Update Sunday, December 15, 2013 at 9:00am:
Preliminary storm snow totals as of 6am:
ANCHORAGE NWS..............12.6" ANCHORAGE HILLSIDE.........13.5" 9 SE ANCHORAGE.............13.0" 5 E ANCHORAGE..............11.2" EAGLE RIVER................10.5" 6 SE ANCHORAGE..............9.4"
Issued Saturday, December 14, 2013 at 9:00am (information provided below expires in 24 hours):
Anticipated danger for Sunday: Considerable
See the danger scale for further description: North American Public Avalanche Danger Scale
The Front Range and Eagle River area Chugach has received ~4″ of new snow so far at the mid elevations (2000-2500′). Expect slightly more at higher elevations (above 2500′).
In the Eagle River area and northern Front Range, winds shifted from northerly to SSE and intensified early this morning (~3am). In the southern Front Range and northern Turnagain Arm, winds have picked up considerably but have not shifted – remaining ENE. Winds are currently strong enough to provide for transport of new, loose, and relatively low density snow. This has likely contributed to wind loaded areas of snow, especially above 2500′, that may be significantly deeper than the initial 4-6″ deposit.
Expect wind loaded areas (lee slopes and cross-loaded terrain) to be the most reactive and dangerous today, with the possibility for wind slabs deeper than 6″. In the Eagle River area and northern Front Range, expect wind slab development on predominantly N to NW aspects. In the southern Front Range and northern Turnagain Arm, expect wind slab development on predominantly W to SW aspects. In all areas of the Front Range and Eagle River, be on the lookout for wind slabs on cross-loaded terrain (like gullies). In areas without wind-loading, expect modest sloughing and the possibility of soft slabs 4-6″ thick where the terrain is steep enough.
Wind slab clues may include areas of denser, more consolidated snow with a hollow feel and/or pillowy, fat appearance. Shooting cracks, whoomphing, collapsing, and recent avalanche activity are all red flags.
Considering the hard, slick melt-freeze and rain crusts at the mid to upper elevations dusted with a cm or two of very fluffy, dry, and low density snow from recent flurries and showers, prior to this storm, the new snow isn’t expected to bond well or quickly to the old surface snow; expect tender and reactive instabilities at the new/old snow interface through the weekend and possibly into early next week.
Light snow or showers, with minimal accumulation, are expected until this afternoon – when snowfall is expected to again intensify through this evening. Snowfall is expected to taper off through late night/early morning, ending Sunday. There’s a possibility for another 10″ through Sunday morning at lower to mid elevations, with chances for more at upper elevations.
While winds aren’t expected to change considerably from their current state, they will likely continue to blow moderately and with the ability to provide for continued snow transport and loading. Wind direction varies across the Front Range and Eagle River area Chugach; be on the lookout for wind loaded areas across all aspects.
Expect mountain temperatures in the mid-upper teens.
Be safe out there! The AAC will provide another update as soon as we are able to get out and re-assess conditions or if the weather forecast changes significantly.
If you’re out and about in Chugach State Park, please submit your observations. Your obs are one of our most valuable resources!