Avalanche Warning:
High winds and heavy snowfall will create a HIGH avalanche danger in the
backcountry. Triggered and natural
avalanches are probable. Avoid steep
slopes and avalanche run out zones.
Hello and good morning, this is Toby Weed of the
Current Conditions:
Yesterday’s inverted snowfall made
for tough trail breaking and slow turning conditions. The wind effected and moisture filled snow on
the surface capped lighter snow and you’d sink to your shins with every step. Expect more of the same today. With a high avalanche danger at upper
elevations, continuing strong southwesterly winds, and heavy snowfall you’ll
want to stick to sheltered low angled or low elevation terrain.
Avalanche
Conditions:
The heavy new snow is piling up on
highly suspect weak faceted or sugary snow on many slopes. Last week’s cold put a strong temperature
gradient through the shallow snowpack causing rapid rates of water vapor sublimation. As the water vapor moves upward though the snowpack,
the individual snow grains are transformed into faceted crystals lacking cohesion. In the Bear River Range, you can find large
grained facets or depth hoar near the ground from October and November on upper
elevation north facing slopes and small grained facets formed near the snow
surface (or throughout the preexisting shallow snowpack) in the early December
snow on most slopes. Yesterday, the preexisting
snow seemed crumbly, falling apart as I dug test pits like Mom’s cornbread.
Avalanches are probable today on
slopes where significant new snow stacks up on preexisting weak snow. The problem will be exacerbated by wind
drifting, and winds accompanying periods of high precipitation rates will lead
to extensive loading over large areas and well off ridge lines. Yesterday, we noted periods when the snow appeared
to fall in wind-driven sheets, rapidly accumulating in the usually sheltered
bowl. We backed off our intended line in
fear of the very rapidly building slab. Soft slab avalanches consisting of new snow in
the 1 to 2 foot deep range are likely today.
In some cases the additional load
from today’s heavy snow may be enough to cause a deeper release into old faceted
or sugary snow from October and November on steep shady slopes at upper
elevations. And, smaller wind drift or storm snow avalanches may have the
potential to step down into old weak snow near the ground creating
significantly larger and more dangerous avalanches. Deeper slab avalanches up to 3’ deep are
possible on some slopes. Pay attention to obvious signs of instability like recent
avalanches on similar slopes, collapsing or woomphing
noises, cracking, or hollow sounding snow, and be willing to reassess your
route.
Bottom Line:
There’s
a HIGH avalanche danger
in the backcountry today. Both triggered and natural avalanches are likely on many
slopes steeper than about 35 degrees and above around 8000’ in elevation. Avoid steep slopes and obvious avalanche paths
or run-out zones.
Mountain Weather:
Strong southwesterly winds and
heavy pre-frontal snowfall will persist through the morning hours. Expect a short-lived break in the action this
afternoon ahead of a strong cold front that will cross the region this
evening. Lightning, strong winds, much
colder temperatures, and heavy snowfall are all in store for the frontal
passage. Upper elevations in the
General Information:
Check out photos of avalanches in
the Logan Area on our images page.
Go to the Avalanche Encyclopedia if
you have any questions about terms I use in the advisory
I'm very interested to know what
you're seeing out there. Please e-mail observations to me at
[email protected] or leave me a message at 755-3638, especially if you see
or trigger an avalanche in the backcountry. We keep all observations
confidential.
This advisory will expire in 24
hours from the posting time.
The information in this advisory is from the U.S. Forest
Service, which is solely responsible for its content. This advisory
describes general avalanche conditions and local variations always occur.