Sun, April 07, 2024 Turnagain Pass Avalanche Forecast

Sun, April 7th, 2024

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

2 - Moderate

Mon, April 8th, 2024

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

2 - Moderate

Mon, April 8th, 2024

Alpine

Above 2,500'

2 - Moderate

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 new avalanches observed yesterday. The most recent activity was last Tuesday, April 2, following the April Fools’ day storm.

Avalanche Problem 1

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

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

The weather is looking to be fairly quiet today, but after a small bump in the winds last night we will be on the lookout for lingering wind slab avalanches around 6 to 12″ deep in the alpine. These will be most likely to be found on steep slopes below ridgelines, convex rolls, and steep gullies. For assessing this type of avalanche problem, pay attention to how the snow is behaving on the surface. The most suspect slopes will have stiffer snow sitting on top of softer snow. You may also notice cracks shooting out from your ski tips or snowmachine.

These lingering wind slabs shouldn’t be huge today, but they may be getting big enough to bury a person, and they can have serious consequences in bigger terrain. If you are trying to get into steeper terrain, take a minute to assess the surface conditions by hopping off your snowmachine or stepping off the skin track. Look for the best riding and safest conditions on slopes that have been sheltered from the winds.

Avalanche Problem 2

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

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

The chances for wet loose avalanches will increase as temperatures heat up later in the day. Models are showing partly to mostly cloudy skies, but that can actually help to heat the snow surface quicker by trapping in heat reflected from the snow surface. We noticed this yesterday while we were headed back down to the parking lot, and are expecting similar conditions today.

You don’t need to master the physics of snowpack energy balance to predict wet loose avalanches today. Pay attention to changing surfaces, and start moving to shaded terrain if you notice the snow become wet and sloppy as temperatures rise. The earliest indicator slopes will be steep southerly slopes with rocks or trees. Solar aspects should have supportable crusts this morning, which will likely soften as temperatures climb, and then start to fall apart if it gets warm enough. Be aware of increasing danger if you start to see rollerballs falling down slopes.

Wet Loose debris on steep south-facing terrain off the Lipps ridgeline. 04.06.2024

Additional Concern

Persistent Slabs

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.

More info at Avalanche.org

Earlier in the week we saw multiple avalanches failing on a weak layer of snow on top of a crust that was buried by last weekend’s storm. These were unusually large for storm slabs, and they were also remotely triggered – both of which are hints that a persistent weak layer may have been involved. The layer is roughly 1 to 3 feet deep and was most problematic on southeast to southwest slopes. We haven’t seen any avalanche activity that we are aware of on the layer on northerly slopes. From everything we have seen, it appears this cycle was a matter of timing, with people out in steep terrain immediately after the storm while conditions were the most reactive. This layer has shown signs of gaining strength, and we do not expect it to produce avalanches at this point. These layers can be tricky, so it is still worth keeping in mind if you are considering bigger terrain today.

Weather

Sun, April 7th, 2024

Yesterday: Skies were partly sunny to mostly cloudy with easterly winds averaging 5 to 15 mph and gusts to 30 mph. High temperatures were in the mid 20s F at ridgetops and high 30s to low 40s F at lower elevations. We received 1-2” snow overnight equaling 0.1-0.2” SWE, with rain at sea level but snow above around 100-200’.

Today: Scattered snow showers should finish this morning, with a trace to an inch of snow possible before the clouds start to break up. Winds are expected to be light out of the east at 5 to 15 mph, with gusts of 15 to 20 mph. High temperatures should be in the mid 20s to mid 30s F with lows in the mid teens to 20 F. Skies are expected to be mostly cloudy to partly sunny, with a trend towards clearing skies later in the day.

Tomorrow: The weather should remain fairly quiet tomorrow with partly cloudy skies and no precipitation expected. Winds are likely to be light out of the northwest at 5 to 10 mph with gusts of 10 to 15 mph. High temperatures are expected to be in the mid 20s to low 30s F with lows in the upper teens to low 20s F.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	29	tr	0.1	97
Summit Lake (1400′)	27	0	0	45
Alyeska Mid (1700′)	31	2	0.1	113
Bear Valley – Portage (132′)	37	rain	0.22	–
Grouse Ck (700′)	34	0	0.1	72

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	18	ENE	7	30
Seattle Ridge (2400′)	23	SE	7	15

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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