Monday-Thursday 4/17-4/20

Issued: Mon, Apr 17, 2017 at 8AM

Expires: Thu, Apr 20, 2017

Plan your mountain adventures with knowledge that daytime warming weakens and loosens the snow. Avoid steep solar affected slopes in late afternoon.

Give cornices wide berth.

Sagging snowbridges and low ground near crevassed areas on glaciers should be avoided.

Above 2,500ft Moderate

1,800 to 2,500ft Moderate

Below 1,800ft Moderate

Degrees of Avalanche Danger ?

1. Low
2. Moderate
3. Considerable
4. High
5. Extreme

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

MONDAY TUESDAY WEDNESDAY & THURSDAY

DANGER SCALE

 

 

WET AVALANCHES:
Elevation:
   Below 5500′
Aspect:
   East in AM, South all day, then West in PM
Terrain:
Steep terrain near rocks and vegetation.
Sensitivity:
   Touchy when warmed.
Distribution:
   Specific.
Likelihood (Human Triggered):
  Possible
Size:
  Small-Large
Danger Trend:
   Increasing quickly each day with warming temperatures, falling with freezing at night
Forecaster Confidence:
   Good

CORNICE FALL:
Elevation:  all
Aspect:   
all
Terrain:
corniced ridgelines
Sensitivity:   
Responsive 
Distribution:   
Specific
Likelihood (Human Triggered): 
Possible
Size:  
Small to Large
Danger Trend: 
Increasing
Forecaster Confidence: 
 Fair

WIND SLAB:
Elevation:   Above 3000′
Aspect:   Southerlies
Terrain: Near ridgelines, rollovers and gully walls.
Sensitivity:   Responsive to Touchy when sitting on sun crust.
Distribution:   Specific.
Likelihood (Human Triggered):  Possible
Size:   Small
Danger Trend:  Steady
Forecaster Confidence:   Fair

AVALANCHE PROBLEM SCALE DESCRIPTORS:
Sensitivity: Non-reactive, Stubborn, Responsive, Touchy
Distribution: Isolated, Specific, Widespread
Likelihood: Unlikely, Possible, Likely, Nearly Certain
Size: Small, Large, Very Large (size scale <here>)
Danger Trend: Increasing, Steady, Decreasing
Forecaster Confidence: Good, Fair, Poor

AVALANCHE PROBLEM TOOLBOX <here>

SNOWPACK DISCUSSION:

Continental (Interior) Specific:  It has been over a week since the last significant precipitation. Our snow has typical springtime variability. Preserved, settled powder is still being found on upper elevation northerly aspects. Everywhere else is a mixed bag of texture and depth due to wind and sun affect. While the valley snow is melting quickly, average snowpack depth is still more than three feet near Thompson Pass with less interior.

Northerly outflow wind has been keeping surfaces cool. The exception is solar aspects, especially those that are wind protected and steeper than 35 degrees; a meltfreeze cycle is thawing during the day and re-freezing at night causing wet loose activity peel the layers down like an onion.

April 14 brought reports of cornice failure triggering slab avalanches- give corniced ridges wide berth.

Expect small pockets of windslab built by northeast wind near ridgetops. Inspect how the windslab is attached to the varied surfaces below.

Facets and depth hoar near the ground lend poor support to the rest of the snowpack. With springtime warming, expect full depth, climax avalanches to ground possible.

Sharing your observations creates an informed community.

Recent Avalanche Activity

Continental (Interior) Specific: 

  • April 14: reports of cornice failure triggering slab avalanches on steep upper elevation slopes in the Continental zone (see photo)

    April 14 Cornice failure triggered slab avalanche in the Nelchina area    Photo: Jed Workman

  • March 31: skier triggered size D2 avalanche at 3500′ North aspect. 40-60cm storm slab failed on buried near surface facets with a old windslab as the bed surface. A possible sympathetic released lower on the same slope, with a crown depth 60-100cm, harder slab.

Recent Weather

See Maritime Zone for updated weather.

Additional Info & Media

Weather Quicklinks:

SNOW CLIMATE ZONES:

  • coastal-zone-iconMaritime (Coastal) – from the Port of Valdez to Thompson Pass, all waters flowing into Valdez Arm and everything south of Marshall Pass.
  • intermountain-zone-iconInter-mountain (Transitional) – between Thompson Pass and Rendezvous Lodge.
  • interior-zone-iconContinental (Interior) – the dry north side of the Chugach (north of 46 Mile, including the Tonsina River).

Photo of Thompson Pass

thompson-pass-ski-runs

Interactive Map of Valdez Forecast Areas w/ Many Resource Layers (Trevor Grams)

climate-zones-topoclimate-zones-satellitegoogle-earth1

Run Map of Thompson Pass Area (Sean Wisner) (2MB download)
VAC Run Map Thompson Pass

NEWS: Our region is “one of the snowiest places on earth” – Serendipity / Rendezvous snowfall record set in 1963 <here>.

Free smart phone avalanche forecasts at: http://www.avalancheforecasts.com/

Posted in Continental Forecasts.
Sarah Carter

Forecaster: Sarah Carter