Weekend Avalanche Outlook for December 13-15

Issued Friday, December 13 at 1:00pm:

The National Weather Service is currently forecasting 7-10″ of new snow for Anchorage through Sunday morning.  This should equate to significantly more in the alpine, especially that of the southern Front Range.

Considering hard, slick melt-freeze and rain crusts in the mid-upper elevations dusted with a cm or two of very fluffy, dry, and low density snow from recent flurries and showers, new snow isn’t expected to bond well or quickly to the old surface snow.  As the new snow is likely to come in light and dry (at least initially), this will further require more time for bonding with the old snow surface.

If we get the forecast amount of new snow, expect tender and reactive instabilities at the new/old snow interface through the weekend and possibly into early next week.

Additionally, winds are currently light to moderate and northerly (stronger in the southern Front Range than Eagle River) but expected to shift to the southeast and intensify by Saturday.  This will contribute to significant loading if there’s enough new, loose snow available for transport as expected by the NWS forecast.  These fresh wind slabs are expected to be very sensitive and reactive, could be more than a foot deep by Saturday, and would have the potential to provide for unpleasant rides down slick and thinly covered (rough and rocky) slopes at the least.

As winds are forecast to shift, wind slabs have the potential to develop in many areas across various aspects.  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.

Be safe out there!  The AAC will provide another update as soon as we are able to get out and re-assess conditions after we receive some snowfall 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!