Valdez

Forecast as of 12/29/2018 at 22:00 and expires on 12/31/2018

Above 2,500ftModerate

1,800 to 2,500ftLow

Below 1,800ftLow

Degrees of Avalanche Danger

Avalanche Problems

Problem Details

The Bottom Line: The overall hazard is moderate above treeline due to a challenging snowpack structure and wind loaded slopes. There is a low probability of triggering any avalanche but the consequence could be high.

Problem 1: Persistent Slab.

Location: all aspects below 4000' and possibly even higher near shallow parts of the snowpack such as rock outcroppings. Size: large+. Likelihood: unlikely. Sensitivity: stubborn-unreactive. There are multiple rain crusts layered with facets throughout the region (reported only up to 4000'). There are also basel facets (weak sugar snow) at the bottom of the snowpack . . . These problem layers are gaining strength and potentially either dormant or waiting for a large load such a big storm or snow machine hitting a sweet spot. If you choose to ride on slopes over 35deg choose slopes with clean run-outs and careful selection of group spacing and safe zones.

Problem 2: OLD Wind Slab.

Location: all wind affected aspects above treeline. Size: small. Likelihood: unlikely. Sensitivity: stubborn-unreactive. Wind Slabs up to 2' thick have formed predominantly lee to the NE. Winds slab can be identified by dense, cohesive snow, cracking, and a hollow or drum like feel. Look for wind slab below exposed ridge lines and close to Thompson Pass. Stiff wind slabs can lure riders well onto the slab before failing. Stick to wind-protected areas where the surface snow is still soft and fluffy (better riding conditions usually anyway).

Additional Concern: Glide Avalanches.

There are open cracks from the port to 42 mile between 3500-4000' on multiple aspects. The current list of open glides cracks from West to East: Mile High Pk SE, Hogsback SW, Stone Mtn NE, Loveland S, Catcher's Mit S, Goodwill's S, Python NE, Crudbuster NE and NW. It is important to remember glide cracks can release into full-blown avalanches at any time and are not associated with human triggers. The best way to manage this problem is to limit (AKA avoid) travel underneath and beside them.

 

Avalanche Activity

1 large avalanche was reported on Dec 23rd: a slab avalanche near the ridgeline of RFS, below the cornice. It was reported as possibly a size 2.5, persistent slab that ran 800-1000'.

Over the past few days several small wind slabs released near Thompson Pass from human triggers and several more small cornices released naturally, south facing 3-4000'.

Please share your field observations including signs of stable snow HERE.

Weather

The most up to date NWS Rec Forecast can be found HERE

409 PM AKST Sat Dec 29 2018
The Thompson Pass Mountain Forecast covers the mountains (above
1000 ft) surrounding Keystone Canyon through Thompson Pass to
Worthington Glacier.
                   Tonight      Sun

Temp at 1000`      20 F         28 F

Temp at 3000`      22-28 F      25 F

Chance of precip   70%          90%

Precip amount
(above 1000 FT)    0.05 in      0.21 in

Snow amount
(above 1000 FT)    0-1 in       2-5 in

Snow level         sea level    sea level

Wind 3000` ridges  E 3-10 mph   SE 10-25 mph

Additional Information

BIG PICTURE: The snowpack has been settling since the last major round of storms that ended Dec 19th. Since 12-19 there has been 6" of snow in Valdez with 1" SWE; 7" of snow on Thompson with 0.5" SWE and a trace at 46mile. Above 4000' the snowpack averages over 300cm deep and has good strength and structure (few lemons). Below the rain line from the historically warm and wet October, 3500-4000', the snowpack is significantly shallower and has more problem layers: facet-crust combos and basel facets (all the way to sea level). There is barely enough snow to build a slab avalanche or travel off trail anywhere below 1500'.

TREND NYE through Jan 3, 2019:

NWS is forecasting several days of warm, wet and possibly windy storm days this next week. New snow will likely form NEW storm slabs and wind slabs. If enough moisture falls then older weak layers that are currently dormant could awaken and release PERSISTENT SLABS with significant avalanches up to size D3. If we get rain on snow then small wet avalanches will also be possible. The next forecast will be Friday Jan 4th.

If you get out riding, please send in an observation!

Do a rescue practice with your partners. Always carry a beacon, shovel, and probe, and KNOW HOW TO USE THEM. 

Practice good risk management, which means only expose one person at a time to slopes 30 degrees and steeper, make group communication and unanimous decision making a priority, and choose your terrain wisely: eliminating unnecessary exposure and planning out your safe zones and escape routes.

Alerts

The overall hazard is MODERATE due to unlikely but possibly LARGE Persistent Slab avalanches. The hazard and type of avalanche problem will change soon with the approaching warm, windy, and wet storm. All 3 zones have the same forecast. Please click 'full forecast' to get more info. Have a safe New Years and all the best in 2019 from your community supported Valdez Avalanche Center.