Thursday-Sunday 1/18-1/21

Issued: Thu, Jan 18, 2018 at 8AM

Expires: Sun, Jan 21, 2018

We’ve had 2-4′ (30-60cm) of new snow since January 16. If you see natural avalanches, stay far away from slopes of similar aspect/elevation.

Above 2,500ft Considerable

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

THURSDAY FR
IDAY
SATURDA
Y& SUNDAY
2-moderate 2-moderate

DANGER SCALE

 

 

STORM SNOW:
Elevation:   Above 1800′
Aspect:   All
Terrain:   35+ degrees steepness
Sensitivity:   Responsive
Distribution:   Widespread
Likelihood (Human Triggered):   Possible
Size:   Small – Large
Danger Trend:   Steady
Forecaster Confidence:   Good

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

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

LIST OF AVALANCHE PROBLEMS <here>

SNOWPACK DISCUSSION: 

Recent Storm totals range from 18’’ (46cm) near Kenny Lake/Chitina to 41’’ (104cm) at Thompson Pass. Expect wind slabs and storm snow to be a concern. As the recent storm snow settles, we expect to see it become increasingly cohesive, demonstrating slab characteristics.  Additionally, moderate winds can easily transport this relatively low density snow creating wind slabs to the lee of ridges and gullies.

Previous to this storm there were concerns of a persistent weak layer about 1-2’ under the snow surface. This persistent weak layer is now buried 3-4’ down.  Be on the look out for natural avalanche activity on this old layer. If you see natural avalanches on this layer, use extreme caution on slopes of similar aspect/elevation.

Recent Avalanche Activity

No recent reports of natural or human triggered avalanches since Tuesday, 1/16.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  19/ 26
Ridgetop Wind Forecast (direction/mph): N / 3-8
Snowfall (in): 0-Trace
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   1 / W  20 / NE
Max Wind Gust (mph) / Direction  4 / NE  31 / NE
Temperature Min / Max (*F)  29 / 37  17 / 29

Weather Forecast:  Temperatures have decreased to below freezing throughout the advisory area and will continue to drop steadily over the next several days to below 0*F (-17*C) in the interior.  Expect light to moderate winds from the Northeast with overcast to broken cloud cover through the weekend.  Trace of snow possible.

Additional Info & Media

SNOW HISTORY: Valdez 1/14 AM Thompson Pass 1/14 AM
24 Hour Snow / Water Equiv. ~”/ ~” ~″ / ~″
Storm Snow /Water Equiv. (1/13-present) rain” / 0.45″ 12″ / 0.45″
Current Snow Depth 25″ 78″
January Snow / Water Equiv. 13.25″ / 4.19 ″ 44″ / 3.55″
Total Winter Snowfall / Water Equiv. 77.1″ / 20.49” 252″ / 27.75″
Snowload in Valdez 45 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS / STORM TOTAL / STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): ~” / ~” / ~”
Upper Tsaina at 1750 ft (in): ~” / ~” / ~”
Sugarloaf at 550 ft (in): rain” /rain” / 0.4″
SNOW DEPTH & WATER SURVEY (2/1/2017) Depth Snow Water Equivalent
Milepost 2.5 Valdez  ″  ″
Milepost 18
Milepost 29 Worthington Flats
Milepost 37 Tsaina River bridge
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.

Forecaster: Ryan Van Luit