The National Weather Service Forecasts-

TODAY...SNOW AND OCCASIONAL LIGHT FREEZING RAIN IN THE MORNING... THEN RAIN IN THE AFTERNOON. SNOW ACCUMULATION TO 1 INCH. MINOR ICE ACCUMULATIONS EXPECTED. HIGHS AROUND 35. LIGHT WINDS BECOMING SOUTHEAST 5 MPH IN THE AFTERNOON.

TONIGHT...RAIN. LOWS AROUND 34. SOUTHEAST WIND 10 MPH.

FRIDAY...RAIN. HIGHS AROUND 38. SOUTHEAST WIND 10 MPH.

Temperatures continue slightly warming today. Temperatures have come up by 32+ degrees in the last 72 hours. Temperatures yesterday climbed above freezing at the Mt Roberts Tram Summit and touched freezing at the Eaglecrest summit placing freezing rain around the region at all elevations.

We received 3+\" of snow during the cooling portion of the storm on the night of Sunday 27th. This left a layer of super cold dry snow that does not tend to bond well.

We received considerable windloading along the channel shortly thereafter with winds from 20-40. Yet a fair amount less on Douglas Island with winds only reaching the mid 20's for a period of time.

This layed down a weak layer topped with a wind slab in some areas on lee slopes. We can assume it is more of a concern in places with the more prominent winds.

During the coldest period of the event we did not receive very much snow yet as the precip began temperatures started their rising trend. This tends to lay down heavier denser snow over looser lighter snow... and in our case this is all on top of some tender shallow wind slabs spread spatially throughout the snowpack.

Also a concern it the temperature gradient it left in the snowpack That is now locked in place by the additional new snow. With as much as a 6c degree change over 10cm this starts the faceting process in those layers which tend to weaken the crystal structure more and more over time until the gradient goes away.

We have received 32mm (over 1.2\") of precip in the last 48 hours and over 40mm in 54hours. This left about 20cm or 8\" of snow at the Mt Roberts Tram Weather Station after settlement is taken into consideration. All of this during a major temperature swing creating an upside down snowpack on top of the shallow wind slab we said my be present in places.

Of interesting note is the Mt Juneau new weather station at the top of the White Avalanche Path. Sunday we layed down the 4\" of new snow... then the wind event stripped all of it away... even reducing the new snow depth more than at the beginning of the event. Then in the last 30 hours we added only 4\" of new snow. So overall during the last 5 days the Mt Juneau gauge showed no appreciable snow gain. But you can assume that snow ended up somewhere adding to the backside of the stability equasion someplace else.

This shows us the spatial variability nature of this recent new snow fall event. In some areas you may only have a few inches of new snow that is slightly upside down... in other areas you may see 1-2' of new snow with a weak layer, a windslab, and an additional upside down snowpack resting on top of that slab...

Spatial Variability remains the word of the day.

With .45\" of precip in the forecast for the next 24 hours, only about 2 degrees of warming, and light to moderate winds avalanche danger remains MODERATE today.

Natural avalanches unlikely, yet possible with this weak layer, windslab, and upside down snowpack seeing some additional loading. The ice layer is starting to be able to support a little weight and connects weaker places with stronger places but it can break and collapse under the right conditions.

Human triggered avalanches remain possible, especially if you find the mouse trap burried spatially in our upside down snowpack.

Please avoid the Flume and Perseverence Trails. Please do not walk above the gates in the Berhands neighborhood. Please do not park, walk, or job along thane road.

If you choose to head out into the backcountry today be aware of these conditions. Evaluate the snow conditions where you choose to recreate to see if you have the shallow weak layer or the deeper instability.

Avoid terrain traps, steep convex rolls, unsupported slopes and choose your routes wisely!

Have a great day!

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.