Avalanche Advisory Archive Pre-2016

Date Issued:2010-03-21
Danger:2
Trend:3
Probability:5
Size:2
Problem:0
Discussion:

The National Weather Service Forecasts- TODAY, MOSTLY CLOUDY. HIGHS AROUND 39. LIGHT WINDS.

TONIGHT...CLOUDY. A SLIGHT CHANCE OF SNOW IN THE EVENING, THEN
SNOW LATE. RAIN MIXING WITH SNOW AT TIMES SOUTH OF DOWNTOWN
JUNEAU LATE. SNOW ACCUMULATION UP TO 2 INCHES. LOWS AROUND 31.
EAST WIND 10 TO 20 MPH. CHANCE OF PRECIPITATION 90 PERCENT.

TUESDAY...RAIN AND SNOW IN THE MORNING...THEN RAIN LIKELY IN THE AFTERNOON. SNOW ACCUMULATION 1 TO 2 INCHES. HIGHS AROUND 39. EAST WIND 15 TO 20 MPH. CHANCE OF PRECIPITATION 90 PERCENT.

Over last weekend we saw several days where the temps went well above freezing at tram elevations. Then on Tuesday we had a great day of sun. This has given most of the last 2 weeks new snow time to settle and bond.

Temperatures are cooler now so the lower end of the snowpack is starting to stiffen up. With the exception of the new snow from the last few days.

Thursday you could see trees, cornices and rocks dropping snow. During todays sun this is going to continue. In steep areas this caused lots of TINY class 1 avalanches. Class 1 activity is more like high.. But we are more concerned with the larger slides.

During Thursdays field work I was able to observe a class 2 slide off the West Face on Mt Juneau leading down into Salmon Creek that was started by a cornice fall.

This cornice fall point release, then propagated into a soft slab surface avalanche that was about 5\" deep. This places a lot of stress on the rest of the snowpack.

Often times if there was a greater deeper instability in the same area this would have pulled it out and shown us the deeper weakness was present.

In long steep areas even these small wet slides can pile up quite a bit of snow.

Yesterday above the Flume Train in the Chop Gulley avalanche area you could see more of this activity.

Snowpit tests in Upper East Bowl outside of the Eaglecrest Ski Area and on Showboat ridge Thursday showed multiple weak layers within the last 2 weeks snowpack.

Compression tests released: CT9@55cm, ct17 at 95cm and ct24 at 155cm. All results were q1 shears. Extedned column tests did not support these results in the same area.

All the lower layers were One Finger penetration to Pencil. Quite stiff.

It appears it would talk a great deal to pull below the last 4 days new snow layers. Yet in the backcountry on super steep pitches, near cornices, or on convex slopes with the presence of a human trigger there is a little more concern. And wet slide activity will be seen during todays diurinal fluctuation(mid day warming from the radiant energy of the sun)

Thursday afternoons field results from Mt Juneau were a little different. Mt Juneau receives direct sun. Mt Juneau often times has warmer temperatures from the upwelling along the channel.

Snow pit tests showed a very uniform snowpack all the way down to the old snow in place from over 2 weeks ago now.

We saw a CT 24 @ 120cm Q1 on a very prominant weak layer.

You could then pick up the column and turn it sideways and shake it and it wouldnt break. I then dropped it onto my backpack and the column still didnt break. So this hard slab has developed into a quit stiff layer. It appears it would take a great deal of stress to fracture to this depth.

If we saw tremendous warming or heavy rains it could start to raise concerns, yet things are quite stable at this time.

Looking at Mt Juneau and Mt Roberts above Thane road you can see the great areas of accumulation from the heavy winds. In these areas the layer of weakness may be even deeper.

These wind drifts and wind deposited slabs are a little harder to predict stability on, but all upper layers appear to be holding at the present time.

Friday we received several inches of new snow and moderate windloading. Near the summit pockets of instability exist. With cool temperatures today, moderate winds and not much moisture avalanche danger is moderate.

With the presence of human triggers there is a possibility of avalanches in the backcountry.

Tip:

For those interested there may still be seats available for the University of Alaska Southeasts Avalanche Level 1 Course.

Avalanche Evaluation and Theory Level 1
University of Alaska Southeast
March 23 - April 4

An intensive course of avalanche study covering rescue, terrain analysis, snow study and stability evaluation, route finding, decision making, and safe travel. Combines both in-class and field oriented backcountry experience as required course components. For more information, contact University of Alaska Southeast.

http://www.uas.alaska.edu/humanities/programs/ods/courses.html