Avalanche Forecast

Generally light rain and snow, and perhaps mixed precipitation in the Cascade Passes should add little load to the existing snow surfaces or effect the overall avalanche danger on Tuesday.  Relatively moderate snow levels should destroy recently buried surface hoar at lower elevations away from the Cascade passes but may allow these layers in other areas to become buried and problematic during future loading.  

Nearly 2 weeks has passed since any rain, snow or other form of precipitation has graced the Pacific Northwest.  This period has been remarkable for the abundant sunshine and high freezing levels seen during the stretch.  Strong temperature inversions were common, and periods of moderate easterly flow kept the Cascade passes cooler and cloudier than elsewhere in the Cascades.  Crowns are still visible from the last major storm cycle in mid-January which produced storm slab avalanches up to size D3 on wind loaded aspects near and above treeline.  Numerous natural wet-loose avalanches were seen on solar aspects immediately following the cycle.  Since then, solar aspects have experienced natural pinwheeling with softening of the upper snowpack during the day but natural wet-loose slides have been confined to steeper slopes, especially near rocky terrain.  Most recently,  NWAC observer Dallas Glass reported a natural size 1.5 wet loose avalanche Sunday at 4500 ft on a SE slope of Lichtenburg Mtn near Stevens Pass.   

Snow surfaces across the region are highly variable, with firm conditions at low and mid elevations with a rain crust reported on many non-solar aspects, breakable crusts in the trees, melt-freeze crusts on exposed solar aspects softening to corn in the afternoons and wind affected snow on higher lee slopes. Recycled powder likely exists on some sheltered northerly aspects, but has not been widely reported.  A generally favorable mid and lower snowpack of crust layers and melt form crystals should still be an appropriate regional description (see photo below). The avalanche danger is especially low on many south slopes and at lower elevations where there is little snow and ample terrain and vegetation anchors. (see photo below from Hurricane Ridge)

Isolated areas of cold slab layers are still surviving on some lee shaded slopes where some faceting has been occurring in the upper snowpack.  It's been about a week since NWAC observers at Hurricane and Nason Ridge near Stevens Pass reported moderate or hard test results with sudden fractures. However, extended column tests did not indicate a tendency for propagation and there have been no known avalanches on these layers. Keep these potentially isolated layers of concern in mind moving forward this week.

Surface hoar growth continues to be widely reported this week, reaching into the above tree-line zone and with significant growth in the more sheltered areas, up to 20-30 mm thick!   Also keep these layers in mind as we receive new loading this week. 

East facing terrain near Hurricane Ridge, Photo by Katy Reid 1-25-14

Test pit profile shows crusts and moist 1F snow with no layers of concern on SW Aspect @ 5000 ft near Artist Point, Mt. Baker, Photo by Jeff Hambelton 1-27-14. 

Open crevasse on Silverstar Glacier in North Cascades, Photo by Jeff Ward 1-23-14

Local non-avalanche hazards:  On January 13th a heavy local freezing rain event occurred in the Snoqualmie Pass area above about 4500 feet, covering the surface with about a 2-3 inch ice crust. This crust should break down over time but a fall on a slope on this surface could result in a long and dangerous ride!  

Additionally, guides in the North Cascades have noted some thin snow bridges spanning crevasses on lower glaciers. Assume that crevasses do not have their usual and relatively thick snow bridges during this lower than normal snow season.