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Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, April 15th 2018 5:17 am by Heather Thamm
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is LOW this morning and will rise to MODERATE in the afternoon. Triggering a small to large wet avalanche will be possible with daily warming on sunlit aspects. In the Alpine, triggering a slab avalanche 1-2’ thick remains possible above 3000’ on shaded aspects in areas where the snowpack is generally thinner. Give cornices extra space. 

MONDAY AVALANCHE OUTLOOK:
No avalanche forecast will be issued tomorrow, Monday April 16th. The avalanche outlook will be the same message tomorrow as for today due to a similar weather pattern in the forecast. 


 Show the Complete North American Avalanche Danger Scale
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Special Announcement

The snow is melting fast at lower elevations and the following areas have been closed to snow machining on the Chugach National Forest: Twenty mile, Snow River, Primrose, Lost Lake. Snug Harbor access to Lost Lake remains open at this time. Keep an eye on the riding status at the bottom of this page for current updates. 

Be aware some summer hiking trails like Byron Glacier trail in Portage have steep avalanche terrain above them and the potential for a natural avalanche exists later in the day on slopes getting lots of sun in the afternoon. 

CNFAIC is transitioning to spring time hours in preparation for the end of the season in two weeks. Beginning Monday, we will issue forecasts 4 days/wk on Sat, Sun, Tue, Thur. The final forecast will be on April 28th. You can check out springtime tips on the final Summit Summary HERE. 


Avalanche Problem 1

Wet Loose

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Chance

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The corn cycle has finally arrived and with it a potential for wet loose activity in the afternoons. Several nights of clear skies and freezing temperatures have formed a supportable crust adding strength to the snow in the mornings. As the day heats up and the crust melts and loses strength, the danger rises - making it possible to trigger a wet avalanche on steep sun exposed terrain features. Today's weather looks similar to yesterday with temperatures expected to reach the mid 40F’s by early afternoon. Remember solar noon is around 2pm and warm wet snow surfaces will last through the early eveningObservations over the last two days have found the weakest wet snow conditions below 2500’ on very steep East to South aspects. There is more potential for wet snow to entrain a larger avalanche in this elevation band. Don't let this catch you off guard if you start out in the upper elevations and the snow quickly changes as you descend. Pay attention to surface crusts as they break down and become moist. When the snow becomes wet and 'mushy' and your skis or snowmachine track start trenching into wet snow, it's time to find supportable surfaces. Even a small wet avalanche could be hard to manage especially in a terrain trap. As we move away from a rain event that occurred mid-week, and water drains out of the snow, it's becoming less likely for someone to trigger a wet slab. 

Cornices: Daily warming and sunnier weather can make cornices more unstable. As always, give cornices plenty of space and limit exposure underneath them.

A melt/freeze crust exists on shaded Northern aspects to ~3000' and was not warming by mid afternoon on Tincan. South aspects had 3-5" of wet surface snow the alpine mid day. 

 

East and South aspects have been warming significantly over the last few days. Note the shiny look of the East aspects in Lynx Creek area. 

 


Additional Concern

Persistent Slabs

Triggering a lingering storm slab or a persistent slab 1-2’ deep is becoming less likely with time. Old weak snow (facets) buried within the top 2’ of the snowpack have been found in the upper elevations over the last few weeks. Northerly aspects above 3000’ with dry snow may harbor this set up. So far there have been no reports of any avalanche activity on these shaded slopes following the mid-week storm that ended Wednesday. However the periphery of our forecast zone is more suspect, Crow Pass area and Johnson Pass to Summit Lake, where a thinner (weaker) snowpack remains. Before committing to steeper slopes in the upper elevations, take a moment to evaluate the terrain for consequences should a slab release.  


Mountain Weather

Yesterday was clear and sunny and no precipitation was recorded. Temperatures reached the low 50F’s near sea level and mid 40F’s in the mid elevations. Ridgetops were in the mid to low 30F’s during the heat of the day. Overnight temperatures dropped into the upper 20Fs to low 30F’s. Winds were light (5-15mph) from the West.

Today will be similar with sunny skies and another warm day on tap. Temperatures should again reach the low 50F below 1000’ and mid 30F’s in the upper elevations. Winds will be light (0-10mph) from the Southeast. Overnight temperatures should drop into the upper 20F’s to low 30F’s. 

Monday and Tuesday look to be a mix of partly cloudy to partly sunny weather with a slight chance for a few snow flurries. If we see precipitation it will be minimal. Daytime temps are expected to be in the mid 40F’s and overnight lows in the upper 20F’s. Winds are expected to be light. Wednesday into the Thursday there is a chance for precipitation (rain and snow) as low pressure moves through the Gulf of Alaska. At this point coastal areas look to be the most impacted. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 40  67 
Summit Lake (1400') 35  24 
Alyeska Mid (1700') 38  63 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 29  WNW  17 
Seattle Ridge(2400') 35  WNW   25

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: Dec 01, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed November 21 due to inadequate snow conditions. #hopeforsnow
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

Subscribe to the Turnagain Area Avalanche Advisory:

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.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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