Above 3,500ft Moderate
2,500 to 3,500ft Moderate
Below 2,500ft Low
Degrees of Avalanche Danger ?
A Moderate Avalanche Hazard exists for Persistent Slabs today. It will be possible to human trigger Persistent slabs on all aspects, at mid and upper elevation on slopes above 35º.
A Low Avalanche Hazard exists for Wind Slabs today. Expect small avalanches in isolated areas or extreme terrain on SW > NE aspects, at upper elevation, on slopes above 35º.
It is still possible to human trigger or remotely trigger a wind/persistent slab that steps down into the old persistent weak layer, as seen in many natural avalanches earlier this week.
Expect wet-loose activity to become the norm on southerly aspects as we trend towards warmer weather and the Alaskan sun shines longer every day. Expect wet-loose sluffs, small in size, on south through southwest aspects on slopes above 40º in the afternoon.
PERSISTENT SLAB AVALANCHE PROBLEM
A Moderate Avalanche Hazard exists for Persistent Slab avalanches at all elevations on all aspects, on slopes 35º and steeper. Expect avalanches to be up to D2 –D3 in size, and 2-4 feet deep. Evidence of this layer exists in portions of terrain, but is not always obvious. This problem will most likely be stubborn to trigger.
Evidence of this problem is specific and continues to linger in the depths of the snowpack. This problem is deeper on northerly aspects and shallower on southerly aspects. Most persistent slab activity occurred during the natural cycle on 3/19, after a wind event, and a rapid storm load that deposited upside down snow. This storm stressed the already weak, poor structure, and tipped the stability balance. Stability has improved considerably, but it is still possible to trigger this type of avalanche. Either a natural, or more likely a remotely triggered avalanche, was observed 3/23, on the lower SE ridge of Marmot , E aspect, 3000′. See PICTURE below.
Don’t let powder fever sabotage your human factor decision-making abilities. Storm slabs and wind slabs have healed and stabilized for the most part, making it more unlikely for these problems to step down into the persistent weak layers.
This low probability/high consequence hazard will continue to alternate through dormancy and reactivation the rest of the season. It will be difficult predicting where and when persistent slab avalanches will occur. This avalanche problem may allow multiple riders on the slope before avalanching.
Continuing to practice safe travel protocol and choose safer terrain that avoids funneling into terrain traps. Use communication devices, spread out, let your partner know when you think you should be spreading out, use safe and effective safe zones out of the runnout the the avalanche problem you are concerned with. Anticipate avalanche runout being further than you may think! See HERE.
Carry a probe, beacon, shovel, airbag if possible- practice with and know how to use these tools.
WIND SLAB AVALANCHE PROBLEM
A Low Avalanche Hazard exists for Wind Slab avalanches today at upper elevations, on SW through NE aspects, on slopes 35º and steeper. 11″+ new snow this week combined with moderate winds have formed slabs 6-12″ thick slabs. Expect mostly small avalanches, D1 to D1.5 in size.
Winds slabs will be stubborn to unreactive to trigger near and below ridgelines, and on side wall gullies at upper elevations. Visual clues will be obvious.
It will be possible for wind slabs to step down into the deeper, weaker persistent grains under the Valentines Day layer. This could be 2-3 feet deep or deeper in isolated locations.
Expect wind slab instabilities to continue to improve.
WET LOOSE AVALANCHE PROBLEM
Recent Avalanche Activity
Numerous natural avalanches occurred during and after the last storm cycle on 3/19.
One , likely remotely human triggered, persistent slab, was observed on 3/23 on the south ridge of Marmot, E facing gully, 3000′.
For more avalanche pics, see OBSERVATIONS here.
Conditions are variable. Expect to find a little bit of everything, from snow that makes you work for it- to-dreamy powder and everything in between including: sastrugi, wind slab, wind crusts, firm sun crusts, and cakey powder. Timing is everything right now.
This week’s weather at 3550′:
Temps averaged 22ºF, with a low of 8ºF and a high of 35ºF.
IM reported about 11″ of new snow between 3/18 and 3/19 with 1″ of water (SWE).
Overnight at 3550′:
Temps averaged 18° F.
No new snow overnight.
This week’s weather at 4500′:
Temps averaged 18ºF, with a low of 7ºF and a high of 31ºF.
Winds averaged ESE 5 mph, max ESE 15 mph . Gusts averaged ESE 12 mph, max gusts ESE>NE 29 mph.
Overnight at 4500′:
Temps averaged 17ºF overnight.
Winds averaged 2 mph overnight, with a max gust 6 mph, varying direction E>NW>SSW>S.
NWS recreational forecast for Hatcher Pass here
NWS point forecast here
State Parks snow report here
Additional Info & Media
Expect the avalanche hazard to remain the same through the weekend.
NWS is calling for temps 24º at 3000′. Winds NE 5-25 mph today, increasing to NE 15-30 mph tonight.