Friday-Monday 3/10-13

Issued: Fri, Mar 10, 2017 at 8AM

Expires: Mon, Mar 13, 2017

Avoid wind loaded terrain near ridges and rollovers with fresh pockets of  windslab. These slabs can release dramatically into crushing blocks.

Test and evaluate the stability in areas without consequence before moving into steeper and larger terrain.

Above 2,500ft Moderate

1,800 to 2,500ft Low

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

FRIDAY SATURDAY SUNDAY & MONDAY

DANGER SCALE

 

WIND SLAB:
Elevation:
  Above 2000′
Aspect:
   Lee to northerly winds
Terrain:
  Near ridgelines, rollovers, and gully walls
Sensitivity:
  Responsive
Distribution:
Specific
Likelihood (Human Triggered):
  Possible
Size:
Small – Large
Danger Trend:
  Decreasing
Forecaster Confidence:
   Fair

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

It has been 2 weeks since a snowflake has fallen from the sky and 11 days since the strong north winds started wreaking havoc on our snowpack. These extreme winds, that peaked near 90 mph, have scoured deep into older snow and drifted snow into low lying gullies, trees, crevasses and rollovers.  Many natural wind slab avalanches released throughout our region while few human triggered were reported, likely due to the inhospitable conditions. Wind affected areas have knife hard windslab, sastrugi, rain/melt-freeze crusts and wind scoured bare ground. The main concern is windslab over ice crust, buried surface hoar and near surface facets. Steep southerlies in the lower elevations are melting out to bare ground.

The Interior region of the Chugach has seen significantly less precipitation compared to coastal areas. Ground level facets (sugar snow) were found on a widespread scale through out this part of the range. These facets take time, possibly even an entire season to change their structure into something less avalanche prone. The likelihood of triggering an avalanche on these facets is low, but the consequences could be fatal.

Thompson Pass gap winds still scouring into the snowpack.

Rain Crust from mid Feb.

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: 

  • Mar. 2: Just up the road at Milepost 40, human triggered winds slabs were triggered on lee aspects of a cross-loaded ridgelet. Expect similar in the continental zone where basal facets further complicate things.

Human triggered windslab below Crudbusters. Photo via Jed Workman

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