Monday – Thursday 3/27-30

Issued: Tue, Mar 28, 2017 at 8AM

Expires: Thu, Mar 30, 2017

Avoid steep windloading slopes: rollovers and west facing gully walls are where humans are likely to trigger a windslab avalanche today.

Avalanche Center Tsaina Lodge Spring Full Moon Bon Fire FUNraiser

Friday April 14 presenting Acoustic Avalanche

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

MONDAY TUESDAY WEDNESDAY & THURSDAY

DANGER SCALE

 

 

WIND SLAB:
Elevation:  
Above 3000′
Aspect:
   Lee to northerly winds
Terrain:
 Near ridgelines, rollovers, and gully walls
Sensitivity:
  Responsive
Distribution:
 Specific
Likelihood (Human Triggered):
Likely
Size:
 Small – Large
Danger Trend:
  Increasing
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:

intermountain-zone-iconInter-Mountain (Transitional) Specific: 

Two inches snow overnight at Thompson Pas with north wind to 40mph, fresh drifts are 6-12″ deep. The snowfall is forecast to continue with 12 inches possible by Wednesday or Thursday. This new windslab is building over a thinner and weaker snowpack than we are used to this time of year.

With windslab building over the 5-12″ snow from March 20th, the concern is variability:

  1. Windslab may be sensitive to human trigger where it isn’t bonding to the near surface facets that were observed before the snow began to fall
  2. Where slab is building on wind blown surfaces there may not be cohesion.
  3. Overall poor structure (verified by recent reports of whumphing) could lead to an avalanche stepping down to old facets: deep persistent slab is low probability, high consequence. Most likely to be triggered by heavy loads ie. snowmachines or several people, in thin areas such as near ridgelines or rollovers.

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

intermountain-zone-iconInter-Mountain (Transitional) Specific:  

  • Human triggered avalanches sizes D2-2.5 likely on steep wind affected rollovers, ridgelines, and gully walls.
  • March 25 reports of upper elevation (>4500′ elevation) human triggered windslabs to a foot thick releasing off steep slopes. With a D1.5  remotely triggered slide on a southerly aspect between 4,500′-5,500′.

    Loose snow triggered soft slab: ~30cm crown. Gully One (Vertigo)

  • March 24: Small D1 R1 skier triggered wind slab on the west facing wall of Snatch (Gully 2). Recently loaded by NE outflow winds
  • March 22: Small skier triggered slide in Nick’s, size D1, west facing, wind loaded slope.

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 Intermountain Forecasts.
Sarah Carter

Forecaster: Sarah Carter