CBJ 6pm Updated Avalanche Forecast:

...WINTER STORM WARNING IN EFFECT UNTIL 6 PM AKST MONDAY...
.TONIGHT...SNOW. SNOW ACCUMULATION 4 TO 8 INCHES. LOWS AROUND 27.
SOUTHEAST WIND 10 TO 20 MPH.
.MONDAY...SNOW...MIXED WITH RAIN IN THE AFTERNOON. SNOW
ACCUMULATION 3 TO 7 INCHES. STORM TOTAL SNOW ACCUMULATION OF 7 TO
15 INCHES. HIGHS AROUND 35. EAST WIND 10 TO 20 MPH.

Updated NWS winter storm-warning calls for significantly more snow, with an additional 10-20 inches over the next 24 hours. We have received several inches since this morning.

Winds will be out of the East 10-20mph, and have been peaking near 30mph out of the South since early this morning.

Temperatures will remain near or below freezing at sea level.

We had reports yesterday of some upper elevation point releases in the Thane and Cross Bay paths. Additionally, stability near our Urban starting zone elevations was reported to be good. The dry snow has been running far and fast, especially with most gullies and alders so well covered at this point in the season, but there are lee surface deposits varying from unconsolidated snow to wind packed slab.

Avalanche Danger has been moved to CONSIDERABLE given the quantity of snow being called for in addition to moderate East winds. Expect Westerly slopes, including our Urban start zones, to be loading significantly throughout the night.

The wind-driven new snow may create a significant hazard. Additionally loading of the previously cross-loaded start zones could trigger a slide that steps down below the wind slab from this last week, making a larger slide. Natural avalanches in our Urban paths capable of causing destruction may reach developed areas, and human triggered avalanches are likely.

At middle elevations on shaded or slopes oblique to the sun above the snow line, there is a surface hoar layer that may pose a hazard beyond new snow instability.

Avoid Perseverance and Flume Trails through the forecasting period and possibly beyond.

Wind is capable of moving large quantities of snow. This can bury cars, houses, as well as loading or scouring mountain slopes. The ability of wind to transport snow is impacted by the character of the snow itself.

If snow is falling as precipitation, and is light and dry, lower wind speeds are required to drive it. Wind will always affect where the snow falls

If snow is already on the ground, we have to ask several questions:
-Is it newly fallen or packed in? Foot or ski penetration in snow can give you a good general idea of this, and is one sometimes used to determine the amount of snow that is available for wind transport.
-Is it wet and heavy, or dry and loose? Heavier snow will take higher winds to move it. Often here in southeast we can see snow sticking to rock faces and tree trunks even at high wind speeds.
-If snow is being picked up by the wind, how is it moving? Does it move across the ground, or is it being picked up into the air in plumes?

A few days ago we saw light to moderate winds picking up dry, light snow, and moving it great distances and not much snow was deposited in lee zones. The coming storm should provide a contrast to that, with similar wind speeds, but warmer and heavier snow.

A good reference for winds and snow can be found here:
http://www.meted.ucar.edu/afwa/avalanche/navmenu.php?tab=1&page=3.3.3