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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, February 2nd, 2024 - 7:00AM
Expires
Sat, February 3rd, 2024 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is MODERATE at all elevations today. Human triggered and natural avalanches 1-2′ deep caused by wind transported snow are the most likely type of avalanche to encounter. Glide avalanches are also a concern on slopes with existing glide cracks. We recommend avoiding spending time underneath glide cracks because these avalanches release randomly and are very large and destructive.

Special Announcements

Tomorrow – if temps are warm enough – Anchorage (Glen Alps): The Avalanche Rescue Skills Workshop was rescheduled for Feb 3rd. 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.

SnowBall 2024:  Mark your calendars for Valentine’s Day, Feb 14 (7-11pm @ 49th St Brewing). Details and tickets HERE. The evening promises costumes, finger food, a rocking band, silent auction, and of course plenty of great company. Join us in supporting Chugach Avy as well as our friends at the Alaska Avalanche School.

Fri, February 2nd, 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
Sat, February 3rd, 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
Sat, February 3rd, 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

The active wind transport yesterday caused a natural avalanche near Goat Mountain in the Crow Creek area that ran down from upper elevations into treeline elevations (ob here). In addition there was a small skier triggered avalanche about 10″ deep on Lipps at about 2000′ on a wind loaded feature. We did not observe further avalanche activity, but given the widespread wind transport across the region there was likely many more small wind slabs releasing naturally.

Powder cloud from a natural avalanche on Goat Mountain near the road up to Crow Pass trailhead. Photo from Jeffrey Snegden 2.1.24

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

The combination of 8-20″ of light, cold snow on the surface plus moderate winds was forming fresh wind slabs in exposed areas yesterday. Thanks to the recent cold temperatures the new snow that fell last weekend is still very light which makes it prone to wind transport with relatively low wind speeds. Today we are expecting similar conditions with wind slabs 1-2′ deep capable of being triggered by a person or releasing naturally. At upper elevations there may not be much soft snow left to transport given how much flagging we observed yesterday. To identify areas harboring wind slabs look for active snow transport, snow surface textures indicative of recent winds, and shooting cracks on small, steep test features. In areas exposed to gap winds, like Turnagain Arm, the winds are expected to be stronger and wind slabs could be found on exposed slopes at lower elevations.

We are suspicious that the old snow surface that was buried by 8-20″ of new snow last weekend could develop into a persistent weak layer. So far we have not received any observations of larger avalanches with wider propagation occurring at this interface, but it may just be a matter of time until there is enough of a slab on top to cause larger avalanches. This type of avalanche problem might develop more quickly in areas that received more new snow last weekend, like Girdwood and Portage/Placer. We recommend a conservative approach to entering bigger terrain and carefully evaluating how well the new snow is bonding to the old snow surface.

Small skier triggered avalanche on a wind leaded feature at about 2000′ on Lipps. Photo 2.1.24

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

Glide avalanches continue to be a concern across the forecast area. Keep an eye out for glide cracks on slopes above you and try to avoid spending time underneath them. If you can’t avoid them then we recommend spreading out and travelling as quickly as possible underneath glide cracks. Glide avalanches release at random and cause very large and destructive avalanches.  It has been a few days since the last confirmed glide avalanche, but there are still plenty of glide cracks lurking along many popular travel routes.

Weather
Fri, February 2nd, 2024

Yesterday: Clear skies and very cold temperatures in the negative single digits throughout the region. Winds were out of the NW at 5-10 mph with gusts to 25 mph. No new snowfall.

Today: The pattern of cold and clear weather continues today, with temperatures expected to remain in the negative single digits F at all elevations. Winds are expected to remain light to moderate today with averages of 5-15 mph and gusts to 25 mph. In areas exposed to outflow winds, like Turnagain Arm, we expect stronger wind speeds of 15-20 mph with gusts up to 40 mph today.

Tomorrow:  On Saturday temperatures are expected to climb back up into the positive degrees F, and a small storm system will enter the area in the afternoon. Cloud cover should increase in the afternoon and winds will shift to the east with averages of 5-15 mph ahead of the expected snowfall. Timing of the snow varies between weather models, with some showing snow starting around 3pm and others closer to 6pm. Snow accumulation from Saturday afternoon through Sunday afternoon is expected to be about 2-4″. Temperatures will stay plenty cold enough to keep snow falling down to sea level.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) -2 0 0 79
Summit Lake (1400′) -11 0 0 n/a
Alyeska Mid (1700′) -5 0 0 84
Bear Valley – Portage (132′) -3 0 0 –
Grouse Ck – Seward (700′) -8 0 0 56

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) -7 NW 9 26
Seattle Ridge (2400′) -3 NW 6 12
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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