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Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, March 10th 2019 7:00 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger remains HIGH above treeline and is CONSIDERABLE below treeline. Human triggered large slab avalanches will be likely on steep windloaded slopes. Slabs will be in the 2-3' thick range and may be found in sheltered zones. These could be triggered remotely from ridgelines or from below. Additionally, cornice falls will be likely. The consequences of triggering a dangerous avalanche or cornice fall is high and travel in avalanche terrain above treeline is NOT recommended.  

PORTAGE VALLEY:  Strong winds will continue through Portage Pass and natural avalanches remain possible. Travel in runout zones from avalanches that may occur above is not recommended. This includes venturing along and past the Byron Glacier Trail.

SUMMIT LAKE:  Despite only a few inches of new snow, this area has a very shallow and weak snowpack. Strong winds may have overload buried weak layers and caution is advised if heading to this area.

LOST LAKE:  Caution is advised in the Seward region. Large human triggered avalanches should be expected in this zone as well above treeline.


 Show the Complete North American Avalanche Danger Scale
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

After a good shock to the system late yesterday, the mountains are slowly recovering. The third wave in this 'spring break storm cycle' is heading out this morning and we can expect light snow/rain showers today. Yesterday's event turned out to be more blow than snow. Ridgetop winds hit an impressive 111mph at the Sunburst weather station and averaged well into the 60's mph. Although winds have quieted down, they are still forecast to remain strong enough to move snow and load slopes (20-30mph from the east). For snowfall, an additional 10-16" fell yesterday in the Girdwood and Turnagain areas with only a few new inches in the Summit Lake zone. Here is a quick rundown on storm totals to date.

Estimated storm totals (mid-upper elevations) beginning Thursday ending Sunday 6am:

  • Turnagain Pass:  20 - 26" snow (2" water)  *Significantly less snowfall seen on the southern end of Pass near Johnson Pass.
  • Girdwood Valley:  28 - 36" snow (2.7 - 3.5" water)
  • Summit Lake:  2 - 5" snow (~0.2 water)
  • Bear Valley (Portage):  30 - 40" snow (3.5" water)
  • Seward/Lost Lake area:  25 - 35" snow (~3" water)

For anyone headed into the backcountry today, know that the likelihood of triggering a large and unsurviveable avalanche increases with elevation. Dialing back our terrain choices and sticking to slopes 30 degrees or less with nothing steeper above is wise, especially above the trees. The snowpack needs time to adjust to the wallop from last night. The old snow surface that now sits 2-3' below the new snow is a mixture of facets, surface hoar and crusts. The bonding at these upper elevations should be viewed as poor until proven otherwise.

Slopes that are in the 'trees' (below ~2,500') were showing signs that the new snow was starting to bond yesterday due to warm temperatures. This is good news, but with another foot on top, cautious routefinding and conservative decision-making is required for these areas. Quick hand pits to see how much new snow has fallen and how it is bonding with the old surfaces will be key. Additionally, watch for cracking and collapsing (whumpfing). For the lower elevations, rain has been falling below 1,000', saturating the thin snow cover and wet sluffs are possible. 

 

 

Cornice falls along the lower portion of Tincan's CFR ridgeline. Strong winds have been loading leeward slopes such as this for almost 2 days now.

Yesterday we found a foot of new snow from Friday night's storm, there is now another foot of snow that fell overnight for a total of roughly 2 feet at treeline on Tincan. 

 


Strong winds and new snow seen yesterday - VIDEO LINK HERE.


Mountain Weather

Yesterday:  Overcast skies, heavy snowfall and strong easterly winds were over the region. The third wave in a storm series peaked in the evening hours with ridgetop easterly winds sustained in the 60's mph with gusts to 111mph. Rain/snow line was ~7-800' before falling to near 100' in the evening. Snow totals in the past 24 hours are generally 12-16" at the mid-elevations in Girdwood and Turnagain with lesser amounts south of Turnagain Pass.

Today:  Cloudy skies with light snow showers will be over the area as the main system is moving east. We may see between 2-5" of snow above 5-800' with light rain below. Ridgetop winds are slowly decreasing and should average in the 20-30mph range from the east with stronger gusts. Temperatures will remain in the 20’s F along ridgelines and in the mid 30’s at the low elevations  

Tomorrrow:  Continued cloudy skies and showery weather will be over the region tomorrow. The snow line will possibly make it back to sea level as cooler air looks to move in. A few inches of new snow are possible along with moderate easterly winds. Skies look to break on Tuesday with a short clearing period before another strong front moves in for Wednesday into Thursday. 

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')    31  12"  75
Summit Lake (1400')  33 2-3"  0.15  28 
Alyeska Mid (1700')   29  16" (estimate)  1.2  76 

 

RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  21 NE  44  111 
Seattle Ridge(2400') 26  *N/A   *N/A  *N/A 

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).

Winter snowmachine use open/closed status and riding conditions updates

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: May 06, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: ClosedClosed as of 5/6. Thanks for a great season all, see you next winter!
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClose as of 5.1.2019
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Closed

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The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.


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