December 21, 2017

Issued: Thu, Dec 21, 2017 at 8AM

Expires: Sun, Dec 24, 2017

Good visibility will make it tempting to test new areas. Cautious route finding and conservative decision making essential. Re-group out of harm’s way.  Don’t be tempted to follow other’s tracks if they don’t match your risk tolerance.

 

Above 2,500ft Considerable

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

Tuesday’s (12/19) 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 larger wind pillows.

We’re expecting the storm snow to become increasingly cohesive.

On steep slopes, we expect loose snow to become easily entrained.

Last snowfall ended Dec. 19 leaving 10-15″ (25-38cm) of dry snow. The Dec.2-14 storm snow totaled 110″. Current Thompson Pass depth is 6+ feet (200cm) with depth increasing with elevation. On Little Girls at about 3500′, Dec.15, an observer reported finding an average snowpack depth of 8-9′ with 4-5′ of that being December’s storm snow.

Recent Avalanche Activity

Yesterday’s clearing trend continues, allowing for great visibility.  Tuesday’s (12/19) storm is settling and adjusting to the additional load with minimal winds since the storm cycle ended Tuesday evening. At various aspects throughout the advisory area, a few pockets of windslab and loose snow to size D1 (and one size D2) were observed primarily above 3000′ lee of ridges and gully walls, and near rocky outcrops.

Most of the evidence of avalanche activity prior to the 12/19 storm is becoming obscured with the additional new snow.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):   18/26
Ridgetop Wind Forecast (direction/mph):  E/2-12
Snowfall (in/water equivalent): 0.1″ /0.01″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   4 /NE 20 /NE
Max Wind Gust (mph) / Direction   11 /NE  29 /NE
Temperature Min / Max (*F) 19 /28 12/22

Weather Forecast:

Clear skies with calm to light wind. Wind gusting in the upper elevations across peaks and ridges.

Additional Info & Media

 

SNOW HISTORY: Valdez 12/21 AM Thompson Pass 12/21 AM
24 Hour Snow / Water Equiv. 0”/ 0.01″ 0″ /0.11″
Storm Snow /Water Equiv. [12/10-18]  3.5″ /3.5″snow+rain 46″ /6.4″
Current Snow Depth 16″ 60″
December Snow / Water Equiv. 38″ /13.17″ 132″ / 17.6″
Total Winter Snowfall / Water Equiv. 51″ /15.42” 197″ / 23.1″
Snowload in Valdez 45 lbs/sq. ft.

 

SNOWFALL at OTHER STATIONS:
LAST 24 HRS (12/19 AM)/STORM TOTAL (12/10-18)/STORM WATER EQUIV.:
Nicks Valley at 4200 ft (in): 0″ / ?” / ?”
Upper Tsaina at 1750 ft (in): 0″ / 6″ /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:

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.

Forecaster: Ryan Van Luit