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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sun, February 1st, 2009 - 7:00AM
Expires
Mon, February 2nd, 2009 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

GENERAL ANNOUNCEMENTS

Good morning backcountry travelers, this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, February 1, 2008 at 7am. This will serve as a general backcountry avalanche advisory issued 5 days a week Wednesday through 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…

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

recorded no new snow. The current temp is 5F with a total snowpack depth of 65 inches.

-The Sunburst weather station at 3800 feet in Turnagain Pass-

recorded winds averaging 10-15 mph out of the East with gusts in the 20’s.

-Max’s weather station at 3200 feet in the Girdwood Valley-

recorded winds averaging 5-10 mph out of the SE and East with gusts in the teens and 20’s.

-General Weather Observations-

As of 4:00 am this morning, mountain temperatures were in the single digits F with light winds blowing 5-10 mph out of the N and W, except at 43 Mile Peak where they were blowing 15-20 mph out of the N. Today, a weak low pressure system in the gulf will influence our weather. Mountain temperatures will remain in the single digits, and northwesterly ridgetop winds will blow 10-15 mph with stronger winds closer to the coast. Mostly cloudy skies will produce some scattered snow showers this morning with skies clearing by afternoon.

AVALANCHE HAZARDS

Primary avalanche concerns

-Surface wind slabs above treeline

AVALANCHE AND SNOWPACK DISCUSSION

This week 6-10 inches of snow fell in Turnagain Pass and the Girdwood Valley. Localized strong winds blew this low-density new snow into 2-12 inch windslabs above treeline on a variety of aspects. Most of these windslabs are small, soft, manageable slabs that will fracture right under your skis, board, or sled. At the higher elevations closer to the ridgetops, thicker windslabs exist. On Thursday, Matt intentionally triggered a soft windslab on the north side of Tincan at 3900 feet. This slab was up to 12 inches deep and 50 feet wide and ran 1000 feet down Todd’s Run. Ski cuts are very effective with these new soft slabs if you know how to do them safely. The main hazard would be unexpectedly triggering one above steep complex terrain. Harder, drum-like slabs also exist, especially at the higher elevations above 3000 feet. These are the ones to look out for because they are not manageable and will fracture unexpectedly above you.

Yesterday, 12 of our observers braved the sunny skies and blower powder all in the name of science. A BIG thank you goes out to the Friends of the CNFAIC and all of our observers for their valuable time and energy! Carl’s group on Tincan found pockets of 12 inch deep soft slab with 20 ft. shooting cracks near the ridgetops above 3500 feet. Ben triggered a 6 inch deep, 75 ft. wide surface soft slab on a steep convex rollover at 3100 feet on a SW aspect. I also triggered a small soft shallow wind slab on a convex rollover on Sunburst. These slides were easy to ski through and pretty much harmless. Matt’s group checked out the back bowls on the motorized side and found good stable skiing that was more protected from the winds.

On long steep unsupported slopes, especially those approaching 40 degrees or steeper, it is certainly possible to trigger loose snow avalanches. These sluffs may be large enough to catch and carry a person in steep terrain, and they can pile up fairly deep if given a chance to run.

On slopes below 2800 feet elevation, the new snow is sitting on a thick crust that formed during our mega-meltdown two weeks ago. Right now this is not much of a concern because the new snow is so light. Once we get more of a load, however, the crust will be an excellent bed surface for future avalanches.

Deep slab instabilities may exist at the higher elevations above 3000 feet where temps are colder and the facets remain weak and sugary. An unlikely, but outside chance remains of triggering a deep slab avalanche in thin, rocky starting zones in these higher elevations.

This concludes today’s advisory; the next advisory will be Wednesday, February 4th. If you are out in the backcountry and have the chance, please send us your observations. Simply click on “Submit a snow observation online” at the top of the advisory page and fill in the blanks. Thanks and have a great day!

The weather forecast for:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SUN FEB 1 2009

.TODAY…MOSTLY CLOUDY IN THE MORNING THEN BECOMING PARTLY

CLOUDY. ISOLATED SNOW SHOWERS EXCEPT LIGHT SNOW NEAR PORTAGE IN THE

MORNING. SNOW ACCUMULATION UP TO 2 INCHES. HIGHS 10 TO 20 ABOVE.

NORTHWEST WIND 10 TO 15 MPH EXCEPT NORTH TO WEST 20 TO 35 MPH NEAR

SEWARD AND WHITTIER.

.TONIGHT…PARTLY CLOUDY. LOWS 5 BELOW TO 15 ABOVE…COOLEST

INLAND. NORTHWEST WIND 10 TO 15 MPH EXCEPT NORTH TO WEST 15 TO 30 MPH

NEAR SEWARD AND WHITTIER.

.MONDAY…PARTLY CLOUDY IN THE MORNING THEN BECOMING MOSTLY

CLOUDY. SCATTERED SNOW SHOWERS. HIGHS 5 TO 15 ABOVE. NORTHWEST

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

CHILLS 5 BELOW TO 20 BELOW IN THE MORNING.

.MONDAY NIGHT…MOSTLY CLOUDY IN THE EVENING THEN BECOMING PARTLY

CLOUDY. LOWS 10 BELOW TO 10 ABOVE…COOLEST INLAND. NORTHWEST

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

.TUESDAY…PARTLY CLOUDY. HIGHS 5 TO 15 ABOVE. VARIABLE WIND TO 10

MPH.

TEMPERATURE / PRECIPITATION

SEWARD 19 5 13 / 20 0 0

GIRDWOOD 13 -2 9 / 20 0 40

Sun, February 1st, 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.