Avalanche Forecast

Temperatures should be 5-10 degrees cooler Sunday than over the previous few days, but sun or filtered sun and light winds should continue to soften and slowly melt surface snow on steeper sun exposed terrain, mainly at mid and higher elevations.

If skies become overcast Saturday, watch for a poor re-freeze by Sunday which may help get the day off to potential wet-loose slides later Sunday.  Be aware of quickly softening surface snow in the late morning on solar aspects. Natural pin-wheels or sinking in more than ankle deep means it is time to get off that slope and out of the way of steeper southerly slopes and avoid terrain traps. 

Continue to approach wind loaded slopes with caution, isolated wind slab may linger on N thru SE aspects near and above treeline zones.   

 

The most recent storm cycle to impact the PNW ended Tuesday after lasting for nearly a week depositing 2 - 4 feet (60 - 120 cm) of snow for most west slope Cascade sites and Hurricane Ridge in the Olympics. A fair amount of westerly wind accompanied the event from Friday through Monday and redistributed new snow onto lee slopes near ridges. The tail end of the storm cycle from Sunday afternoon through early Tuesday was accompanied by a warming trend that brought rain to mid elevations and deposited a heavy dense snow layer at higher elevations. The main avalanche activity with this cycle occurred last Sunday with large to very large D2 to D3 natural avalanches reported throughout the west slopes with start zones mainly in the near and above tree-line zones on wind loaded aspects. Natural avalanches released within the storm snow with isolated but larger slides up to 5' were produced by local ski patrols with explosives down to older crusts. 

Tuesday through Saturday has seen a return to very mild temperatures and sunshine. The warmer and drier weather has allowed for snowpack settlement of about 6-12+ inches since late Sunday.  Last weeks storm snow is now generally well-bonded.  At higher terrain snow surfaces vary from dense powder on wind and sun sheltered aspects...to chalky wind board on lee slopes...to sun crusts or soft shallow wet snow on solar aspects, depending on time of day.  Due to the low winter sun angle the somewhat supportable rain crust at low and mid elevations on non-solar aspects remains firm during the day.  On a better note, there have been many nice reports of good spring-like corn snow on sun exposed terrain at higher elevations over the past several days.

NWAC observer Tom Curtis on Wednesday from Jove Peak reported a sudden collapse and a clean shear in a compression test on an east aspect near-treeline.  However, this layer did not propagate in an Extended Column Test but suggests there may still be some lingering but increasingly isolated wind slab on lee slopes, though four days of mild weather may have now settled this layer. 

Photo by NWAC observer Tom Curtis on Jove Peak at 5400 ft

The warm and sunny weather activated solar aspects with large wet-loose avalanches reported Tuesday and Wednesday that ran into the below tree-line zone in the Stevens Pass area.  

Photo from the Smithbrook area near Stevens on Tuesday by NWAC observer Dallas Glass and a short video of the wet loose slides:  https://www.youtube.com/channel/UCXKN3Cu9rnnkukkiUUgjzFQ

For the Olympics and west slopes of the Cascades a generally favorable mid and lower snowpack exists and is expected to consist of crust layers and melt form crystals. The avalanche danger is locally lower in the Olympics where the snowpack on windward and solar aspects near and below tree-line has less snow and ample terrain anchors.  

Local non-avalanche hazard Snoqualmie Pass area:  On Monday a heavy local freezing rain event occurred in the Snoqualmie Pass area above about 4500 feet, reported to the top of Alpental above 5500 feet covering the surface with about a 2 inch clear ice crust.  This crust should break down over time but a fall on this surface would result in a long and dangerous ride!