Avalanche Forecast

New shallow wind slabs will develop throughout the day Friday on wind loaded slopes near and above treeline. These avalanches will grow larger and become easier to trigger as the day goes on. Use visual clues such as blowing snow, plumes, snow drifts, and fresh cornices to identify and avoid slopes where wind is depositing snow. With plenty of snow available for transportation, wind slabs may grow large in the afternoon.

Conditions will not allow for much, if any change in the persistent slab problem. You are most likely to trigger this weak faceted layer on large open slopes greater than 35 degrees. Other avalanches may also step-down and trigger this weak layer. Stay away from large open terrain where these large persistent slabs may occur. This avalanche problem is not going away. Continue to give yourself wide safety buffer to handle the uncertainty of this difficult problem.

Excellent travel conditions can still be found in many locations. Lower angled slopes, treed terrain, areas away from larger avalanche paths can provide more conservative terrain options.

Following last weekend's storm cycle, the upper snowpack consists of 2-4 feet of soft settled snow. In many locations this snow sits on top of weak sugary facets. These facets can be easily located just above the most recent (2/8) crust layer. Several avalanches, collapses, and whumphs have been triggered on this persistent weak layer. Snowpack test and observations from around the region continue to demonstrate that this layer can fail and produce avalanches.

Loose surface snow conditions have been reported in most areas. Small loose dry avalanches have been observed in very steep terrain.

A thin rain crust formed and was buried on 2/17 near and below 4000’ in the Snoqualmie area. Limited information about this snowpack layer has been reported other than it is ski-supportable. 

Below the 2/8 crust there are no significant layers of concern.

Observations

Stevens and Snoqualmie Pass

An avalanche professional at Stevens Pass reported snowpack tests Wednesday indicating the weak facet layer could fail and produce avalanches. These were the most recent of numerous snowpack tests conducted over the last several days. All observations supported the same conclusion.

Several large persistent slab avalanches were triggered Saturday through Monday in both the Snoqualmie and Stevens Pass backcountry (Stevens Pass-Hollywood Bowl-2-19). These avalanches failed on facets just above the 2/5 crust.

South

On Friday NPS rangers in the Paradise area reported 3-4 feet of snow over weak facets. No wind transported snow was observed.

NWAC Forecaster Dallas Glass observed a large audible whumph caused by a collapsing weak layer Tuesday near Paradise. Snowpack tests in the area indicated the persistent weak layer could fail and produce avalanches up to 4 feet deep.

No recent observations have been received from the Crystal backcountry. A higher level of uncertainty exists in this area.