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Archived

Avalanche Forecast

Jan 28th, 2018–Jan 29th, 2018
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Olympics.

Warm wet weather Monday will lead to an increasing danger. Wet snow avalanches will become likely with some avalanches potentially becoming very large and potentially destructive. Travel in avalanche terrain is no recommended near or above treeline. In lower elevation terrain, chose very conservative terrain, well away from avalanche paths or runout zones.    

Detailed Forecast

Avalanche danger will increase on Sunday with warm temperatures and increasing rain to all elevation bands. The avalanche problem will shift from dry snow to wet snow avalanches.  Above freezing air temperatures and rain will extend well into the near treeline band. Wet avalanches will be likely as a result of the rain and warm temperatures. 

Wet avalanches can be very difficult to predict. The exact timing and size of these avalanches depends on numerous weather and snowpack factors. Resulting avalanche may be large and potentially destructive. 

Continued rain or heavy wet snow will wet and stress the deep recent snowfall. It will be very difficult to travel safely Monday in most avalanche terrain. 

Any avalanche occurring Monday may entrain significant amounts of snow causing them to become larger and run farther than typical in this zone. Avalanches may travel into common travel routes. 

Snowpack Discussion

Sunday was a transition from the recent very active storm cycle to very mild conditions with light amounts of rain or wet snow. The mild temperatures and light rain have allowed the deep recent storm snow to settle some 6-8 inches as of Sunday afternoon.   

A very active stormy period continued in the Olympic Mountains Saturday with warming towards the midday. Warm air temperatures, additional snow, and strong southerly winds formed deep wind slabs on lee slopes.

Winds throughout the storm cycle, that began Jan 16th, has reshaped the snow cover near and above treeline, creating a variety of snow surfaces. Scoured crust, firm wind slabs, and soft snow can all be found depending on location.

Below treeline, warming Saturday and Sunday and light rain created wet surface snow conditions.

Observations

No observations were received Sunday, as the road remained closed due to the elevation threat of large avalanches under current warming conditions. 

NPS rangers reported several natural avalanches Saturday, several that deposited debris to the road. 

On Friday, Jan 26th, pro-observer Matt Schonwald reported on the tremendous change in the snowpack since this storm cycle began. Southerly winds plus nearly continuous snowfall sculpted the landscape near and above treeline. Large and very easy to trigger cornices, deep wind rolls and huge snowdepth variations were observed. Snowdepth on a south aspect at 5000' measured 120 cm vs. 370 cm at the same elevation on a northerly lee aspect.

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: Likely

Expected Size: 1 - 2