Hello, this is Toby Weed of the
Current Conditions:
The
prolonged heat-wave burned off many lower elevation slopes, but there’s still a
lot of snow up high. The Tony Grove
Snotel still reports 5 feet of total snow on the ground and 70% of average water
content for the date. Thankfully, mountain temperatures are forecast to fall
drastically overnight with the arrival of colder air courtesy of a splitting
Northern Pacific spring storm. Temperatures should drop into the upper
teens for several hours at 9000’. We are also likely to pick up 6 to 8 inches of
snow in favored upper elevation areas, and there’s hope for fairly nice shallow
powder conditions on Wednesday. You may have to cross some melted-out barren
ground on your way up through the lower elevations, so be mindful, stay on
route, and try to limit potential resource damage.
Avalanche
Conditions:
Wet
loose and slab avalanches were common across the region over the weekend, but
cooler temperatures today probably settled things down a little. From lower
Even
though it’ll be much cooler on Wednesday, wet avalanches will still be possible
on lots of steep slopes in the region.
The refreeze will not have been long-lived enough to solidify suspect
deeply buried persistent weak layers that have been moistened and made weaker by
melt water that made its way down through the snowpack during the heat-wave. You
might trigger wet slab or partially refrozen slab avalanches (“corn slabs”) on
some steep slopes, especially on slopes which absorbed lots of solar heat during
the recent warm spell. Watch out
for slopes with moist and un-cohesive basal snow or depth hoar near the
ground. Sunny slopes at higher
elevations with shallow overall snow cover are the most suspect. In spite of the cooling, a few
spontaneous glide
avalanches, where the entire snowpack slowly slides along the ground until
it releases, are also possible in some steep sunny areas with smooth ground or
rock slab underlying surfaces.
These often occur during the initial drop in temperatures after a
prolonged warn spell and are possible at any time of day or night. Obviously, you should stay out from
under suspect steep slopes and obvious glide cracks, which have opened up on
some slopes in the past couple days.
The forecast 15 to 20 mph
northwesterly ridge top winds will be strong enough to build drifts and
sensitive soft slabs on lee slopes near ridge lines and around exposed terrain
features. As usual you should avoid
fresh drifts on steep slopes. These
are generally made up of stiffer snow, often sport a chalky appearance, and can
sound kind of hollow as you pass over them. I recommend digging down to the
interface of the old and new snow and testing the bond between the two
layers. Sometimes a drastic
temperature difference or particular crust formation can lead to a weak bond
leading to increased wind slab sensitivity and/or storm snow soft slab
activity. More snow or stronger
wind than forecast will create larger potential avalanches.
Bottom Line:
There’s a MODERATE danger in the backcountry, and
triggered wet and wind slab avalanches are possible on steep slopes in the
region. You’ll find freshly formed wind slabs consisting of tonight’s new snow
in exposed terrain at upper elevations, most likely on slopes facing north
through southeast. A lingering
danger of wet avalanches can be found on any slope with substantial snow cover
and moist un-consolidated basal layers. Wet slab and isolated spontaneous
natural glide avalanches are most likely on upper elevation slopes facing
northeast through south, which absorbed lots of solar heat in the last
week. Use good snow assessment and
safe travel techniques to minimize risks.
Mountain Weather:
The storm is here and rain is
falling in
General Information:
Check out photos of last week's
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 also recommend the recently-released Media Page, which
shows the forecast danger for our coverage areas across the state.
Please e-mail me at
[email protected] or leave me a message at 755-3638 if you see or trigger
avalanches in the backcountry. The information you provide may save
lives...
This advisory will expire on Wednesday
night. I will update it again on Thursday evening.
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.