Avalanche Forecast

Partial clearing Saturday night along with cool temperatures, should allow any moist to wet snow to re-freeze and form a thin crust layer, especially near and below treeline on all but steep northerly facing terrain. 

The next frontal precipitation is expected to arrive late Sunday morning and gradually increase along with ridgetop winds through the afternoon. Shallow new wind slabs may become locally sensitive in areas that receive rapid accumulations Sunday afternoon.  

Recent winds have been mostly S-SW, so firmer wind slab should be found mainly on NW-N-SE slopes near and above treeline. Expected increasing winds Sunday should be similar, mostly S-SW.

Recent cornices are very large in many areas. Make sure to avoid areas on ridges where there may be an overhanging cornice as well as travel on steep slopes below cornices! Natural cornice releases and resulting slab avalanches are unpredictable. See a blog post regarding cornices here.

Special Note: For more information on the massive natural cornice triggered avalanche on the north side of Ruby Mountain on Sunday 3/19 and general thoughts about low-likelihood/high consequence avalanches, please look for NWAC's upcoming blog post that will be issued this weekend. 

Weather and Snowpack

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/mid elevations along the east slopes of the Cascades. 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/Mission Ridge. 

A strong low pressure system brought 6-12 inches of snow in 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 feet in the northeast and central-east Cascades and likely 7000 ft in the southeast Cascades by Saturday morning 3/18. 

During this past week, weaker fronts crossed the Northwest from Tuesday through Saturday with light amounts of new snow along the east slopes of the Cascades, mainly near and above treeline and near the Cascade crest. The Barron Yurt near Hart's Pass reported about 20 cm (8 inches) of recent storm snow as of Saturday afternoon. About 6 inches of storm snow had accumulated in the Mission Ridge area.   

Recent Observations

North

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.

Reports from the Barron Yurt on Friday and again Saturday indicate the recent wind transport was mainly shallow but evident near ridges. Recent SW winds were building shallow wind slabs as of Saturday and were avoided. There were a few small natural avalanches that occurred on very steep shaded terrain, mainly above 40 degree's. These were D1-D1.5 in size and unknown whether they loose-dry or shallow wind slabs. No triggered slides were observed Saturday. 

Central

On Friday, Mission Ridge pro-patrol reported very sensitive storm and/or wind slab up to 6-8 inches deep on lee aspects near and above treeline. NW aspects were especially sensitive.

NWAC pro-observer Tom Curtis was on the lower slopes of Mt. Cashmere Friday below treeline. About 5 cm (2 in.) of new snow had accumulated in this area. On steep test slopes, Tom easily triggered loose wet avalanches entraining moist underlying snow with the potential to become large. Although not directly observed, Tom heard several large natural avalanches release up the Trout Cr drainage along ridge-crest in the morning. It is possible these avalanches were cornice triggered.  

South

No recent observations.