’ve certainly made up for lost time in 2020, and this already impressive month looks to end with a bang.
Problems
Wind Slabs
Winds will transport new snow and developing fresh wind slabs. Use caution around steep slopes with newly wind-drifted snow. Check the bond of the new snow to the crust underneath, using small test slopes. Look for signs of wind transport, such as blowing snow, cornice development, and stiff, textured snow surfaces. Where you see these signs, avoid slopes steeper than 35 degrees.
Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 27th, 2020 10:00AM
