Archived

Avalanche Forecast

Apr 11th, 2014–Apr 12th, 2014

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

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

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: Northwest Inland.

Winter transitions into spring! Rapid warming and intense solar radiation can increase the avalanche danger quickly. Check out the new Forecaster Blog which is directly focused on the Northern Regions.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

A strong ridge, with a northwest flow dominates the region bringing clear skies and rapidly rising freezing levels. Saturday: Mainly sunny. Alpine temperatures high of 2.0 degrees. Ridgetop winds light from the NW. Freezing levels rising to 1800 - 2100 m for the 24 hr period.Sunday: Mainly sunny skies with possible cloud. Alpine temperatures high of 5.0 degrees and freezing levels rising to 2100 m. Ridgetop winds light from the SW.Monday: Cloudy with sunny periods. Alpine temperatures high of 4.0 degrees and freezing levels 2000 m. Ridgetop winds light from the SW.

Avalanche Summary

A couple of size 1.5 wet slabs were reported around 1000 m and continued loose wet surface sloughing below treeline. Below is a link showing natural avalanche activity over the past couple of days, sometimes photos say more then words...Hankin-Evelyn Trail-crew update

Snowpack Summary

Up 30 cm of new snow fell at upper elevations and up to 40 mm of rain. A strong rain crust exists up to 2000 m on all aspects. At higher elevations the new snow fell onto a variety of old snow surfaces consisting of surface hoar, facets and melt freeze crusts. Strong SW winds have built thick wind slabs on leeward aspects and a poor bond may exist, especially on a buried crust.At lower elevations (1200 m and below), surface snow is moist and/ or wet, creating melt-freeze conditions.Two persistent weak interfaces exist deeper in the snowpack. The early March layer can be found down 75 - 100cm. The early February crust/facet/surface hoar combo is down 150 - 200cm. Recently, these layers have become overloaded with the new load from snow, rain and wind. They should remain on your radar, and could become reactive with solar radiation and high freezing levels.

Avalanche Problems

Wind Slabs

Recent strong SW winds have transported new storm snow to leeward slopes and behind terrain features. These wind slabs may be easily triggered by the weight of a person. Solar radiation and warming can make large, looming cornices weak.

Avoid cross loaded and leeward slopes at or above treeline.>Extra caution needed around cornices with current conditions.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Deep Persistent Slabs

Two buried weak layers exist in the snowpack. These weak layers could be activated by cornice fall, a surface avalanche in motion, a rider finding the sweet spot, or warming and intense solar radiation.

Be aware of the potential for large, deep avalanches due to the presence of buried facets and surface hoar.>Minimize overhead exposure; avalanches triggered by warming and/ or cornice fall may run farther and faster then expected.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 7

Loose Wet

With warming and intense solar radiation a loose wet avalanche cycle will be likely.

Avoid slopes when temperatures rise and the surface snow becomes moist or wet and shows signs of instability, like pinwheels and natural avalanches.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4