The National Weather Service Forecasts-

TODAY...SNOW MIXING WITH RAIN IN THE MORNING. RAIN IN THE
AFTERNOON. SNOW LEVEL RISING TO 400 FEET. HIGHS AROUND 35.
SOUTHEAST WIND 5 TO 15 MPH.

TONIGHT...RAIN AND SNOW. SNOW ACCUMULATION TO 1 INCH. SNOW LEVEL 400 FEET. LOWS AROUND 34. SOUTHWEST WIND 5 TO 15 MPH.

MONDAY...RAIN AND SNOW. WET SNOW ACCUMULATION AROUND AN INCH. SNOW LEVEL 400 FEET. HIGHS AROUND 37. SOUTHEAST WIND 5 TO 15 MPH.

We received roughly 12cm of new snow since 6pm last night depending on your locations. Temperatures have risen by 2C+ degrees during that time. Winds have been 20-40 mph on both Douglas and the Mainland.

Remember this new snow is comint to rest on a snowpack that is quite faceted in places.

Temperatures are forecast to rise another few degrees during the morning hours today. Winds are predicted to stay in the 20+ range at upper elevations throughout the day. With as much as another .9\" of moisture predicted at upper elevations in the next 24 hours and as much as .4\" throughout the morning, Avalanche danger is CONSIDERABLE at this time and slowly rising.

Natural avalanches possible. Human triggered avalanches probable. Especially in windloaded pockets as this storm and windloading continues.

Be increasingly cautious in or under steeper terrain and in avalanche zones.

The snow volumes are not huge. The warming has been less than expected. But winds will play a big part in the equasion today.

This new upside down snowpack is also coming to rest on dry light snow which does not have great ability to support it.

Look to see small to moderate sized avalanches around the region today. Be aware of the fact that it does not take a very large avalanche to bury or injure a skier.

Limit your exposure to the terrain, especially terrain traps where small avalanches will pile up much deeper and the escape routes are limited or dont exist.

We still have a fair amount of anchors in the Berhands and White Paths. Should avalanches occur I do not expect them to be large enough to pose a significant threat. Yet I would avoid spending time above the neighborhoods on the old road beds where people often walk their dogs.

The Chop gulley path above the Flume trail is another area of concern as it is quite long and funnel shaped gathering quite a bit of mass into a limited runout zone.

Thane road may see some activity at snowslide creek depending on how much wind, warning, and precip we receive. I do not expect there to be enough mass at this point to hit the road and yet I would not recommend stopping or walking along the roadway or above it through that zone.

Be safe out there and enjoy another powder day Juneau. Looks like we may be spared of the biggest part of the warming that was predicted.

Remember if your traveling in avalanche terrain you should ALWAYS have a well trained partner and both of you should have an avalanche transceiver, probes, and shovels!

Practice with your equipment! Know your safe routes, your escape routes, and what your going to do in the event of an accident.

Faceted snow:

Faceted snow causes the lion's share of avalanche fatalities in North America with surface hoar as a close second. And no wonder. It seems like made-to-order plot device out of a very scary movie. It grows like a parasite within the snow--often out of sight--until it's too late. It becomes inexorably more and more dangerous during the seemingly most benign conditions--clear skies, cold temperatures--and it lays in waiting, sometimes for weeks, until it's brought suddenly to life by a fresh load of snow or rapid warming. Then, when its victim bumbles into the wrong place, it pulls the rug out from under them, rockets them down the mountain at a terrifying speed, ripping them limb from limb as they bounce off trees and rocks and finally entombs them under tons of icy, hard snow.

