Avalog
Register
Get forecast notifications
Create an account to receive email notifications when forecasts are published.
Register
Login
Archived

Avalanche Forecast

Jan 15th, 2015–Jan 16th, 2015
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
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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.

New storm and wind slab mainly on lee aspects may bond poorly to the existing snow surface, especially near and above treeline. Watch for unstable slab layers and avoid steep lee slopes that may have received wind transported recent snow, especially steep NW thru NE facing slopes.  

Detailed Forecast

A period of moderate to briefly heavy precipitation expected overnight should build storm slab layers, especially near treeline and above. 

New storm and wind slab should be likely Friday, especially near and above treeline. Strong winds overnight Thursday will have likely built unstable slab layers on NW-NE facing slopes, mainly below ridges.

Light and decreasing snow showers are expected through the day Friday with a cooling trend. This should allow for slowly improving avalanche conditions as storm layers begin to settle.  

On backcountry travel safety note, watch for terrain hazards (exposed rocks, trees, streams, etc.) at lower elevations and on wind scoured aspects.

 

Snowpack Discussion

A very shallow snowpack exists around the Hurricane Ridge areas of the Olympics, consisting of well consolidated melt freeze or crust layers. Light rain and snow has begun Thursday afternoon at moderate temperatures. There was no report of any surface hoar as of Thursday morning, however, it should not be ruled out as a possible layer that may be present on some sun protected slopes, mainly below tree line where it may have formed during this past week's high pressure. 

The one favorable condition with the frontal precipitation that is moving into the Olympics Thursday afternoon is the fact it should begin as rain at those elevations where the surface hoar is most likely to exist, helping to destroy it before it becomes buried. 

Strong surface crusts have good surface roughness and this may help bond incoming storm snow.  There are also plenty of terrain anchors near and below treeline with the current shallow overall snow depths. NWAC observer Katy Reid at Hurricane on Saturday reported areas of bare ground and a stable snowpack that only averaged 8 inches.

Avalanche Problems

Storm Slabs

Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-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.

 

You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.

 

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 1