Avalanche Advisory Archive Pre-2016

Date Issued:2013-01-22
Danger:2
Trend:2
Probability:1
Size:1
Problem:0
Discussion:

The National Weather Service Forecasts-

TODAY...MOSTLY CLOUDY. AREAS OF DENSE FOG WITH VISIBILITY ONE
QUARTER MILE OR LESS AT TIMES IN THE MORNING. CHANCE OF RAIN IN THE AFTERNOON. HIGHS AROUND 40. EAST WIND 5 TO 15 MPH.

TONIGHT...PERIODS OF RAIN...MIXING WITH SNOW LATE. SNOW
ACCUMULATION TO 1 INCH. LOWS AROUND 32. EAST WIND 5 TO 15 MPH.

WEDNESDAY...RAIN AND SNOW LIKELY. SNOW ACCUMULATION 1 INCH OR
LESS. SNOW LEVEL RISING TO 900 FEET IN THE AFTERNOON. HIGHS AROUND 35. SOUTHEAST WIND 5 TO 15 MPH.

Night before last we received an inch of precipitation that only left very small amounts of new snow in our mountain regions. This small amount of snow came in very wet and will tend to bond fairly well. There was windloading during the event and at uppermost elevations you may find very small pockets of windslab.

Since that time temperatures have continued to rise and are now above freezing in all our mountain starting zones.

Overall we have a fairly stable snowpack. Yet it is quite water saturated and nearly isothermal.

Be aware that on super steep unsupported slopes we may have some slight instabilities as this slurpee like snow that is currently at the point of freezing does not have much of that below freezing glue holding it together.

With almost no precip in the forecast and a cooling temperature trend to start over the next 24 hours I will keep avalanche danger at moderate for small avalanches.

Natural avalanches are unlikely and yet slightly possible on very steep slopes with no anchors and no support from below. This snow may move like sands through the hourglass as small lower mountain sections release themselves.

Human Triggered avalanches are unlikely as well. Yet once again on steep slopes that are unsupported and unanchored you may have the ability to get a little snow to move.

Be aware of terrain traps. No not expose yourself accross the tops of cliffs on steep convex slopes.

As the cooling begins stability will improve.

Tip:

Often times when we think about a surface weak layer in the snowpack and there are other weak layers present deeper down in the snow as well, we are concerned with the possibility of an avalanche stepping down.

Stepping Down:

When multiple weak layers exist in the snowpack, often a smaller, shallower avalanche will travel a few feet to a few yards and the added weight and stress will trigger a deeper weak layer, which results in a much larger and more dangerous avalanche. These types of avalanches can be especially dangerous to people because the following scenario: First, the person who triggers the smaller avalanche will ride the first slide down. As the smaller avalanche descends, it triggers a deeper avalanche. By the time the deeper avalanche picks up speed and descends to the bottom, the victim has stopped at the bottom of the slope and the secondary, larger avalanche will pile debris on top of the victim, often burying them very deeply with no hope of a live recovery.

When you deal with a snowpack that has the potential to step down into deeper weak layers, it?s important to notch back your level of exposure because of the dangerous consequences.

These are very difficult conditions to predict accurately and this is why it is important to reconsider all routes, terrain features and possibilities.