Avalanche Forecast

Moderate to heavy rain or snow early Wednesday morning should turn to showers by mid-morning Wednesday.  Mixed precipitation in the passes should end by mid Wednesday morning as they switch to free-air snow levels . The storm should come in "right side" up with a gradual cooling trend during the day on Wednesday.  

A very slick crust extending well up into the near tree-line and some cases above treeline zones on non-solar aspects makes the quality of new snow bond to the crust dubious at best despite beginning at warm temperatures. Newly formed wind slab on this slick crust found on lee N thru E aspects should be the greatest and most widespread concern Wednesday.  

Rain initially at low and mid elevations may produce wet loose slides on solar aspects where there is not a firm crust.  

Future avalanche concerns:  Existing surface hoar will most likely be preserved near the Cascade passes due to a light freezing rain crust formed Tuesday and at higher sheltered elevations near the Cascade crest that did not see rain. This avalanche concern should not be widespread throughout the Olympics and Cascade west slopes but will present challenging terrain management for backcountry travelers moving forward in the week as additional loading stresses this recently buried weak layer. Look for shooting cracks and listen for whumpfing even in low angle terrain as a clear sign that this persistent weak layer exists and may extend into avalanche terrain.

Nearly 2 weeks of mild and dry weather came to end on Tuesday. During the dry stretch strong temperature inversions were common, and periods of moderate easterly flow kept the Cascade passes cooler and cloudier than elsewhere in the Cascades. Since the last major storm cycle in mid-January, natural avalanche activity has fallen off rapidly except for natural wet-loose slides confined to steeper slopes, especially near rocky terrain.  NWAC observers reported smaller wet loose avalanches over the past weekend on steep solar aspects near Table Mtn near Mt. Baker and Lichtenburg Mtn near Stevens Pass.   

Snow surfaces across the region are highly variable heading into a more active weather pattern with firm conditions at low and mid elevations with a smooth rain or melt freeze crust (the source of many sliding accidents over the weekend) reported on many non-solar aspects, breakable crusts in the trees, rougher melt-freeze crusts on exposed solar aspects 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 low on many south slopes and at lower elevations where there is little snow and ample terrain and vegetation anchors. 

No new information has been received about instability related to persistent weak layers found near Hurricane Ridge and just east of Stevens Pass last week.  These layers are not expected to be major avalanche concern during the upcoming week.  

On the other end of the spectrum surface hoar growth has been reported during the last week with generally shallow growth at Cascade pass levels but reaching into the above tree-line zone and with significant growth in the more sheltered areas near the Cascade crest up to 20-30 mm thick!   NWAC observers in the Rainy Pass area below treeline on Tuesday reported a light rimed crust capping nearly 30mm of surface hoar and preserving this layer for additional loading (see photo and video below). Shallower surface hoar was found as they travelled to near 5500 ft.  WSDOT avalanche professionals at Stevens Pass reported a shallower and less worrisome layer of surface hoar affected by moderate east winds. 

NWAC observers video 1-28-14 from Rainy Pass: https://www.youtube.com/watch?v=7Kh_nvcDxxs

Surface hoar with thin rimed crust near Rainy Pass @ 4600 ft 1-28-14, Photo by Jeff Ward and Dallas Glass

Test pit profile shows stable mix of crusts and moist 1F snow in the upper and mid snowpack on a 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. New snow may easily scrape off this surface and still present a sliding hazard. 

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.