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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, January 22nd, 2010 - 7:00AM
Expires
Sat, January 23rd, 2010 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday January 22nd 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).

ANNOUNCEMENTS

There are still spots available for tomorrow’s snowmachine avalanche workshop in Turnagain Pass. Sign up at the Alaska Avalanche School (alaskaavalanche.com) or call (907)345-0878. They will cover rescue procedures and snow assessments with some class room and lots of field work.

Our Summit Lake Area Advisory is debuting today. It will be a general advisory posted on Friday and Saturday morning. The Summit Lake Area is part of the Chugach National Forest, it has been a goal of the CNFAIC to include more of the Forest for 9 years. Check it out !

WEATHER ROUNDUP

Hindcast (Last 24 hours)

3800′ -Sunburst Wx Station-

Current temp is 24 (2 degree warmer than yesterday) Winds have been light averaging 8mph out of the east with a gusts of 14-16 mph. The winds are increasing slightly this morning.

2400′-Seattle Ridge Wx Station-

Winds have been calm to light averaging 5 mph out of the NNW with gusts of 7-14. We are currently replacing the temperature sensor on this station.

1800′-Center Ridge Wx Station-

Current temp is 17 (2 degrees warmer than yesterday) Zero inches of water and zero inches of new snow has fallen. Total snowpack is 67″.

Temps are a couple of degrees warmer this morning with inversions from G-Wood to Summit Lake. Expect 5-12 degrees temperature inversions this morning. These inversions are a sign of a stable air mass. There is a better chance that they will mix out today with increasing winds. The winds will be driven by the 1000 mb -986 mb pressure gradient that exists over our area. Scattered showers on the radar and satellite this morning. Expect clearing skies for the weekend as a weak low pressure trough exists from Central AK to CA.

Forecast

AKZ125-230100-

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST FRI JAN 22 2010

…STRONG WIND THROUGH THIS AFTERNOON NEAR WHITTIER…

.TODAY…CLOUDY WITH SCATTERED SNOW SHOWERS IN THE MORNING…THEN

PARTLY CLOUDY IN THE AFTERNOON. HIGHS IN THE LOWER 20S TO MID

30S…COLDEST INLAND. VARIABLE WIND 10 MPH EXCEPT NORTH WIND 20 TO

35 MPH NEAR SEWARD AND WEST 30 TO 45 MPH NEAR WHITTIER.

.TONIGHT…MOSTLY CLEAR. LOWS IN THE LOWER TEENS TO UPPER 20S…

COLDEST INLAND. VARIABLE WIND TO 10 MPH EXCEPT NORTH AND WEST WIND

20 TO 35 MPH NEAR SEWARD AND WHITTIER.

.SATURDAY…MOSTLY SUNNY. HIGHS IN THE LOWER 20S TO LOWER 30S…

COLDEST INLAND. LIGHT WINDS EXCEPT NORTH AND WEST 15 TO 30 MPH NEAR

SEWARD AND WHITTIER.

.SATURDAY NIGHT…PARTLY CLOUDY. LOWS IN THE LOWER TEENS TO LOWER

30S…COLDEST INLAND. LIGHT WINDS EXCEPT NORTH 15 MPH NEAR SEWARD.

.SUNDAY…MOSTLY SUNNY WITH ISOLATED SNOW SHOWERS. HIGHS IN THE

LOWER 20S TO MID 30S. VARIABLE WIND 10 MPH EXCEPT NORTH 10 TO 15 MPH

NEAR SEWARD.

.SUNDAY NIGHT…MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS. LOWS

15 TO 25.

TEMPERATURE / PRECIPITATION

SEWARD 29 18 28 / 40 0 0

GIRDWOOD 20 11 18 / 20 0 0

AVALANCHE DISCUSSION

The main avalanche concern continues to be the slippery rain crust underneath the 1.5-2.5 feet of newer snow especially between 2000′-3000′. This slippery rain crust formed on Thursday Jan 7 and is widespread on all aspects from Girdwood to Seward.

We have been seeing a common feature in the snowpack throughout the advisory area. The newer storm snow likes to fail about ½ inch above the top rain crust with hard failures in the lower 20 range on compression tests with clean shears (Q2) where the shear plane is smooth but does not slide readily.

What this means according to the avalanche guidelines is that these test scores… “generally indicates good stability (in these particular test pit locations) but a compact group of skiers/snowboarders, a snowmachine, or explosives may trigger an avalanche. Natural avalanches are rare”.

These test scores are still on the low end of good stability and the structure of the snowpack is poor right now because it has the three main ingredients for an avalanche: a slab (the new 1.5-2.5 feet of snow) on top of a weaker layer (last week’s 6 inches of light dry snow) on top of a slippery bed surface (rain crust). Parts of our current snowpack and this advisory point toward low avalanche danger. However, I think of it like this. The danger scale only has one more level below our current rating of moderate. I know that stability could be better, thus I’m reserving the low for such a snowpack. Also, Lisa got a RB2 Q1-2 on a reuschblock yesterday at 2000 ft. (RB2=failure occurred when person stepped onto the block, Q1-2 means it had a very clean sheer). Don’t let the weather and snow quality shut off your brain this weekend.

Terrain management is key right now. If big lines are on your agenda-keep big eyes wide open. Make good risk assessments, travel one at a time, watch your partner, have an escape route, use terrain that avoids terrain traps, and have a rescue plan with all the rescue equipment needed for companion rescue. In the backcountry you are the rescue party. When responding to avalanche burials, organized rescue is organized recovery.

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 Saturday January 23rd.

Fri, January 22nd, 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.