Tue, March 15, 2022 Turnagain Pass Avalanche Forecast

Tue, March 15th, 2022

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

1 - Low

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.

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

For anyone trying to squeak out a backcountry outing before this next series of storms heads in tonight, there are still some avalanche concerns in the upper elevations to look out for. The main one will be triggering an avalanche that breaks 1-2′ deep on a layer of buried surface hoar. This is our current persistent slab avalanche problem.

This layer of buried surface hoar caused a couple of near misses on Friday and Saturday. It is a tricky layer to find as it doesn’t exist everywhere; even hand pits or regular pits don’t always give us all the clues. We have also seen it release on fairly low angle slopes (around 30 deg). With time on our side and the spotty nature of the layer in general, triggering this type of avalanche is becoming harder. But that doesn’t mean we can forget about it. If choosing to head into terrain over 30 degrees in the Alpine, especially the northerlies where the snow is softer and lacking sun crusts, consider the consequences if a slab releases. Watch closely for red flags (cracking in the snow around you and collapsing/whumpfing). Also, be sure to keep with safe travel protocol (expose only one person at a time, have an escape route planned, watch your partners closely). Remember, this type of avalanche can break after several people have been on a slope, as was seen a few days ago in the near misses mentioned above.

Lingering Wind Slabs: A bump in easterly wind on Sunday was able to form shallow wind slabs in the upper elevations. These were up to a foot deep at most and becoming stubborn yesterday. That said, watch for wind loaded pockets on steep slopes. Even a small wind slab can be dangerous in steep rocky terrain.

A bit of wind effect along the Sunburst ridge yesterday. A surprise 1-3″ of snow late Sunday afternoon at Turnagain Pass made for improving turning conditions!

Glide Avalanches: New glide cracks are starting to pop out more and more. This is in addition to those we’ve been watching for some time that are staring to slowly open. Although we have not seen any of these release into an avalanche yet, they are completely unpredictable and can fail at anytime. As always, it’s a great idea to limit any exposure under glide cracks.

With clouds forecast to move in later today, solar warming should be limited and wet loose avalanches are not likely to occur. Cornices are always a normal caution hazard, but the weather today should not make them any more unstable – tomorrow will be another story however.

Glide crack on the SE face of Seattle Ridge that we have been watching for some time. It sits just to the south of the motorized up-track at the top of the Repeat Offender slide path. It looks to be slowly opening and whether or not it will release, only time will tell. Photo: Troy Tempel 3.13.22.

Weather

Tue, March 15th, 2022

Yesterday: Mostly sunny skies were over the region with some valley fog near Turnagain Arm yesterday. Ridgetop winds were light and variable. Temperatures climbed to near 30F with daytime warming and have dropped into the teens to single digits in valley bottoms overnight.

Today: Mostly clear skies above the valley fog this morning will give way to clouds by this afternoon as the next storm system moves in tonight. Ridgetop winds will be light from the east till sunset when they should climb into the 10-20mph range. Temperatures are chilly in valley bottoms this morning (5-15F) but should warm into the mid 20’sF during the day. Snowfall should begin tonight with 3-5″ falling by tomorrow morning to sea level.

Tomorrow: Heavy snow, strong ridgetop easterly winds and warming temperatures are expected tomorrow. The rain/snow line looks to reach 1,000′ by midday tomorrow. Right now we are expecting around 6-10″ of snow through the day on top of the 3-5″ expected tonight. Stay tuned on tomorrow’s forecast!

From the National Weather Service Recreation Forecast for Turnagain Pass area:

Steady snow begins tonight and increases in intensity through the morning. Precipitation will persist nearly
continuously through the week and into the weekend.

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

	Temp Avg (F)	Snow Depth (in)
Center Ridge (1880′)	23	91
Summit Lake (1400′)	20	39
Alyeska Mid (1700′)	24	N/A

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	N/A*	N/A*	N/A*	N/A*
Seattle Ridge (2400′)	22	variable	1	4

*The sunburst weather station has lost power, we are working to get it back online as soon as possible.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster
04/15/24	Turnagain	Observation: Taylor Pass	John Sykes Forecaster
04/15/24	Turnagain	Observation: Seward Highway – Tern Lake to Portage	Joel Curtis
04/14/24	Turnagain	Observation: Sunburst	T. Olsen-Lund, R. Sullivan I. Adams
04/14/24	Turnagain	Observation: Turnagain Pass Snomo	K. Gallaher
04/13/24	Turnagain	Observation: Spokane Creek	Everet Megli
04/11/24	Turnagain	Observation: Tincan	John Sykes Forecaster
04/10/24	Turnagain	Avalanche: Seattle Ridge	Schauer/ Keeler Forecaster
04/10/24	Turnagain	Observation: Cornbiscuit South Face	Todd Kelsey
04/10/24	Turnagain	Avalanche: Tincan	N. Dumont J. Carlberg

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