Monday-Thursday 1/23-1/26

Issued: Mon, Jan 23, 2017 at 8AM

Expires: Thu, Jan 26, 2017

Windslab feels stiff and punchy. Improve your FUN and reduce your risk of triggering an avalanche by avoiding windslab on steep slopes. Getting raked through rocks with a bunch of washer machines is not FUN.

Above 2,500ft Moderate

1,800 to 2,500ft Low

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

MONDAY TUESDAY WEDNESDAY & THURSDAY

DANGER SCALE

WIND SLAB:
Elevation:
 Above 1800′
Aspect: Shifting winds have stripped and loaded (top and cross-loaded) all aspects 
Terrain:
Ridges, gullies, steep unsupported bowls, rollovers
Sensitivity:
 Stubborn
Distribution:
 
Specific
Likelihood (Human Triggered): 
Possible
Size:
 Large
Danger Trend: 
Decreasing 
Forecaster Confidence: 
Good

PERSISTENT SLAB:
Elevation: 
Mostly above 2500′
Aspect: 
All
Terrain: 
Steep rocky slopes where facets exist under old and between windslab, especially interior of Thompson Pass
Sensitivity: 
Stubborn
Distribution: 
Specific
Likelihood (Human Triggered): 
Possible
Size: 
Small – Large
Danger Trend: 
Decreasing 
Forecaster Confidence: 
Poor

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

LIST OF AVALANCHE PROBLEMS <here>

SNOWPACK DISCUSSION: Thompson Pass and most of the upper elevation terrain is scoured and wind textured from outflow north wind.

The best snow is found in wind protected valleys where the Jan.13-17 snow has settled to 6-18″. The cold, dry air has promoted near surface faceting.

Wind Scoured Pass

Wind Scoured Pass

If you are venturing into the wind affected areas, expect hard windslab on lee features.  Temperatures in the single digits F at Thompson Pass and inland slow the bonding of new windslab to old surfaces.

Large whumphs reported in the last week, remind us we cannot fully trust the snowpack where weak structure still exists. Especially inland of MP 33, we have to stay suspicious of a persistent slab problem.  There remains the slim possibility of large loads, such as multiple machines and riders in steep rocky terrain, triggering a surprising avalanche that could injure or kill.

The forecast weather will likely bring cold snow over the various bed surfaces of faceted sugar old snow, surface hoar, and windslab. As the residual northerly outflow winds are turned around to onshore southerlies, expect a warm slab of new snow sitting over the weaker interface beneath. Expect poor stability by Wednesday.

Find more photos and observations at the bottom of the page. Sharing your observations creates an informed community that everyone benefits from at some point.

Recent Avalanche Activity

Some pockets of windslab have popped off naturally in the last few days since the storm ended January 17.

coastal-zone-iconMaritime (Coastal):

  • Dec. 19: Wind slab/cornice releases during the day above the airport and on the roll-overs below South Odyssey Couloir
Windslab release off ridge above airport

Windslab release off ridge above airport ran to alders (lines mark crown and toe of debris)

  • Dec. 17: Reported mid-storm debris below the N face of Benzine sliding into the popular ski line. Many others seen in steep gullies.

intermountain-zone-iconInter-Mountain (Transitional):  

  • Dec. 19: Several new wind slab releases in windloaded gullies below Max High
Release Near Max High

Release Near Max High

Old debris seen day before off summit of Max High, but today wind slabs peeling out in loaded gullies.

Old, storm related avalanche ran off summit of Max High (see arrow), but Thursday’s wind slabs peeled out in loaded gullies below (see crown lines).

  • Dec 18: Max High Peak had some old-ish (mid-storm?) debris below the SE aspect at about MP 35 (see Trevor’s map link below for location)

interior-zone-iconContinental (Interior):

MP 51 Boulder Creek/Rice Mountain Release to ground.

Dec 19: MP 51 Boulder Creek/Rice Mountain Release to ground. Possibly storm initiated, for debris in gully seemed filled in.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  -15 / 25
Ridgetop Wind Forecast (direction/mph): NE-SE / 25/10
Snowfall (in):  4-6
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   5 / E  25 / NE
Max Wind Gust (mph) / Direction  16 / ENE  35 / NE
Temperature Min / Max (*F)  12 / 19  -15 / 0

Weather Forecast:      Snow coming for the foreseeable future in the upper elevations. Above freezing temperatures possible at sea level from Tuesday afternoon through Thursday afternoon. Starting Tuesday a foot of heavy wet snow at Thompson Pass possible by Wednesday. A total of three feet of new snow may accumulate at Thompson Pass by Saturday afternoon.

Additional Info & Media

SNOW HISTORY: Valdez 1/23 AM Thompson Pass 1/22 AM
24 Hour Snow / Water Equiv. 0” /0′ 0″ /0.0″
Storm Snow /Water Equiv. (1/13-1/17) 46.4” /3.2″ 54″ /4.2″
Current Snow Depth 37″ 30″ (wind scoured)
January Snow / Water Equiv. 46.9″ /3.2″ 54″ / 4.2″
Total Winter Snowfall / Water Equiv. 142.8″ / 13” 197″ / 18.6″
Snowload in Valdez 47 lbs/sq. ft.

 

SNOWFALL for LAST 24 HRS at OTHER STATIONS:
Nicks Valley at 4200 ft (in): 0″
Upper Tsaina at 1750 ft (in): 0″
Sugarloaf at 550 ft (in): 0″
SNOW DEPTH & WATER SURVEY (1/3/2017) Depth Snow Water Equivalent
Milepost 2.5 Valdez  22.7″  4.7″
Milepost 18 27.9″ 5.9″
Milepost 29 Worthington Flats 44″ 9.9″
Milepost 37 Tsaina River bridge 33.8″ 5.6″
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>
  • Thompson Pass RWIS weather station <here>
  • MP 30 Nicks (Happy) Valley weather station at 4200 feet <here> (scroll to Nicks Valley)
  • Valdez Glacier UAF weather station at 6600 feet <data here> <map here>
  • Further weather resources <here>

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 VAC Forecasts.
Pete Carter

Forecaster: Pete Carter