CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, February 27th 2019 7:00 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
Previous ForecastNext Forecast
BROUGHT TO YOU BY
The Bottom Line

A generally LOW avalanche danger exists across all elevations bands for the Turnagain area. Steep rocky southerly facing slopes may heat up enough by the afternoon for a person to initiate wet sluffs. Give cornices a wide berth and avoid travel under glide cracks. Good travel habits, such as exposing one person at a time, watching your partners and grouping up in safe zones are, as always, key ways to minimize risk. 

SUMMIT LAKE / SILVERTIP / JOHNSON PASS: *** We want to emphasize the difference here. More caution is advised South of Turnagain Pass.*** Keep in mind a thin snowpack with buried old weak layers exist. There is more potential for triggering a large slab avalanche in this zone. Choose terrain wisely. Please read the Additional Concerns below. 


 Show the Complete North American Avalanche Danger Scale
1 Low Alpine / Above 2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Special Announcement
  • Don't miss an evening with renowned snow scientist Ed Adams on March 7th!! The American Society of Mechanical Engineers is hosting an evening lecture delving into snow micro-structure and how it relates to the white stuff we love to play on. More details HERE.

Avalanche Problem 1

The Turnagain, Girdwood and Placer zones have entered the "Normal Caution" regime of backcountry hazards. What this means is triggering an avalanche is unlikely but not impossibleWhat to keep in mind in the backcountry today:

  • Wet sluffs on steep south facing slopes - watch for snow on steep south facing slopes to become wet and punchy by the afternoon. In this case, triggering a wet sluff will be possible if the slope is steep enough. Most southerly slopes have already gone through several melt-freeze cycles and natural wet loose activity is not expected today. 
  • Outlier slab avalanches - It's unlikely but not out of the question that person could trigger an old wind slab in steep terrain, all aspects - shaded or sunny.
  • Cornice falls - Cornices that are baking in the sunshine can become weaker and more unstable. We need to continue giving these a wide margin. 
  • Glide avalanches - It's always best to limit exposure under glide cracks. Please let us know if you see a glide crack release into an avalanche. The last known glide avalanche was on Goat Mt. in the Girdwood Valley 8 days ago. 

Today will be the 6th day of sunny and springtime weather; sunglasses have entered back into the morning checklist. The warmest day so far was Monday 2/25. Several wet loose avalanches were seen on steep rocky slopes. A few slabs popped out on Monday as well under rock bands triggered by wet loose debris. These slabs, seen in the photo below, were likely composed of the 10-16" of settled storm snow from 2/16-2/20. Today is not expected to be as warm as Monday but tomorrow has a chance. Keep close tabs on how the snow surface is heating up during the day. It is springtime and time to consider travel routes for late in the day. 

 

Steep rocky southerly facing slopes are feeling the springtime sun and warm ambient air temperatures. Many wet loose avalanches released Monday afternoon 2/25 during the warmest day seen this season (this one pictured is from Crow Ck drainage).


Additional Concern

Persistent Slabs

South of Turnagain - Summit Lake/Silvertip/Johnson Pass zones:  A shallow snowpack with a generally poor snowpack structure exists in these areas. A variety of weak layers sit in the mid and base of the snowpack and were re-activated last Thursday by the outflow wind event. Many natural avalanches were seen on windloaded slopes in the Summit Lake area. Although whumpfing has been observed in the Summit area, no signs of instability may be encountered before a slab is triggered. 

Again a quick recap of the weak layers sitting in the pack:

  • Valentine's Layer:  Small facets, 10"-16" deep, last avalanches on 2/21 due to wind event region-wide. Not showing signs of reactivity in Turnagain/Girdwood/Placer currently. Layer was responsible for the 2/19 snowboarder remotely triggered slab on Seattle Ridge.
  • MLK Jr Layer:  Buried surface hoar, 2-3' deep, last avalanches seen in this layer 2/21 in the Summit Lake region. All natural slides.
  • Basal facets (large faceted snow near the ground): This layer has only been found in the Summit Lake region and produced at least one very large natural avalanche on Thursday, 2/21.

If you're headed this way, remember the snowpack becomes more complex - evaluate terrain exposure and the snowpack as you travel. 

Natural avalanche on Fresno Pk from last Thursday, 2/21. This slide was triggered by significant wind loading from the outflow wind event. It broke in weak layers deeper in the snowpack. 


Mountain Weather

Yesterday:  Sunny skies with light and variable ridgetop winds were once again over the region. Daytime temperatures warmed to the mid 30'sF from valley bottoms to the high peaks. Overnight, the nocturnal inversion set back in and single digit temperatures are being reported at Portage and in low-lying areas along the Seward highway such as Johnson Pass

Today:  Sunny skies will again be over the region. Winds are expected to be a bit more organized along ridgetops and blowing light 5-10mph from the NW. Temperatures should warm to the mid 30'sF by the early afternoon in the lower elevations while the upper elevations will remain in the low 30'sF. 

Tomorrow:  Sunny skies and light winds are on tap tomorrow. However, we could see a few degrees warmer daytime temperatures at all elevations according to the weather models. The ridge of high pressure over Southcentral AK will keep the skies mostly clear through the week. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 25  60 
Summit Lake (1400') 16  0 29 
Alyeska Mid (1700') 24  56 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 30  12 
Seattle Ridge(2400') 29 

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: Mar 22, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Open
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: Open
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Open
Lost Lake Trail: ClosedClosed as of 3/22. Unfortunately HEAVY rain over the past week has washed much of the snow off the lower stretches of this trail.
Primrose Trail: OpenPlease stay on trail to avoid resource damage through forested areas.
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: Open
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Open

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
© 2019 Chugach National Forest Avalanche Information Center. All rights reserved.
FCNFAIC