Avalanche Forecast

Showers should decrease late Saturday morning through mid-day and become light and scattered in the afternoon. Sunbreaks are possible in the afternoon, especially for the central and southwest Cascades. The air mass will be cooler, but it's spring-time and solar effects should push temperatures near to above freezing at lower and mid-elevations in the afternoon.  

We continue to load and stress our snowpack. Don't push it in consequential avalanche terrain - keep it simple and conservative and wait for this pattern to break. Recent storm/wind slab concerns up high and loose wet potential on steeper solar aspects/lower elevations will challenge us to manage terrain safely. Cornices have recently proven dangerous and unpredictable and capable of triggering very large avalanches.   

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

New storm snow is expected to bond well due to a cooling trend Friday night but storm slab may still become locally sensitive in areas that receive rapid accumulations Friday night or Saturday morning. 

Subtle daytime warming and/or potential sunbreaks Saturday afternoon will increase the potential for loose wet avalanches on steeper solar slopes and at lower elevations. Loose wet avalanches won't be listed as an avalanche problem, but watch for surface wet snow deeper than a few inches, pinwheels and increasing natural releases. Avoid steeper slopes with terrain traps where even 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.

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 read 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 stations along the west slopes of the Cascades piled up about 3 to 8 ft of snow with the most at Mt Baker.

The 2nd week of March was equally active with non-stop Pacific frontal systems pummeling the PNW. Unfortunately, these systems delivered far more rain than snow. At least two regional avalanche cycles occurred during the stretch. Significant snowpack consolidation occurred over this period due to rainfall and warmer temperatures. 

A strong low pressure system brought several inches of rain to the west slopes of the Cascades outside the Cascade Passes on Friday 3/17 and caused another wet snow avalanche cycle in the Mt. Baker area Friday night into early Saturday morning. 

This past week has also been active weather-wise, but water amounts/snowfall totals have been slightly lower relative to the extreme wetness of the past few weeks. In the last 24 hours ending at 5 PM Friday, Mt. Baker and Paradise have picked up 12-18", Crystal 10" with 6" or less inches in the Passes (the top of Alpental's snowboard was likely wind affected.) A slight warming trend occurred during the day on Friday. 

Recent Observations

North

NWAC pro-observer Lee Lazzara was in the Mt. Baker backcountry on Thursday. Lee found the newest 10" (25 cm) of snow bonding well to the underlying moist snow. He observed evidence of two natural wind slab releases on east aspects of Mt. Herman near treeline. Storm slabs were possible in isolated areas of steep terrain but not widespread. Mt. Baker pro-patrol had minimal results during control work Thursday morning with a few pockets of stubborn wind slab noted. NWAC received second hand information that a skier triggered loose wet avalanche on the Shuskan Arm Thursday had caught and carried the skier 150 yds and into trees, resulting in non-critical injuries. 

Central

The Alpental patrol on Wednesday reported about 2 additional inches of new moist or wet snow on the thick crust with triggered small loose wet avalanches remaining possible.

South

NWAC pro-observer Jeremy Allyn was out in the Paradise area on Thursday and found wind distributed snow variably spread across the compass near treeline. Wind slab was not particularly sensitive but up to 80 cm deep in places. Some windward aspects were scoured to the most recent rain crust. Sunshine on Thursday did not cause loose wet avalanches. Also of note but above our forecast area, serac fall had triggered a larger slab avalanche in the vicinity of the Furher Finger/Wilson Headwall, likely within the last 24-48 hours.    

On Friday, as the snow-line crept up during the day natural loose wet avalanches occurred along the Paradise Road above 5000'.  NPS rangers estimated the loose wet slides entraining about 8-10" of the recent storm snow. 

Crystal pro-patrol reported sensitive and widespread 8-12" storm slab particularly on lee slopes during morning control work. Similar to Paradise, as temperatures warmed Friday skier triggered loose wet avalanches became the biggest hazard below about 5500 feet on steeper slopes. Frequent NWAC contributer Shane Robinson reported widespread natural activity in the Crystal backcountry seen during a brief clearing in the afternoon, consisting of natural loose wet and storm slab activity on steep slopes.