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Issued
Mon, January 11th, 2010 - 7:00AM
Expires
Tue, January 12th, 2010 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Monday, January 11th at 7am. This will serve as a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (advisory does not apply to highways, railroads, or operating ski areas).

WEATHER ROUNDUP

No new snow fell in the last 24 hours in Turnagain Pass. Actually our last significant snowfall was 16 days ago on Dec 26. Yesterday ridgetop winds were light while mountain temperatures ranged from the mid 20’s to low 30’s. High clouds moved in by afternoon, and a low band of fog lingered for most of the day. As of 4 am this morning, skies are clear while ridgetop winds in Turnagain Pass are light and variable. Temperatures plummeted overnight and are anywhere from 10 to 25 degrees colder than this time yesterday. There is a 10 degree temperature inversion this morning with temps ranging from 19F at 3800 feet to 9F at sea level. The occluded front will weaken today with most of the rain and snow remaining offshore. Some clouds may move in by this afternoon with mountain temperatures remaining in the low to mid teens. Ridgetop winds could get gusty but should remain on the light and variable side.

-The Center Ridge Wx Station at 1800 feet/Turnagain Pass-

recorded no new snow in the last 24 hours. The current temp is 8F (23 degrees colder than yesterday) with a total snowpack depth of 56 inches.

-The Sunburst Wx Station at 3800 feet/Turnagain Pass-

recorded light northeasterly winds yesterday averaging 5-10mph. The current temp is 19F (10 degrees colder than yesterday) with winds averaging 5mph out of the northeast.

-The Summit Lake Wx Station at 1200 feet-

recorded no new snow in the last 24 hours. The current temp is 1F (27 degrees colder than yesterday) with a total snowpack depth of 29 inches.

-The Fresno Ridge Wx Station at 3400 feet/Summit Lake-

recorded light southeasterly winds yesterday averaging 10-15mph with gusts in the 20’s. The current temp is 16F (11 degrees colder than yesterday) with winds averaging 5mph out of the south.

The weather forecast for:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST MON JAN 11 2010

…STRONG WIND THROUGH TONIGHT…

.TODAY…SUNNY. HIGHS IN THE LOWER 20S TO LOWER 30S…COLDEST

INLAND. NORTH TO WEST WINDS 15 TO 30 MPH WITH GUSTS TO 45 MPH NEAR

SEWARD AND WHITTIER. VARIABLE WINDS 5 TO 15 MPH ELSEWHERE.

.TONIGHT…INCREASING CLOUDS. LOWS ZERO TO 20 ABOVE…COLDEST INLAND.

NORTH TO WEST WINDS 15 TO 25 MPH WITH GUSTS 30 TO 45 MPH NEAR SEWARD

AND WHITTIER. LIGHT WINDS ELSEWHERE.

.TUESDAY…CLOUDY WITH A SLIGHT CHANCE OF SNOW. HIGHS IN THE MID

TEENS TO LOWER 30S…COLDEST INLAND. VARIABLE WIND TO 10 MPH. EXCEPT

NORTH TO WEST WINDS 15 TO 30 MPH NEAR SEWARD AND WHITTIER.

TEMPERATURE / PRECIPITATION

SEWARD 30 20 28 / 0 0 30

GIRDWOOD 21 8 22 / 0 0 20

AVALANCHE DISCUSSION

Today, a LOW avalanche danger exists on all slopes which means that natural and human-triggered avalanches are unlikely. You may find a few lingering small, hard, windslabs above 3000 feet in isolated areas like steep windloaded couloirs or crossloaded gullies near ridgetops. We are looking at generally stable avalanche conditions, but as always, evaluate the snow and terrain carefully and always use good travel habits.

Not much has changed since yesterday CNFAIC Staff than we have a new batch of surface hoar growing on top of the recent rain crust with faceted crystals forming underneath…future weak layers for sure that we will watch closely. A few small point release wet slides happened during the rain event midweek, but that’s about it for recent avalanche activity. The rain line reached about 2800 feet this past week, so this current rain crust (aka future slick bed surface) is much higher in elevation than the previous rain crusts that topped out at 2000 feet. Matt and Jon toured up Magnum yesterday and felt that this may become the first bad weak layer we’ve seen at the upper elevations since the facets on the ground earlier this season. The slick crust is at a location where slope angles start getting steeper and folks might get false data from snowpits up high.

This past week we found various instabilities in the top 6-12 inches at the higher elevations, but they have not been reactive to skiers or riders. These weak layers include old buried facets, decomposing stellar crystals, and density changes between windslabs. Below 2200 feet, the old buried surface hoar from the second week of December is buried 1-1.5 feet down but has not been reactive in our stability tests.

Some Summit Lake observations from Friday 1/8…Alex found 3 separate layers of small buried surface hoar in the top 1.5 feet sandwiched in between hard windslabs at 2700 feet on a south aspect of Fresno Ridge. They were not especially reactive in his isolated column stability tests (CT22,23 both Q2’s), but they are still layers of concern.

Matt 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.

Mon, January 11th, 2010
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. 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.