December 19, 2017

Issued: Tue, Dec 19, 2017 at 8AM

Expires: Fri, Dec 22, 2017

With the shift to southeast wind, observe where new windslab is forming. Expect the visibility to decrease this afternoon and plan your day accordingly. Cautious route finding and conservative decision making essential. Re-group out of harm’s way.

 

Above 2,500ft Considerable

1,800 to 2,500ft Moderate

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

Yesterday northeast wind transported the dry surface snow building fresh windslab on lee features. Observers in Moonlight Basin reported windslab to 8″ deep sensitive to skier trigger.  Deeper pockets lee of ridges and gullies could be sensitive to human trigger. As of midnight, a moderate southeast wind has been blowing. Expect to find cross loaded features.

Last snowfall ended Dec. 17 leaving 4-5″ dry snow. The Dec.2-14 storm snow totaled 110″. Current Thompson Pass depth is 5 feet 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 clear weather allowed for the first visuals since the last storm cycle. Much of the storm avalanche activity was buried and not clearly identifiable. A few pockets of windslab to size 1 were observed primarily above 3000′ lee of ridges and gully walls. Similarly, in Moonlight Basin skiers triggered shallow windslab which propagated across the feature.

Near the port, some stormslab avalanches to size 2 fell out of steep rocky rollovers above 3000′. Some evidence of wet avalanches to size 2 in steep gullies below 3000′ from the Dec.2-14 storm.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):   14/32
Ridgetop Wind Forecast (direction/mph):  SE/8-30
Snowfall (in/water equivalent): 2-10″ /0.84″
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   4 /NE 20 /ENE shift to SE
Max Wind Gust (mph) / Direction   12 /NNE  24 /SSE
Temperature Min / Max (*F) 24 /34 14/18

Weather Forecast:

Increasing cloud this afternoon with flurries becoming heavy snowfall by evening. Accumulation to 10″. Forecast precip. amounts to 1″ water by Wednesday. Moderate southeast wind increasing this morning 20-30mph as the front moves in.

Additional Info & Media

 

SNOW HISTORY: Valdez 12/18 AM Thompson Pass 12/18 AM
24 Hour Snow / Water Equiv. 1”/ 0.06″ 2″ /0.1″
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.
Sarah Carter

Forecaster: Sarah Carter