Hatcher Pass Avalanche Center
Hatcher Pass

Hatcher Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, March 31st, 2024 - 7:00AM
Expires
Mon, April 1st, 2024 - 7:00AM
Forecaster
Allie Barker
Avalanche risk The Bottom Line

The avalanche danger is CONSIDERABLE above 2500′ for WIND SLABS. The danger is MODERATE below 2500′.

Expect STORM SLABS to build throughout the day and to be likely to human trigger by the afternoon. Natural avalanches will be possible.

A major winter storm with strong winds will bring an additional 6-10″ of new snow throughout the day.

Our stale avalanche paradigm has come to an end, winter has returned, and it’s time to readjust our avalanche eyeballs with a conservative mindset.

Sun, March 31st, 2024
Upper Elevation
Above 3,500'
3 - Considerable
Avalanche risk
Mid Elevation
2,500'-3,500'
3 - Considerable
Avalanche risk
Low Elevation
Below 2,500'
2 - Moderate
Avalanche risk
Mon, April 1st, 2024
Upper Elevation
Above 3,500'
3 - Considerable
Avalanche risk
Mid Elevation
2,500'-3,500'
3 - Considerable
Avalanche risk
Low Elevation
Below 2,500'
2 - Moderate
Avalanche risk
Mon, April 1st, 2024
Upper Elevation
Above 3,500'
3 - Considerable
Avalanche risk
Mid Elevation
2,500'-3,500'
3 - Considerable
Avalanche risk
Low Elevation
Below 2,500'
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

No recent avalanches have been observed or reported due to poor visibility and stormy conditions. As soon as visibility allows, forecasters will go in the field to assess recent avalanches.

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

Wind slabs 8-16″ thick will be likely to human trigger on west to northeast (clockwise) aspects at mid and upper elevation, on slopes steeper than 30º. Natural avalanches are possible.

Wind slabs will be possible to human trigger at low elevation where winds have increased early this morning. Natural avalanches are unlikely.

A major winter storm has initiated with strong winds and extreme gusts reporting SE winds gusting 31-47mph for the past 9 hours on Marmot @ 4500′ and SE 40-62mph for 13 hours on Hatch @4561′. A few factors will play a role in this avalanche problem today.  New snow over the past 18 hours combined with the small amount of low density snow previously available for transport (prior to this storm) will reduce the size of wind slabs. Expect slabs to be small this morning and build in size throughout the day.

As of 6 am this morning 5-10″ of new snow has been reported at our snotel sites.  6-10″ of additional snow combined with strong winds is forecasted over the next 24 hour.  Expect wind slabs to be reactive and easy to initiate and to fail on weak sugary snow (buried near surface facets).

Marmot station web cam at 4500′ showing significant wind transport and sustained winds

Use hand pits and pole probes to identify wind slabs. Look for hard snow sitting over weaker snow, smooth and rounded or lens shaped features.  Shooting cracks or whumping are signs of instability and indicators of this avalanche problem.

 

 

Avalanche Problem 2
  • Storm Slabs
    Storm Slabs
  • Aspect/Elevation
  • Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic (D4-5)
    Very Large (D3)
    Large (D2)
    Small (D1)
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

10″ of new snow and 0.6″ SWE has been reported as of 6 am this morning at 3550′.  Expect storm slabs to build in size as the storm intensifies and deposits an additional 6-10″ of new snow throughout the day. By the afternoon, STORM SLABS 6-12″ thick will be likely to human trigger and natural avalanches will be possible at mid and upper elevations, on all aspects, on slopes 30º and steeper. It will be possible to human trigger small storm slabs at low elevation in the afternoon.

The Hatcher Pass lodge snowstake at 5am resembles what winter looks like!

To identify this avalanche problem use formal stability tests and hand pits to see if the new snow is behaving like a slab.  Shooting cracks and whumping will be a red flag for this avalanche problem.  Storm slabs are typically reactive for a few hours to a couple days.

Weather
Sun, March 31st, 2024

NWS AVG Forecast here.

NWS point forecast here.

Marmot Weather Station here.

Independence Mine Snotel here.

Frostbite Bottom Snotel here.

State Parks Snow Report and Motorized Access information here.

XC trail grooming report for Mat-Su, Anchorage, and Kenai here.

Observations
Recent Observations for Hatcher Pass