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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.  Itís Friday March 28th, at 7:30 in the morning.Todayís 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 itíll 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 thereís a southwest wind averaging around 15 mphÖ

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). ††Iím 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 8000í 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 thereís 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.Itíll be mostly cloudy and weíll 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 seasonís 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.