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 that will spill over the Cascade crest into the east 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 immediately adjacent to the Cascade crest, but daytime warming is likely below treeline and further away from the Cascade crest 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. The new snow available for transport will decrease dramatically further away from the Cascade crest. 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 especially in areas where the sun makes an appearance.   

Storm slabs should be a lower concern Thursday. Shallow 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.

Due to recent sensitive storm slab releases on a suspected spotty 3/12 buried surface hoar layer, we are currently listing it as a persistent slab. Though it may be spotty and not widespread it should nonetheless get attention from backcountry travelers in the NE zone.

Weather and Snowpack

About 2-3 feet of snowfall accumulated along the east 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 6-12 inches of consolidation of the recent snow along the east 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.

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 east slopes accumulated a few inches of snow above about 4000 feet through Wednesday morning.

A spotty layer of surface hoar likely formed and was buried on about 3/12 mainly the northeast Cascades with the terrain most suspect being N through E facing slopes.

No avalanches have been noted for quite some time on a persistent buried surface hoar layer from February 27th in the Washington Pass area and to a lesser extent the central-east zone. Avalanches on this layer are now unlikely.   

We are also no longer tracking layers of concern formed earlier this winter in the mid or lower snowpack due to lack of recent activity at these interfaces and confirming field observations. 

Recent Observations

The North Cascades Heli Skiing operation skied extensively on a non-solar slope in Cedar Creek on Monday 3/21 and did not observe any avalanche activity in nearby terrain.

The North Cascade Mountain Guides at Washington Pass area Friday to Sunday 3/18-20 reported no results from ski cuts and no signs of instability. On Friday a loose wet avalanche that triggered a small 40 cm deep slab. Cornices in this area area were sagging greatly and snow in the below treeline was moist and heavy in the afternoons. 

NWAC pro-observer Tom Curtis tested conditions along the Nason Ridge area to Rainy Pass Saturday, March 19th. No significant layers were found in test pits or on slopes. In general, shallow wet snow was found below treeline with shallow stubborn wind slabs on some isolated features near ridges that were gaining strength. 

Reports via guides and a private email to the NWAC indicate 2 recent cornice releases in the Washington Pass area with a large size 3 storm slab and car sized blocks running to the valley floor.