Avalanche Forecast | Hatcher Pass Avalanche CenterAvalanche Forecast | Hatcher Pass Avalanche Center 01/08/2022

Sat, January 8th, 2022

Upper Elevation

Above 3,500'

2 - Moderate

Mid Elevation

2,500'-3,500'

2 - Moderate

Low Elevation

Below 2,500'

2 - Moderate

0 - No Rating

1 - Low

2 - Moderate

3 - Considerable

4 - High

5 - Extreme


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 since Wednesday.

See forecast here for avalanches earlier in the week.

Large avalanche video here from Jan 2/3

Avalanche Problem 1

Persistent Slabs
Certain

Very Likely

Likely

Possible

Unlikely

Likelihood
Historic (D4-5)

Very Large (D3)

Large (D2)

Small (D1)

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

Large persistent slabs will be possible to human trigger in isolated locations at mid and upper elevation on SE to SW aspects on slopes above 30º. It will be unlikely but not impossible to trigger a slab on other aspects. It will be possible for avalanches to fail above you, making escape difficult. Natural avalanches are unlikely.

The Jan 2-3 Bora wind event transported and drifted low density snow, building slabs on SE to SW aspects. As a result, numerous large natural avalanches occurred on Sunday and Monday, one within 50′ of hitting the road. This added stress to the already weak snowpack.

These locations will continue to be problematic. Our main concern today are locations where stiff firm slabs are sitting on top of the rain crust and carry the potential for stepping down into the weak sugary facets, increasing the size and consequence of an avalanche.

Expect slabs on SE to SW to vary in thickness from 6″ to 3′ thick and to be sitting on rain crusts mixed with weak sugary snow. Identifying these wind slabs sill be easy, look for smooth wind drifted snow. Use hand pits and poles/probes to detect this avalanche problem. Cross loaded gullies and leeward features are areas where this problem will be found. Wind slabs will stick out like a sore thumb because the remaining terrain at Hatcher Pass is shimmering firm rain crusts.

The video below highlights snowpack variability and the locations where previous wind loading is a concern today.

Rain crusts from 12/26 make travel challenging

Today we will practice safe travel protocol, never exposing more than one person at a time and avoiding large slopes with terrain traps. We will use good communication including radios. We will be carrying and know how to use the appropriate safety gear for companion rescue.

The only positive thing I can say about the snowpack is that it will give Level 2 avalanche course students something to talk about.

Weather

Sat, January 8th, 2022

NWS AVG Forecast here.

NWS Rec Forecast here.

NWS point forecast here.

State Parks Snow Report and Motorized Access information here.

Observations

Recent Observations for Hatcher Pass