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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, February 7th, 2009 - 7:00AM
Expires
Sun, February 8th, 2009 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

GENERAL ANNOUNCEMENTS

Good Morning backcountry travelers, this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Saturday, February 7, 2009 at 7am. This will serve as a general backcountry avalanche advisory issued 5 days a week Wednesday-Sunday for the Turnagain Arm area (Turnagain Pass is the core advisory area). Local variations always occur.

MOUNTAIN WEATHER ROUND UP

In the last 24 hours…

-General Weather Observations-

Well, well, well – what a nice weather window we have. Yesterday the clouds parted and the winds died off. Today looks like more of the same if the fog lifts. Cooler temps in the teens this morning in most areas, but look at Moose Pass -4 and Summit 2 deg F.

The DOT weather station near the crest the highway at Turnagain Pass at 1000 feet

Is recording a temp of 12 degrees (3 deg cooler than yesterday) with light to calm winds.

The NRCS Center Ridge weather station at 1800 feet in Turnagain Pass

Has a temp of 5 degrees (13 degrees cooler than yesterday). 0 new precip. Total snowpack depth is 64″.

The Sunburst weather station at 3800 feet in Turnagain Pass

Shows a temperature of 5 degrees (10 degrees cooler than yesterday). Winds have been calm to light.

-Surface Analysis Maps-

Three low pressure systems to our southwest, but nothing effecting us directly.

-Radar-

Clear sailing. Fog may be present at lower elevations.

AVALANCHE HAZARDS

Primary avalanche concerns

-Surface wind slabs on slippery bed surface on alpine ridges above 3000 feet

Secondary avalanche concerns

-Rain crust (ice layer) from January below 3000ft

AVALANCHE AND SNOWPACK

Bottom Line

We have been running with some pretty stable avalanche conditions over the last three weeks. Although subtle, this is changing! We need to raise our level of awareness this weekend as an increased number of human triggered avi observations have trickled in.

Moderate avalanche hazard exists today. Natural avalanches unlikely. Human triggered avalanches possible today. Areas of concern include an elevation band from 800 to 1500 ft where the January rain crust is faceted and creating a weak layer. The second area of concern lies near alpine ridges were sensitive wind slabs live.

Discussion

Heavy rains slammed the area 4 weeks ago. This rain left behind a rain crust up to ~3000ft. This crust is 1 to 1.5 ft deep at 1000 ft. A slight temperature gradient has formed around this crust in the last couple of weeks, most significantly between 800 and 1500 ft. This temperature gradient has developed weak faceted snow around this crust. My main concern with this band exists if you found yourself above terrain traps at these low elevations.

Of more concern to me is the higher elevation wind slabs. These are obvious and predictable. If the snow looks fat and wind loaded, it’s a wind slab. The good thing is we know where they live and they’re predictable. We can stay away from them if we choose. Thursday’s strong winds re-energized these slabs. These wind slabs have been running on multiple aspects over the last week. Shooting cracks and drum sounding snow will indicate wind stiffened snow and a possible wind slab. If these conditions are present, lower you slope angle or return to softer, lighter snow.

Yesterday a great observation was reported from Lips in T-Pass. Ridge top wind slabs were trigged and the debris pulled out 1 to 1.5 ft slabs as it ran to the valley bottom. This is plenty avalanche to injure or bury a person, especially if a terrain trap is involved.

These skier triggered wind slabs pulled out additional surface slabs as the debris ran to the valley floor! photo-Munter,2006.02.06

Keep your human factors and decision making in check today, The snow “stoke” meter will be pegged for some of you today!!! Make good decisions in complex terrain. One at a time and look for escape routes, use runs with fan shaped run-outs not cliff bands or terrain traps!!!

WEATHER FORECAST

WESTERN PRINCE WILLIAM SOUND-

I500 AM AKST SAT FEB 7 2009

.TODAY…MOSTLY SUNNY. HIGHS IN THE 20S. NORTHWEST WIND 10 TO 15 MPH.

GUSTS TO 35 MPH NEAR SEWARD AND WHITTIER.

.TONIGHT…PARTLY CLOUDY. PATCHY FOG. LOWS 10 TO 20 ABOVE…

COOLEST INLAND. NORTHWEST WIND 10 TO 15 MPH EXCEPT NORTH 20 TO

30 MPH NEAR SEWARD.

.SUNDAY…PARTLY CLOUDY. HIGHS IN THE LOWER TO MID 20S. NORTHWEST

WIND 10 TO 15 MPH EXCEPT NORTH 20 TO 30 MPH NEAR SEWARD.

.SUNDAY NIGHT…MOSTLY CLEAR. LOWS 5 TO 20 ABOVE…COOLEST INLAND.

VARIABLE WIND TO 10 MPH. NEAR SEWARD…NORTH WIND 10 TO 20 MPH.

.MONDAY…PARTLY CLOUDY IN THE MORNING THEN BECOMING MOSTLY

CLOUDY. A CHANCE OF SNOW. HIGHS IN THE LOWER TO MID 20S. LIGHT

WINDS EXCEPT NORTH 10 MPH NEAR SEWARD.

TEMPERATURE / PRECIPITATION

SEWARD 26 19 24 / 0 0 0

GIRDWOOD 21 9 19 / 0 0 0

This concludes today’s avalanche advisory the next advisory will be on Sunday, February 8th. Thanks and have a great day.

Sat, February 7th, 2009
Alpine
Above 2,500'
0 - No Rating
Avalanche risk
Treeline
1,000'-2,500'
0 - No Rating
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
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.