Avalanche Forecast

Cool NW flow should deliver a taste of winter in late March with light to moderate orographic snow showers along the west slopes Thursday. From late Wednesday night through Thursday, new snow should layer right side up as temperatures cool behind the cold front Wednesday night. Deep post-frontal moisture should prevent widespread solar affects, but some daytime warming is likely below treeline at lower elevations Thursday afternoon despite the seasonally cool air mass overhead. 

Persistent westerly winds will load lee slopes near and above treeline. Wind slab will be the primarily hazard on Thursday. By avoiding obviously wind loaded slopes, you can enjoy some fine late season conditions. Firm wind transported snow and snowpack cracking can be good signs of wind slab layers.

Loose dry avalanches should be small but likely on steeper non-solar slopes. Be aware of terrain traps where even a small loose avalanche could have unintended consequences in the wrong terrain. Loose wet avalanches will not be listed as the primary loose snow avalanche problem, but loose wet avalanches will be possible on steeper solar slopes.   

Storm slabs should be a lower concern Thursday. Storm slabs will be more likely in areas that see subtle warming Thursday. During more intense showers Thursday, watch for graupel layers that can become bed surfaces for storm slabs. 

Recently formed cornices have grown large. If traveling along ridgelines, be aware that cornices break much further back than expected and you don't want to go for a ride with a chunk of cornice. Despite the cool weather, cornice releases can be unpredictable during the spring.

Although not listed as an avalanche problem, glide avalanches can release unexpectedly so avoid areas below steep unsupported slopes or rock faces. 

Weather and Snowpack

About 2-4 feet of snowfall accumulated along the west slopes March 9-15th.

A combination of sun, mild temperatures and then some rain was seen for several days ending about Sunday 3/20. This weather caused about 10-20 inches of consolidation of the recent snow along the west slopes. Surface snow conditions became highly variable, ranging from cold snow or wind buffed surfaces on non-solar slopes to morning crusts and wet snow on solar slopes.

Older winter avalanche problems of wind and storm slab along the west slopes will have mostly settled and stabilized during the mild weather.

Frequent March storms have built large cornices along ridges in many areas.

A low pressure system crossed the Northwest on Monday and Tuesday. NWAC stations along the west slopes accumulated a few inches above 4000 feet during this time. 

The mid and lower snowpack along the west slopes should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

The Alpental pro-patrol reported on Tuesday afternoon 3/22 that sun breaks were giving widespread, point release, small loose wet avalanches with 1-2 feet of debris.

NWAC pro-observer Dallas Glass was on Skyline Ridge at Stevens Pass on Tuesday 3/22 and found 6 inches of new snow at 5000 feet. Wind had formed small isolated wind slab which was not reactive with no releases. Ski cuts on specific steep test slopes were giving loose wet avalanches which were running fast and good distances but staying within the cut and not propagating.

The Mt Baker ski area reported small, natural loose wet avalanches releasing from steep rocks or walls on Monday 3/21.

NWAC pro-observer Lee Lazzara was out near the Mt Baker ski area on Sunday 3/20 and found the top 30 cm of snow moist to wet and no significant layers in the top 1 m of snow. He saw debris from recent small loose wet avalanche and glide avalanches and big hanging cornices.

Powerful glide avalanches remain possible in isolated terrain features such as on steep slopes with smooth bed surfaces and especially where the slabs are unsupported from below. These avalanches are not predictable in the sense that they are not tied to short term warming or rain events. Specifically in the Mt. Baker backcountry, we want to highlight the low likelihood-high consequence of this sporadic but ongoing avalanche hazard during this wet winter (the last glide avalanche was observed 3/15).