Issued: Sat, Feb 03, 2018 at 7AM

Expires: Sun, Feb 04, 2018

Hatcher Pass Avalanche Center Annual Fundraiser and Cabin Fever Reliever,

Saturday, February 10th at the Moose Lodge in Palmer.

Get your tickets online here! or cash only at Backcountry Bike and Ski or Active Soles in Palmer. Come bid on dozens of awesome silent auction items. Bring your dancing shoes and shake the Mananuska winds away! This is your chance to show your support for your local avalanche center!

Above 3,500ft Considerable

2,500 to 3,500ft Considerable

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 Considerable Hazard exists for Wind Slab Avalanches. Strong Easterly winds picked up on 1/28 through 2/2, transporting low density snow and building Wind Slabs on Southwest to Northwest aspects, with the highest concentration on West aspects, at mid to upper elevations. Human triggering avalanches in specific portions of terrain will be likely today. Natural avalanches will be possible if strong winds continue.

A Low Hazard exists at low elevation.

 


WIND SLAB AVALANCHE PROBLEM

A Considerable Hazard exists for Wind Slab avalanches at mid to upper elevations. A Low Hazard exists at low elevation.

Strong, sustained, Easterly winds gusting throughout the week and into the 50’s mph yesterday have built touchy wind slabs, approximately 6 inches to 2 feet deep, sitting over weak, faceted, sugary snow, mostly on Southwest to Northwest leeward aspects and cross-loaded features and gullies. Avalanches will be mostly D1 in size, but some will be capable of reaching D2 in size in specific, broad, wind loaded locations today.

Wind slabs can have a smooth appearance and a drummy, hollow like sound when traveling over them. Pole/probe tests can easily reveal the structural problem of stiffer snow overlying weaker snow. Both soft and hard slabs exist. Hard slabs will have the ability to propagate longer distances and result in larger, more dangerous avalanches. They may also be triggered remotely from a distance, adjacent to, from below, or break above you. Whumphing and shooting cracks are bulls eye clues for this avalanche problem.

Wind slabs will be sensitive to trigger on slope angles as low as 30° and may be remotely triggered from lower angle slopes. On Friday, we triggered a significant avalanche from a location on a slope at 28°, which propagated 300 feet onto a steeper slope that maxed out at 35°.

Buried surface hoar has been found lurking in the snowpack and may be partially responsible for some of the natural wind slab activity earlier in the week. Buried surface hoar was found in the snowpack in the avalanche mentioned above, however, the weak layer that failed was comprised of faceted grains and did not contain surface hoar. Further testing at this site found that surface hoar in another layer in the snowpack was unreactive, and scarce. Both surface hoar and faceted grains will have the ability to propagate long distances, especially with stiff wind slabs overlying them. Staying safe in these conditions will require you to identify features of concern and avoid those locations.

Test slope, wind slab avalanche triggered from 28 degree slope location, propagated 300 feet, 6 – 24 inches deep. West, 3700′, 28-35 degree slope. R3D1 in size.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Pit profile here

Recent Avalanche Activity

Several small natural wind slab avalanches were observed and reported -observations here- Feb 1 and 2 after the wind spiked.  Most avlanches occured on west aspects at mid and upper elevations on slopes above 30º. Cracking, collapsing , and whumping were observed on lower angle 28º slopes on 2/2 and resulted in triggering a 300ft wide 6-24″ deep wind slab on a west aspect at 3500′.

2/2 – Winds transporting snow on Rae Wallace ridgeline and previous, older, natural wind slab avalanches indicated by arrows. There are more in the picture, but these are the easiest to see, and depict the pattern of wind slab development from strong easterly winds cross-loading specific features. Strong winds can transport snow well beyond the crest of ridgelines and breakovers, and deposit wind slabs mid slope. Strong winds top loading and cross-loading features adds complexity to the loading pattern and requires sharp observational skills to identify problem areas.

2/2 – East winds transporting snow on X4068

Observed on 2/2 – Natural wind slab avalanche on South Ridge of Marmot Mountain, SSW, ~2900, D1 in size

Observed on 2/2 – Natural wind slab avalanche East of and above Motherlode, W, ~3300′, ~D1-1.5 in size

2/2 – Hard Slab, Intentionally human triggered test slope, D1, New snow (wind slab)/Old Snow

2/2 – Same as above showing the point at which the avalanche was triggered

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CONDITIONS – Wind sculpted hard and soft snow, sastrugi, scoured windward ridgelines, snow drifted road. Powder difficult to find.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Recent Weather

This week’s weather at 3550′:

Temps averaged 14ºF, with a low of 6ºF and a high of 21ºF.

0″ of new snow this week.

Overnight at 3550′:

Temps averaged 14.5° F.

0″ new snow overnight.

This week’s weather at 4500′:

Temps averaged 11ºF, with a low of 0ºF and a high of 20ºF.

Winds averaged E 12 mph, max E 36 mph . Gusts averaged E 22 mph, max gusts E 59 mph. Strong gusts sustained for over 12 hours on 2/2 E 48-59mph.

Overnight at 4500′:

Temps averaged  12ºF overnight.

Winds averaged 1E 5 mph overnight, with a max gust of E 48 mph.


NWS recreational forecast for Hatcher Pass here


NWS point forecast here


State Parks snow report here

Additional Info & Media

The avalanche hazard will remain elevated through the weekend and may be slow to stabilize.

Winds are forecasted to diminish today. NWS is calling for NE 3-13 mph today and about the same tonight.

 

 


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Posted in HPAC Forecasts.
Allie Barker

Forecaster: Allie Barker