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Logan area Avalanche Advisory

7:30, Saturday March 1, 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 1st, at 7:30 in the morning.  This advisory is brought to you in part by the Friends of the Utah Avalanche Center in Logan with help from Avalanchetools.com.

Current Conditions:

Expect a blustery and rather warm morning, giving way to a quick-hitting and energetic snowstorm this afternoon. Temperatures are hovering right around freezing on the highest peaks, and only radiant cooling will have re-built the surface crust present on the sun-baked snow on most slopes.  A southwest wind picked up overnight, increasing ahead of a cold front that will arrive early this afternoon. The Campbell Scientific Logan Peak wind sensor is reading average wind speeds in the mid-thirties range this morning, with gusts as high as 55 mph, and the thermometer is reading 31 degrees at 9400’.   Sheltered upper and mid-elevation north facing slopes are the ticket for lingering pockets of soft re-crystallized snow, and most other slopes are crusty or moist and sloppy

  Avalanche Conditions:  

 Now it’s rather old news, but there were several human triggered avalanches in the Logan Area backcountry since last weekend’s storm. (South Cornice Ridge photos).   Most recently, a snowmobiler triggered a small slab on the very steep East Face of Mount Magog and a skier triggered a small wet slide north of the mouth of Logan Canyon in the heat of the day on Thursday.  Yesterday, sunny mid and upper elevation slopes continued to produce a few natural wet, point-release type avalanches involving saturated snow.  

Yesterday we noticed frost crystals or surface hoar on shady and sheltered mid and upper elevation slopes, which could be a nice weak layer for today’s wind slabs to ride on.  Stiff wind drifts probably formed in some areas overnight with the small amount of available transportable snow.  Strong winds accompanying snowfall this afternoon will quickly build fresh wind slabs on lee slopes and in fetch areas. Watch for and avoid obvious drifts on steep slopes.  Possible clues include smooth chalky looking snow, hollow sounding stiff snow, shooting cracks, or whumpfing noises.

Dropping temperatures with today’s early afternoon storm will help to alleviate the wet avalanche problem.  But this morning, solar warming and possible “green housing” will heat up the moist snow in some sheltered and/or sunny areas, and crusts that re-formed overnight will again soften on many slopes.  Wet avalanches will be possible on steep slopes in the middle of the day as the surface snow is re-warmed and becomes saturated.   Watch for roller balling and other recent wet avalanche activity on similar slopes, and leave or reevaluate your route if the snow on the slope you’re on gets sloppy. 

 

   Bottom Line:  There’s a LOW danger on most steep slopes in the backcountry, and avalanches are generally unlikely, especially in sheltered and shady terrain.  Pockets with a MODERATE danger exist on slopes exposed to wind drifting or sun-warmed slopes with saturated surface snow, and triggered avalanches are possible on some slopes steeper than about 35 degrees in the backcountry.  Periods of heavy snowfall and strong wind will cause a MODERATE danger of fresh wind slab avalanches on slopes with deposits of drifted snow.  Use good snow assessment and safe travel techniques to minimize your risks.

  Mountain Weather: The National Weather Service issued a Snow and Blowing Snow Advisory  for the mountains of Northern Utah from noon today till 11:00 tonight.  The approaching cold front, expected early this afternoon, will drop temperatures significantly and herald a period of fairly heavy snowfall.  Meanwhile, the wind will stay strong as it shifts around from the west and then northwest.  We could see some lingering snow showers and cloudiness tomorrow, but winds will gradually diminish and it’ll clear up by afternoon.  Temperatures will warm on Monday in advance of the next round of storminess scheduled for late Tuesday into Wednesday.  

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.