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Issued
Tue, January 26th, 2010 - 7:00AM
Expires
Wed, January 27th, 2010 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Tuesday January 26 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

Hindcast (Last 24 hours)

3800′ -Sunburst Wx Station-

Current temp is 27 (5 degrees warmer than yesterday) Winds have been calm to light averaging 0-6 mph out of the WNW with a light max gust of 7 mph

2400′-Seattle Ridge Wx Station-

Winds have been calm to light averaging 1-6 mph out of the NE with a light max gust of 10mph

1800′-Center Ridge Wx Station-

Current temp is 23 (3 degrees warmer than yesterday) Zero inches of water and zero inches of new snow has fallen. Total snowpack depth 64” after 1” of settlement

Nowcast

Temps are warmer at all wx stations this morning by 3-7 degrees. Current temps range from 16 degrees F at sea level to 27 at 3800′; so, there is still a slight inversion. There is zero new precip at the snotel sites this morning. Winds are currently calm to light at all ridgetop wx stations this morning. The Middleton and Kenai radars are mostly clear.

Forecast

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST TUE JAN 26 2010

.TODAY…MOSTLY CLOUDY. PATCHY MORNING FOG. HIGHS IN THE

MID 20S TO MID 30S. LIGHT WINDS EXCEPT NORTH 10 MPH NEAR SEWARD.

.TONIGHT…MOSTLY CLOUDY. ISOLATED SNOW SHOWERS AFTER MIDNIGHT.

LOWS IN THE MID TEENS TO LOWER 30S…COLDEST INLAND. EAST WIND

10 TO 15 MPH EXCEPT NORTH 15 TO 25 MPH NEAR SEWARD.

.WEDNESDAY…MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS. HIGHS IN

THE LOWER TO MID 30S. EAST WIND 10 TO 20 MPH EXCEPT EAST 15 TO

30 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

Temperature / Precipitation

SEWARD 30 24 34 / 0 20 50

GIRDWOOD 24 18 33 / 0 0 30

Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass

Sea-level: GFS shows a trace of 0.05 inches of water forecasted today

3000′: temps are forecasted between 23-32 degrees F with winds 5 mph

6000′: temps forecasted between 14-23 degrees F with winds 5 mph

AVALANCHE DISCUSSION

Today’s weather should not contribute to the avalanche danger today at Turnagain Pass.

Today’s avalanche conditions should be generally safe with a LOW danger rating.

We will most likely not see any major problems till we get more snow or wind. We could have some serious avalanche dangers in the future after the next rapid change with the weather. I know we are starting to sound like a broken record, but the reality is that we still have a poorly structured snowpack with a persistent weak layer up to 3000′. This weak layer has not been reactive to any significant avalanches recently. One reason for the lack of avalanches is probably due to the fact that there is not enough of a load on top of it.

My most recent pit near Warm Up Bowl on Seattle Ridge found the same trend that we have been seeing on both sides of the highway. We are still finding moderate-hard failures with smooth shear planes in the lighter density snow slightly above the rain crust. What is very alarming to me is that these test scores are not improving. Usually I will see improved stability on these types of layers over an 8-10 day period. I’m not seeing that improvement in my pits, and it seems that CNFAIC Staff folks are getting similar results. The U.S. avalanche observation guidelines classify my pit data as “good” stability but I have not been seeing what is classified as “very good” stability yet. That is not much of a problem right now, because there is not enough of a slab on top of this weak layer. That makes me think that we might have some serious problems after the next big storm. The difficulty meter is very high for forecasting this type of avalanche situation.

The main avalanche concern today is that slippery rain crust underneath the 1.5-2.5 powder/newer snow. This slippery rain crust formed on Thursday Jan 7 and is widespread on all aspects up to 3000′ from Girdwood to Seward.

A secondary concern exists today below 2000′ on facets and surface hoar near the rain crust. This lower elevation problem layer is still showing signs of instability. One of our best observers that is in the mountains all the time in lots of different locations reported, “one of the loudest whoomps I have heard in my life when we were climbing out of a gully onto a deposition pillow” down in the trees near Tincan on Sunday. This lower elevation weak layer could become a serious problem in places like Placer Valley, where we have steep slopes at lower elevations, especially after the next storm.

Always remember that safe backcountry travel requires training and experience. You control your own risk by choosing where, when, and how you travel.

Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Wednesday January 27th.

Tue, January 26th, 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.