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Logan area Avalanche Advisory


7:30, Saturday March 29, 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 Saturday March 29th, 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:

After dropping only a couple inches on the Bear River Range, the snowfall focusing cold front is on its way south to set up camp across the central part of the state.  Expect snow showers and cloud cover to gradually diminish today, while west winds will continue to rake high ridge-lines.  You’ll be able to find fairly good spring powder conditions today, especially in sheltered terrain at mid and upper elevations in the northern part of the forecast zone… The Tony Grove Snotel reports around 3 inches of water equivalent gain at upper elevations in the last 8 or 9 days, which means lots of new snow.  It was windy again last night, with the CSI Logan Peak wind sensor reporting hourly average wind speeds in the 30 mph range for several hours overnight with gusts of around 50 mph from the southwest.  Its 18 degrees at 9400’ and 34 in Smithfield….

  Avalanche Conditions: 

The productive westerly flow in the past week 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.  Thursday’s storm dumped around a foot of fresh snow at upper elevations in the Central Bear River Range and persistent west winds caused extensive drifting of the fresh snow in exposed terrain.  We noticed a number of natural avalanches involving new snow and triggered a few small wind slabs with cornice drops in the Steam Mill Canyon Area, (3-27 photos) and (new photos).  Yesterday, settlement and water vapor sublimation within the new snow caused the snow to be remarkably more stable, but we could still trigger long running sluffs and cornices were still sensitive.   As is typical in the springtime, wet avalanches may become possible on steep slopes as warmth turns the fresh surface snow into slush.   You might find even smallish wet avalanches entraining lots of mass and traveling far.   Relatively cool temperatures and lingering cloud cover should help to keep the snow dry, but this time of year any solar warming can be very intense and when the fresh snow becomes saturated is prone to avalanching.

With strong southwest winds overnight and plenty of fresh driftable snow about, freshly formed wind slab avalanches are my primary concern. 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.  Fresh drifts should be fairly obvious, and you should avoid them on steep slopes.  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.  The huge cornices in the region now present an obvious danger, especially when it’s windy or warm.  Large cornices will be sensitive to your weight today and may break further back than you expect.   

Bottom Line: 

  Overall there’s a MODERATE avalanche danger in the backcountry, and you could trigger wind slab avalanches on some slopes steeper than about 35 degrees.   The greatest danger is on steep drifted or corniced slopes in the Central Bear River Range in exposed terrain at upper elevations, and dangerous triggered wind slab avalanches are possible.  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 cold front is on its way south to set up shop over Provo and the Western Uinta Mountains.  We’ll see lingering snow showers this morning and diminishing cloud cover this afternoon, with continued westerly winds likely.   We should see a few more inches of accumulation tomorrow, but most of the storminess looks like it’ll stay to the south.  Another storm will affect the region mid-week.

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.