Thu, March 28, 2024 Turnagain Pass Avalanche Forecast

Thu, March 28th, 2024

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

2 - Moderate

Fri, March 29th, 2024

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

2 - Moderate

Fri, March 29th, 2024

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

No new avalanches were observed yesterday. People did report a few new wet avalanches on the front side of Seattle Ridge on Tuesday. With clearing skies today we will hopefully get a better sense of the extent of any avalanche activity from the past few days that we have not been able to see.

Avalanche Problem 1

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

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

It’s looking like we should see a brief break in the weather today, with calm winds and a good chance for the sun making an appearance, along with some low-level clouds. Temperatures dipped down into the upper 20s F last night, but lingering clouds have kept snow surfaces warm and lower elevations were not able to refreeze last night. It is uncertain how high up you need to travel before you find supportable crusts, but it is likely somewhere around 1500′. Surfaces will likely soften as things heat up during the day, and the chances for wet snow avalanches will increase as surfaces lose strength. Loose wet avalanches will be the most likely avalanches to encounter, but they may also pull out small slabs as they run downhill.

Be on the lookout for deteriorating stability through the day as the snowpack warms. If the sun does come out, the first warning signs will be rollerballs or pinwheels rolling down steep southerly slopes, initiating near trees or rocks which warm quicker than big open snow-covered slopes. We may see surfaces heating up even if we’re stuck in the low-level clouds which can have a greenhouse effect, trapping any heat that filters through the clouds and radiating it back to the snow surface. At lower elevations, conditions are already primed for wet loose avalanches since we haven’t seen a solid refreeze in nearly 5 days.

Crusts on the surface were just barely supportable yesterday, and it shouldn’t take a whole lot of heat to break them down and increase the chances of wet avalanches. Photo from Tincan Ridge, 03.27.2024

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

The weak snow that was buried earlier this month is becoming less and less likely to make avalanches. We can still find it in snowpits, but it is not producing as many concerning test results and it has been over a week since we saw any avalanches failing deeper in the snowpack. These persistent weak layers always have some uncertainty, so we’re not writing it off entirely just yet. It’s worth keeping in mind if you are considering traveling in bigger terrain, especially since the most likely place to find the layer will be at upper elevation shaded slopes. That said, we would be surprised if someone were to trigger an avalanche deeper in the snowpack today.

The layer of surface hoar that was buried earlier this month was still visible in the snowpit yesterday, but did not produce any alarming results. 03.27.2024

Weather

Thu, March 28th, 2024

Yesterday: Skies were mostly cloudy with some sun poking through in the afternoon. We received a trace to 2” snow, with rain staying below 100 to 200’. Winds were light and variable at around 5 mph. High temperatures were in the mid 30s to low 40s F, with lows overnight in the mid 20s to low 30s F.

Today: It is looking like we’ll see a break in the clouds today before stormy weather returns tomorrow. Skies should be partly cloudy with low-level clouds possible and little to no wind. High temperatures should be in the upper 20s to mid 30s F with lows in the mid 20s F. No precipitation is expected.

Tomorrow: The first round of stormy weather is expected to arrive tomorrow, with more on the way for the weekend. It is looking like wind will be the main event, with easterly winds picking up to 20 to 40 mph and gusts up to 50 mph. We may see 1 to 3” snow with rain line starting to creep up but staying below around 200-300 feet. Skies should be mostly cloudy with temperatures in the mid 20s to low 30s F.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	32	tr	0.1	95
Summit Lake (1400′)	34	tr	0.1	41
Alyeska Mid (1700′)	33	tr	tr	98
Bear Valley – Portage (132′)	37	rain	0.1	–
Grouse Ck (700′)	36	0	0	63

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	25	WNW	2	6
Seattle Ridge (2400′)	27	N	2	6

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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