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Issued
Tue, November 23rd, 2010 - 7:00AM
Expires
Wed, November 24th, 2010 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Kevin Wright with the Chugach National Forest Avalanche Information Center on Tuesday, November 23rd 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).

ANNOUNCEMENTS

All areas designated for snowmachines are still closed. We are measuring the snow in these areas daily and will open them as soon as there is enough snow to protect the ground and vegetation from being torn up by the tracks of a snowmachine. Thanks for your patience.

WEATHER ROUNDUP

I’m sure everybody noticed the crazy weather yesterday in the form of freezing rain. The temperature inversion finally broke yesterday morning. We picked up only a small amount of measureable precipitation with the weather stations. Alyeska showed up to .2 inches of rain at the base area. The form of freezing rain is more significant to our snowpack than the amount. We’re starting to get more rain and snow this morning and more is forecasted through the week. Wind in the last 24 hours has been relatively light.

AVALANCHE DISCUSSION

Today the avalanche hazard will be MODERATE. This rating is based on limited field observations. Right now we’re playing catch-up to figure out what is going on with the snow. Yesterday Lisa noticed that the glide crack epidemic seemed to have accelerated. This may be due to the extreme temperature inversion that we had until yesterday morning. Ridgetop weather stations were reporting temperatures into the lower 40s. Sunburst weather station had above freezing temperatures for 66 hours before cooling off yesterday. Our precipitation yesterday was limited, but you probably noticed that it was freezing rain. I don’t think we got enough additional load to cause problems in the middle layers of the snowpack with the absence of significant weak layers. More rain and snow is forecasted for today so the general hazard is on an increasing trend.

At upper elevations pay attention to the wind slab near the ridge tops. This may be sensitive to human trigger, especially as we get more snow load this week.

We’ll have to pay attention to the distribution of the freezing rain layer when we get additional snow. This could be an ideal sliding surface in the future and contribute to instability.

I 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 TUE NOV 23 2010

.TODAY…RAIN. RAIN MAY BE MIXED WITH SNOW AT TIMES AT HIGHER

ELEVATIONS. NO SNOW ACCUMULATION. HIGHS IN THE MID 30S TO LOWER 40S.

LIGHT WINDS EXCEPT EAST 25 TO 40 MPH THROUGH PORTAGE VALLEY AND

TURNAGAIN ARM.

.TONIGHT…RAIN AND SNOW. SNOW ACCUMULATION UP TO 2 INCHES AT HIGHER

ELEVATIONS. LOWS IN THE 30S. LIGHT WINDS EXCEPT EAST WIND 25 TO 40

MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

.WEDNESDAY…RAIN AND SNOW. SNOW ACCUMULATION UP TO 4 INCHES AT

HIGHER ELEVATIONS. HIGHS IN THE MID 30S TO LOWER 40S…COLDEST

INLAND. LIGHT WINDS EXCEPT EAST 25 TO 40 MPH THROUGH PORTAGE VALLEY

AND TURNAGAIN ARM.

.WEDNESDAY NIGHT…RAIN AND SNOW. LOWS IN THE MID 20S TO MID 30S.

LIGHT WINDS INLAND. THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…EAST

WIND 15 TO 30 MPH DECREASING TO 10 TO 15 MPH AFTER MIDNIGHT.

.THANKSGIVING DAY…SNOW AND RAIN. HIGHS IN THE 30S. VARIABLE WIND 10

MPH EXCEPT NORTH 10 TO 25 MPH NEAR SEWARD.

.THURSDAY NIGHT…MOSTLY CLOUDY WITH A CHANCE OF SNOW. LOWS IN

THE 20S.

.FRIDAY THROUGH SATURDAY…MOSTLY CLOUDY WITH A CHANCE OF SNOW.

HIGHS IN THE 20S. LOWS IN THE TEENS.

.SATURDAY NIGHT THROUGH MONDAY…MOSTLY CLOUDY WITH A CHANCE OF

SNOW. LOWS 5 TO 15. HIGHS IN THE TEENS.

TEMPERATURE / PRECIPITATION

SEWARD 40 36 40 / 100 100 100

GIRDWOOD 38 36 41 / 100 100 80

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Light wind from the east. Temperatures dropped from 42 yesterday morning to the mid 20s where they remain this morning.

-2600′ Seattle Ridge Wx Station-

Recorded the strongest wind speeds in the area with east wind in the teens to lower 20s. The inversion was less pronounced and temperatures have dropped to the high 20s.

-1800′ Center Ridge Wx Station-

Showed only a .1 inch increase in precip. Temperatures dropped to a current temperature of 31. Snow depth continues to settle with anCNFAIC Staff inch lost in the last 24 hours.

Tue, November 23rd, 2010
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. 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.