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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   CNFAIC Staff  
Tuesday, February 16th 2010
Created: Feb 16th 7:02 am
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
4 High Alpine Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Below Treeline Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
 Show the Complete North American Avalanche Danger Scale
Subscribe to the Turnagain Area Avalanche Advisory:
The Bottom Line
Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Tuesday February 16th at 7 am. This will serve as 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).


WEATHER ROUNDUP
The height of our most recent storm hit us Sunday night, but we have continued to get noteworthy weather.
-The winds have backed off slightly at all ridgetop weather stations and are currently moderate averaging 16-19mph. In the past 24 hours, however, Sunburst had moderate to extreme winds averaging up to 43 mph with an extreme max gust of 70mph.
-The current radar is full of precip over PWS moving west directly towards us.
-In the last 24 hours (4am-4am), the snotel sites recorded .7 inches of water at Turnagain Pass, 1.0 inches at Grandview, and .2 at Summit Creek. Snowfall totals range 2-7 inches of new snow. There has been about 3.5 inches of new water weight at Grandview since the snowmachine-triggered avalanche on Saturday.
-Temps are about the same at all wx stations this morning compared to yesterday. Temps range from 34 degrees F at sea-level and 25 degrees F at 3800.


AVALANCHE DISCUSSION
Todays avalanche danger will remain at HIGH. Right now, the driving factor with snowpack stability hinges on current weather. Since the Saturday, we have only seen additional weight and wind adding additional stress to a snowpack that has been avalanching since everyday since Friday. Just because the weather is less intense today does not mean that the avalache danger has improved significantly. At the very best, the snowpack stability has stayed the same since yesterday, and large natural avalanches were observed at Turnagain Pass yesterday.

The height of the storm cycle may have passed by Sunday night, but the avalanche cycle is still active. Plus there are a lot of variables in our snowpack right now that we dont have the answers to. We are still within 24 hours of significant weather that will affect stability in our snowpack. A general rule with avalanches is that 90% of avalanches occur during storms and within 24 hours following a storm. We are still in that window. We need to carefully approach our snowpack on a day by day basis. We are now involved in a new weather cycle with some more strong wind and a little bit more precip forecasted by the National Weather Service today. Large to very large human-triggered avalanches are a serious concern today because we have 2 dangerous weak layers in our snowpack that have both been avalanching everyday since Friday.

Let me be clear about this.Based on data, recent observations, knowledge of historical avalanche reports, statistics and experience.its my perspective that you might die in an avalanche if you get on steep slopes today.
-The snowpack became reactive to natural triggers starting last Friday 2/12/2010
-The snowpack was also reactive to human-triggers last Saturday 2/13/2010 resulting in fatalities
-Sunday night 2/14/2010 was the most intense part of the recent weather, but we continue to get additional weight and stress added to our snowpack with .7 inches of new water last night and extreme average wind speeds
-New natural avalanches were observed on both sides of the highway at Turnagain Pass as of yesterday morning 2/15/2010.

Traveling in avalanche terrain is not recommended today. STAY HOME! GO TO THE RESORT! Do something CNFAIC Staff than travel in backcountry avalanche terrain today. If you go to Turnagain Pass, then stay away from avalanche run out zones and keep your slope angles less than 25 degrees. This is not the time to get first tracks.

There are two main weak layers in our snowpack.
1.A thin breakable melt-freeze crust with surface hoar on top of it. We have seen this weak layer up to 3000 on multiple aspects on both sides of highway at Turnagain Pass. This weak layer is generally buried 3-5 feet deep. Surface hoar has been observed on top of this layer in many pits, as recently as Sunday 2/15/2010. Not all pits show the surface hoar, and these feathery crystals get smaller as you gain elevation, but you have to give a weak layer like this lots of respect. This combination of surface hoar on top of a crust is historically responsible for the majority of avalanche surprises and fatalities.

2.The Jan 7 rain crust is generally buried 5-7 feet deep. This particular weak layer has been reactive to explosive triggers and most likely has been naturally triggered during our current avalanche cycle. This persistent weak layer has been showing significant signs of instability since its formation last month. This weak layer is widespread on all aspects up to 3000 feet.

WEATHER FORECAST (National Weather Service)
WESTERN PRINCE WILLIAM SOUND-
INCLUDING...WHITTIER...SEWARD...GIRDWOOD...MOOSE PASS
500 AM AKST TUE FEB 16 2010

...STRONG WIND TUESDAY EVENING THROUGH THURSDAY THROUGH PORTAGE
VALLEY AND TURNAGAIN ARM...
.TODAY...RAIN AND SNOW. NO SNOW ACCUMULATION. HIGHS AROUND 40. NORTH
AND EAST WIND 10 TO 25 MPH.
.TONIGHT...RAIN AND SNOW SHOWERS. LITTLE OR NO SNOW ACCUMULATION.
LOWS IN THE UPPER 20S TO MID 30S. EAST WIND 10 TO 25 MPH. THROUGH
PORTAGE VALLEY AND TURNAGAIN ARM...EAST WIND 15 TO 30 MPH INCREASING
TO 30 TO 45 MPH AFTER MIDNIGHT.
.WEDNESDAY...RAIN AND SNOW. NO SNOW ACCUMULATION. HIGHS IN THE
MID 30S TO LOWER 40S. EAST WIND 10 TO 15 MPH EXCEPT EAST 35 TO
50 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

Temperature / Precipitation

SEWARD 43 33 40 / 100 90 80
GIRDWOOD 40 34 42 / 60 60 40

Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass
Sea-level: temps are forecasted between 34-42 with between .25-.5 of water today
3000: temps are forecasted in the range of 23-32 degrees F with winds 20-25 mph
6000: temps are forecasted in the range of 23-32 degrees F with winds 45 mph

WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS
3800-Sunburst Wx Station
Current Temp: 25 (1 degree colder than yesterday)
Winds: Averaged light to extreme 14-43mph with extreme gust of 70mph
RH: 97 (same as yesterday)
2600-Seattle Ridge Wx Station
Broken. We will fix as soon as possible.
1800-Center Ridge Wx Station
Current Temp: 31 (1 degree warmer than yesterday)
Precip: 0.7 of Water and apprx 2 of wet snow for total depth of 105
RH: 100 (same as yesterday)
Thanks for checking todays avalanche advisory. The next one will be posted tomorrow Wednesday February 16th.

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: Nov 25, 2014 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedClosed as of April 23rd.
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: Closed
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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 regarding CNFAIC operations or winter recreation management, please email wendy@chugachavalanche.org
© 2014 Chugach National Forest Avalanche Information Center. All rights reserved.
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