Avalanche Advisory Archive Pre-2016

Date Issued:2014-03-05
Danger:1
Trend:3
Probability:0
Size:2
Problem:0
Discussion:

From the National Weather Service Forecast:

Today: Sunny. Highs around 24. Northeast wind 10 to 20 mph increasing to 15 to 25 mph in the afternoon near downtown juneau and douglas and out of interior passes. Otherwise...east wind increasing to 15 mph.

Tonight: Clear. Lows 10 to 20...except around 1 above in wind sheltered areas. Northeast wind 15 to 25 mph with higher gusts near downtown juneau and douglas. Otherwise...east wind 5 to 15 mph.

Thursday: Sunny. Highs around 29. Northeast wind 15 to 25 mph.

The last 24 hours have seen winds around 20kts, and temperatures steady around 15f.

The hazard remains LOW today with our blustery, moderate winds and cold temps keeping the bite in the air, but not generating much change in the snow. Expect the same weather to continue throughout the next 24 hours. The potential for large slides that would come close to urban zones and structures is very small.

Isolated near surface faceting was observed below the wind slab yesterday in fieldwork above the tram, but only where the ridge tops were not blasted clean down to our large melt-freeze layer.

Warming snow may be an issue in wind sheltered south facing terrain. A faceted layer still exists just above the melt-freeze where it has not been exposed by the wind. High spatial variability was observed.

Human triggered slides are still possible in backcountry locations. Watch lee slopes for windslab. If you are sledding or skiing keep that in mind and travel accordingly.

Tip:

If you've been watching the weather, you may have noticed this special announcement put out by the NWS:

http://forecast.weather.gov/showsigwx.php?warnzone=AKZ025&warncounty=AKC110&firewxzone=AKZ025&local_place1=
6+Miles+SE+Snettisham+AK&product1=Special+Weather+Statement#.Uxc7CvRdWTY

It looks like winter is not done with us yet. We will see what this incoming storm actually produces in terms of precipitation, but lets prep our brains while we wait. Here are a handful of general considerations for storm snow:

-New snow tends to be of a lighter density than snow that has settled on the ground for some time. Consider the underlying surface. Have you traveled on the snow recently? It is quite hard, and many unprotected spots are icy, glazed or have been stripped down to the large melt-freeze layer by the wind. New cold snow will have difficulty bonding to the old snow in many spots.

-Panhandle storms tend to warm as the snow falls, commonly leading to an 'upside down' snowpack where heavy, wet snow overlies lighter, dryer snow. This is a structurally unstable situation, and often leads to a touchy snowpack.

-Low density snow is easier to move. Light to moderate winds can transport falling snow and redistribute snow on the ground rapidly, loading lee slopes. This will present a particular problem given the somewhat poor bonding surface that will underlie the snow. Always keep an eye on where current and previous winds have been blowing especially when there is transportable snow.

-Storm snow instability can last hours or days, and transitions into other problems easily, such as wind slab. Be smart about where you plan travel, be conservative with your decisions, and don't ignore other existing complexities.

Expect the avalanche forecast to change as this weekend approaches.

Forecaster:Peter Flynn