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Issued
Mon, February 14th, 2011 - 7:00AM
Expires
Tue, February 15th, 2011 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

Good morning backcountry travelers. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Monday, February 14th at 7am. 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).

BOTTOM LINE

The avalanche danger today is MODERATE on slopes with a shallow snow cover or in steep rocky terrain for deep slab avalanches. There remains a possibility to trigger a deep slab avalanche in these thin snowpack areas. In addition, there is a MODERATE danger for wind slabs on slopes receiving recent wind drifting in the new storm snow.

AVALANCHE DISCUSSION

We received a report yesterday of a skier triggered deep slab avalanche in the Johnson Pass area on Friday, Feb 11, that broke in the loose facets near the ground. The slide was on a northwest facing slope around 36 degrees with the crown estimated at 30 inches. This is the type of avalanche we are most concerned with, one that can be triggered in regions with a shallow snowpack (such as Johnson Pass).

In these shallow areas the slab is often strong enough to allow the weight of a person or snowmachine to travel well onto it before it fails, making it very difficult for escape. Safe travel practices, for example, exposing only one person at a time to a potential hazard, is especially prudent. Also, there are possible trigger points lurking in the deeper snowpacks, such as Turnagain Pass, on the more exposed radical terrain.

The lingering snow showers yesterday added an additional 2-4 inches of light powder to the mountains; this is on top of the 5-8 inches from Friday. Loose snow sluffs and shallow wind slabs were easy to initiate again yesterday and mainly confined to the upper 2-6 inches where density changes in the new snow exist. With the cold temperatures the snow surface should remain loose today but sluffing will likely be less widespread.

Although the winds have been fairly well behaved the past couple days, they did pick up last night from the north and I suspect recent wind slabs to be somewhat sensitive today. Watch for cracks shooting from your sled, board or skis on wind loaded terrain. Also, be wary of any hollow feeling drifts or slabs that have stiffened up over the top of the low density storm snow. Near ridgelines and convex rollovers would be likely spots to trigger a wind slab.

Encyclopedia of avalanche terms.

WEATHER ROUNDUP

The snow showers hung on long enough yesterday to lay down a fresh 3-4 inches of low density snow in the Girdwood Valley and Turnagain Pass areas. Overnight, temperatures dropped back into the minus single digits and northerly winds blew 5-10 mph on the ridges, gusting into the mid and upper teens. We should see cold and clear conditions today with temperatures remaining in the single digits. Winds are forecast to pick up from the north, gusting into the 20’s on the ridglines.

ANNOUNCEMENTS

The Friends of the CNFAIC (FCNFAIC) needs your thoughts! With a new staff of forecasters and a list of previously completed goals, the program is growing and potentially heading in new directions. The FCNFAIC wants to know what you have to say about YOUR avalanche center, so please complete the following anonymous survey by February 20th. Thank you in advance for taking it!

Click here to take survey

or cut and paste the address directly:

https://www.surveymonkey.com/s/THWXVCD

Jon will issue the next advisory tomorrow morning at 7am. If you get out in the backcountry give us a call at 754-2369 or send us your observations using the button at the top of this page. Thanks and have a great day.

The NWS weather forecast for:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST MON FEB 14 2011

…STRONG WIND THROUGH EARLY TUESDAY MORNING FOR FOR WHITTIER AND

SEWARD…

.TODAY…SUNNY. AREAS OF BLOWING SNOW…MAINLY NEAR WHITTIER. HIGHS

ZERO TO 15 ABOVE. NORTH TO WEST WINDS 15 TO 30 MPH. NEAR

WHITTIER…SOUTHWEST WINDS 30 TO 45 MPH WITH GUSTS 55 TO 65 MPH. NEAR

SEWARD…NORTH WINDS 15 TO 30 MPH. GUSTS TO 50 MPH.

.TONIGHT…CLEAR. AREAS OF BLOWING SNOW…MAINLY NEAR WHITTIER. LOWS

10 BELOW TO 5 ABOVE…COOLEST INLAND.

NORTH TO WEST WINDS 10 TO 20 MPH. NEAR WHITTIER…SOUTHWEST WINDS 20

TO 45 MPH. HIGHER GUSTS TO 55 MPH IN THE EVENING. NEAR SEWARD…NORTH

WINDS 15 TO 30 MPH WITH GUSTS TO 45 MPH.

.TUESDAY…MOSTLY SUNNY. HIGHS 15 TO 25. NORTH TO WEST WIND 10 TO

20 MPH. NEAR WHITTIER…SOUTHWEST WINDS 25 TO 45 MPH DIMINISHING 15

TO 25 MPH BY NOON. NEAR SEWARD…NORTH WINDS 15 TO 30 MPH WITH GUSTS

TO 45 MPH IN THE MORNING.

TEMPERATURE / PRECIPITATION

SEWARD 13 2 23 / 0 0 0

GIRDWOOD 12 -4 21 / 0 0 0

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Temperature -4 F. Westerly wind 10 mph gusting in the upper teens.

-2600′ Seattle Ridge Wx Station-

Temperature -3 F. North wind 5-10 mph gusting into the mid teens.

-1800′ Center Ridge Wx Station-

Temperature 0 F. 4″ of new low density snow.

Mon, February 14th, 2011
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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. Dangerous avalanche conditions. 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.
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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.