Hatcher Pass Avalanche Center

Hatcher Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, March 27th, 2021 - 7:00AM
Expires
Sun, March 28th, 2021 - 7:00AM
Forecaster
Allie Barker
The Bottom Line

The tides have turned and the persistent slab is active again after receiving approximately 10″ of new snow and 1″ SWE on Thursday. Small to large Persistent slabs will be likely to human trigger today and naturals will be possible on all aspects, although more likely on East to South to West aspects, at all elevations. Dry loose sluffs will be possible to human trigger on steep slopes greater than 40º.

Remotely triggering an avalanche will be likely today which means you, your partner, and other parties are at risk of getting caught. Careful snowpack evaluation, cautious route finding and conservative decision making will be essential this weekend if venturing into avalanche terrain.

 

Special Announcements

Thank you to the Palmer City Council for your generous financial support to HPAC.


Buy a map and support your local avalanche center.  Maps will be available at Alaska Mountaineering and Hiking (AMH), The Hoarding Marmot, Backcountry Bike & Ski and on https://www.kickstepapproaches.com/hatcher-pass-map

These maps sold out in 24 hours but will be available again soon. Stay tuned!

Thanks to our sponsors.
Sat, March 27th, 2021
Upper Elevation
Above 3,500'
Considerable (3)
Avalanche risk
Mid Elevation
2,500'-3,500'
Considerable (3)
Avalanche risk
Low Elevation
Below 2,500'
Considerable (3)
Avalanche risk
Upper Elevation
Above 3,500'
Avalanche risk
Considerable (3)
Mid Elevation
2,500'-3,500'
Avalanche risk
Considerable (3)
Low Elevation
Below 2,500'
Avalanche risk
Considerable (3)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Recent Avalanches

Numerous natural, human and remotely triggered avalanches were observed on Friday, March 26 after receiving 10″ of new snow and approximately 1″ of water.

Most notably is the remotely triggered avalanche on Marmot that crossed and closed the road.

3/26 Remotely triggered avalanche on Marmot 4000′ SE aspect

 

Same avy as above

 

Debris from Marmot avalanche running approximately 2000′ and well below the road on the road run.

 

Debris covering the road from Marmot avalanche.

Other remotely triggered avalanches on Marmot SW face.

Remote trigger, The Catchers Mitt on Marmot , 4000′ W aspect

 

Remote trigger, Marmot 3600′ S aspect. This is the approximate location where the large avalanche on Marmot( that closed the road) was remotely triggered from. See two people on upper left.

 

Naturals on Marmot 3/26

3/26 Natural, Marmot 3500′ SW aspect

 

3/26 Natural, Marmot ESE 3500′

 

3/26 Natural, Gully side wall near Snogo corridor at base of Marmot, 2500′ E aspect.

 

Natural on Divide Ridge

3/26 Natural , Lower Divide Ridge 3200′ SSE

 

Snomachine triggered

3/26 Snomachine triggered avalanche with a lucky escape . Location unknown

Human triggered

3/26 Human triggered , Eldorado 4000′ E aspect

 

 

 

Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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

Small to Large Persistent Slabs, 8″ to 2.5 feet deep, will be likely to human or remotely trigger today on all aspects, although more likely on East to South to West aspects where stout crusts exist, at all elevations. Naturals will be possible. Expect small avalanches in many areas or large avalanches in specific areas.

Thursdays 10″ of new snow and 1″ of water was clearly enough to tip the balance in the snowpack. Storm slabs, shallow wind slabs, and persistent slabs were all observed on Friday. Most notably were the remotely triggered storm slabs failing on persistent grains which stepped down into the old weak sugary faceted snow.

A widespread weak layer of buried near surface facets (and facets/depth hoar in the bottom of the pack) and a widespread crust bed surface exist in much of the terrain at Hatcher Pass.  Finding a slab will be the one variable that determines whether you trigger an avalanche or not.  There are two persistent slab problems.  Shallower problem:  Today it will be possible to human trigger or remotely trigger avalanches failing 8-12″ deep on the buried near surface facets sitting on the suncrust/drizzle crust or drizzle crust, depending on aspect. Deeper problem: The second concern is the deeper weak faceted sugary layer buried 2 to 2.5 feet deep. It will be possible to trigger either or both of these weak layers.

Triggering avalanches remotely can be an especially dangerous situation. Someone does not need to be on slope to trigger the avalanche. Especially in a snowpack with high propagation potential, a person can initiate a fracture from some distance away. We call these “remote” triggers. It’s common to remotely trigger an avalanche from the ridge above a slope, a gentler slope next to the avalanche and especially from a flat or gentle area below the avalanche. Needless to say, if you remotely-trigger an avalanche, the snowpack is extremely unstable and you need to choose your routes very carefully.

Conservative decision making will be the name of the game this weekend.  Tracks on a slope are not an indicator of stability. Red flags such as cracking, collapsing, whumping are signs of instability.

Safe Travel Habits Save Lives

 *Make a plan and keep eyes on your partner
* Ski/Ride one at a time
* Get out of the way at the bottom
* Carry and know how to use rescue gear

 

 

Avalanche Problem 2
  • Dry Loose
    Dry Loose
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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

Small to large dry loose sluffs will be possible to human trigger today on slopes steeper than 40º.

Thursday’s 10″ of new snow combined with near surface facets and cooler temps overnight will sluff easily today, although slower moving, and fail on the sun/drizzle crust which will make for a good bed surface.

We recommend using good sluff management if you decide to step out into steeper terrain. No matter the size, these avalanches can catch, carry and sweep you through hazards, if not managed properly.

Weather
Sat, March 27th, 2021

Independence Mine received approximately 10″ of new snow and 1″ SWE on 3/25 with moderate too strong SW wind gusts for a short duration throughout the storm.

 

Temps past 24 hrs at 3550′

 

Winds past 24 hrs at 4500′

 

IM 3550′ past 24hrs

 

 

 


NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

Observations
Recent Observations for Hatcher Pass