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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, March 20th, 2020 - 7:00AM
Expires
Sat, March 21st, 2020 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

A generally LOW avalanche danger exists in the mountains surrounding Turnagain Pass. Low doesn’t mean no danger and there are several ‘Normal Caution’ issues to keep in mind. Watch for wet loose avalanches on any steep southerly slope that heats up this afternoon. Also, watch for dry sluffs on steep shaded slopes and shallow wind slabs in steep rocky terrain. As always, give cornices a wide berth.

SUMMIT LAKE:  A much shallower snowpack exists from the Johnson Pass and Silvertip trailheads south to Summit Lake. In this area, there remains a chance a person could still trigger a larger slab avalanche due to weak snow in the mid and base of the pack. Extra caution is advised.

*Roof Avalanches:  Heads up that roofs are still shedding their snow during the warm afternoons.

Special Announcements

A big THANK YOU to everyone who has sent us their observations! Please keep them coming if you are heading out in the mountains.

The CNFAIC will continue to produce daily avalanche forecasts, under current guidance from the USDA, and so long as the health of our small staff remains intact. Our field operations are being impacted, so your information is invaluable. Even if all you have to report is that you did not see any avalanches or that you did not see any signs of instability, please take the time to send that important info! And of course, you can always choose to remain anonymous. Submit an observation on our observation page or send an email to staff@chugachavalanche.org. Play safe and stay healthy.

Fri, March 20th, 2020
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.
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

Another spring day is on the doorstep. Although some high clouds should filter through and patches of valley fog are expected, many slopes should see a good dose of sunshine today. Without a big temperature increase expected, we are back into a Normal Caution regime in our core forecast area of Turnagain Pass. That said, paying attention to any unforeseen changes in weather, especially warming, is always critical.

Normal Caution avalanche issues to keep in mind:

Wet loose avalanches:  Solar aspects should heat up enough to soften surface crusts by the afternoon. If and when this happens, triggering wet sluff on steep sunny slopes will be possible. Natural wet sluffs are also possible in steep rocky terrain that is baking in the sun and saturating the snow surrounding rocks/vegetation.

Dry loose avalanches:  Many shaded steep slopes harbor loose faceted surface snow. If headed into this terrain, watch your sluff.

Wind slabs:  There was a 5-hour period of moderate westerly winds early this morning along ridgelines. Although there is not much loose snow for the winds to transport, it’s still prudent to keep a lookout for any new wind slabs that may have formed. Also, there could be some old lingering wind slabs that may still be reactive.

Cornices:  This is the time of year cornices will slowly warm and start to peel off. Give these guys a good margin from above and limit exposure below.

Glide avalanches:  A few new glide cracks have been seen opening up. Just one more thing for us to keep our eye out for as spring progresses.


A mix of surface conditions exist. This example is from Silvertip and shows wind effect in the foreground and sun effect with wet loose avalanche activity in the back. 



Soft snow also exists in many areas on the northerly aspects as well the sunny once the crusts soften. Thank you to Blue Ristra for these photos from Wednesday 3.18.20.


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

Triggering a large slab avalanche that breaks in weak old faceted snow deeper in the snowpack remains a concern in areas that have a shallow overall snow depth. These areas are south of Turnagain Pass and include Johnson Pass to Silvertip area, Summit Lake and Palmer Creek. Watch for areas that have a harder wind packed layer of snow over weak sugary snow. Additionally, southerly facing slopes that are heating up during the day are more likely to avalanche once the surface crusts soften.

As always, practice safe travel protocol. Exposing one person at a time, watching our partners and having an escape route planned.

 

Facets found a foot below the surface in a shallow, wind scoured, area on Magnum. The total snowpack here was only 20″, yet it was over 6′ thick just 100 yds away.  This pit resembles areas to the south of the Pass and in Summit Lake where the general snowpack is thinner and more concern exists for triggering a persistent slab avalanche. 3.18.20. Photo: Jamie Lyons

Weather
Fri, March 20th, 2020

Yesterday:  Overcast skies were over the region as high clouds filled the region. Ridgetop winds were light and variable before turning westerly and picking up into the 15-20mph range overnight. Temperatures bumped to the low 30’s°F along ridgetops and up to 40°F at sea level. Overnight, temperatures have dropped to ~20°F in the high elevations and the mid 30’s°F at sea level.

Today:  Mostly sunny skies with patchy fog is forecast. Ridgetop winds should remain westerly in the 10-15mph range. Temperatures are slated to warm to 30°F along ridgetops and 40°F at sea level.

Tomorrow:  A weak weather system heads over the area early Saturday morning. This will bring a chance for 1-3″ of snow through tomorrow. Snow should fall to sea level, or very close to that. Winds will shift back to an easterly direction with the snowfall and be in the 10-20mph range. Temperatures should be in the 20’s°F in most areas.  Skies clear out again on Sunday and Monday.

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

Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 34 0 0 66
Summit Lake (1400′) 32 0 0 30
Alyeska Mid (1700′) 30* 0 0 76

RIDGETOP 24-hour data (6am – 6am)

Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 26 W 11 39
Seattle Ridge (2400′) 30 var 7 18

*The Aly Mid station temperature is an estimate as the station stopped reporting yesterday at 4pm.

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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.