|Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
|Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
|Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential.
|Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
|Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
|Likelihood of Avalanches
|Natural and human-triggered avalanches unlikely.
|Natural avalanches unlikely; human-triggered avalanches possible.
|Natural avalanches possible; human-triggered avalanches likely.
|Natural avalanches likely; human-triggered avalanches very likely.
|Natural and human-triggered avalanches certain.
|Avalanche Size and Distribution
|Small avalanches in isolated areas or extreme terrain.
|Small avalanches in specific areas; or large avalanches in isolated areas.
|Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.
|Large avalanches in many areas; or very large avalanches in specific areas.
|Very large avalanches in many areas.
We did not observe any recent avalanches during our tour on Friday. We anticipate some natural wind slabs to have occurred overnight.
Prior to Friday’s wind, no recent avalanches have been observed or reported since 3/7-8.
|Size (D scale)
|Unlikely to bury a person
|Can bury a person
|Can destroy a house
|4 & 5
|Can destroy part or all of a village
Extreme winds gusting ENE/E/ESE 30 to 48mph for 14 hours on Friday built wind slabs at 4500′. It will be likely to trigger a 4″ to 8″ thick wind slab at upper elevation, near ridgelines and cross loaded features. Natural avalanches are possible at upper elevation.
At 3500′, winds gusted ESE 20 to 47mph for 10 hours. It will be possible to trigger a 2″ to 4″ thick wind slab at mid elevation.
Expect wind slabs to be found on SW to NW aspects, on slopes steeper than 35º and sitting on firm crust bed surfaces that will NOT bond well.
The bad news, other than not having new snow since 2/28, is that most snow surfaces on 30º and steeper terrain on East to West aspects are firm and/or breakable crusts. More specifically, steep SE to SW aspects literally feel bulletproof. These old firm snow surfaces will have limited the amount of low density snow available for transport. Typically we would expect thicker wind slabs due to the duration and intensity of the wind, but not in this circumstance. So despite the strong to extreme winds, wind slabs will remain small in many locations.
We have come to desperate times. On our tour yesterday we quickly transitioned from skinning uphill to booting up Marmot because of firm conditions. No ones edges are sharp enough for this! Some soft snow can be found in protected locations in the flats for snowmachining but crusts can be catchy and make riding challenging.
A visual clue of strong winds and drifting snow is flagging or pluming at ridgelines. Wind slabs are easy to identify. Look for hard snow sitting over weaker snow, smooth and rounded or lens shaped features. Shooting cracks or whumping are signs of instability and indicators of this avalanche problem.
Expect the wind slab problem to improve within 24-48 hours after winds subside.
The video above shows extreme winds transporting snow, building wind slabs, eroding and scouring snow surfaces on Friday on Marmot and $1000 Run. Thanks Aimee for the $1000 run video.
If you head into avalanche terrain today, utilize strict safety travel protocols, travel one at a time from safe zone to safe zone, only have one person on slope at a time, ensure all members of your party are carrying and know how to use beacons, shovels and probes, and avoid slopes with terrain traps.
Strong to extreme winds have transported snow to leeward aspects, building large cornices over the past 24 hours. Give cornices a wide berth as they can break further back than you think. Cornices are unpredictable.
Winds gusted ENE/E/ESE 30-48mph for 14 hours on Friday at 4500′.
NWS AVG Forecast here.
NWS point forecast here.
Marmot Weather Station here.
Independence Mine Snotel here.
Frostbite Bottom Snotel here.
State Parks Snow Report and Motorized Access information here.
XC trail grooming report for Mat-Su, Anchorage, and Kenai here.