Avalanche Forecast

Monday should be the warmest day this week. Increasing mid and high clouds Sunday night may preclude a solid refreeze of the snow surface. Light rain or snow is possible for the north Cascades early Monday, but all areas should give way to mostly sunny or at least filtered sunshine by Monday afternoon with freezing levels 7000-8000 feet. Cool east winds near the Passes could mitigate warming effects and locally lower the avalanche danger.    

The equinox has passed and we've officially moved into spring; wet loose avalanches remain possible on sun exposed terrain especially in the late morning and afternoon hours. Watch for wet surface snow deeper than a few inches, pinwheeling of surface snow and small natural wet loose releases that usually precede more major wet loose snow avalanches. Wet loose avalanches may be larger and entrain more snow than over the weekend due to the warmer temperatures and sun, and could in isolated areas step down to lingering slab instabilities weakened my meltwater in the upper snowpack.  

Wet loose concerns should be heightened in the north Cascades where less solar input was received over the weekend and temperatures have been cooler. 

However, continue to watch for lingering but likely isolated wind slab generally on lee north through easterly slopes near and above treeline. Watch for cracking or firmer wind transported snow in steep exposed terrain. A large cornice fall could provide the right natural trigger for a wind slab to release on a lee slope. Cornices should be more likely to fail on Monday, and should be given a wide berth.

Recent Weather and Avalanches (Granite Mtn info at bottom)

We have shifted avalanche concerns to the more recent storm layers and moved away from deeper snowpack concerns for the near term.

A wet front last weekend stalled over the Olympics and the north Cascades producing mainly rain before changing to snow in a north to south fashion across the area. A favorable temperature trend with gradual cooling occurred with this storm. NWAC sites along the west slopes picked up 5-20 inches of snow last weekend through Monday. Some storm and wind slab avalanches were seen following the last front but instability was not widespread due to the cooling trend, good bonding to the old snow surface and short lived storm layers. The new snow was generally reported to be over wet snow in the upper snow pack, with numerous reports of wet snow reaching down to 1 meter or greater in depth in snowpits.  

The latest cold front crossed the Northwest late Wednesday. This caused increasing winds, rain and snow and a cooling trend on Wednesday and deposited mainly 3 to 16 inches of new snow by Thursday morning, with the highest totals from NWAC stations at Mt. Baker and the top of Alpental. Lesser amounts were seen further south of Snoqualmie Pass. Temperatures remained cool Thursday with a few light snow showers. Reports from Alpental pro patrol Thursday AM indicated shallow soft storm slabs easily releasing from ski cuts and explosives and there had been a limited avalanche cycle Wednesday night.  By Thursday midday some shallow daytime warming effects were creating slightly increased surface slab character as low density surface snow began consolidating.

NWAC received a report about an accident that occurred early Thursday afternoon. The second skier entering a steep chute triggered a 6-8" soft slab that broke 75' across within the recent storm snow in a chute called Fleur di Lis in the Mill Valley area of Stevens Pass. The first skier was in a safe area and the person who triggered the slab was caught and carried, lost gear, but fortunately was uninjured. The crown released near the chute entrance at the top at roughly 5400 ft on a mainly NNW aspect. 

NWAC observers Dallas Glass near Paradise, MRNP Thursday and Jeff Ward at Jim Hill near Stevens Pass on Friday saw evidence of recent wind affects producing wind slab on some exposed lee N through E aspects near treeline and small wet loose on more solar aspects. Recent storm layer failures from snowpit tests were not particularly reactive and are expected to have settled over the last few days. See more of Jeff's observations from Friday in this video.  Backcountry reports on the NWAC observation page from Ruby Mtn Friday told a similar story with mainly well bonded snow but some storm snow instabilities still lingering 25-30 cm down near treeline and 1 small skier triggered soft slab on a convex roll on this layer near the summit. Jeff Hambelton reported from the Stevens Pass area Friday of a natural shallow soft slab that released due to daytime heating on a west aspect near treeline (5600 feet). A backcountry report from Crystal mountain Saturday told of small but increasingly larger natural and skier triggered wet loose on SE aspects through the day. Light snowfall near Mt. Baker Saturday afternoon and night created some 4-6" wind slab on lee aspects, but pro patrol reported them as pockets and not particularly touchy Sunday.  

Updated Granite Mt Accident Information as of Sunday afternoon: Around 4:45 PM on Saturday afternoon 2 skiers and a dog descending the looker's left (or skier's right) avalanche path on the south side of Granite Mt (visible from I-90) triggered a slab avalanche that stepped down to a deeper slab. Upon review of crown photos (below) and conversations with local avalanche professionals from Snoqualmie Pass it seems most likely that the initial slab failure on this cross loaded path included the Wed/Thu storm snow and the second slab of similar depth included last Sun/Mon storm snow with the bonds between these layers weakened by strong solar input and potential melt water in the upper snowpack during the afternoon. The best estimate right now is that both slabs were at least 1 foot in depth.

The skier caught and eventually killed in the slide left the ridgeline at about 5200 ft in elevation and skied onto a steep (40+ degrees) slope. The avalanche became a large and destructive wet slab funneling down to around 2300', entraining increasingly saturated snow lower in the avalanche path and at times gouging to the ground. Initial size estimates are at least D3/R3. The other person was in a safe zone and not affected. The skier who was caught was buried under 20 feet of debris but was recovered Sunday morning by local search and rescue efforts.  Another party of two lower on Granite was not caught and aided in the preliminary search efforts. 

We don't believe the upper snowpack structure that led to this accident is common throughout the west slopes.  However, we are increasingly concerned about wet snow avalanches on Monday, including those in isolated areas that could lead to wet slab avalanches. 

Images of Granite Mt avalanche taken 3-23-14 by Jason Skipper