Saturday-Tuesday 2/18-21

Issued: Sat, Feb 18, 2017 at 8AM

Expires: Tue, Feb 21, 2017

First sun on soft snow can weaken bonds and lead to loose avalanche activity. Monitor those steep south faces above you taking in the solar radiation.

Despite calmer winds today, expect previous snow transport in exposed terrain and wind slab formation that is not quite bonded yet. Investigate before committing.

Above 2,500ft Considerable

1,800 to 2,500ft Moderate

Below 1,800ft Low

Degrees of Avalanche Danger ?

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

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

SATURDAY SUNDAY MONDAY & TUESDAY

DANGER SCALE

 

LOOSE SNOW:
Elevation: All
Aspect: All
Terrain: All
Sensitivity: Responsive
Distribution: Wide Spread
Likelihood (Human Triggered): Possible
Size: Small – Large
Danger Trend: Steady
Forecaster Confidence: Fair

WIND SLAB:
Elevation: 
Above 1800′
Aspect: 
Mostly north and west
Terrain:
Near ridgelines, rollovers, and gully walls
Sensitivity:
Responsive
Distribution:
Specific
Likelihood (Human Triggered):
Likely
Size:
Small – Large
Danger Trend: 
Decreasing
Forecaster Confidence:
Good

PERSISTENT SLAB:
Elevation: 
All
Aspect:
All
Terrain:
Most
Sensitivity:
Non-reactive
Distribution:
Widespread
Likelihood (Human Triggered):
Unlikely
Size:
Small – Large
Danger Trend: 
Steady
Forecaster Confidence: 
Poor

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: 

Only a handful of inches have fallen in the interior since last week’s big event. Southeast wind picked up February 14th and drifted the 2 feet plus of new storm snow near ridgelines above and inland of the 46 Mile area.

The intense and heavy storm snow, combined with windloading, stressed and failed old weak layers which led to widespread natural avalanche cycle north of Milepost 46/Stuart Creek.  This continental snow climate zone has a relatively shallow snowpack with weak basal facets, that makes human triggered avalanches more likely.

Prior to the storm, sudden collapse and propagation in between crusts and in depth hoar, was possible Sunday Feb.12 above 50 Mile.

Find more photos and observations at the bottom of the page. Sharing your observations creates an informed community that everyone benefits from at some point.

Recent Avalanche Activity

Continental (Interior) Specific: 

Reported Tuesday and Thursday Feb 14 & 16:

  • Beyond 46 Mile: Widespread very large avalanche activity releasing to depth hoar at ground on Mt. Tiekel, Rice Mtn and more

Dramatic Persistent Slab Failures at the ground on Rice Mountain

  • Avalanches at 50 Mile were reported to run as far as the pipeline Tuesday Feb.14.

Wilburs/MP 40: lower central slab was deeper and looked like it pulled out to rocks…similar to those in the Continental Zone.

Recent Weather

See Maritime Zone for updated weather.

Additional Info & Media

Weather Quicklinks:

  • NWS forecast for Northeast Prince William Sound <here>
  • NOAA NWS spot forecast for Thompson Pass <here>
  • Thompson Pass RWIS weather station <here>
  • MP 30 Nicks (Happy) Valley weather station at 4200 feet <here> (scroll to Nicks Valley)
  • Valdez Glacier UAF weather station at 6600 feet <data here> <map here>
  • Further weather resources <here>

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.

Forecaster: Kevin Salys