Saturday-Tuesday 1/7-1/10

Issued: Sat, Jan 07, 2017 at 8AM

Expires: Tue, Jan 10, 2017

Clear skies, a lowering of winds, and warming temperatures will tempt many to get out and play today, but do so conservatively and intentionally.

Firm and variable snow surfaces will test your skills and fresh wind slabs could catch you off guard.

A lot of snow moved around yesterday and may not be bonded to underlying layers quite yet.

You are likely to be the additional load that triggers an unpredictable and larger than expected avalanche.

 

Above 2,500ft Considerable

1,800 to 2,500ft Considerable

Below 1,800ft Moderate

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′
Aspect: mostly south and west
Terrain: Near ridgelines, gullies and rollovers
Sensitivity: Responsive
Distribution: Specific
Likelihood (Human Triggered): Likely
Size: Small to Medium
Danger Trend: Increasing
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: 
Medium
Danger Trend: 
Steady
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, Medium, Large, Very Large (size scale <here>)
Danger Trend: Increasing, Steady, Decreasing
Forecaster Confidence: Good, Fair, Poor

LIST OF AVALANCHE PROBLEMS <here>

SNOWPACK DISCUSSION: Not much was protected from the recent extreme, outflow wind event that started late Jan 5th and is finally starting to let up today. We saw gusts into the 90’s on Thompson Pass and the 80’s in town. Beyond a significant loading of lee slopes, it also tested our iconic salmon in town and dry-docked boats. A haze of airborne snow filled the skies as much of our soft snow sublimated away. A drive through the pass reminded me of very early season conditions….thin and rocky with alders that were once laying down popping back up here and there. Sadly, this thinning of our snowpack won’t do much for the future strengthening of our structure. Expect nearly all lee (mostly southerly and westerly facing) terrain features (rollovers, ridges and gullies) to be loaded up with new wind slabs. These new slabs are resting on the variable and questionable snow structures throughout our region. Evaluation of new slabs on Thursday demonstrated pretty good bonding with underlying layers…resulting in non-planar breaks that took some force to fail. This is reassuring and supports the lack of more natural avalanches in the last 24hrs. This does not mean that these findings are consistent everywhere in our mountain range.

VAC 20170106 Town Wind EventVAC 20170106 Wind Event

coastal-zone-iconMaritime (Coastal):
This region is generally harboring a thicker snowpack in the upper elevations that has seen consistently warmer temperatures…especially the last few days. This combination has resulted in a stronger, more predictable snow structure. The most recent avalanche activity has only involved the newest, surface snow. If you can navigate your way through the alders in the lower elevations, enjoyable conditions can be found.

intermountain-zone-iconInter-mountain (Transitional):
A large variance in depth and structure dominates this region. Weak, early season facets at the ground and between layers of windslab remain a concern, especially in steep, shallow and unsupported snowfields. Many of the storms this season have not pushed interior very far, so areas further from the ocean are generally thinner and more questionable. It has been colder on the interior side as well. These circumstances support persistent weaknesses that have been showing themselves thoughout the inter-mountain region. In the upper Tsaina Valley and north of Mile Post 36 along the highway corridor, the snow is reacting very similar to the continental region: weak, shallow structure that fails easily when loaded.

interior-zone-iconContinental (Interior):
More interior beyond Mile Post 46 and out past Billy Mitchell, the snowpack is thin and incredibly weak: mostly facets. Recent avalanches are readily stepping down to ground. This region will require significant amounts of new snow and an avalanche cycle to turn things around.

Find more photos and observations at the bottom of the page. Sharing your observations helps others make informed decisions.

Recent Avalanche Activity

Please report avalanches you see or trigger. The Valdez Avalanche Center does not dwell on the who or why an avalanche incident may have occurred, but would like to be informed about how the snow is behaving out there. This benefits all of us who recreate in this region.

coastal-zone-iconMaritime (Coastal):

  • Jan 6: Several loose dry & 1 wind slab size 1-2 avalanches out of steep rocks above 3000′.
  • Jan 6: Handful of wind slabs pulled off southerly aspects on a rocky Hogsback Ridge at MP 7 and at the hairpin below Moonlight and Odyssey.

VAC 20170106 Wind Slab S Odyssey

intermountain-zone-iconInter-Mountain (Transitional):  Avalanches inland of Thompson Pass proved there is still a dangerous buried weak layer (facets at the ground) that has a lower probability of triggering, but high consequence due to hard windslab to 2-3 feet overtop.

  • Jan 6: Two size 2 (D2) wind slabs released out of south-facing, windloaded, rocky pockets near ridgeline above Tsaina Valley on Three Stooges (MP 31)

VAC 20170106 3 Stooges above Tsaina

  • Jan 5 & Dec. 30: Wind loaded south face above Mile Post 37 near 3 Pigs: D2 slabs pulled out of steep and rocky terrain and immediately stepped down to ground

VAC 20170105 Natural Slabs 3 Pigs

  • Jan. 4: Three, size 2, south facing, slab avalanches seen looking up the Tsaina Valley: One failed on a broad face, mid slope, while the other two crowns were near a rocky, steep ridgeline.
  • Jan.1: Two size 2 slab avalanches released to ground above MP 36, south aspect above 3000′
  • Dec.31 A couple human triggered destructive size 1-2 windslab avalanches on the steep slopes of the road run
  • Dec.30: A couple destructive size 2 (D2) storm slab avalanches pulled out on North face of Berlin Wall: stepped down to rocky ground in places (crown depth estimated ~4 feet) and hit the glacier.
  • Dec.30: South facing steep, rocky gully at Mile Post 42 and ran to aldered apron

interior-zone-iconContinental (Interior):

  • Dec. 30: D2 storm slab avalanche pulled out to ground mid south slope of Mt Tiekel over Mile Post 46

 

 

Recent Weather

WEATHER FORECAST for NEXT 24 HRS at 3,000 ft:
Temperature Forecast (Min/Max *F):  0/ 20
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 25 / NE 48/ NE
Max Wind Gust (mph) / Direction 64/ NE 94 / NE
Temperature Min / Max (*F) 21 / 34  3/ 11

Weather Forecast: While our arctic blast that tested structures and our patience finally begins to drop off, don’t get too excited as cold, arctic air and pressure gradients in the interior will continue to drive a solid outflow wind into next week. Temperatures are already rising and another inversion, less severe than last week, could develop with 20*F temps at 3000′. A shift looks to possibly arrive mid-day Thursday next week which will usher in clouds, shifting of winds and hopefully a solid precipitation event.

Additional Info & Media

SNOW HISTORY: Valdez 1/4 AM Thompson Pass 1/4 AM
24 Hour Snow / Water Equiv. 0” /0.0” 0″ /0″
Storm Snow /Water Equiv. (12/30-12/31) 5” /0.68″ 18″ /1.6″
Current Snow Depth 29.5″ 31″
January Snow / Water Equiv. 0″ /0″ 0″ / 0″
Total Winter Snowfall / Water Equiv. 95.9″ / 8.16” 143″ / 14.4″
Snowload in Valdez 23 lbs/sq. ft.

img_20161228_130954img_20161228_130730

Photos of our new Nicks Valley Weather Station Python to the east, Berlin Wall to the west.

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″  Jan.3
Milepost 37 Tsaina River bridge 33.8″ 5.6″  Jan.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