A MODERATE avalanche hazard exists for persistent slab, wind slab and loose dry avalanches at upper elevations. Human triggered avalanches are possible and natural avalanches are unlikely.
Slab avalanches are the main concern, up to 1-5 feet deep (consistent with the depth of the snowpack), and large enough to bury, injure, or kill a person.
A LOW hazard exists at low to mid elevations, natural and human triggered avalanches are unlikely.
AVOID STEEP SLOPES WITH TERRAIN TRAPS; choose slopes with gentle, fanning runouts.
PREVIOUS ADVISORIES AND UPDATES HERE
Problem 1: PERSISTENT SLAB
Poor structure in the snowpack has been slowly stabilizing over time, but flaws in the snowpack still exist.
A number of weak, faceted layers in the snowpack will make triggering slab avalanches 1-5 feet deep possible at upper elevations, on all aspects. It may be possible to trigger avalanches in surprising ways, from adjacent slopes, from the flats below, or from connected terrain. Upper elevations have a thicker snowpack and more pronounced wind loading and cross loading on a variety of aspects. Avalanches will be more likely to trigger on unsupported slopes, in rocky terrain, with slope angles 35° and steeper. Avoid slopes with terrain traps.
At mid to lower elevations slab avalanches will be unlikely, but may be possible in extreme terrain or in isolated locations. Look for, and be cautious around, an upside down snowpack consisting of stiff, strong snow overlying weaker, sugary snow. Mid to lower elevations have a thinner, more stable snowpack, which has faceted out with recent cold weather, diminishing the load on weak layers, degenerating the slab component, and leaving the entire snowpack with fist to four finger sugar (faceted) snow.
Pictured below, a snow pit from 1/11 shows that it takes strong force to initiate or trigger an avalanche, but once triggered the propagation potential is present and could result in a large avalanche.
Problem 2: WIND SLAB
Recent WSW winds have loaded small wind slabs on leeward aspects and cross loaded features, generally North to East, at upper elevations. It will be possible to human trigger small wind slabs up to 2-6" thick. Triggering small wind slabs will not be a major hazard, unless it carries you into other terrain traps, such as rocks and cliffs. Our snowpack is thin and rocks are lurking just below the surface.
Additional Problem: LOOSE DRY
Low density, loose, dry snow exists in some locations, especially in wind protected areas. If you are able to find soft snow, you will likely be able to trigger small volume loose dry avalanches on slopes 40° and steeper. These avalanches are not likely to be big enough to bury you, but may knock you off your feet or carry you into other hazards.
Many small natural and human triggered dry loose avalanches were observed this week.
It is possible, but unconfirmed, that a few, small, shallow, human triggered wind slab avalanches occurred this week.
Small loose dry avalanche on Martin Mine:
Human triggered, small, loose dry avalanches with possible small wind slab(s) triggered on Marmot Mountain, SW Face yesterday:
Cross loaded slopes and terrain features with wind texture on Bullion Mountain, SE, above approx. 3900':
Wind scoured east ridge of x4068 with sastrugi:
Old, likely natural, slab avalanche from New Year wind event (Dec 30-Jan 2) on Punk Spines, West, approx. 3900', viewers left of Stairstep. This is representative of the potential avalanche hazard that may still be human triggered in isolated locations. Any significant, rapid new load, such as new snow or wind, may activate similar activity.
This week’s weather at 3550′:
Temps averaged 7ºF, with a low of -5ºF and a high of 16ºF.
IM reported 1" of new snow.
Overnight at 3550′:
Temps averaged 7°F.
No new snow.
This week’s weather at 4500′:
Temps averaged 3ºF, with a low of -8ºF and a high of 11ºF.
Winds averaged S 3 mph, max 12 mph . Gusts averaged SW 7 mph, max gust SW 29 mph.
Overnight at 4500′:
Temps averaged 3ºF overnight, with a Low of -4ºF.
Winds averaged SSE 6 mph overnight. Max gust SSE 19 mph.
NWS Rec Forecast HERE
State Parks Snow Report and Motorized Access information HERE
View past advisories in the archives HERE.
Light to moderate winds today and into tonight will not be increasing the avalanche hazard. Models show light to moderate wind speeds continuing through Sunday. While wind speeds will be strong enough to transport snow, there is not much available snow left to transport.
A trace of snow is in the forecast for tonight.
The avalanche hazard is expected to remain the same through the weekend.
NWS point forecast HERE
Mark your calendars for the annual Hatcher Pass Avalanche Workshop coming up on Saturday January 19th. Please carpool as parking is limited.
Save the date: HPAC Annual Fundraiser and Cabin Fever Reliever, Saturday,February 2, 2019 at the Moose Lodge in Palmer. Tickets available now for $20 HERE or $25 at the door.
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