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Issued
Thu, February 4th, 2010 - 7:00AM
Expires
Fri, February 5th, 2010 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Thursday February 4th 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).

WEATHER ROUNDUP

There are no major storms nearby on the surface maps. The radars show scattered precip moving mostly toward Cordova. Ridgetop winds have been calm to light at all wx stations in the past 72 hours and are still currently calm to light. Temps have continued to drop at all wx stations and are colder by 6-13 degrees F compared to yesterday. Temps range from 20 degrees F at sea-level and 12 degrees at 3800′. There has been zero new snow or water recorded at any of the snotel sites. Even though the weather forecasts are calling for strong wind near Whittier, nothing else indicates anything significant that will affect the snowpack today.

AVALANCHE DISCUSSION

Today’s avalanche danger for the Turnagain Pass area will remain at LOW with pockets of MODERATE.

Stability has been good recently because there is probably not enough snow on top of the rain crust that formed on Jan 7 to create enough of a load to cause avalanches. Just because stability has been good recently doesn’t mean we are good to go after the next storm. If you want to see some examples of our future weak layer, take a couple minutes to look at some recent stability tests on the forecaster video link on the top left of this page or click or copy and paste the following links for YouTube. After watching these, ask yourself how comfortable you will be after the next big RAPID load falls on our current snowpack.

Widowmaker Peak 2/2/2010

http://www.youtube.com/user/ChugachAvalanche#p/a/u/0/QHRseipMQ7s

Eddies 1/31/2010

http://www.youtube.com/user/ChugachAvalanche#p/a/u/0/5awB3GZSWwU

We have been digging stability test pits all over Turnagain Pass on both sides of the highway at multiple aspects and elevations. We have started to see some variable results compared to what we saw last week when we saw instabilities just above the rain crust with hard failures on 99% of our pits. Now, we have seen improve test scores or shear quality in some locations; however, we are also starting to find cleaner faster shears in CNFAIC Staff locations. This is alarming to me because this weak layer is almost 1 month old. Usually, we see much better test scores on this type of weak layer after 1 month. This is unusual, and anytime I see something unusual in the snowpack, it raises a red flag in my head.

The variability in our test pits might indicate that we are moving away from a widespread avalanche problem for the future, to more of a problem with isolated pockets of instability in the future. Identifying the locations of all those isolated pockets will be difficult; so, it might be like walking through a mine field after we get the next RAPID load of snow, wind, sun or rain.

Our weather history, snowpit data, and field observations all hint toward the rain crust being more developed below 3000′. That’s why places like Widowmaker Peak, CNFAIC Staff Seattle Ridge bowls and Eddies on the non-motorized side of Turnagain Pass are areas for future concern. These places have steep slopes at these lower elevations. CNFAIC Staff places with steep slopes at lower elevations include Placer Valley, Girdwood Valley, Kern and Peterson Creeks.

The reason why we keep dwelling on this rain crust problem is because the snow above the rain crust has a poor structure with all 3 of the main ingredients for avalanches: a bed surface (slippery rain crust), a weak layer (lighter density snow sitting on top of rain crust), and a slab of denser snow on top that weaker snow.

Always remember that safe backcountry travel requires training and experience. You control your own risk by choosing where, when, and how you travel.

WEATHER FORECAST (National Weather Service)

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST THU FEB 4 2010

…STRONG WIND TODAY NEAR WHITTIER AND SEWARD…

.TODAY…SNOW SHOWERS. SNOW ACCUMULATIONS 1 TO 3 INCHES. LOCAL AREAS

OF BLOWING SNOW. HIGHS IN THE 20S. LIGHT WINDS. NEAR SEWARD AND

WHITTIER…NORTH TO WEST WINDS 10 TO 25 MPH WITH GUSTS 35 TO 45 MPH

THIS MORNING.

.TONIGHT…SNOW LIKELY. SNOW ACCUMULATIONS 1 TO 4 INCHES. LOWS IN

THE MID TEENS TO LOWER 30S…COLDEST INLAND. LIGHT WINDS EXCEPT NORTH

10 TO 20 MPH NEAR SEWARD.

.FRIDAY…SNOW LIKELY…POSSIBLY MIXING WITH RAIN IN THE AFTERNOON.

SNOW ACCUMULATIONS 1 TO 4 INCHES. HIGHS IN THE UPPER 20S TO MID 30S.

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

Temperature / Precipitation

SEWARD 26 23 32 / 40 50 80

GIRDWOOD 22 17 34 / 20 40 60

Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass

Sea-level: temps are forecasted between 17-34 with up to inches of water today

3000′: temps are forecasted between 14-23 degrees F with winds 5 mph

6000′: temps are forecasted between 5-14 degrees F with winds 5-10 mph

Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Friday February 5th.

Thu, February 4th, 2010
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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. Dangerous avalanche conditions. 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.