Avalanche Forecast

A frontal system will slowly move across the Cascades Thursday night with light new snow accumulations expected along the east slopes of the Cascades. Skies should remain cloudy on Friday with showers increasing in the afternoon. There will likely be sunbreaks further east of the crest in the afternoon.  After a subtle cooling trend Thursday night, snow levels should rise during the day on Friday.  

There should be just enough new snow and wind to elevate storm related hazards on Friday and create locally dangerous conditions primarily near and above treeline.

Recent winds have been mostly S-SW, so firmer wind slab should be found mainly on NW-SE slopes near and above treeline. However due to periods of recent E-SE winds, watch for wind slab on all aspects, especially in areas of complex terrain.

In the central-east and southeast zone, shallow new storm snow is expected to bond well to the existing snow surface Thursday night but storm slab may still become locally sensitive in areas that receive rapid accumulation Thursday night or Friday.  

Snow levels will creep up Friday. Loose wet avalanches won't make the cut to be listed as an avalanche problem but are still possible in the below treeline band. Watch for surface wet snow deeper than a few inches, pinwheels and increasing natural releases. Avoid steeper slopes with terrain traps where small loose wet avalanches could have unintended consequences. 

You need to avoid areas on ridges where there may be a cornice and slopes below cornices! Natural cornice releases and resulting slab avalanches are unpredictable and as seen above in the special note, cornices have triggered major slab avalanches as of late. See a blog post regarding cornices here.

Weather and Snowpack

Special note:

A major load has been placed on our snowpack over the past two weeks, especially in the north Cascades. This has resulted in many large avalanches and a few very large to historic avalanches. For example, from March 9-19, Mt Baker received nearly 15 inches of water equivalent! About 5 inches of water equivalent was received at the NRCS Harts Pass and Lyman Lake station during the same period. In terrain above 7000 feet, much or all of this fell as snow along with very strong winds. We are in a situation where hard to predict and low probability but very high consequence avalanches are possible. This situation may stick with us for awhile during the spring. Most recently:

 Deep hard slab triggered by a massive natural cornice failure on Ruby Mountain, Sunday afternoon, 3-19. Photo via the NWAC Observations page.

The first week or so of March was very cool and snowy. NWAC and NRCS stations indicate about 2 feet of snow in the northeast Cascades with less elsewhere along the Cascade east slopes. 

The 2nd week of March was equally active with non-stop Pacific frontal systems pummeling the PNW. Unfortunately, these systems delivered more rain than snow to lower and mid elevations along the east slopes. At least two regional avalanche cycles occurred during the stretch. The most recent cycle from mid-March had many massive slides that covered Hwy 20 near Washington Pass up to 40' deep in places! Significant snowpack consolidation occurred over this period due to rainfall and warmer temperatures. Far less precipitation was seen further east of the crest during this period for areas like Blewett Pass and Mission Ridge. 

Another strong low pressure system brought 6-12 inches of snow to the northeast and central-east slopes of the Cascades Friday 3/17 and mostly rain for the southeast Cascades. This was followed by snow levels rising to 6000-6500 ft in the northeast and central-east Cascades and likely 7000 ft in the southeast Cascades by Saturday morning 3/18. Rapid cooling began mid-day Saturday. 

Weaker fronts crossed the Northwest on Tuesday and Wednesday with light amounts of new snow along east slopes of the Cascades, mainly near and above treeline and near the Cascade crest. The Barron Yurt near Hart's Pass reported 10-15 cm (4-6 inches) of recent storm snow Thursday. Most areas saw sunshine Thursday ahead of the next incoming Pacific frontal system. 

Recent Observations

North

On Sunday, the NCH operation was in the Silver Star and Varden Creek drainages and found evidence of recent storm slab releases in unsupported steeper terrain mainly above treeline, but that recent storm slabs were becoming less sensitive to human triggering.

Guides near Washington Pass Tuesday, 3/21 reported hearing many natural avalanches near midday following a prolonged sunbreak and subsequent brief warm up. Numerous avalanches were likely small, however, some avalanches sounded much larger, likely involving deeper layers below the relatively shallow recent storm snow.  

NCH reported no significant new avalanche activity observed outside of one small natural storm slab on a north aspect above treeline Thursday. 

Central

No recent observations. 

South

No recent observations.