Tuesday-Friday

Issued: Tue, Nov 29, 2016 at 8AM

Expires: Fri, Dec 02, 2016

Need some winter gear? Winter Gear Swap today November 29 4-8pm at the PWSC atrium.

Tune in to KCHU Wednesday morning 9-10am for Coffee Break with Valdez Avalanche Center.

Visibility might be challenging today with ground blizzard-like conditions at Thompson Pass.

If you adventure into the alpine, 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 without wind affected slab snow.

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 None

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

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

DANGER SCALE

PERSISTENT and WIND SLAB:

Elevation: 2500′ and above
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>

SNOWPACK DISCUSSION: While we haven’t quite reached avalanche threshold in the lower elevations, above 2500′ pockets of windslab with a persistent weak layer beneath can be found lee to ridge lines, rollovers and gullies. Adding your weight could trigger an avalanche that knocks you over rocks or into a terrain trap. 

We have on average 21″/55cm of snow at Thompson Pass. The depth is variable due to wind distribution. Wind forecasted to 75 mph Tuesday will strip ridges and windward slopes. Pockets of hard windslab are forming with sastrugi growing in texture and depth. In places, this windslab sits on facets (sugar snow) that has the potential to fracture and propagate.

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

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

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

Some isolated pockets of windslab popping off near ridgetops to size 2, mostly south and west aspects.

Recent Weather

WEATHER FORECAST for TODAY at 3,000 ft:
Temperature Forecast (Max *F): 7-13
Ridgetop Wind Forecast (mph):  NE/30-55
Snowfall Expected Next 24 Hrs (in): 1-5″
WIND & TEMPERATURE Past 24 Hours: Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction 6 / NNE 47 / NE
Max Wind Gust (mph) / Direction 14 / NNE 58 / NE
Temperature Min / Max (*F) 22 / 27 3 / 8

Partly cloudy with flurries accumulating less than 1 inch. Cooling temperatures in the single digits fahrenheit in the alpine and interior of Thompson Pass. Northeast wind ramping up to 75 mph at ridgetops and Passes. Blowing snow with significant windchill.

Additional Info & Media

SNOW HISTORY: Valdez 11/29 AM Thompson Pass 11/29 AM
Current Snow Depth 13″ 22″
24 Hour Snow / Water Equiv. o.1” /0.01″ 1″ / 0.1″
Storm Snow /Water Equiv. (11/26-29) 6” / 0.8” 12″ / 1″
November Snow / Water Equiv. 22.3″ / 4.1″ 49″ / 5.9″
Total Winter Snowfall / Water Equiv. 22.3″ / 4.1” 72″ / 8.3″
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>
  • Nicks (Happy) Valley MP 30 USGS NRS snotel at 4400 feet <here>(drop down menu – Nicks Valley)
  • 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