How faceted snow is formed:

Faceted snow forms from large temperature gradients within the snowpack. Big word alert!--temperature gradient. A temperature gradient is simply how fast temperature changes over a certain distance within the snowpack. Why? Because it's a fact that warm air holds more water vapor than cold air. This means that temperature gradients also create what we call \"vapor pressure gradients\"--more water vapor in one place than another. And what happens when you concentrate something--especially a gas? It wants to diffuse--move from areas of high concentration to areas of low concentration. When water vapor RAPIDLY diffuses it changes rounded crystals into faceted ones--changes strong snow into weak snow. In other words, temperature gradients create potential weak layers that can kill us. That's why we pay so much attention to them.
Here's another way to explain it. Imagine an old woman with strong perfume walking into a cocktail party. As the perfume diffuses through the room, the people standing nearby would smell the perfume the strongest and the people standing against the opposite wall would be able to smell it the least. Next, pretend that wherever the perfume RAPIDLY diffuses through the room, it changes people to frogs. Soon there would be nothing but frogs around the old woman where the perfume is diffusing rapidly and the rest of the room would stay the same since the perfume around them is diffusing more slowly. Finally, imagine 20 old women with strong perfume spread equally through the crowd. Now, there's no more strong diffusion because the perfume has the same concentration everywhere in the room. Since there's no more diffusion, all the frogs magically turn back into people again.

A stupid example, I admit, but maybe you get the idea. The point is that it's a completely reversible process. Strong gradient turns rounds to facets. Weak gradient turns facets back to rounds. The process in reverse, however, occurs much slowly because it takes so much energy to create a faceted crystal that when we take the energy source away (the strong temperature gradient) it take a lot of time for the crystal to return to its equilibrium state (rounds). In other words, it might take a week or two of a strong temperature gradient to form large faceted crystals but after you take the temperature gradient away, it can take weeks or months for them to stabilize, depending on the ambient temperature of the snow and how much compressive load is on top. In cold climates without much load on top of the faceted snow, it may never gain much strength--even without a temperature gradient. The take-home point here is that: small temperature gradients make the snow stronger; large temperature gradients make the snow weaker. Got that?

So, large temperature gradient?how large is large? For snow of an average snowpack temperature, say around -5 degrees C, the critical temperature gradient is about one degree centigrade per 10 centimeters (1 deg C. / 10 cm.). In cold snow, say colder than -10 deg. C, you need a higher temperature gradient to cause faceting and in warm snow you need slightly less.

For example, let's stick two thermometers into the snowpit wall, one 10 centimeters above the other (about 4 inches). Say we measure a difference of only 1/2 deg. C. in 10 cm., it means that equilibrium snow is growing (snow is getting stronger). If we measure a temperature difference of 2 deg. C. in 10 cm., it means that faceted snow is growing (snow is getting weaker). All you have to do is to find a faceted layer in the snowpack, measure the gradient and you know whether the layer is gaining strength of loosing strength. Cool, huh? This is actually a powerful forecasting tool.

Density, Snow:

The stability of the snowpack is influenced by many factors, but two of the most important is the strength of the weak layer and the load it has to support. The weight of the snow resting on a weak layer is a factor of the depth of the slab and its density. Snow density can be thought of in technical terms and numbers (% density, kg/m3) but most people have an intuitive feel for snow density, even if you don?t realize it. Snow that is light and billows up in your face while you?re riding is very low density, while high density snow feels thick, heavy, or even wet.

New snowfall has an initial density, usually in the 3-20% range. Once it accumulates on the old snow surface, metamorphism takes over causing the snow to gradually become more dense. The rate at which new snow becomes densifies depends on temperature, among other things. We all know warm weather can quickly ruin light powder snow, while cold temperatures can slow down the densification process and preserve powder for quite some time.

Another important factor to consider regarding snow density is trends during a storm. If the temperature is warm when the snow starts falling, and then becomes colder, we have what we call a ?right side up? storm. The snow is light and fluffy on top and becomes more dense with depth. A far less desirable scenario is called an ?upside down? storm and is the result of increasing temperatures during snowfall. The result is heavy, denser snow on top of lighter snow -- you can see what we?re getting at can?t you? An upside down storm can result in a slab (dense snow) over a weak layer (less dense snow), providing the necessary ingredients for slab avalanches.