Sunday-Wednesday 4/9-4/12

Issued: Sun, Apr 09, 2017 at 8AM

Expires: Wed, Apr 12, 2017

Springtime conditions: avalanche danger decreases with overnight cooling and increases with daytime warming.

Plan your day to minimize your exposure to steep slopes later in the afternoon.

Friday April 14: VAC Full Moon Spring Fling FUNraiser with Acoustic Avalanche at the Tsaina Lodge

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

SUNDAY MONDAY TUESDAY & WEDNESDAY

DANGER SCALE

WET AVALANCHES:
Elevation:
   Below 5000′
Aspect:
 South, East in AM, West in PM
Terrain:
Steep terrain near rocks and vegetation.
Sensitivity:
   Touchy when warmed.
Distribution:
   Specific.
Likelihood (Human Triggered):
   Likely
Size:
  Small-Large
Danger Trend:
   Increasing quickly each day with warming temperatures, falling at night
Forecaster Confidence:
   Good

PERSISTENT SLAB:
Elevation:
  Above 2500′
Aspect:
 All
Terrain:
Slopes > 35*
Sensitivity:
   Stubborn on northerlies, Touchy when warmed by sun
Distribution:
   Widespread
Likelihood (Human Triggered):
   Possible
Size:
  Small – Large
Danger Trend:
   Decreasing
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:  Monitor where surface hoar and near surface facets are being buried by fresh flurries.

The storm that ended April 6 laid down 2-4 inches of water equivalent in our upper elevations; 3-4 feet of snow up high on the coastal side with rain below ~3600′. Much less precipitation fell interior of Thompson Pass.

The storm snow is reportedly settling and bonding well to old layers. The exception is a few upper elevation areas where buried near surface facets are still reactive. South wind during that storm formed new cornices and some pockets of windslab near and below ridgelines. The tail end of the precipiation, April 4-6, pushed temperatures above freezing to 4500′ on the north side of the pass and up to 5500′ in the maritime.

Daytime green house effect (short wave radiation bouncing between the snow surface and cloud cover) and periods of direct sunshine caused wet loose activity to entrain and step down, releasing slab avalanches to size D3 April 6-8. In really shallow areas, wet loose has scoured directly to the ground.

Persistent slab problems are still a concern in colder, thinner and more continental areas. The structure is very poor and the potential for a storm slab or hard slab to step down to weak basal facets is scary. Continue to monitor this structure as temperatures rise and weaken the firmer, overlaying structure.

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:  

  • April 6-8: wet loose avalanches on southerlies have stepped down to large D3 slabs (peeling entirety of the last storm snow off old firm surfaces) that have run far into the flats. Mostly in lower elevations under 4500, but some higher.
  • Large wet debris running far into flats on south side of Tone’s Temple

    Slabs pulling out from wet loose off of southerlies along Worthington Glacier

    More fresh releases off Girls Mountain south face.

  • April 3 small D1 avalanches triggered on southerly aspects at high elevations.
  • April 3: Hard wind slab collapse reported near the top of couloirs/ridgeline
  • April 2: human triggered small (D1) wind slab avalanche reported on a southerly aspect, released from thin coverage on rocks above
  • March 31: D2 human triggered avalanche on N aspect at 3500′

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 Intermountain Forecasts.
Sarah Carter

Forecaster: Sarah Carter