Saturday-Tuesday

Issued: Sat, Nov 26, 2016 at 8AM

Expires: Tue, Nov 29, 2016

Despite the desire to get out there and play in the fresh snow on this long weekend, make sure you travel wisely. Start in low angle terrain….utilizing ridges and small rollovers to do some testing and evaluation. Considering variability and wind loading before working your way onto steeper slopes.

Not only do you have to consider the moving surface snow, but also the high possibility of poor bonds beneath it. Our clear and cold periods have created some weak surface crystals that could make things touchy out there.

Areas of buried hard slabs with a persistent weak layer beneath are scattered about the higher, wind-exposed slopes lee to ridge lines, rollovers and gullies.

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

Above 2,500ft Moderate

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

PERSISTENT SLAB:

Elevation: 1800+
Aspect: Southerlies lee to NE wind
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: Strong NE winds are transporting and loading new and previously loaded slopes. Not only should you be concerned with new slabs, consider the older, weakly-bonded, hard slabs that were highly sensitive due to poor bonding (CTV & ECTP3: Q1 SC) with the buried facets below. Just because they are deeper and out of sight doesn’t mean they should be out of mind.

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:

New snow will continue to stack up on a variety of old surfaces: scoured ground, hard windslab, surface hoar or faceting soft snow. As always, time with help with the bonding of new snow to old, but freshly buried facets and surface hoar could delay this and cause problems. The only way to know is to investigate for yourself.

While the older snow being buried was right side up (strong at the bottom and getting softer near the surface) in places, other wind loaded features had some weak bonds with buried NSF (near surface facets) failing easily (CTV and ECTP3). These persistent grains should be respected and monitored where they are found.

That makes for two main weak interfaces that are worth tracking and testing. Please let us know what you find out there!!!

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 recently seen avalanche activity.

Recent Weather

WEATHER FORECAST for TODAY at 3,000 ft:
Temperature Forecast (Max *F): 22
Ridgetop Wind Forecast (mph):  SE/15-25
Snowfall Expected Next 24 Hrs (in): 6-9″
WIND & TEMPERATURE Past 24 Hours: Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction 9 / NE 22 / NE
Max Wind Gust (mph) / Direction 17 / ENE 40 / NE
Temperature Min / Max (*F) 22 / 28 2 / 8

Due to the weak momentum of this most recent storm front, 8 inches of nice snow accumulated in town, 1 flake landed at 10 Mile, and maybe 1-2 inches hit the pass.  With this next cycle we can expect a bit more…up to another 6-9 inches to stack up by Sunday morning. This next front will bring stronger onshore winds from the SE, pushing more interior and over the pass.  Sadly, the storm will likely end warm….topping the the snow off  in the low elevations with with a rain crust frosting……mmmm.

Additional Info & Media

SNOW HISTORY: Valdez 11/26 AM Thompson Pass 11/26 AM
Current Snow Depth 11″ 19″
24 Hour Snow / Water Equiv. 8” /0.8″ 1″ / 0.1″
Storm Snow /Water Equiv. (11/20) 8” / 0.8” 1″ / 0.1″
November Snow / Water Equiv. 15″ / 3.7″ 38″ / 5″
Total Winter Snowfall / Water Equiv. ?″ / ?” 61″ / 7.4″
Snowload in Valdez ?
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.

Weather Quicklinks:

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

Forecaster: Kevin Salys