Issued: Sat, Mar 24, 2018 at 7AM

Expires: Sun, Mar 25, 2018

Above 3,500ft Moderate

2,500 to 3,500ft Moderate

Below 2,500ft Low

Degrees of Avalanche Danger ?

1. Low
2. Moderate
3. Considerable
4. High
5. Extreme

Avalanche Danger Rose ?

Avalanche Problems ?

Problem Details

BOTTOM LINE

 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.

Natural or remotely triggered avalanche, 3/23 E aspect 3000′ , lower Marmot ridge gully.

2 mm Facets that are rounding- still buried deep in the pack HS 7.5′ deep (230 cm) , weak layer 3.5′ deep (110-115cm )


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.

Stairstep Rib, 3/19, Large natural avalanche with scary terrain trap below.


 

WET LOOSE AVALANCHE PROBLEM

A Low Avalanche Hazard exists for Wet-Loose avalanches on steep southerly aspects today in the afternoon. Expect sluffs to be small in size. 

 

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.

 


 

Marmot avys that crossed road, cleared debris, natural 3/19

Marmot SW face, naturals, debris came within 100 ft of road, 3/19

South of Birthday Pass, likely 3/20, SE 4500′ , failed on persistent slab

Arkose, near Banana Couloir, W, 3800′, natural ,likely from 3/19

Marmot, SW 4000′. Triggered via Daisy Bell 3/20, SS-Xc-R3D2.5-O

 


Conditions

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.

 

Wind effect on lower Eldorado

Amazing wind sculpting on top of Eldorado

 

 

 

 

Recent Weather

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.

 

 

 

 

 

Posted in HPAC Forecasts.
Allie Barker

Forecaster: Allie Barker