Sat, November 25, 2023 Turnagain Pass Avalanche Forecast

Sat, November 25th, 2023

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

3 - Considerable

Sun, November 26th, 2023

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

2 - Moderate

Sun, November 26th, 2023

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

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

The glide avalanche cycle continues, with widespread activity near Girdwood and Turnagain pass. This includes glide avalanches and fresh glide cracks continuing to form on Raggedtop, Max’s, Penguin, Seattle Ridge, and Sunburst, to name a few.

Avalanche Problem 1

Wet Loose
N E S W NW NE SE SW

Aspect/Elevation
Certain

Very Likely

Likely

Possible

Unlikely

Likelihood
Historic (D4-5)

Very Large (D3)

Large (D2)

Small (D1)

Size

Wet Loose

Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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

As the warm and wet weather continues, wet loose avalanches remain the primary concern today. We’ve now seen four consecutive days with rain, and although the rain line is slowly starting to drop it looks like we can expect rain to around 2000-2300′ today. All of this moisture in our mid- and low elevations is saturating the snowpack, increasing the likelihood and size of wet loose avalanches.

Be on the lookout for wet loose avalanches in steep terrain today, and be aware of natural activity as well as the good chance that a person will be able to trigger an avalanche today. Even a small loose avalanche can have severe consequences if you get carried through terrain traps like trees, alders, gullies, or rocks.

Debris from multiple wet loose avalanches above the Placer Valley, just south of Skookum. 11.24.2023

Glide avalanches like this one on Max’s continue to release across the advisory area. 11.24.2023

Avalanche Problem 2

Wind Slabs
N E S W NW NE SE SW

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

Likelihood of Avalanches

Size of Avalanches

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

For elevations above 3000′, all of the precipitation in the past four days has fallen as snow, adding up to 1-2′ of new snow for most of the advisory area. Moderate to strong easterly winds are expected to continue today, making sensitive wind slab avalanches 1-4′ deep in the high alpine. Some avalanches may release naturally while the wind is still blowing, and the likelihood for a person triggering a wind slab avalanche remains high in these upper elevations.

This new snow is loading a snowpack with older buried persistent weak layers. We haven’t seen many signs of activity on these deeper layers since the storm began, but there is also a higher level of uncertainty because we have really limited observations. Higher uncertainty requires wider margins of safety, so if you are trying to get into the high country today be sure to be thorough with your snowpack assessment and cautious with your terrain choices.

Additional Concern

Glide Avalanches

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.

More info at Avalanche.org

We have seen a lot of glide activity over the past week, with multiple glide avalanches and new glide cracks continuing to open up. These avalanches are large, destructive, and unpredictable. With all of the recent activity and a similar weather pattern continuing today, we are expecting to see more glide activity before it stops. You can limit your exposure by avoiding spending any time below glide cracks.

Weather

Sat, November 25th, 2023

Yesterday: We saw another day of warm and wet weather yesterday, with most areas picking up around 0.5” water and rain up to 2500-3000’. Portage continued to exceed the rest of the area, picking up 1.64” rain in the past 24 hours. Easterly winds were strongest yesterday morning, blowing 20-30 mph with gusts over 50 mph.

Today: Moisture will continue to trickle in this morning and taper through the day, with the snow line slowly starting to drop back down to around 2200’ by the end of the day. Winds will be out of the east at 15-25 mph with gusts of 20-30 mph. Skies will be mostly cloudy.

Tomorrow: Another pulse of precipitation will pass through tomorrow morning, bringing 0.1-0.5” water with the highest amounts near Girdwood and the rain line slowly dropping to around 1200-1500’ through the day. Winds will be out of the east at around 5-15 mph in the morning, switching westerly as the low pressure system passes in the afternoon. Skies will be mostly cloudy.

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

	Temp Avg (F)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	37	0.2	28
Summit Lake (1400′)	34	0.1	16
Alyeska Mid (1700′)	36	0.66	24
Bear Valley – Portage (132′)	41	1.64	–

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	29	ENE	15	48
Seattle Ridge (2400′)	32	SE	11	22

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/13/24	Turnagain	Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South	H Thamm
05/13/24	Turnagain	Observation: Turnagain Pass non-motorized side	Amy Holman
05/12/24	Turnagain	Observation: Warm up Bowl	Tony Naciuk
05/07/24	Turnagain	Observation: Turnagain Pass Wet Slabs	A S
04/29/24	Turnagain	Avalanche: Turnagain aerial obs	Tully Hamer
04/27/24	Turnagain	Observation: Johnson Pass	Noah Mery
04/23/24	Turnagain	Observation: Turnagain Sunny Side	Travis SMITH
04/21/24	Turnagain	Observation: Bertha Creek	Anonymous
04/20/24	Turnagain	Avalanche: Spokane Creek	Schauer/ Mailly Forecaster
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster

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