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Logan
Hello and good morning, this is Toby Weed of the
Current Conditions:
The
Avalanche
Conditions:
No recent avalanches reported or
observed in the Logan Area, and we’ve noted lots of settlement in the new snow since
the productive Christmas Eve storm, which generally indicates increasing
stability. Faceted snow from November
and early December appears to be smashed down into anchoring bushes and rocks
on many slopes in the region. The young
snowpack looks pretty solid on south facing and lower elevation slopes where
there was little preexisting snowcover prior to the December 19th and
20th storm.
We experienced a fair amount of
wind drifting yesterday at upper elevations. Cornices hanging over north and
northeast facing slopes grew significantly during the day as loads of wind
blown snow was deposited on the slopes below.
Out of respect for their size and overhang, I did not dare approach to test
the sensitivity. Strengthening winds and
continuing snowfall will further build up cornices while forming drifts and wind
slabs in lee slope avalanche starting zones today. In some areas wind slabs may
build on weak sugary surface snow called near surface facets. Watch for
vertical cross loading around terrain features like sub-ridges, rock
outcroppings, and gullies.
I’m still concerned by the
possibility of triggered persistent slab avalanches in some areas, which will
be destructive and potentially deadly.
Suspect weak layers are made up of snow that was on or below the snow
surface in early December. The old
underlying snow is faceted or sugary and weak, and instabilities caused by
overloading slab layers are notoriously slow to heal. In most cases your weight probably won’t be
enough to trigger one of these monsters, but you might be able to trigger one from
a thin spot on the slab. The weight of a few snowmobiles at one time on a slope
or an overrunning smaller avalanche might also do the trick. Watch out for
steep rocky areas and slopes with shallow snowcover. 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:
The avalanche danger will increase this
weekend. Today there’s a MODERATE avalanche
danger, and you could trigger dangerous avalanches on some steep slopes in the
backcountry. Triggered avalanches are most
possible on upper elevation wind drifted slopes steeper than about 35 degrees. With
additional significant snowfall and intensifying southwest winds in the
forecast, the danger is likely to rise to CONSIDERABLE on
steep wind drifted slopes by this evening.
Mountain Weather:
A strong and somewhat moist
southwesterly flow will control the weather pattern through the weekend, and a
high pressure system will build early next week. Southwest winds and snowfall are expected to
increase throughout the afternoon and evening and it’ll be downright blustery
on Sunday. Expect several inches of
accumulation through Sunday morning, with a foot or a foot-and-a-half quite
possible. A high pressure system will
build in on Monday bringing significantly warmer temperatures to the mountains
and haze to
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.
