7:30, Sunday April 13, 2008
Hello
and good morning, this is Toby Weed of the
We’ve issued a Special Avalanche
Advisory due to the rapid warm-up and increasing natural wet avalanche
activity in the mountains. We urge backcountry
travelers to avoid and stay out from under steep slopes with saturated snow and
large ridge-top cornices, especially in the heat of the day…..
Current Conditions:
Overnight temperatures stayed above or near freezing at most
mountain stations and the refreeze of yesterday’s saturated snow is marginal. Surface crusts that formed overnight will
quickly loose strength after exposure to the powerful high angle spring sun and
warmth today. We found nice settled
powder conditions on upper elevation north facing slopes and reasonably solid and
supportable snow on mid-elevation south facing slopes yesterday, but I don’t
expect it will stay that way as today’s heat will surely accelerate the melt-down.
It is currently 34 degrees at The Tony
Grove Snotel, and with 95 inches of total snow, the station sits at 109% of
average water content for the date.
Avalanche Conditions:
We’ve received numerous reports
of natural and triggered wet avalanches involving fresh snow from the past week. The problem is more pronounced in the
Solar
warming from the intense, high angled spring sun and the warmest mountain air
temperatures of the year will cause last week’s new snow to quickly become
saturated and prone to wet avalanching. Upper
elevation snow that’s stayed dry up until now is starting to melt, and we’ve
seen an increase in natural wet avalanche activity as a result. This weekend you should avoid and stay out
from under steep slopes with saturated snow, especially in the heat of
Large
cornices could be sensitive to your weight today and may break further back
than you expect, and they’ll start to sag and deform with the heating. Some are likely to spontaneously collapse
with the heat, a few catastrophically. It is always a good idea in the spring to stay
off of and out from under these monsters.
Bottom Line:
There’s a MODERATE danger in the backcountry, and you could trigger
wet or persistent slab avalanches on steep slopes in exposed upper elevation terrain. Very warm mountain temperatures will cause
the danger of wet avalanches to rise to CONSIDERABLE
on steep slopes with saturated snow at mid and upper elevations. Triggered wet avalanches are probable and
naturals are possible on slopes with recent new snow. Avoid and stay out from under steep slopes
with saturated snow and large ridge-top cornices, especially in the heat of the
day…..
Mountain Weather: A high pressure ridge will be over the
region today and we can expect even warmer temperatures in the mountains. Highs at 8800 feet will approach 50 degrees
today. Monday looks like the warmest day in the series, but with a breeze and
high clouds moving in ahead of a potentially convective cold
front scheduled for Tuesday.
General Announcements:
Even though you can ride
anywhere these days, you should be sure to keep motor vehicles in terrain
that’s open. Riding on public lands designated as “closed to motor vehicles” or
as a National Forest Wilderness only jeopardizes the future of our sport, and
fines for motor vehicle trespass have been recently increased. (MV wilderness trespass
photos)
Check
out the images page for photos of some of this season’s avalanches.
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.