Turnagain Pass RSS

Archives
ARCHIVED - Forecasts expire after 24 hours.
Issued
Mon, March 11th, 2024 - 7:00AM
Expires
Tue, March 12th, 2024 - 7:00AM
Forecaster
Andrew Schauer
Avalanche risk The Bottom Line

The avalanche danger is on the rise today, and will be CONSIDERABLE above 2500′. Another round of snow combined with increasing easterly winds will make it easy to trigger a wind slab avalanche up to a foot deep. Recent snow has buried multiple weak surfaces and is not expected to be bonding well. Dry loose avalanches will be getting bigger and moving faster on sheltered slopes as the snow continues to fall. Be prepared to adopt a more conservative mindset as the avalanche danger rises today through tonight. The danger is MODERATE below 2500′.

PORTAGE/PLACER: The Placer valley is expected to be heavily favored with this round of precipitation and could see 10-12” snow during the day today, with another 8-18” by tomorrow morning. This area has been favored throughout the recent storm cycles, and avalanche conditions are expected to be dangerous on all slopes as the snow rates intensify today, with natural avalanches likely by the end of the day.

Special Announcements

Turnagain Pass Avalanche Awareness Day – Saturday, March 23
Swing by the Turnagain motorized parking lot between noon and 4pm to grab a hotdog, practice your beacons skills (we’ll have a small park set up), chat with the forecast team, and possibly test out a demo snowmachine provided by local dealers. This is a fun day designed to connect with our excellent backcountry community!

Mon, March 11th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
Tue, March 12th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
Avalanche risk
Tue, March 12th, 2024
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
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 slab avalanches were reported yesterday. We did see continued solar-triggered natural dry loose activity in steep, rocky terrain above the valley clouds.

Debris from many natural dry loose avalanches in the Virgin Creek drainage yesterday. We watched a dry loose avalanche run right through the middle of this frame shortly after the photo was taken. 03.10.2024

Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • 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

Another round of active weather is moving into the area today, and this one is looking like it will pack a little more punch than the last few days. We are expecting around 3-6″ low-density snow to fall during the day, with another 6-8″ likely tonight into tomorrow morning. Along with another round of snow, it is looking like the wind is going to start to ramp up mid-day and continue to increase tonight and tomorrow. This is going to increase the avalanche danger, with both natural and human-triggered avalanches likely on wind-loaded slopes today.

As of this morning, there is anywhere from 1-2′ of very low-density snow sitting on firm surfaces with a few weak layers mixed in the upper snowpack. Up until today, there hasn’t been a strong enough slab to make bigger avalanches a real concern, but that is about to change. Expect to find touchy wind slabs forming at upper elevations, especially below ridgelines and convex rolls, or in steep, loaded gullies. Slopes with relatively stiffer snow on the surface will be the most dangerous. Travel has been fairly straightforward for the past few days, but we need to start dialing back terrain use and adopting a more conservative mindset as the avalanche danger rises today through tonight.

Storm Slab avalanches will become likely in areas that are seeing the most intense precipitation today. It is looking like this storm will have the strongest impact on the Placer Valley, which has been favored throughout the recent storm cycles. Use extra caution in this corner of the advisory area, and be aware that you may be able to trigger avalanches even in sheltered terrain.

Dry Loose Avalanches, or sluffs, will be getting bigger, easier to trigger, and moving faster as the snow continues to trickle in. Watch for sluffing on any steep terrain today, and be on the lookout for natural dry loose activity as the weather starts to ramp up.

The next round of snow is on the way. Graphic courtesy of NWS Anchorage, 03.11.2024

Additional Concern
  • Persistent Slabs
    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

For the past week we have been slowly adding more and more snow on top of the weak interface that was buried on March 5. On solar aspects there are a few sun crusts that have formed above that interface, but on many slopes there is around a foot of snow sitting on a weak layer. This layer produced some wide-propagating avalanches when it was first buried, and it may still produce large avalanches. The likelihood of this happening is increasing as we continue to add more load, and it is something we are going to be paying close attention to as the snow continues to fall today and tomorrow.

Weather
Mon, March 11th, 2024

Yesterday: Snow showers tapered off early in the morning, with clouds hanging around in the valleys but clearing at higher levels for some parts of the advisory area. Winds were light and variable, staying around 5-10 mph or less. High temperatures were in the low to upper 20s F with lows in the mid to upper teens F. We received another trace to 2” snow overnight, equaling 0.1-0.15” SWE.

Today: Snow is expected to pick up again today through tomorrow, with around 3-6” expected for most of our area during the day. The Placer valley is looking to be heavily favored for this round of snow, and will likely double those totals. Easterly winds are expected to pick up mid-day, with average speeds of 15 to 30 mph and gusts of 20 to 35 mph. Temperatures are expected to remain in the mid to upper 20s today through tonight, with snow to sea level.

Tomorrow: Continued snowfall tonight and tomorrow, with 6-8” likely tonight, and another 6-8” likely tomorrow for Girdwood and Turnagain Pass, and 1-2’ likely for the Placer Valley. Winds are expected to increase overnight tonight, with average speeds of 20-35 mph and gusts of 30-50 mph. High temperatures should 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′) 20 1 0.1 93
Summit Lake (1400′) 20 1 0.1 46
Alyeska Mid (1700′) 19 2 0.15 99
Bear Valley – Portage (132′) 23 3 0.37
Grouse Ck (700′) 25 1 0.1 66

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 16 ENE 6 22
Seattle Ridge (2400′) 17 N 2 9
Observations
Recent Observations for Turnagain Pass
Date Region Location
05/13/24 Turnagain Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South
05/13/24 Turnagain Observation: Turnagain Pass non-motorized side
05/12/24 Turnagain Observation: Warm up Bowl
05/07/24 Turnagain Observation: Turnagain Pass Wet Slabs
04/29/24 Turnagain Avalanche: Turnagain aerial obs
04/27/24 Turnagain Observation: Johnson Pass
04/23/24 Turnagain Observation: Turnagain Sunny Side
04/21/24 Turnagain Observation: Bertha Creek
04/20/24 Turnagain Avalanche: Spokane Creek
04/16/24 Turnagain Observation: Cornbiscuit
Riding Areas

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


Subscribe to Turnagain Pass
Avalanche Forecast by Email

This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.