Saturday-Tuesday 2/4-7

Issued: Sat, Feb 04, 2017 at 8AM

Expires: Tue, Feb 07, 2017

Warm temperatures persist: consider loose wet avalanches on steep, solar baking southerlies near the port and town.

The extreme winds out of the NE have created peak to peak flagging and drifted loose snow far down windless terrain features (gully walls, rollovers, & ridgelines).  Many sensitive windslabs have been releasing naturally.  Don’t be the trigger on new, larger than expected avalanches.

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

SATURDAY SUNDAY MONDAY & TUESDAY

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 and releasing naturally. Rocky ridges, old crusts and old 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 had similar results yesterday (loose wet to size D2) and could again today. 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 3: Many steep wind loaded slopes releasing loose dry and soft wind slabs to D2 below ridgelines and rollovers
  • Feb 3: Several D2 loose wet avalanches on steep south aspects: influenced by sun and warm air temperatures in the port

Loose Wet on Port Southerlies

  • 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 3: Many D1-2 natural wind slab releases scattered on southerly aspects thoughout the pass corridor.

Windslab Near Vertigo

Windslab Near School Bus

Cracked Ice Wind Slab

  • 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 / 40
Ridgetop Wind Forecast (direction/mph): NE / 15-45
Snowfall (in):  0
WIND & TEMPERATURE
PAST 24 hours
Ferry Terminal Thompson Pass
Average Wind Speed (mph) / Direction   10 / NE  40 / NE
Max Wind Gust (mph) / Direction  31 / E  60 / NE
Temperature Min / Max (*F)  38 / 49  15 / 32

Weather Forecast:    Intense winds out of the NE and warm temperatures in the maritime continue to impact our region. Look for a gradual lowering of both this weekend and a possible build-up of clouds on Sunday afternoon. Monday looks clear, but building clouds seem to prelude the ushering in of precipitation Wednesday through the rest of the week.

Additional Info & Media

SNOW HISTORY: Valdez 2/5 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