Avalanche Forecast

Cloudier weather should be seen Wednesday with light winds and little change in cool temperatures. A few light showers are possible but most parts of the Olympics and Cascades should just end up with clouds.

These conditions should allow for further gradual decrease in avalanche danger as recent wind and storm slabs further settle and further stabilize. 

Recently formed wind slab should further stabilize on Wednesday.  Wind slabs are most likely on SW-NW-NE aspects due to recent strong E-SE transport winds. Watch for recent wind effects near and below ridgelines and avoid steep slopes with obvious signs of recent wind loading. 

Storm slabs should become more unlikely and more stubborn to trigger Wednesday and will be removed as an avalanche problem.

It should be cloudier on Wednesday than the past couple days and further loose wet avalanches seem unlikely. Loose wet avalanches will not be listed as an avalanche problem. Watch for loose wet snow conditions on steep solar slopes if there is unexpected significant sunshine on Wednesday afternoon.

The 12/17 PWL and other persistent weak layers closer to the surface have been unreactive lately in the northeast zone and persistent slabs have been removed from that zone. However, the basal facets in the Mission Ridge area continue to occasionally produce alarming results either in snowpack tests or more recently with very large hard slab avalanches released during control work at Mission Ridge on specific wind loaded slopes. Continue to think about the possibility of low likelihood/high consequence persistent slab avalanches in this area when choosing terrain.  

Weather and Snowpack

An arctic air mass was over the Northwest with fair, cold weather the 2nd week of January. Surface hoar and near surface faceted crystals formed in wind and sun-sheltered areas during this period. Further observations should help to determine if any of these weak persistent grain types remain relevant to the forecast moving forward.

An atmospheric river moved over the Northwest about 1/17 causing heavy snow in the northeast zone. Washington Pass had over 2 feet of snow. A mix of snow, sleet and freezing rain was likely seen in the central-east zone and also in some lower elevation areas east of the crest. Lyman Lake Snotel, Holden Village and Berne Camp east of Stevens saw about a foot or more of new snow while Mission Ridge and Lake Wentachee saw about 6 inches. Rain was likely seen up to about 5-6000 feet in the southeast zone.   

With the arctic air mass finally displaced and cool easterly flow abating Thursday, many lower elevation sites east of the crest warmed to near freezing. Light upslope snow showers may have produced another inch or two along the east slopes Friday. Winds at Mission Ridge summit were light to moderate out of the E-NE.

Showers Saturday and Sunday deposited about 2-5 inches of new snow with further cooling. Local strong S-SE winds Sunday may have built unstable wind slabs on some lee slopes receptive to transport.

Fair weather with light winds and cool temperatures has been seen Monday and Tuesday.

Recent Observations

An observation via the NWAC Observation page from last Saturday 1/14 continued to identify weak persistent grains near the base of the relatively shallow snowpack in the Mission Ridge area. On Thursday, 1/19 the Mission Ridge pro-patrol produced 8-10 foot hard slab avalanches with hand charges that released down to the basal facets formed earlier this winter. These very large avalanches were on very specific wind loaded NE slopes just below ridgelines. Elsewhere, 3" storm slabs could be ski triggered on steeper slopes but were only capable of producing small avalanches.

From the Mission Ridge pro-patrol on January 19. Photo by Taylor Everett.

Observations on Friday from the NCMG found some faceting below a melt-freeze crust around on Delancey Ridge that gave a few sudden collapses during trail breaking at 4000 feet. The melt-freeze crust became thicker, higher in elevation. No direct avalanche activity was observed down to this interface. Storm snow totaled 45-55 cm in this area. 

NWAC pro-observer Jeff Ward was in the Hairpin Valley of Washington Pass Saturday and in specific terrain found reactive tests (PST) on buried surface hoar just under the thin 1/17 crust, buried 65 cm (2 feet) in that area. It is unsure how widespread the buried surface layer is in this zone, so proceed with caution, especially lower elevation and near valley bottom slopes. Jeff provided this video.

NWAC observer Tom Curtis was in the Blewett Pass/Diamond Head area Saturday to assess post storm conditions. The major finding relates to the well documented 10-15 cm of basal facets in that region. Extensive observations in this region determined that significant rounding has occurred with these grains and no facets above the ground remain. The rounding of the basal facets may be limited to this specific terrain, so tests in other areas are encouraged, especially when travelling in terrain of consequence.

A report via the NWAC Observations page indicated SE winds transporting snow at Harts Pass on Saturday.

The NCMG were out on Delancey Ridge and Vasiliki Ridge on Sunday and reported wind transport at 6000 feet. Numerous ski tests gave no results on Delancey. A storm shear was seen at about 25 cm and no results were seen at a 1/17 interface. On Vasiliki ski tests gave very local results on the 1/17 interface.

In Icicle Creek at 4500 feet on Sunday a Stevens pro-patroller reported 20 cm of storm snow which was wet at the bottom and over buried surface hoar and faceted snow was giving collapsing and shooting cracks.

The NCMG were out again on Monday on Delancey Ridge and saw no avalanche results while skiing. Compression tests on a SE slope at 6000 feet indicated a hard resistant planar shear at 45 cm below the 1/17 interface so some of the surface hoar or faceted snow from the 2nd week of January may still be present.