December 20, 2017

Issued: Wed, Dec 20, 2017 at 9AM

Expires: Sat, Dec 23, 2017

Light winds around Thompson pass this morning are deceiving.  Moderate wind during the snow storm yesterday transported significant amounts of low density snow to the lee of gullies and ridges. Cautious route finding and conservative decision making essential. Re-group out of harm’s way.


Above 2,500ft High

1,800 to 2,500ft Considerable

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

Yesterday’s storm included lower density snow and moderate winds – expect windslab on lee features.  Pockets lee of ridges and gullies are likely still sensitive to human trigger.  Expect to find cross loaded features and large wind pillows.

With time and settlement, expect the storm snow to become increasingly cohesive.

We have no new field observations since the storm began yesterday but expect to see significant natural loose snow avalanching on steeper slopes.

Recent Avalanche Activity

Yesterday’s storm left lower density snow covering our advisory area.  Low visibility prevented gathering field observations.   In the past few days, a few pockets of windslab to size D1 were observed primarily above 3000′ in the lee of ridges and gully walls. Similarly, in Moonlight Basin skiers triggered shallow windslab which propagated across the feature.  These concerns remain relevant.

Near the port, some stormslab avalanches to size D2 fell out of steep rocky rollovers above 3000′. Some evidence of wet avalanches to size D2 in steep gullies below 3000′ from the Dec.2-14 storm.  With temperatures consistently below freezing now, we don’t expect further wet avalanche activity.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):   14/28
Ridgetop Wind Forecast (direction/mph):  SE/6-20
Snowfall (in/water equivalent): 0″ /0.1″
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   4 /NE 20 /W shift to SE
Max Wind Gust (mph) / Direction   10/W  39 /SE
Temperature Min / Max (*F) 24 /28 15/24

Weather Forecast:

Cloudy today with light winds. Trace amounts of snow possible.

Additional Info & Media


SNOW HISTORY: Valdez 12/20 AM Thompson Pass 12/20 AM
24 Hour Snow / Water Equiv. 13”/ 0.8″ 10″ /0.1″
Storm Snow /Water Equiv. [12/19]  10.0″ /1.0″snow+rain 10″ /1.0″
Current Snow Depth 27″ 69″
December Snow / Water Equiv. 51″ /13.97″ 142″ / 18.7″
Total Winter Snowfall / Water Equiv. 64″ /16.22” 207″ / 24.2″
Snowload in Valdez 45 lbs/sq. ft.


Nicks Valley at 4200 ft (in): 0″ / ?” / ?”
Upper Tsaina at 1750 ft (in): 0″ / ” /1.9″
Sugarloaf at 550 ft (in): 0″/ ” /3.8″
SNOW DEPTH & WATER SURVEY (12/2017) 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:


  • 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


Interactive Map of Valdez Forecast Areas w/ Many Resource Layers (Trevor Grams)


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:

Posted in Continental Forecasts, Intermountain Forecasts, Maritime Forecasts, VAC Forecasts.

Forecaster: Ryan Van Luit