Friday-Monday 2/3-6

Issued: Fri, Feb 03, 2017 at 8AM

Expires: Mon, Feb 06, 2017

Strong winds out of the NE continue to scour and transport (crossload & topload) loose snow onto downwind terrain features (gully walls, rollovers, & ridgelines)….creating sensitive windslabs that can result in larger than expected avalanches. Evaluate before committing…..

Tonight!!! Feb.3, Luc Mehl, Alaskan adventurer, is sharing his route planning tools before a slideshow of one of his expeditionary traverses. EMBRACING THE APPROACH – TAKING THE LONG WAY TO ALASKA’S MOUNTAINS. 6-9pm. Valdez Civic Center.

Tomorrow!!! Avalanche Rescue Workshop. Get the TRAINING to brush the rust off your rescue skills. Hands-on practice to proficiency is critical when every minute counts. Saturday Feb.4, 9am-5pm. Valdez Civic Center. FREE for youth 10-18 years old.

 

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

FRIDAY SATURDAY SUNDAY & MONDAY

DANGER SCALE

WIND SLAB:
Elevation:
 Above 1800 feet elevation
Aspect: 
most due to shifting winds
Terrain: 
Steeper than 30 degrees: rollovers, ridges, gullies
Sensitivity:
 Responsive
Distribution: 
Specific
Likelihood (Human Triggered): 
Possible
Size: 
Small – Large
Danger Trend:
 Increasing 
Forecaster Confidence:
 Fair

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: Consistently strong to extreme outflow winds from the NE continue to dramatically displace the 1-2′ of loose snow blanketing our mountains. Intense flagging off of peaks/ridges and scouring/drifting is once again reshaping the snowscape and moving the snow onto a variety of downwind terrain features. Rocky ridges, old crusts and windslab are once again exposing themselves from under the soft newer snow. Human triggered windslab and loose snow avalanches are possible near rollovers, ridgelines, and gullies in the mid and upper elevations (above 1800′).

Due to the lack of natural activity and positive/concerning test results involving our buried persistent weaknesses, we have removed the Persistent Slab Problem from our primary concerns. Please let us know if you find anything proving otherwise.

coastal-zone-iconMaritime (Coastal):  Solar radiation and warm air temperatures Wednesday led to quickly softening/weakening new surface snow (5-7″ that fell Jan. 31). This resulted in widespread loose wet activity in steep, southerly, lower elevation terrain on Feb. 1. This very likely has led to a melt-freeze lens on the snow surface on most steep southerly aspects in the maritime. Warm morning temperatures and clear skies could have similar results today, Friday. All of this most recent snow rests on rain crusted snow that extends up to ~2500′. Over 1″ of rain fell Jan 26-27 on two feet of storm snow that started Jan.24.

intermountain-zone-iconInter-Mountain (Transitional):  

  • Near Thompson Pass the Jan.24-28 storm snow settled to about two feet with dry powder on top, available for wind transport in exposed areas. Testing Sunday showed a rough break down about 2′ at the new snow/old snow interface. Soft slabs pockets near ridgelines proved reactive with the introduction of significant forces at the edges of the slab.

interior-zone-iconContinental (Interior):  

  • The Jan.24-28 storm delivered about a foot of new snow, which settled to 6 inches of light dry powder over a breakable, more dense layer. This lays over old layers of weaker faceted snow. While there appears to not be concentrated force, basal facets were collapsing Sunday with testing above MP 40. This uncertainty with the interior snowpack, leaves the slim possibility of human triggered avalanches in upper elevation rocky terrain.

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

coastal-zone-iconMaritime (Coastal):

  • Feb 1: Widespread loose wet activity (up to D2) in steep southerly aspects during first solar radiation post storm.

intermountain-zone-iconInter-Mountain (Transitional):  

  • Feb 2: Small, D1 soft wind slabs and sluffing pulling out of steep, rocky terrain on Thompson Pass
  • Jan 30: MP 42: Human triggered soft slab near ridgeline in wind-loaded pocket from southerly winds
  • Jan 30: Scattered, small loose dry sluffs out of steep, rocky terrain

interior-zone-iconContinental (Interior):  

  • No new observations.

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  15 / 35
Ridgetop Wind Forecast (direction/mph): NE / 20-45
Snowfall (in):  0
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   10 / NE  30 / NE
Max Wind Gust (mph) / Direction  27 / ENE  59 / NE
Temperature Min / Max (*F)  35 / 44  12 / 19

Weather Forecast:    Air temperatures breaking 40*F in the port and lower elevations is mixing with cold outflowing air from the interior. Strong winds out of the north is being driven through our passes and mountain range until it seems it could back down late tonight as the high pressure moves east. Clear skies and no precipitation will dominate until some high clouds could litter the sky on Sunday before breaking up again. Possible next precipitation is far off into the Tuesday night time frame.

Additional Info & Media

SNOW HISTORY: Valdez 2/3 AM Thompson Pass 2/3 AM
24 Hour Snow / Water Equiv. 0”/0″ 0″ /0″
Storm Snow /Water Equiv. (1/31) 5.9” /0.4″ 7″ /0.5″
Current Snow Depth 40″ 40″
February Snow / Water Equiv. 2.7″ /0.2″ 3″ / 0.2″
Total Winter Snowfall / Water Equiv. 180.7″ / 16.1” 242″ / 22.8″
Snowload in Valdez 52 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 (2/1/2017) Depth Snow Water Equivalent
Milepost 2.5 Valdez  41.5″  9.8″
Milepost 18 43.9″ 9.5″
Milepost 29 Worthington Flats 61.5″ 16″
Milepost 37 Tsaina River bridge 42.1″ 9.3″
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.

Forecaster: Kevin Salys