Turnagain Pass
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The avalanche danger is CONSIDERABLE at all elevations today. Wet avalanches are likely due to the warm temperatures and cloud cover over the past several days. Wet loose avalanches will be very easy to trigger and can grow quite large when running down long slopes. Wet slab avalanches are also likely today, which are highly destructive and unpredictable. We recommend avoiding steep slopes where there is wet snow on the surface and melt water running through the snowpack. On northern aspects there are some lingering buried weak layers that could cause a surprise avalanche in steep terrain.
WEDNESDAY – AVALANCHE OUTLOOK: Clouds are expected to clear this evening which should finally give the snow surface a chance to freeze overnight. This should lead to typical spring conditions tomorrow, with a solid crust in the morning adding lots of strength to the snowpack and generally safe conditions. In the afternoon when the crust melts and water starts moving through the snowpack again conditions quickly become dangerous and wet avalanches become likely. It is important to monitor snow surface condtions and move to a shadier aspect once the wet snow on the surface is more than ankle deep.
Avalanche Center End of Season Operations: We are continuing to issue forecasts on Tuesday, Thursday, Saturday, and Sunday mornings. For the non-forecast days we will give an avalanche outlook on the day prior. The final forecast for the season will be April 28.
Wed, April 24th, 2024 |
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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. |
Warm temperatures and cloudy skies have brought the onset of the spring shed cycle to our region, with the first known observation of a large wet slab avalanche coming out of Portage along with many glide avalanches across the forecast area. Coastal areas, like Portage, have seen about 1.5″ of water over the past few days which fell as rain below roughly 2000′. This rapid additional of water to the snowpack creates prime conditions for wet slab avalanches to start releasing. The large wet slab below was observed on a NW aspect at 1400′ near Explorer Glacier in Portage and released naturally sometime on Sunday night or Monday morning.
First proper wet slab of the spring shed cycle, with the crown up to 6′ deep. Photo 4.22.24
A small section of this glide avalanche released naturally on the S face of Cornbiscuit with much more snow waiting to come down. Photo from Anonymous 4.21.24
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 |
Cloudy skies and warm temperatures last night likely prevented a solid refreeze of the wet snow on the surface. After multiple days of warm and cloudy weather the snowpack has rapidly transitioned to springtime conditions and large wet slab avalanches are likely, especially near the coast where an additional 1.5″ of rain over the past few days has weakened the snowpack even more. Wet slab avalanches are very difficult to predict in terms of location, but the timing for wet slabs is prime right now after several days without a solid freeze. These avalanches can be very large and destructive and tend to release naturally once the melt water moving through the snowpack causes existing weak layers to loose strength.
Near the Crow Pass Trail yesterday we found a concerning weak layer about 1′ above the ground where the melt water from the surface was pooling on top of a layer of basal facets from early in the season. The exact depth and weak layer that wet slabs release on is likely to vary across the forecast area depending on the existing snowpack structure. We recommend carefully evaluating the snow surface conditions and avoiding steep slopes where the surface snow has melted and there is water actively moving through the snowpack. To avoid this problem you could try to access higher elevation northern aspects where the snowpack still consists of mostly dry snow.
Wet loose avalanches are also likely today, and can be a precursor to wet slab activity. These are easy to trigger on any steep slope once the snow surface has melted. The size of wet loose avalanches depends on the depth of the wet snow on the surface and the size of slope that the avalanche runs down. These are typically small avalanches but can grow very large under the right conditions.
Glide Avalanches are also releasing naturally and can be very large and destructive. If you can see a glide crack on the slope it is best to avoid spending time underneath because they can release randomly.
Cornice Fall is also likely as the sun weakens the snowpack’s connection with the underlying ridgelines. When cornices are receiving direct sun it is best to avoid being underneath them and give them a wide berth if you are travelling along a ridgeline.
Wet loose avalanche debris along the road to the Crow Pass Trailhead containing some very large chunks of wet snow. Photo 4.22.24
There are some lingering persistent weak layers in the snowpack from earlier in April and late March which could cause an outlier avalanche, especially in steep terrain on northern aspects at upper elevations. These layers do not seem to be very widespread but it would be easy to be caught off guard by a persistent weak layer if you are in the springtime mentality and expecting stable snow conditions. If you are trying to access this kind of terrain we recommend digging a pit to evaluate the snowpack structure and look for suspicious weak layers with stability tests before committing to steep terrain.
Yesterday: A mix of partly cloudy and overcast sky cover across the region, with denser clouds near the coast. Precipitation was isolated to areas near the coast, with 0.2″ of water falling as rain below approximately 2000′ in Portage. Winds were light to moderate at upper elevations with averages around 10 mph out of the east and gusts up to 30 mph. Temperatures reached the mid to upper 40s F at low elevations but stayed in the mid 20s F at upper elevations.
Today: Mostly cloudy skies are expected to start the day, which should give way to some breaks of sunshine in the afternoon and evening. Temperatures are expected to reach highs in the 40s F up to about 2000′ with highs in the low 30s F at upper elevations. Winds should be light with averages of 0-10 mph out of the east. Some rain showers are possible along the coast but are not expected to produce much water.
Tomorrow: A clearing trend is expected overnight with mostly sunny skies throughout the day tomorrow. No new precipitation is expected. Temperatures should reach into the 50s F at low elevations and mid to upper 30s F at upper elevations. Winds look to remain light at 5-10 mph out of the east.
PRECIPITATION 24-hour data (6am – 6am)
Temp Avg (F) | Snow (in) | Water (in) | Snow Depth (in) | |
---|---|---|---|---|
Center Ridge (1880′) | 35 | 0 | 0 | 88 |
Summit Lake (1400′) | 36 | 0 | 0 | 38 |
Alyeska Mid (1700′) | 36 | 0 | 0 | 101 |
Bear Valley – Portage (132′) | 40 | 0 | 0.2 | – |
Grouse Ck (700′) | 39 | 0 | 0 | 65 |
RIDGETOP 24-hour data (6am – 6am)
Temp Avg (F) | Wind Dir | Wind Avg (mph) | Wind Gust (mph) | |
---|---|---|---|---|
Sunburst (3812′) | 24 | ENE | 10 | 28 |
Seattle Ridge (2400′) | 28 | SE | 7 | 16 |
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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