Thu, January 25, 2024 Turnagain Pass Avalanche Forecast

Thu, January 25th, 2024

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

1 - Low

Fri, January 26th, 2024

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

1 - Low

Fri, January 26th, 2024

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

1 - Low

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

Two portions of a glide crack avalanched last night on the Repeat Offender slide path that threatens the motorized uptrack. It’s hard to say, but debris may have covered a part of the uptrack. These avalanches were caught on the Turnagain RWIS camera (Thanks for keeping these cameras operating AK DOT&PF!). Otherwise, there are no other known avalanches in several days.

Time series of two glide avalanches see in the moonlight from the Turnagain RWIS camera last night 1.25.23.

Avalanche Problem 1

Glide Avalanches
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

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

Just when I thought these glide avalanches might be slowing down, and bam, there are two new brown streaks on Repeat Offender. The message continues for backcountry travelers, watch for these cracks and avoid being under them as much as possible. If you do end up traveling under these, go one at a time, go fast, and watch the slope.

If you’ve been reading the forecast daily, you’ve heard this many times before, but these avalanches are not triggered by people. They are a crazy phenomenon where the whole snowpack is oozing down the hillsides creating cracks. Every once in a while the snowpack pulls away quickly and creates a very destructive avalanche full of ice and hard snow. Although a lot of thought has gone into these, as they are common in the region, there is still a lot we don’t know about them. In 2015/16 there was a significant glide cycle that we documented.

Interestingly enough, the snowpack that is stuck to the mountainsides is quite stable. There has not been a human triggered slab avalanche for a couple weeks and it’s unlikely a person would do that today. However, there can always be surprises in the mountains. Be sure to give cornices a wide berth, watch for an unstable wind slab in steep rocky terrain, and sluffs on steep slopes with loose surface snow.

Weather

Thu, January 25th, 2024

Yesterday: Mostly sunny skies were over the region with some valley fog along Turnagain Arm. Winds were agin light from the west ~5 mph gusting 10-15. Temperatures climbed into the 20sF at the mid and upper elevations while valley bottoms remained cold (-15 to +10F).

Today: Another sunny day is on tap. Winds again should be light from the west along ridgetops (~5 mph). Temperatures should remain cold (-15 to 5F) in valley bottoms and much warmer just off the valley floors and along ridgelines, in the teens to 20F.

Tomorrow: The entrenches high pressure over Southcentral may start to break down a bit over the weekend. Friday some clouds could stream in, yet winds should remain light out of the west and temperatures cold. A chance for a few inches of snow exists Saturday through Monday. It doesn’t look like it should amount to much at this point (2-4″). Stay tuned!

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	15	0	0	76
Summit Lake (1400′)	0	0	0	n/a
Alyeska Mid (1700′)	14	o	o	74
Bear Valley – Portage (132′)	-10	0	0	–
Grouse Ck – Seward (700′)	-2	0	0	50

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	22	WSW	6	13
Seattle Ridge (2400′)	21	NE	1	5

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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