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Avalanche Forecast

Archived

Jan 24th, 2020–Jan 25th, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

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Dangerous avalanche conditions continue as new snow and wind build fresh slabs and concern for surprising wet avalanches lingers. Steer around slopes 35 degrees and steeper where you encounter 6in or more of new snow, and avoid travel below steep rocky areas where wet snow could still shed from above.

Discussion

Over the past 3 days, weather stations in the adjacent West North and Stevens Pass zones reported 4-8in of water and significant snowpack settlement. Precipitation came as rain up to 6000ft and saturated the snowpack. The full extent of the wet avalanche cycle in the Mountain Loop Area is unclear. However, in nearby areas, glide cracks are widespread, and numerous glide and wet avalanches have run to at least size D2 (large). Loose wet avalanches were easy to trigger on steep slopes Friday, entraining significant snow and running far downslope.   

Precipitation will continue as snow levels lower to 3500-4000ft over the next 24 hours. As rain transitions to snow, fresh slabs will build at upper elevations and become reactive to human traffic. Despite the gradual cooling trend, the snowpack still needs time to recover from the recent rain event, and the lingering potential for glide and wet avalanches still has us concerned.

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

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). 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.

Glide Cracks

Glide avalanches occur when water lubricates the interface between the snowpack and the ground. These avalanches are difficult to predict and best managed by avoiding terrain below glide cracks.