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ARCHIVED - Forecasts expire after 24 hours.
Issued
Tue, January 30th, 2024 - 7:00AM
Expires
Wed, January 31st, 2024 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger remains CONSIDERABLE at the higher elevations (above 2,500′) where strong easterly winds created wind slabs in the 8-18″ of new light snow from yesterday. Wind slab avalanches should be easy to trigger on slopes with wind deposited snow. The danger is MODERATE below 2,500′ for the chance of finding a new wind slab. At all elevations, watch for shallow storm snow slabs and sluffs, including in sheltered areas. Additionally, glide avalanches remain a concern and cracks could be hard to see and avoid; keep a close look out.

GIRDWOOD/PORTAGE/PLACER VALLEYS:  Highest snow amounts were seen in these areas (up to 18″ of new snow). Avalanches could be much larger and more dangerous than those found at Turnagain Pass.

Special Announcements

CHUGACH STATE PARK:  Over the past 2 days around a foot of new light snow has fallen in Anchorage’s Front Range. Southerly winds bumped up yesterday afternoon, blowing the new snow around and likely into touchy wind slabs. Extra Caution is recommended due to easily triggered avalanches in the new and wind blown snow. Check out these two reports from yesterday HERE and HERE.

RESCHEDULED for Feb 3rd!
Anchorage (Glen Alps): The Avalanche Rescue Skills Workshop will be this Saturday. The event is hosted by the Anchorage Nordic Ski Patrol and Friends of Chugach Avy. Come anytime between 10:30am and 3:30pm to practice with your rescue gear. Several stations will be set up and folks available to assist and ask questions. Cross your fingers the weather isn’t too cold this time.

Tue, January 30th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Wed, January 31st, 2024
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Wed, January 31st, 2024
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice 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.
Recent Avalanches

With cloudy skies and poor visibility yesterday, we have not had a good look around to see if there was much in the way of natural avalanche activity from the new snow on Sunday night/Monday.

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

After a welcome shot of snow Sunday night into Monday (storm totals below), unfortunately the east winds ramped up last night along many ridges. The Sunburst and Max’s weather stations reported gusts of 65 and 67 mph respectively with sustained winds generally in the 20s. The good news is, the wind was short lived and has died off this morning. It is expected to remain light and variable until picking back up tomorrow from the northwest. That said, new wind slabs will be what to watch for today.

 

 

Wind Slabs:  Keep a close eye out for any slope steep enough to slide that has been wind loaded. Chances will be pretty good you’ll be able to trigger an avalanche on those slopes. The new snow is not likely to be bonding very quickly in general and with a new wind slab on top, it’s the perfect recipe for an avalanche. Hence, watching for areas of wind deposited snow, stiffer snow over softer snow, and cracks that shoot out from under you or your machine will be clues you’ve found a slab.

Storm snow soft slabs:  On sheltered slopes with 8 or more inches of new snow, it’ll be good to see if the new snow is ‘slabby’ enough to form a soft slab without any wind effect. Quick hand pits and test slopes can help suss this out. In this case, shallow storm snow avalanches are possible and could be large enough to be dangerous in areas with over a foot of new snow.

Sluffs in the new snow:  Sluffs should be very easy to trigger on steep slopes. If the new snow is loose enough to not form a slab, then sluffs will likely be your biggest concern.

Storm Totals (*estimated mid elevations*)
Turnagain Pass:  6-10″ (0.4″ SWE)
Girdwood Valley:  10-18″ (0.8 to 1.1 SWE)
Portage Valley:  14-18″ (1.3″ SWE)
Summit Lake:   6-8″ (0.5 SWE)
Seward/Lost Lake:   6-10″ (0.7  SWE)
Thompson Pass:  Several feet – jealous! (Valdez Avalanche Center)

Avalanche Problem 2
  • Glide Avalanches
    Glide Avalanches
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
Aspect/Elevation of the Avalanche Problem
Specialists develop a graphic representation of the potential distribution of a particular avalanche problem across the topography. This aspect/elevation rose is used to indicate where the particular avalanche problem is thought to exist on all elevation aspects. Areas where the avalanche problem is thought to exist are colored grey, and it is less likely to be encountered in areas colored white.
Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.
Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Don’t forget about those glide cracks that are hidden under the new snow! These things can avalanche at anytime, as you know if you’ve been reading along this month. Looking for crinkly snow surfaces can help to clue us into these things as well as looking for just the cracks. Any slope with an unnatural look to it is suspect to slide. The advice remains the same; do our best to avoid being under them and if needing to travel under them, go fast, one at at time, and watch the slope as well as out partners.

Weather
Tue, January 30th, 2024

Yesterday: Mostly cloudy to obscured skies were over the area yesterday with light snow showers. An additional 1-5″ of snow fell, favoring the Girdwood and Portage Valleys. Ridgetop winds bumped up from the east in the evening/overnight (20’s gusting 50-65mph). Temperatures plummeted back into the single digits with the increasing winds.

Today:  Partly cloudy skies, patches of sunshine, and valley fog are all expected today as the storm slowly moves out. Ridgetop winds should be light and variable. No precipitation is forecast and temperatures should remain cold at all elevations (-10 to +10F).

Tomorrow:  Clear skies return tomorrow (Wed) with what is looking to be a short outflow wind event. Models are showing northwest winds picking up along ridgetops in the afternoon (15-25mph) and extending into Thursday morning. Otherwise, clear skies and cold temps (-20 to 0F) are expected through Friday.

PRECIPITATION 24-hour data (6am – 6am)

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 7 1 0.1 81
Summit Lake (1400′) 5 1 0.1 n/a
Alyeska Mid (1700′) 5 6 0.4 87
Bear Valley – Portage (132′) 10 4 0.4 –
Grouse Ck – Seward (700′) 15 2 0.2 56

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 17 ENE 17 65
Seattle Ridge (2400′) 10 SE 8 19
Observations
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.
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