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Issued
Thu, March 31st, 2011 - 7:00AM
Expires
Fri, April 1st, 2011 - 7:00AM
Forecaster
Kevin Wright
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Kevin Wright with the Chugach National Forest Avalanche Information Center on Thursday, March 31st 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

Today’s avalanche danger rating is MODERATE with pockets of CONSIDERABLE. The new storm snow was quite reactive yesterday. Small to medium sized natural and human triggered avalanches were seen region wide on all aspects. The sensitivity should be dropping, but reactive pockets may still be out there today.

AVALANCHE DISCUSSION

Tender, hair trigger, sensitive… All accurate words to describe the snowpack over the last two days. The breaks in the clouds yesterday revealed quite a number of small natural avalanches that happened during the storm or soon after. Everything that we saw was confined to the most recent storm layers (March 25th and March 29th storms).

Remote or sympathetic triggers have been relatively common over the last week, which should catch your attention. Even last Saturday we remotely triggered a slope. Now we have an additional 14 inches with deeper wind loaded areas. I’m quite confident that you could find slopes today that would avalanche given the additional weight of a person.

Primary concern is storm snow on top of a crust. There may be surface hoar involved, which could explain the tendency for remote triggers. Take a look at this rough profile from yesterday.

These problems should diminish over time. I think we are still within the timeline of likely human triggers in specific areas. These are going to be found in the classic avalanche terrain: steep slopes, unsupported convex rolls, on the wind loaded side of the ridge. I think higher elevations (2500+) will be the most sensitive where the snow is colder and drier.

Secondary concern is late afternoon warming and increased wet snow concerns. If the sun comes out today watch out for wet snow avalanches on Southern aspects.

Finally, we really want to know if anyone sees avalanches breaking deeper than the storm snow of the last week. It is a less likely concern, but could be much more dangerous if avalanches get deeper and larger.

Encyclopedia of avalanche terms.

WEATHER ROUNDUP

Sunny breaks yesterday between mostly cloudy skies. A trace of snow fell last night in Girdwood and Turnagain Pass. The National Weather Service is calling for a 100% chance of snow today in Turnagain Arm. They are predicting only 2 inches, but any extra precip will contribute to avalanche concerns. Light to moderate wind today from the North and West.

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 AKDT THU MAR 31 2011

.TODAY…SNOW AND RAIN SHOWERS. SNOW ACCUMULATION UP TO 2 INCHES.

HIGHS IN THE 30S. NORTH TO WEST WINDS 5 TO 10 MPH BECOMING 10 TO 20

MPH THIS AFTERNOON.

.TONIGHT…MOSTLY CLOUDY. A CHANCE OF SNOW SHOWERS. LOWS IN THE MID

20S TO LOWER 30S. VARIABLE WIND 10 MPH. NEAR SEWARD…NORTH WIND 15

TO 30 MPH. NEAR WHITTIER…WEST WIND 15 TO 30 MPH.

.FRIDAY…MOSTLY CLOUDY WITH A SLIGHT CHANCE OF SNOW SHOWERS.

HIGHS IN THE MID 30S TO LOWER 40S. VARIABLE WIND TO 10 MPH. NEAR

SEWARD…NORTH WIND 15 TO 25 MPH IN THE MORNING. NEAR WHITTIER…WEST

WIND 15 TO 30 MPH IN THE MORNING.

.FRIDAY NIGHT…MOSTLY CLOUDY WITH A CHANCE OF SNOW SHOWERS. LOWS

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

.SATURDAY…A CHANCE OF SNOW IN THE MORNING…THEN SNOW LIKELY

AND RAIN IN THE AFTERNOON. HIGHS IN THE MID 30S TO LOWER 40S.

NORTH TO EAST WINDS 15 TO 30 MPH. EAST WINDS GUSTING TO 40 MPH

THROUGH PORTAGE VALLEY AND ALONG TURNAGAIN ARM.

.SATURDAY NIGHT…SNOW AND RAIN LIKELY. VERY WINDY. LOWS 25 TO

35.

.SUNDAY…RAIN AND SNOW LIKELY. HIGHS IN THE 40S.

TEMPERATURE / PRECIPITATION

SEWARD 41 29 40 / 60 20 20

GIRDWOOD 38 25 40 / 100 20 20

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Temps in the mid 20s. Light East wind.

-2600′ Seattle Ridge Wx Station-

26 degrees. Light to moderate wind from the ESE.

-1800′ Center Ridge Wx Station-

Temps in the low 30s. A trace of new snow yesterday. 3-4 inches of settlement in the snowpack.

Thu, March 31st, 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. 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.