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

Avalanche Forecast

Jan 2nd, 2015–Jan 3rd, 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
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Olympics.

Watch mainly for lingering local wind slab from early in the week.

Detailed Forecast

An upper ridge will reassert itself over the US coastal waters on Saturday. Northwest flow and moisture should decrease a bit over the Olympics and Cascades. Clouds should decrease a bit during the day and lead to some partly sunny weather especially in the south and east of the crest.

Watch for lingering wind slab from early in the week where the northeast winds redistributed snow mainly near and above treeline.

Sun crusts, while not an avalanche danger on Saturday, are likely on steep south slopes where the sun warmed the snow on Wednesday and Thursday.

Right side up stable powder may also still be found on shaded sheltered slopes on Saturday.

Heads up in advance for Sunday when moderate to heavy snow with warming should bring a significantly increasing avalanche danger.

Snowpack Discussion

A storm system hit the Northwest last weekend with strong west to northwest winds. The NWAC site at Hurricane picked up about 12 inches of storm snow with a good cooling trend. Strong northeast winds hit at the tail end of the storm Monday and Tuesday. This transported snow and formed some local wind slab on exposed slopes and near ridges. But in most areas this layer bonded well and lacked underlying weak layers.

An upper ridge over the coastal waters tilted inland Wednesday and Thursday producing sunny weather and warm temperatures at higher elevations. NWAC observer Tyler Reid was at Hurricane Ridge on Wednesday and reported widespread small wet loose avalanches. Snow on north slopes was more wind affected but he rated slab layers as unlikely. A 3 cm thick graupel layer was seen at 10 cm below the surface which could be something to watch on shaded slopes.

Graupel layer at Hurricane on Wednesday by Tyler Reid.

A weak front is crossing the Northwest on Friday. This may cause some light snow and will bring cooling. The minor new snow if any Friday should not cause significant new layers.

At Hurricane where there is significant snow a strong mid and lower snowpack is expected.

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: South East, South, South West, West, North West.

Elevations: All elevations.

Likelihood: Unlikely

Expected Size: 1 - 1