Turnagain Pass
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The avalanche danger is MODERATE above 2500′ for slab avalanches 1-2′ thick. Triggering a small slab in isolated terrain or a larger slab that could bury a person is possible on steep slopes. Cornices grew last week and could be triggered by the weight of a person or snowmachine. Identify glide cracks and avoid/limit your exposure time under this unpredictable hazard.
SUMMIT LAKE / JOHNSON PASS: Keep in mind buried weak layers exist in the middle and base of the snowpack. More potential for triggering a large slab avalanche exists in this zone, especially in terrain that has seen recent wind-loading.
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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. |
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 |
Although sunny and quiet weather conditions have been over the area for 2 days, there is still the possibility of triggering a lingering slab. Winds, along with several inches of snow, on Wednesday formed slabs that are sitting on weak facets and possibly even buried surface hoar in places. This is the problem, that slabs could be taking more time to stabilize due to the persistent grain type that lies under them. Slab thickness is variable – from 3″ to a foot in general with wind loaded zones that could harbor a section of 2′ slab. Keeping close tabs on the top of the snowpack is key.
Quick hand and/or pole tests to determine stiffer snow over weaker snow as well as watching for cracking around you are ways to asses a slab over a weak layer. Keep in mind smaller and harder slabs could be lurking in steep rocky terrain as well as larger and more connected slabs in bigger terrain. Be suspect of wind-loaded features and as always, evaluate the terrain for consequences and use safe travel protocols.
South of Turnagain – Johnson Pass/Summit Lake zone: A very poor snowpack structure exists in these areas. Multiple mid-pack weak layers of facets and buried surface hoar have been found as well as a facet/crust combination in the bottom of the snowpack. No recent avalanche activity has been observed since the New Year’s storm, but more uncertainty exists for triggering a deeper more dangerous avalanche. If you’re headed this way, it will be important to evaluate terrain and snowpack as you travel. Be on the lookout for signs of instability and maintain extra caution around wind-loaded slopes.
Surface conditions between 2,500 and 3,000′ on Magnum’s West face. Small roller balls are old, from Wednesday’s warm and windy weather. (photo: Trip Kinney)
Glide cracks are still slowly opening. Although we have not heard/seen one of these release for over a week now, limiting exposure under them remains wise. Known areas with cracks are Eddies, Tincan, Sunburst, Magnum, Cornbiscuit, Lipps, Seattle Ridge, Johnson Pass, Lynx Creek, Summit Lake, Petersen Creek, and Girdwood. This avalanche hazard is unpredictable and cracks can release without warning.
Glide cracks on the SW aspect on Magnum, photographed Thursday Jan 17 by Peter Smith.
Yesterday: Clear skies with dense valley fog in places were seen over the region. Temperatures were inverted with teens in valley bottoms and mid-20’sF along ridgetops during the day. Winds were light and variable along ridgelines. Overnight, winds shifted to a more NW direction bringing in cooler air aloft.
Today: Another clear sky day is on tap. Ridgetop winds are expected to remain light from the NW. The inversion is breaking down with the arrival of cooler air from the NW. Temperatures sit in the teens F at all elevations this morning where they are forecast to remain for the day. The exception is Summit Lake, where temperature have dropped into the single digits.
Tomorrow: The last day for this clear sky period is expected tomorrow. Temperatures will continue to decrease and single digits are expected. Clouds, warming temps and a chance for snow move in on Monday, while a higher chance for snowfall is forecast for Tuesday into Wednesday.
*Seattle Ridge weather station was heavily rimed and the anemometer (wind sensor) was destroyed. We are currently working to replace it.
Temp Avg (F) | Snow (in) | Water (in) | Snow Depth (in) | |
Center Ridge (1880′) | 23 | 0 | 0 | 51 |
Summit Lake (1400′) | 9 | 0 | 0 | 20 |
Alyeska Mid (1700′) | 21 | 0 | 0 | 38 |
Temp Avg (F) | Wind Dir | Wind Avg (mph) | Wind Gust (mph) | |
Sunburst (3812′) | 23 | Variable | 3 | 9 |
Seattle Ridge (2400′) | 27 | *N/A | *N/A | *N/A |
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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