Wed, January 12, 2022 Turnagain Pass Avalanche Forecast

Wed, January 12th, 2022

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

2 - Moderate

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

There were no known slab avalanches triggered either naturally or by people yesterday. However, there was not a lot of traffic out testing the slopes. The photo below is of a natural wind slab avalanche from Monday during the stormy weather on the backside of Seattle Ridge in Zero Bowl. Believe it or not, there were several small sluffs triggered midday by the sun warming the top 3-4″ of light new snow, also pictured below.

Wind slab avalanche, likely triggered by a chunk of cornice breaking off, during the storm on Monday, 1.10.22. Photo taken 1.11.22.

Shallow loose snow sluffs triggered by the sun warming the top 3-4″ of new low density snow. 1.11.22.

Avalanche Problem 1

Wind Slabs
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.

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

After a pleasant break in storms yesterday with a bit of sunshine poking through, another weather system has moved in overnight. This has brought increasing easterly winds, light snowfall, and continued warm temperatures. Only 1-2″ of snow has fallen in Girdwood and Turnagain Pass by 6am this morning but another 1-3″ may fall through the day (light rain to 300′ or so). The easterly winds along the ridgetops will be our main concern. They increased to 20-25mph overnight and should continue to rise near 30mph with stronger gusts today. Hence wind slab avalanches forming in Monday’s storm remains the avalanche problem.

The winds today are from the same direction as those on Monday when 10-12″ of new snow fell at Turnagain. That means wind slabs will just be getting a bit bigger than they were. They are sitting on a mixture of weak faceted snow and crusts that was the old surface and may not be bonding very well. Interestingly enough, yesterday we found Monday’s snow to not be very reactive on test slopes and in pits despite the fact they were sitting on weak snow – maybe due to slabs being too thin and not quite heavy enough. Either way, crusts and facets under a slab are not something to write off without more data and we should keep a conservative mindset when approaching the bigger terrain.

Things to watch for if you are headed out today:

Active or previous wind loading? Any wind loaded slope is suspect to slide.
Cracking in the snow around you? Or collapsing (whumpfing) in the snow under you?
Any signs of recent avalanches?
Stick your hand in the snow and see how much of Monday’s snow is on that old crust. That’s the size of a potential slab that could be triggered.

Storm slabs: In areas that have not seen the winds, keep in mind there still may be some lurking storm slabs that we could trigger. These should be on the shallower side (10-12″) and are associated with Monday’s snow over the crust as seen in the video below.

In this snow pit on Seattle Ridge, the new snow wanted to slide off the crust easily when pulled, but at the same time, didn’t want to propagate in our pit tests.

Lower elevations: Monday’s storm created a crust up to 1,500 – 1,800′ and triggering an avalanche is unlikely from around 500′ to 1,500′ due to the crust. What is possible is an avalanche releasing from above and running into this zone.

Rain fell as high as 1,500′ on Monday creating a crust with clearly seen runnels in the 500 to 1,500′ elevations band. Seattle Flats, 1.11.22.

Weather

Wed, January 12th, 2022

Yesterday: Cloudy and obscured skies cleared out yesterday afternoon for some sunshine across Turnagain Pass. Ridgetop winds were light from the east during the day before picking up to 15-20mph with gusts in the 30’s since 6pm last night. Around 1-2″ of snow has fallen overnight and temperatures are in the 20’s along ridgelines and 30’s in valley bottoms.

Today: Cloudy skies with light snowfall (light rain below 300-400′) are expected today. Between 1-3″ of snow could fall through the day. Easterly ridgetop winds should increase to 20-30mph with stronger gusts. Temperatures look to hover in the mid 30’sF at sea level to 1,000′ and in the 20’sF along the ridgelines.

Tomorrow: Increasing snowfall is forecast for Thursday as the storm intensifies. Between 4-8″ of snow is possible with a rain/snow line near 500′ (potentially higher…). Ridgetop easterly winds also look to increase into the 40’s to 50’smph. Models are showing snowfall and wind tapering off on Friday into Saturday.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	31	1	0.1	72
Summit Lake (1400′)	26	0	0	25
Alyeska Mid (1700′)	31	1	0.1	48

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	22	NE	13	36
Seattle Ridge (2400′)	27	SE	12	21

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
10/27/24	Turnagain	Observation: Tincan	Michael Kerst
10/21/24	Turnagain	Observation: Turnagain Pass Road Observation	Trevor Clayton
10/19/24	Turnagain	Observation: Tincan – Below Todds Run	Andy Moderow
10/18/24	Turnagain	Observation: Taylor Pass	Eli Neuffer
10/15/24	Turnagain	Observation: Tincan Common	John Sykes Forecaster
10/14/24	Turnagain	Avalanche: Tincan	CNFAC Staff
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

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