Sunday-Wednesday 2/11-2/14

Issued: Sun, Feb 11, 2018 at 8AM

Expires: Wed, Feb 14, 2018

12-16” of snow is expected to fall on Thompson Pass Sunday evening through Monday. The avalanche danger will quickly rise during this storm, and on Tuesday/Wednesday remain at considerable or even high avalanche danger!

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

Sunday Monday Tuesday
& Wednesday

DANGER SCALE

 

WIND SLAB:
Elevation:
   Above 2000′
Aspect:  
 Lee of ridges, gullies, ridgetops
Terrain: 
  All terrain exposed to wind
Sensitivity:
   Responsive
Distribution:   
Specific
Likelihood (Human Triggered): 
Possible
Size:   
Small – Large
Danger Trend:
 Steady
Forecaster Confidence:
   Good

PERSISTENT SLAB:
Elevation:
   Above 2500′
Aspect:
   All
Terrain: 
  35+ degrees steepness
Sensitivity:
   Stubborn
Distribution:   
Specific
Likelihood (Human Triggered):   
Possible
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

LIST OF AVALANCHE PROBLEMS <here>

SNOWPACK DISCUSSION: 

The talk of the forecast is the 12-16” of new snow that is expected to fall on Sunday/Monday. Before you enter avalanche terrain, give this new snow AT LEAST 24 hours to bond with the old snow surface. The recent cold temperatures have caused a significant layer of hoar frost crystals to grow (Facets/Surface Hoar, 1-3+mm). In addition to the buried hoar frost, the new snow will need an extended period of time to allow the older weak layers deeper in the snowpack to adjust to this newly added weight of 12-16” of powder. Previously to this new snow,  there has been a variety of concerns in the snowpack including the newly buried hoar frost, and stout recently formed windslabs, all of which is sitting on a deeply buried surface hoar layer about 1 CM thick, 2-6 feet down in the snow pack. This deeply buried surface hoar layer is wide spread through out the Valdez/Thompson Pass Region.

Below 2000′ there is a very stout rain crust that will act as a perfect sliding surface for any potential new snow.

Recent Avalanche Activity

No new observations.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  20 / 29
Ridgetop Wind Forecast (direction/mph): VAR / 0-40
Snowfall (in): 12-16”
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   3 / ENE  10 / NE&SE
Max Wind Gust (mph) / Direction  3 / ENE  20 / NE
Temperature Min / Max (*F)  15 / 27  -1 / 23

Weather Forecast:  A decent amount of moisture seems to be heading towards Valdez. According to the National Weather Service, 12-16” are expected to fall on Thompson Pass between Sunday evening and Monday.

Additional Info & Media

SNOW HISTORY: Valdez 2/11 AM Thompson Pass 2/11 AM
24 Hour Snow / Water Equiv. 0”/ 0″ 0″ / 0″
Storm Snow /Water Equiv. (2/6) 1.5” / 0.1″ 3″ / 0.2″
Current Snow Depth 25″ 72″
February Snow / Water Equiv. 1.5″ / 0.1″ 3″ / 0.2″
Total Winter Snowfall / Water Equiv. 79″ / 22.15” 293″ / 30.5″
Snowload in Valdez 39.5 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS / STORM TOTAL (Jan.13-16) / STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 0″ / 22″ / ?”
Upper Tsaina at 1750 ft (in): 0″ / 19″ / 2″
Sugarloaf at 550 ft (in): 0″ /rain” / ?”
SNOW DEPTH & WATER SURVEY (2/5/2018) Depth Snow Water Equivalent
Milepost 2.5 Valdez  22″  7.6″
Milepost 18 32.5″ 9.6″
Milepost 29 Worthington Flats 62″ 19.4″
Milepost 37 Tsaina River bridge 52.6″ 16.4″
This survey is done the first week of each month.

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, Intermountain Forecasts, Maritime Forecasts.
Kyle Sobek

Forecaster: Kyle Sobek