Avalanche Advisory Archive Pre-2016

Date Issued:2010-02-04
Danger:2
Trend:3
Probability:2
Size:1
Problem:0
Discussion:

The National Weather Service Forecasts- TODAY...CLOUDY. PERIODS OF LIGHT RAIN AND BREEZY IN THE AFTERNOON. AREAS OF FOG IN THE MORNING. HIGHS AROUND 40. LIGHT WINDS BECOMING SOUTHEAST 15 TO 25 MPH IN THE AFTERNOON.

TONIGHT...RAIN LIKELY. BREEZY. LOWS AROUND 38. SOUTHEAST WIND 15 TO 25 MPH WITH HIGHER GUSTS IN EXPOSED LOCATIONS. CHANCE OF RAIN 70 PERCENT.

SATURDAY...RAIN LIKELY. BREEZY. HIGHS AROUND 39. EAST WIND 25
MPH. CHANCE OF RAIN 70 PERCENT.

We received about 4 \" of soft snow on Wednesday night that is bonding well to the old snow surface. During that time we had prominent winds between 10-20 mph through most of it. This new snow accompanied by loading winds is placed a few weak slabs in windloaded areas, near ridgetops and in open, exposed areas.

With very little new snow in the last week things are farily stable at this time.

We have seen more above freezing temperature on Mt Roberts and Mt Juneau than below freezing temperatures in the last week. This was slowly weekening the snowpack. The last two days tempsvdropped back below freezing and the lower layers are starting to solidify. But today we are once again seeing above freezing temperatures on most of the mountain.

As long as rain or snow comes in slowly or not at all danger levels should remain moderate.

Currently at lower elevations the bottom 2/3 of the snowpack is moist, warm, and rotten. There is some bonding and bridging above this layer. Yet the weakness is quite present and needs quite a bit of time at below freezing temperatures if it is to resolidify.

Tip:

Below freezing temperatures are like the glue that helps to hold the snowpack together. During periods of above freezing temperature the bonds that have formed between the crystals erode and disappear. The longer the period of warm temperature the more the snowpack tends to weaken.

Rain has this same effect by rapidly warming the snowpack as well as eating away at the corners of the flakes and the bonds holding them together.

Once the snowpack warms it takes a tremendous amount of time and energy to bring it back down in temperature.

The most recent snow came in as rain and slowly turned into snow. It has gotten colder in the last 48 hours. This warm snow sticks well to the old snow surface. With cooling during the cycle we are now placing lighter snow on top of heavier snow. This typically leads to a more stable snowpack. Today we will start to again see warmer temperatures. Look to see avalanche danger levels rise as the temps start to warm back up during periods of continued snow and rain.