Wasatch-Cache National Forest: In partnership
with: Utah State Parks and
Recreation, Friends of the Utah Avalanche Center-Logan, and Utah State
University College of Natural Resources.
Logan area Avalanche Advisory
7:30, Friday March 28, 2008
Hello
and good morning, this is Toby Weed of the Utah Avalanche Center with your Logan Area backcountry avalanche and mountain weather advisory.
It’s Friday March 28th, at 7:30
in the morning. Today’s advisory is
brought to you in part by the Friends of the Utah Avalanche Center in Logan with help from Import Auto.
Current Conditions:
Clear and sunny weather this morning will give way to
increasing clouds and some snowfall this afternoon as the moist westerly flow
continues to affect the region. Compared
to the rest of the state, the Central Bear River Range has been doing quite well this week with
fresh new snow. Although spread out
considerably, the Tony Grove Snotel reports around 3 inches of water equivalent
gain in the last week. The station
reported 10 inches of nice new snow yesterday morning, but strong west winds roared
across exposed terrain at mid and upper elevations, once again building stiff
drifts and cornices and scouring snow from windward slopes and dumping it into lee-slope
fetch areas. We found fine bottomless powder
conditions in sheltered mid elevation terrain, but the deep stiffening drifts
on the ridges made trail-breaking challenging and it’ll be easy to get your
machine stuck in drifted snow today if you lose momentum. Its 7 degrees this morning at the Campbell
Scientific weather station on Logan Peak and there’s a southwest wind averaging
around 15 mph…
Avalanche Conditions:
The productive westerly
flow has been very generous to the farthest north mountains and the region near
the Idaho State Line, while leaving points south fairly dry. Accordingly, avalanche conditions vary greatly
across the region. While avalanches are
generally unlikely but possible in the southern part of the forecast zone,
triggered slides are probable in exposed terrain at upper elevations in the
north. Yesterday in the Central Bear
River Range, strong
west winds caused extensive drifting of the fresh snow in exposed terrain. We noticed a few natural avalanches and
triggered a few small wind slabs with cornice drops in the Steam Mill Canyon
Area, (new photos). I’m still concerned by the possibility of
isolated persistent slab activity and I continue to find a clean and energetic
shear failure in test pits on a layer consisting of graupel and small faceted grains
one to two feet below the snow surface.
This is the same layer that failed on the East Face of Naomi Peak last
weekend, (photos from 3-22-08). Especially if
the sun peaks out this morning, wet avalanches may become possible on steep
slopes again as warmth turns the fresh surface snow into slush. You might find even smallish wet avalanches
entraining lots of mass and traveling far. Cooling and cloud cover should help to keep things
solid, but this time of year any solar warming can be very intense.
Wind
slab avalanches are most likely on steep upper elevation slopes with
significant deposits of recently drifted snow, mainly in the Central Bear River Range. Large
cornices will be sensitive to your weight and may break further back than you
expect. Many avalanche slide paths in the area are
well filled-in and smooth, so even relatively small wind slab avalanches might
run far or fast.
Isolated
persistent slabs are also still possible on very steep slopes above 8000’ in
elevation and facing the northern half of the compass, and smaller wind slab
avalanches or cornice falls might initiate step-downs into buried weak layers
creating deeper and much more dangerous avalanches.
Bottom Line:
Overall
there’s a MODERATE avalanche
danger in the backcountry, and you could trigger wind slab avalanches on some
exposed slopes steeper than about 35 degrees. A CONSIDERABLE
danger exists on steep drifted slopes in the Central Bear River Range in exposed terrain at mid and upper elevations, and
triggered wind slab avalanches are probable. Some isolated avalanches may step down into
buried weak layers, and be large, dangerous and destructive. Although rather unlikely today, wet avalanches
may become possible on some slopes in the midday heat if the fresh surface snow is warmed and becomes saturated.
Mountain Weather: The moist westerly flow will return to
the region this afternoon and snowfall will develop ahead of a cold front that
will move through the area tomorrow morning.
It’ll be mostly cloudy and we’ll see increasing southwest winds and
warming temperatures today with snowfall restarting this afternoon. Saturday morning should bring several more
inches of accumulation before the cold front moves south and stalls over the central
portion of the state.
General
Announcements:
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.
