The Bottom Line: The hazard rating above treeline is MODERATE while noting the consequence of triggering one of these DEEP and WIDE avalanches.....There is a buried layer of surface hoar that is widespread. This SCARY problem could persist into the springtime....
Problem 1: Persistent Slab
Distribution: All aspects above treeline. Size: Large-Very Large. Likelihood: Possible. Sensitivity: reactive.
Description: Above 3000', natural avalanches up to size D3 with up to 4' crowns have been observed, particularly on north aspects. There is a widespread buried weak layer (surface hoar). There have not been recent slab avalanches reported but this weak layer is still WIDESPREAD and deadly. Snowpit stability tests can be falsely reassuring - such as ECTX, because the buried weak layer is deep and also slowly gaining strength. Evaluate ALL avalanche terrain carefully, choose mellower terrain, AND consciously choose group spacing. If SNOW is the Question, Terrain is the Answer. Now is NOT the time to casually choose large terrain features or objectives.
Problem 2: Loose Avalanches - dry likely, wet possible.
Distribution: All aspects and elevations. Size: Small. Likelihood: Possible. Sensitivity: Reactive.
Description: Nearly an inch of new moisture just arrived and has been shedding as natural dry loose avalanches. As the sun and warm temperatures continue over the next few days more small natural dry loose, and wet loose below 1000', avalanches are expected. Remember that point-release avalanches may be small but they can still knock a rider off of or into a terrain trap.
Problem 3: Glide Avalanches.
There are open cracks from the port to 42 mile between 3500-4000' on multiple aspects. There have been multiple full releases near Girls Mtn and on the Deserted Glacier. It is important to remember glide cracks can release at any time and are not associated with human triggers. New snowfall is covering up these gaping, crevasse-like features so use caution particularly when traveling in FLAT LIGHT. The best way to manage this problem is to limit (AKA avoid) travel underneath and beside them.
The current list of known open glides cracks from West to East:
On Feb 6 numerous point releases from steep south and west aspects are observable around Valdez. There are no signs that these loose avalanches are stepping down into slabs.
On Feb 6 around Thompson Pass there were many point releases with no step downs or crowns. A few specific observed point-releases are: N. Odyssey, Catchers Mitt, and Moonlight Basin.
A large slab avalanche has been easily observable in Benzene Alley, probably from Jan 29. There is up to 15' of debris. SS-N-R3~-D2.5-3 (ran 2000'~). Pictures on VAC Facebook page.
On Jan 30th multiple remote triggered and natural avalanches were observed between Nicks (gulley 3) and RFS. Crown heights were up to 4 FEET, above 3000' on north and south facing aspects. Reports continue to CONFIRM surface hoar was the weak layer, This layer is widespread and was buried on Jan 23.
Please share your field observations including signs of stable snow HERE.
The most recent NWS rec Forecast can be found HERE:
340 PM AKST Thu Feb 7 2019
The Thompson Pass Mountain Forecast covers the mountains (above
1000 ft) surrounding Keystone Canyon through Thompson Pass to
Temp at 1000` 20 F 28 F
Temp at 3000` 24 F 22-28 F
Chance of precip 0% 0%
(above 1000 FT) 0.00 in 0.00 in
(above 1000 FT) 0 in 0 in
Snow level sea level 400 ft
Wind 3000` ridges LGT/VAR LGT/VAR
SNOWPACK BIG PICTURE: The older snowpack is quite stable (good strength and structure). Any new snow since Jan 23 that HAS NOT AVALANCHED is likely to be sitting on widespread surface hoar and is current STILL UNSTABLE. Above 3500' there is up to 4' of new slabs sitting on this week layer.
Recent snowpack history, from top to bottom:
Feb 3-6: 0.7" SWE and 8" of snow from Valdez to Thompson Pass. 8" on 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 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'.
Jan 13-22: Mostly clear and dry with light to moderate north winds. Widespread Surface Hoar growth and Near Surface Faceting.
Jan 12-13: 3-10" of new snow with little wind.
Jan 4-12: was 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.
Above 4000' the snowpack averages well over 300cm deep and has good strength and structure (few lemons). Below 4000', the snowpack is significantly shallower and has old problem layers that are bonding well (rounding) and currently dormant: facet-crust combos and BASEL facets (all the way to sea level).
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.
The current hazard rating is MODERATE above 2000' because of a buried weak layer that has recently produced large avalanches. Triggering these avalanches is becoming less likely; but the consequence will be the same: deep crowns, wide releases, 2 story debris piles, and long runouts. More info is available by clicking FULL FORECAST below.
Please share your field observations HERE.
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