Hello and good morning, this is Toby Weed of the
Current Conditions:
Yesterday’s incessant and dangerously strong west
winds diminished significantly overnight and switched around from the
north. But the damage is done…In a few
hours, thousands of acres of fine powder from a two-week-long freight-train of
cold storms turned into a highly varied and wind-hammered mess. You’ll be able to find all kinds of
challenging wind affected snow in the backcountry today, with wind crusts,
thick drifts, and large cornices at all elevations and vast windward slopes now
scoured to the bone. Yesterday’s storm
also produced heavy, dense snow, which stacked up on the fluffy powder causing
inverted snow, (heavier on top). This
makes for difficult traveling conditions, where you have to work hard to break
trail and you’re fairly likely to get your sled stuck if you get bogged down in
a drift. The Tony Grove Snotel reports
an increase of 1.2 inches of water equivalent in 8 or 9 inches of snowfall over
the last 24 hrs, and with 103 inches of total snow on the ground the station is
at 103% of average water for the date. It’s
currently 7 degrees at the Campbell Scientific weather station on
Avalanche
Conditions:
Extensive drifting caused numerous
natural and triggered wind slab avalanches across the mountains of
Strong
west winds yesterday drifted tons of snow into avalanche starting zones and built
up huge cornices and stiff, thick wind slabs. Heavy snowfall accompanying the wind caused
extensive loading over large areas. Today
you’ll find the most substantial wind deposits and greatest avalanche danger at
mid and upper elevations, under large growing cornices, and near ridge
lines. But significant drifting also
occurred well off ridge tops and on exposed slopes at lower elevations where
generally weaker snow exists. Also, vertical
cross-loading led to substantial wind slab formation near sub-ridges, in
gullies, and under cliff bands. The wind
built stiff heavy drifts on much lighter powder that was previously on the
surface, creating a truly unstable situation.
In most cases these instabilities should heal up fairly quickly, but in
some areas drifts formed on slopes with buried persistent weak layers, which
may result in lingering instability and future triggered avalanches.
Bottom Line:
There’s a CONSIDERABLE danger on steep wind drifted slopes in the
backcountry today, and triggered avalanches are likely on a variety slopes steeper
than about 35 degrees and possible at all elevations. Many slopes with significant recent deposits
of wind drifted snow may now be hanging in a delicate balance, only needing a
trigger to produce a dangerous avalanche, and continued drifting from moderately
strong west winds may cause some natural avalanches in exposed terrain. Today a HIGH danger
may well be lingering on steep slopes in some areas. Avalanche training and experience are
essential for safe travel in avalanche terrain, and you should avoid and stay
out from under steep drifted slopes and obvious or historic avalanche paths in
the backcountry…
Warming this weekend will likely cause a CONSIDERABLE danger of wet avalanches at
lower elevations……
Mountain Weather:
Expect continuing moderately
strong west winds, cloud cover, and some snow showers today, with 8000’ temperatures
up in the mid-twenties. It will warm up
significantly over the weekend, and we’re likely to see a bit of sunshine
tomorrow. Mid elevation temperatures are
forecast to be well above freezing on Sunday. Warming in the next couple days is likely to
cause significant problems with wet avalanches, especially at lower elevations. Storms moving off the Pacific should split
apart or stay to our north next week.
General Announcements: This
advisory will expire in 24 hours from the posting time.
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.
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.