The Bottom Line: The hazard rating is Considerable throughout the advisory area with both loose wet avalanches & wet slab avalanches likely, and storm slabs possible. Avoid all Avalanche terrain.
Problem 1: Wet Avalanches
Distribution: All aspects below 3000'. Size: Small to Large. Likelihood: Likely. Sensitivity: Touchy - Reactive.
The freezing level has been as high as 4000'+ in the past several days. Heavy rain on snow means wet avalanches - both Wet Slab and Wet Loose, and they could be LARGE (D3+ is possible). Avoid all avalanche terrain below the freezing level and avoid traveling within the runout zone.
Problem 2: Storm Slab
Distribution: All aspects above Treeline. Size: Small- Large. Likelihood: Possible. Sensitivity: Stubborn.
Description: In the past several days there have been numerous natural and skier triggered LARGE (D3) avalanches. The snowpack is adjusting to the most recent precipitation but our observations are limited regarding the storm snow concern.
Special Note: Glide Avalanches.
There are open cracks from the port to 42-mile between 3500-4000' on multiple aspects; but predominantly on solar aspects. There has been much more glide activity through the main part of the winter than normal. There have been multiple other full releases near Girls Mtn, Deserted Glacier, and Town Mtn. It is important to remember glide cracks can release 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.
The current list of known open glide cracks from West to East:
Please share your field observations including signs of stable snow HERE.
The most recent NWS rec Forecast can be found HERE:
The Thompson Pass Mountain Forecast covers the mountains (above
1000 ft) surrounding Keystone Canyon through Thompson Pass to
Temp at 1000` 42 F 33 F
Temp at 3000` 32 F 30 F
Chance of precip 80% 80%
(above 1000 FT) 0.23 in 0.21 in
(above 1000 FT) 0-3 in 0-3 in
Snow level 2000 ft 1100 ft
Wind 3000` ridges S 0-10 mph E 0-11 mph
SNOWPACK BIG PICTURE: Above 3000' there is 4'+ of new snow sitting on a variety of old surfaces. Mostly, the new snow is bonding well to the old surface; but further interior (north of 35 mile) now has buried facets and surface hoar. The January 23rd buried surface hoar has been dormant for several weeks. Except for rare, interior, isolated slopes, our avalanche problems are within the new snow or at the new/old interface. Below 2500' the snow is moving towards isothermal.
Recent snowpack history, from top to bottom:
March 16-Present: An atmospheric river dominates the forecast with light winds, steady rain in the lower elevations, and accumulating snow in the upper elevations. 4" of rain (SWE)! Below 3200' (roughly) the snowpack is diminishing. 4+ feet of new snow is accumulating in the upper elevations. There has been reports of natural and human triggered slab avalanches during this time period and numerous small wet loose avalanches in steep, low & mid-elevation terrain.
March 7-16: A consistent series of gulf lows produced slow and steady precipitation. 2.4" SWE in Valdez, and 3.1" at Thompson Pass which produced up to 3' of new snow above 3000'. There has been light-moderate south and easterly winds loading north and west faces slightly more than east and south faces. There were no reports of natural slab avalanches during this time period, but numerous small wet loose avalanches in steep, low elevation terrain.
Feb 22-March 7: Calm high pressure with overall warm temps (40F in town on multiple days) and only a few hours of moderate north winds. There have been no signs of the Jan 23rd persistent weak layer in the maritime region. There has been widespread surface facet formation; especially further north/interior.
Feb 20-22: High N-NE winds, rapidly transporting any available snow (70mph gusts). In certain places the wind built new slabs and alternatively stripped all the new snow back to old layers and rain crusts.
Feb 16-18: Over 2" SWE and 2' of snow with little wind.
Feb 7-14: Nearly 0" new snow and building north winds (70mph NE gusts on Feb 14 at Thompson Pass.) Widespread surface hoar growth up to 6mm. In windy locations, and close to the pass, most of this surface hoar has been knocked down. A 'drizzle crust' formed near the pass up to 5500' and was observed buried 55cm down on Loveland at 5000' (on Feb 20.)
Feb 3-6: 0.7" SWE and 8" of snow from Valdez to Thompson Pass. 8" of new snow was recorded at 5500' on Catcher's Mitt. Freezing level was sea level throughout this cycle.
Jan 30-Feb 1: Natural avalanche cycle on all aspects above 3000', up to size D3. Most ran on buried surface hoar (Jan 23rd layer).
Jan 28-30: 2" SWE in Valdez, moderate winds, freezing level 1000'.
Jan 23-25: Multiple days of warm and wet with periods of rain up to 2500' which buried the Jan 23rd Surface Hoar layer.
Jan 13-22: Mostly clear, cold, and dry with light to moderate north winds. Widespread Surface Hoar growth (up to 15mm) and Near Surface Faceting.
Jan 12-13: 3-10" of new snow with little wind.
Jan 4-12: VERY cold and dry: moderate winds and wind chill reaching -50F. Pockets of surface hoar and widespread near surface faceting.
Dec 30-Jan 3: The New Year's Eve storm brought nearly 2.5" of SWE to Valdez and almost another 1" (SWE) on the 2-3rd of January. The rain line was 1200' during the Jan 2-3 storm, forming a 1-3" crust locking up all the snow beneath it. These storms accumulated over 3' above 2000' near Thompson Pass. Both of these storms had little wind.
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.
It has rained up to 4000' in the past 72 hrs. And the advisory area has received 4" of water (SWE) in the past week. Small to large avalanches are likely at all elevations. The hazard rating is Considerable at all elevations and aspects in all 3 zones.
Click FULL FORECAST for more information.
Please share your field observations HERE.
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