Avalanche Forecast
Regions: Cascades - North West.
Very large and destructive natural avalanches are expected across the Mt Baker region Monday. Avoid all avalanche terrain including where avalanches may run and stop. Avalanches may become larger and travel farther than expected, overrunning common travel routes.
Detailed Forecast
Continued high freezing levels and heavy rain, or wet heavy snow and very strong winds at the highest elevations, will persist Monday.Â
These conditions will continue to load and stress the snowpack, maintaining very dangerous avalanche conditions. Avoid all avalanche terrain including where avalanches may run and stop.
Avalanches will entrain significant amounts of snow growing very large and potentially destructive. Avalanches may travel significant distances and extend far into their runouts, or to valley bottoms.
Monday will be another day to sit this out and wait until this active avalanche cycle ends.
Snowpack Discussion
The Mt Baker areas has received 12 feet of snow in the past 10 days, a massive amount even for Mt Baker standards! Warming temperatures and rain arrived early Sunday with nearly 2 inches of rain falling by Sunday evening, reaching above treeline. The deep storm snow sits over a strong crust layer now buried 6-9 feet or more.
Winds have redistributed snow creating deep wind slabs on lee slopes near and above treeline.
Numerous natural avalanche cycles have occurred over the storm period.
Observations:
NWAC professional observer Lee Lazzara was in the Mt Baker backcountry Saturday. Lee report several large natural avalanches in the backcountry area. Poor visibility limited detailed descriptions or more extensive observations. Observations found strong surface snow over soft weak storm snow from Friday. Shooting cracks and small slope tests all pointed to storm and wind slabs being easy to trigger. Even basic travel in the deep heavy snow was difficult.
Avalanche Problems
Wet Slabs
Release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slab avalanches can be very destructive.
Avoid terrain where and when you suspect Wet Slab avalanche activity. Give yourself a wide safety buffer to handle the uncertainty
A Wet Slab avalanche. In this avalanche, the meltwater pooled above a dusty layer of snow. Note all the smaller wet loose avalanches to either side.
Wet slabs occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoiding avalanche paths when you see pinwheels, roller balls, loose wet avalanches, and during rain-on-snow events.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1 - 2
Wind Slabs
Release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Very Likely
Expected Size: 1 - 2