Fri, February 14, 2020 Turnagain Pass Avalanche Forecast

Fri, February 14th, 2020

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

Sunny skies yesterday provided a good look around at any recent avalanches that occurred during Wednesday’s snowfall event (Feb 12) and also yesterday’s wind event (Feb 13th). The winds spared much of Turnagain Pass, but did create plumes and at least four natural avalanches in the Summit Lake and Lost Lake areas. We also received a report of a possible human triggered avalanche on the backside of Seattle Ridge.

Natural large wind slab occurring yesterday on Roaring Ridge in the Summit Lake Area. 2.13.20. Photo: Alex McLain

Two natural wind slabs were triggered by winds cross-loading slopes on the SE face of Seattle Ridge sometime on Wednesday, Feb 12th. This photo was taken Feb 13th from the motorized parking lot at Turnagain Pass.

Natural slab avalanche on the lower norther ridge of Wolverine (SW facing) that appears to have released early in the storm on Feb 12th. Likely triggered by a cornice fall.

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

After a dose of 10-18″ of new snow and wind over the past two days, today’s partly cloudy skies and light winds are not expected to affect the snowpack. As the pack slowly adjusts, we are trending into a ‘SCARY MODERATE’ avalanche danger. What this means is there is still a chance a person could trigger a large and dangerous avalanche, but that likelihood is decreasing. We are heading into a Low Probability / High Consequence situation (click HERE for more insight into this).

We can’t forget that 2-4′ below the snow surface lies weak faceted snow and in places buried surface hoar. These layers caused several avalanches over the past two weeks and with small snowfall events incrementally adding to the slab, the size of these potential avalanches is growing. What can we do? We know the snowpack isn’t likely to give us signs of instability until it’s too late. It could be the 10th person on the slope that triggers the slab and it could even be triggered remotely, from below or the top. We can choose to stick to lower angle terrain and avoid slopes ending in terrain traps. We can think to ourselves, ‘where will I end up if the slope slides?’ Approaching the backcountry with a conservative mindset is key now and will be for the foreseeable future.

Video link HERE.

Avalanche Problem 2

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

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 today, triggering a wind slab, or soft slab composed of the new snow from Wednesday is still possible. Watch for slopes that have been previously wind loaded or steep gullies that have been cross-loaded. These slabs could be anywhere from 6″ thick to 2′ and quite hard in places the wind was strong and softer where winds were more moderate. Cracking in the snow around you, a hollow/drum like feel of the snow surface and a generally stiffer layer of snow over softer snow are all signs of a wind slab. Heads up that a wind slab avalanche may overload deeper weak layers and initiate a much larger slab.

Cornices: These have grown over the past 36 hours and we can’t forget to give them a wide berth from above and limit time under them from below.

Plumes in the Summit Lake and Seward areas of the Kenai Mtns. 2.13.20. Photo: Alex McLain

Weather

Fri, February 14th, 2020

Yesterday: Sunny skies with cold northerly winds were over the region. Weather stations at Turnagain Pass were reporting ~10mph averages, but much stronger wind was noted further south on the Kenai. Temperatures were in the teens to single digits at all elevations.

Today: Partly cloudy skies with some periods of blue sky are forecast as a band of high clouds is moving over Southcentral AK. Ridgetop winds turned easterly last night and expected to remain light from the east today (5-10mph). Temperatures should remain in the teens at most locations. No precipitation is forecast.

Tomorrow: Again, partly cloudy skies should be over the region tomorrow with a chance for a few snow flurries at times. Winds look to swing around back to the west and remain light. A storm system is expected to push in Sunday night with snowfall slated for early next week.

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

	Temp Avg (F)	Snow Depth (in)
Center Ridge (1880′)	15	67
Summit Lake (1400′)	9	25
Alyeska Mid (1700′)	14	63

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	10	W	7	28
Seattle Ridge (2400′)	12	Variable	5	17

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

Riding Areas

The riding areas page has moved. Please click here & update your bookmarks.