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Issued
Thu, January 14th, 2010 - 7:00AM
Expires
Fri, January 15th, 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 Thursday January 14th 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-

Temperatures have stayed steady between 23-24 degrees F with light average winds between 2-10 mph out of the E with a moderate max gust of 17 mph

Current temp is 23

2400′-Seattle Ridge Wx Station-

Winds have been light averaging 7-16 mph out of the ESE with a moderate max gust of 22mph

1800′-Center Ridge Wx Station-

Not working this morning

Nowcast

Most weather stations are down this morning so we have limited real time data. Current temp in Girdwood this morning is 27 and its 23 at 3800′ in Turnagain Pass. Winds are currently light at all ridgetop wx stations this morning. The Middleton radar shows steady moderate precip moving N over the middle of PWS, and the Kenai radar shows light precip building to moderate precip moving N directly toward Anchorage.

Forecast

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST THU JAN 14 2010

.TODAY…RAIN AND SNOW. SNOW ACCUMULATION 1 TO 3 INCHES. HIGHS IN THE

MID 20S TO MID 30S. LIGHT WINDS.

.TONIGHT…CLOUDY WITH A CHANCE OF SNOW. LOWS IN THE MID TEENS TO

MID 20S…COLDEST INLAND. LIGHT WINDS.

.FRIDAY…SNOW LIKELY. SNOW ACCUMULATION UP TO 2 INCHES. HIGHS IN

THE MID 20S TO LOWER 30S. VARIABLE WIND 10 MPH.

.FRIDAY NIGHT…SNOW. LOWS IN THE LOWER 20S TO LOWER 30S. EAST WIND

10 TO 20 MPH.

Temperature / Precipitation

SEWARD 39 34 40 / 80 60 80

GIRDWOOD 39 22 35 / 60 40 40

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

Sea-level: GFS shows 0.25 inches of water forecasted today

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

6000′: temps forecasted between 14 and 23 degrees F with winds 5-10 mph

AVALANCHE DISCUSSION

Today’s weather probably will not contribute to the avalanche danger today at Turnagain Pass. There is some new precip forecasted, but not very much. Plus the winds have been light and the NWS calling for continued light winds today. Today’s weather forecast does not look like it will pack too big of a punch.

The main avalanche concern today and for the near future is and will be that slippery rain crust that has been observed as high as 3000′ on both sides of the highway at Turnagain Pass. If there was 3 feet of new snow today, then avalanche conditions would be deadly. However, the biggest snow depth measurement has been 10.5 inches of new light density snow at the Eddies parking lot in the past 48 hours. There is probably anCNFAIC Staff inch or two since last night. As far as avalanches, there is not quite enough snow on top of that slippery bed surface to create large avalanches yet, but, small avalanches and sluffs are very easy to trigger on any steep slope at all elevations; so, use elevated caution if you find one of those deeper stiffer pockets of snow especially near ridgelines or highmarking on a steep rollover on Sunnyside.

The new snow has been sneaking up on us because it has been coming in slow and steady, which is OK for today. The weather forecast continues to call for more snow over the next couple days with a bigger storm coming in from the Aleutians. Let’s be smart about the rain crust if new snow keeps accumulating over the next couple days. That slippery rain crust is by far the most dangerous weak layer we have seen in our snowpack all season. It will most likely become a serious problem after it gets more snow on top of it.

Today’s avalanche danger will remain at LOW with pockets of MODERATE due to small wind slabs near ridgetops, and easily triggered small slabs on steep rollovers at all elevations.

LOW is defined as: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human triggered avalanches unlikely (except glide cracks are possible). Small avalanches in isolated areas of extreme terrain.

Pockets of MODERATE is defined as heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely, human-triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas.

A wild card right now are the glide cracks. One of these crevasse like features avalanche on Jan 4th for no obvious or apparent reason (see photo gallery). Nostradamus couldn’t have predicted that one; so, it adds to the theory that glide cracks are like cornices in that they are very difficult to predict. Sometimes they avalanche when it’s cold, sometimes when it’s warm, sometimes when it rains, sometimes when it snows, sometimes for whatever reason possible. I don’t mean to turf this avalanche problem into the unknown, but the avalanche community really does not have a good handle on what causes glide cracks to fail. We have not seen or had any reports of any more glide crack failures in the past week, but it would still be wise to avoid traveling on, near, or underneath the path of any glide cracks.

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 Friday January 15th.

Thu, January 14th, 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.