Avalanche Forecast

An upper ridge and surface high pressure should begin to strongly build west of the US west all the way to the Gulf of Alaska on Monday. Light snow showers on both sides of the crest should decrease and end on Monday. New snow along the east slopes from Sunday should be mostly in the 4-8 range in the above treeline by Monday morning.

A mix of likely dangerous winter and spring avalanche conditions is likely persist in the above treeline along the east slopes on Monday. The sun is getting much stronger and new snow will be reactive to solar effects.

Loose wet avalanches should be likely in the above treeline on solar slopes on Monday. Avoid avalanche terrain if you start seeing pinwheels or initial small natural loose wet avalanches. Be aware of terrain traps where even a small loose wet avalanche could have unintended consequences.

New wind slab of a foot or more is likely on lee slopes mainly in the above treeline on Monday. This is most likely on north to east slopes but possible on other aspects. Watch cracking and firmer or chalky wind transported snow. Remember that snow pits may not be helpful due to variability in the snowpack.

New storm slab layers may linger into Monday where there was rapidly accumulating snow for more than a few hours on Sunday. Pay special attention to slope convexities where storm slab is mostly likely to be triggered.

Cornices have grown large recently. Cornices can break much further back on ridges than expected and releases can be unpredictable during the spring.

Weather and Snowpack

Snow accumulations Wednesday to Friday following the last front varied based on proximity to the Cascade crest and higher terrain with about 12 inches at the NRCS Lyman Lake Snotel, 6 inches at Harts Pass and next to nothing at Blewett, Mission Ridge and Berne weather stations. Crest level westerly winds were strong and sustained at the Mission Ridge station through Thursday afternoon.

A strong front and upper short wave crossed the Northwest Sunday morning. This is being followed by a large upper trough and cool unstable air mass Sunday afternoon and evening.

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

A spotty layer of surface hoar was buried on about 3/12 mainly in the northeast Cascades with the terrain most suspect being N through E facing slopes. The last known human triggered avalanche on this layer was in the Washington Pass area on 3/19. 

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

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.

On Wednesday 3/23 NWAC pro-observer Tom Curtis was in the Blewett Pass/Table Mountain area and found dust on a mostly supportive crust prior to the incoming frontal system. Also of note, many windward and solar slopes were nearly or completely melted out up to about 6000 feet. 

Mission Ridge pro-patrol reported strong west winds Thursday morning but little in the way of avalanche concerns in area due to the lack of new snow. On Saturday they reported minor small point release loose wet avalanches and minor rollerballs.