December 5, 2017

Issued: Tue, Dec 05, 2017 at 8AM

Expires: Fri, Dec 08, 2017

Avalanche danger is increasing with the rapid rise in temperature and continued heavy precipitation.

Above 2,500ft High

1,800 to 2,500ft High

Below 1,800ft Considerable

Degrees of Avalanche Danger ?

1. Low
2. Moderate
3. Considerable
4. High
5. Extreme

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

Above the rainline, new storm snow is accumulating over sturdy bed surfaces from November windslab and early season facets. The new snow is being transported by moderate southerly wind.

Anticipate:

  1. 2-3 feet of storm/wind slab collapsing over weaker facets, and
  2. upside down snowpack – heavy warmer storm snow over weak old snow

Below the rainline, rain is saturating the snowpack and decreasing strength.

Excellent field reports <here>. Thanks Gareth and PWS College avalanche class.

Recent Avalanche Activity

Large avalanches heard during 12/3 night from valley floor. Roofs are sliding. Wet loose releasing in the steeps at sea level.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):   28/32
Ridgetop Wind Forecast (direction/mph):  SE/20-40
Snowfall (in/water equivalent): 7-12″ /1.5 “
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   0-5 /var  30 /SE
Max Wind Gust (mph) / Direction   8 /W  45 /SE
Temperature Min / Max (*F) 30 /37 25 /30

Weather Forecast:

This week’s accompanying atmospheric river may have as much as a foot of water (!) which will deposit a lot of snow in the upper elevations. Expect rain at sea level. With the warm wet air pushed up the Copper River through the Tsaina gorge and into the lower elevations of the continental snow climate zone north of Thompson Pass, the freezing level may rise above the elevation of Thompson Pass.

Additional Info & Media

 

SNOW HISTORY: Valdez 12/4 AM Thompson Pass 12/5 AM
24 Hour Snow / Water Equiv. 14”/2.08″ 10″ /1.1″
Storm Snow /Water Equiv. [12/3-pres]  14″ /2.08″ 30″ /3.1″
Current Snow Depth 17″ 39″
December Snow / Water Equiv. 14″ /2.08″ 30″ / 4.4″
Total Winter Snowfall / Water Equiv. 79″ /8.88” 95″ / 9.9″
Snowload in Valdez 44 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (12/4 AM)/STORM TOTAL (12/2-present)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 13″ / 20″ / ?”
Upper Tsaina at 1750 ft (in): 2″ / 2+rain” / 1.1″
Sugarloaf at 550 ft (in): 13″/ 13″ /?”
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:

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, VAC Forecasts.
Pete Carter

Forecaster: Pete Carter