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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, March 11th, 2023 - 7:00AM
Expires
Sun, March 12th, 2023 - 7:00AM
Forecaster
John Sykes
Avalanche risk The Bottom Line

The avalanche danger is LOW at all elevations. Generally safe avalanche conditions exist in the majority of the forecast area. Human triggered avalanches in isolated locations are unlikely but not impossible, so it is important to continue evaluating conditions in your area. Using safe travel protocols will stack the deck in your favor just in case you encounter an area with lingering unstable snow.

PETE’S / JOHNSON PASS / SILVERTIP: On the southern end of our forecast zone the snowpack is generally thinner and weaker and there are still persistent weak layers in the upper snowpack. In this corner of the forecast zone the likelihood of human triggered avalanches is higher and we recommend careful snowpack evaluation before entering avalanche terrain.

SUMMIT LAKE: The Summit Lake area also has a thinner and weaker snowpack and tends to see stronger winds during outflow events like we have had the past 2 days. Lingering wind slabs are more likely in this area and the recent wind loading could also make buried weak layers more sensitive to human triggering.

Special Announcements

Ever struggle to understand snowpit test results when reading observations? We put together a blog post to help explain what we are looking for when we do stability tests and how each test is carried out (check out the post here). Hopefully this will make our observations more accessible for everyone using our forecast products!

Turnagain Pass Avalanche Awareness Day – Mar 18, 2023:  Mark your calendars and swing by on your way to or from your backcountry ride or ski!! Test your beacon skills, chow down on hot dogs, and bring your questions for CNFAC forecasters. The Alaska Avalanche School will be there along with a chance to demo snowmachines from Alaska Mining and Diving Supply and Anchorage Yamaha and Polaris. More details HERE!

Sat, March 11th, 2023
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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

On the northern end of Seattle Ridge below the weather station we spotted a recent looking glide avalanche release yesterday. It is possible that this has been there for awhile and we just didn’t notice it due to the denser tree cover along the road corridor on this end of the pass. Either way there are a fair number of glide cracks opening up across the forecast region and this is a good reminder that they can release spontaneously and the best way to avoid them is just to not spend time underneath them.

Avalanche Problem 1
  • Normal Caution
    Normal Caution
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
More info at Avalanche.org

The avalanche conditions are generally safe, but that does not mean there is a 0% chance of triggering an avalanche. Over the past few weeks we have seen minimal new snow and plenty of wind and sunshine that has helped create generally stable avalanche conditions. However, lingering wind slabs in steeper terrain, small wet loose avalanches on steep south facing slopes in the afternoon, cornice fall, and glide cracks are all normal mountain hazards that continue to require some attention to identify and avoid.

We recommend you continue to use safe travel practices like travelling one at a time in avalanche terrain and grouping up in safe zones to minimize your exposure to these hazards. In addition the snowpack on the southern end of Turnagain Pass and the northern end of Johnson Pass (Pete’s N, Center Divide, Groundhog) has a much weaker structure than most of the forecast area and triggering a larger persistent slab avalanche in these areas is possible (see additional concern for more info).

The clear skies and cold temperatures at lower elevations this week has lead to some impressive surface hoar growth in meadows below treeline. Photo 3.10.23

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

The most recent large human triggered avalanche in our forecast area was on March 6th in the Bench Peak area near Johnson Pass. This avalanche released after several skiers had already descended the slope and produced a wide propagating fracture that wiped out the old tracks. These are common signs of a lingering persistent weak layer that may be stubborn to trigger but could produce a large avalanche. The snowpack near Johnson Pass and on the southern end of Turnagain Pass is more similar to Summit Lake than it is to the rest of our forecast area, with widespread weak layers that are easier to initiate with the weight of a skier or rider due to the overall shallower snowpack depth. The potential for large human triggered avalanches is higher in this area and we recommend careful evaluation of the snowpack and conservative terrain selection if you head to this area.

Weather
Sat, March 11th, 2023

Yesterday: Sunny skies with NW winds and temperatures in the upper teens to 20s at upper elevations. At lower elevations the temperatures ranged from the mid 20s to mid 30s. The winds were mostly light in Turnagain Pass with averages below 10 mph and occasional gusts reaching 15-20 mph. Stronger winds were observed along Turnagain Arm and through Portage.

Today: Another day of mostly clear skies with light NW winds averaging 0-5 mph. Temperatures will remain in the mid teens to mid twenties.

Tomorrow: Sunday looks similar to Saturday, except cloud cover is expected to start building in the morning and increase throughout the day. Winds are expected to remain light with temperatures remaining around 20 F during the day before decreasing toward the single digits Sunday night.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29 0 0 64
Summit Lake (1400′) 21 0 0 37
Alyeska Mid (1700′) 28 0 0 65
Bear Valley – Portage (132′) 27 0 0

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 20 NW 6 20
Seattle Ridge (2400′) 24 N 4 17
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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.