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

Avalanche Forecast

Dec 15th, 2015–Dec 16th, 2015
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
1: Low
The avalanche danger rating below treeline will be low
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Olympics.

Previous wind and storm slab layers from the weekend should be the main concerns on Wednesday. Greater caution would be necessary if the weak front Tuesday night and Wednesday morning brings more snow than expected.

Detailed Forecast

A weak cold front will cross the Northwest Tuesday night and Wednesday morning. This may bring some very light amounts of new snow but should not greatly change conditions. Some fair weather should be seen by Wednesday afternoon. Light or moderate northwest winds and cool temperatures should also continue on Wednesday.

Previous wind slab layers from the weekend will possibly linger on previous lee mainly north to east slopes near ridges and summits on Wednesday. Storm slab from the weekend should become unlikely by Wednesday but would be found in what were calmer areas if it still exists.

Use more caution and watch for new small wind slab or small storm slab if the weak front Tuesday night and Wednesday morning brings more snow than expected.

Terrain anchors are still causing significant anchoring at the lowest elevations. Use caution near creeks which are still open in some areas.

Snowpack Discussion

An atmospheric river caused warm very wet weather last week. This caused consolidation and stabilizing of the older part of the Olympics snowpack with the Waterhole snowdepth dropping to around 18 inches.

A stormy pattern with cooling was seen late last week and over the weekend with about 2.5 feet of snowfall at Hurricane.

A Park Ranger at Hurricane Ridge Sunday midday reported a storm slab release below the Sunrise Ridge likely on an east facing slope near Hurricane. The slide was likely triggered but this was not confirmed.  The avalanche crown was estimated at 2-3 feet and released about 150 wide and ran about 100 feet vertical - big enough to get into serious trouble.

Cool weather with little new snow has been seen Monday and Tuesday. This will have mostly caused some consolidation and further stabilizing.

 

Avalanche Problems

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: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1

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: Unlikely

Expected Size: 1 - 1