Avalanche Forecast

A moderate to strong frontal passage will move across the area Wednesday evening bringing a period of moderate to heavy precipitation through the evening then cooling a shift to moderate showers along the west slopes. The strong westerly flow should maintain showers along the west slope areas and over the volcanic peaks through Thursday morning at further cooling. This storm should build unstable wind slab layers on many lee slopes near ridges ranging from NW through SE aspects.  The cooling trend by Thursday should help with the new snow profile and limit storm slabs sensitivities but keep an eye for layering using a variety of quick probes and hand shears within the new snow.  

Crest level winds should remain strong overnight Wednesday through much of Thursday which will continue to transport falling snow as well as earlier deposited snow thus continuing to build unstable wind slab as well as some cornices. 

Less snow and lighter winds as well as continued low snow depths should not appreciably increase the danger at lower elevations. 

Another front should begin spreading renewed precipitation over the area late Thursday afternoon or evening to again lead to an increasing danger, but mainly after dark Thursday. 

 

 

 

The last significant storm crossed the area last Thursday, initially producing rain or wet snow before transitioning to snow at lower elevations. New snow amounts varied from north to south and with elevation. Upper elevations in the north received about 20-30 cm (8-12 inches) of new snow with lower elevations and areas in the south getting about 10-20 cm (4-8 inches).

Sunny weather with increasingly warm temperatures were experienced over the weekend and produced some small loose wet slides on solar aspects. Less warming was seen in the passes due to cooler easterly flow. 

Generally good bonding was seen from the last storm snow to crust interface, however some exceptions occurred, such as a few sensitive storm and wind slab releases last Saturday in at least 2 different human triggered incidents. A climber triggered 2 separate slides and was caught in a 1 foot storm or wind slab in the east facing bowl below Chair Peak near Snoqualmie Pass at about 5500'.  The climber was not seriously injured.

A skier also triggered but was not caught by a 1-1.5 foot storm or wind slab on a south facing slope on Mt Herman near the Mt Baker ski area at about 5700 feet. The bonds here may not have been as good between the recent and old snow with the old crusted snow acting as a bed surface. Sunshine may have helped to activate this slope.

Surface hoar formed with clear cool nights this weekend in the lower elevations of the cooler Cascade passes and on shaded aspects throughout the west slopes. This surface layer should have been destroyed by the warming temperatures Monday night and Tuesday along with rain at lower elevations and freezing rain/mixed precipitation in the passes.  Generally light amounts of new snow at mid and higher elevations received Tuesday and Tuesday night should have bonded well to the old snow surface.

A stronger storm moving into the region Wednesday is beginning to add additional load to the upper snowpack as well as build new unstable wind slab layers on many lee aspects ranging from NW-SE.

There should be less danger increases in areas that received less recent storm snow snow such as Hurricane Ridge and Crystal Mountain, however heavier precipitation expected overnight Wednesday should quickly change that.