Monday-Thursday

Issued: Mon, Nov 28, 2016 at 8AM

Expires: Thu, Dec 01, 2016

Free Avalanche Awareness Tonight: Monday November 28 at the Prospector 6-7:30pm
Get your winter brain turned on, ready for adventure.

With almost a foot of new snow in town, Thompson Pass received 9 inches Saturday-Monday morning. The Pass is getting closer to looking like winter wonderland. Quite a bit of bush and some open creeks still limit where you can travel. Once you get above these access issues, the avalanche avoidance game is in full swing.

Pockets of slab with a persistent weak layer beneath can be found on wind-exposed slopes lee to ridge lines, rollovers and gullies. Pay attention to how the snow sounds and feels. If it begins to get punchy or sounds like a drum, get off that slope and choose another route option.

It still is early season: Early season dangers explained here (link to summary by Avalanche Canada).

Above 2,500ft Considerable

1,800 to 2,500ft Low

Below 1,800ft None

Degrees of Avalanche Danger ?

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

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

GENERAL DANGER RATING OUTLOOK

MONDAY TUESDAY WEDNESDAY & THURSDAY
3-considerable 3-considerable 2-moderate

DANGER SCALE

PERSISTENT and WIND SLAB:

Elevation: 1800+
Aspect: South aspects lee to NE wind and West gully walls where facets are buried by windslab
Terrain: Ridgelines, rollovers, crossloaded features
Sensitivity: Responsive
Distribution: Specific features
Likelihood (Human Triggered): Possible
Size: Small to Medium
Danger Trend: Increasing continued snow & wind loading
Forecaster Confidence: Fair
Details: North wind has and will continue to load more weight and stress on persistent facets (sugar snow) lower in the snowpack.

AVALANCHE PROBLEM SCALE DESCRIPTORS:

Sensitivity: Non-reactive, Stubborn, Responsive, Touchy
Distribution: Isolated, Specific, Widespread
Likelihood: Unlikely, Possible, Likely, Nearly Certain
Size: Small, Medium, Large, Very Large (size scale <here>)
Danger Trend: Increasing, Steady, Decreasing
Forecaster Confidence: Good, Fair, Poor

LIST OF AVALANCHE PROBLEMS <here>

FURTHER SNOWPACK BREAKDOWN:

We have on average, 60cm of snow at Thompson Pass. The depth is variable due to wind distribution.

We have new snow falling on a variety of old surfaces: scoured ground, hard windslab, surface hoar and near-surface facets.

While the older snow is mostly right side up (strong at the bottom, getting softer near the surface), there are some wind loaded features that have buried NSF (near surface facets) failing easily in tests (CTV and ECTP3).

PICTURES:

20161123: Wind Slab on facets!!!! ECTP3 Q1 SC on 1mm NSF

20161123: 1F+ Wind Slab on facets!!!! ECTP3 Q1 SC on 1mm NSF

20161123: At least the snow is well bonded to the ground.

20161123: At least the snow is well bonded to the ground.

Find more photos and observations below: at the bottom of the page. Sharing your observations helps others make informed decisions about where and how to go.

Recent Avalanche Activity

No new activity reported. Expect to see isolated pockets of windslab pop off near ridgetops to size 2.

Recent Weather

WEATHER FORECAST for TODAY at 3,000 ft:
Temperature Forecast (Max *F): 23
Ridgetop Wind Forecast (mph):  NE/20-30
Snowfall Expected Next 24 Hrs (in): 1″
WIND & TEMPERATURE Past 24 Hours: Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction 9 / NE 31 / NE
Max Wind Gust (mph) / Direction 11 / NE 40 / NE
Temperature Min / Max (*F) 28 / 29 9 / 13

Partly cloudy with flurries accumulating 1-2 inches today. Cooling temperatures when clouds clear, single digits Fahrenheit at the Pass and interior. Northeast wind to 40 mph at ridgetops and Passes. Blowing snow.

Additional Info & Media

SNOW HISTORY: Valdez 11/28 AM Thompson Pass 11/28 AM
Current Snow Depth 13″ 23″
24 Hour Snow / Water Equiv. 6” /0.3″ 5″ / 0.4″
Storm Snow /Water Equiv. (11/26-28) 6” / 0.8” 11″ / 0.9″
November Snow / Water Equiv. 22″ / 4.1″ 48″ / 5.8″
Total Winter Snowfall / Water Equiv. 22″ / 4.1” 71″ / 8.2″
Snowload in Valdez 5.2 lbs/sq. ft.
SNOW DEPTH & WATER SURVEY (date) 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 beginning in December.

Weather Quicklinks:

  • NWS forecast for Northeast Prince William Sound <here>
  • NOAA NWS spot forecast for Thompson Pass <here>
  • Thompson Pass RWIS weather station <here>
  • Valdez Glacier UAF weather station at 6600 feet <data here> <map here>
  • Further weather resources <here>

SNOW CLIMATE ZONES:

  • Maritime (Coastal) – from the Port of Valdez to Thompson Pass, all waters flowing into Valdez Arm and everything south of Marshall Pass.
  • Inter-mountain (Transitional) – between Thompson Pass and Rendezvous Lodge.
  • Continental (Interior) – the dry north side of the Chugach (north of 46 Mile, including the Tonsina River).

Photo of Thompson Pass <here>

Map of Valdez Forecast areas and recreating zones <here> (Thank you Trevor Grams!)

Run map of some of the forecast area <here>

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 VAC Forecasts.
Sarah Carter

Forecaster: Sarah Carter