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Logan area Avalanche Advisory

7:30, Wednesday February 13, 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 Wednesday February 13th, 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 EK USA.

Current Conditions:  The National Weather Service has issued a Winter Storm Warning for the mountains of Northern Utah from 8:00 this morning until 10:00 tonight. You can expect very heavy snowfall and possible lightning with an intense frontal passage later this morning. We could pick up 6 to 10 inches in short order today.   Northwest winds will be quite strong during the event, switching around from the north with frontal passage.  Currently the wind is from the southwest on Logan Peak, with the CSI weather station recording 30-40 mph hourly averages and gusts up to 54 mph, and its 20 degrees.  Most folks report somewhat poor snow conditions, with a widespread rime crust plaguing all elevations of the Central Bear River Range, and sun, warmth, and wind affected snow elsewhere in all but the highest elevation sheltered terrain.

  Avalanche Conditions:  An observer reports a recent large hard slab avalanche on the Richmond Bench, but details as to when and why this happened are lacking.  I’d love to hear more, and any additional information you might have would be greatly appreciated.  Strong winds blasted the region last week leading to a fairly widespread natural avalanche cycle, (photos).   Other, more recent local activity includes continued loose wet avalanches at lower elevations and large cornice falls up high.   Large cornices are still somewhat sensitive and are likely to become more so as they build anew today.

Strong northwest winds accompanying heavy snowfall will rapidly build shallow wind slabs in the midst of today’s intense storm.  The wind slabs may not bond well with the old snow surface, which is plagued by a rime crust and in some places, well developed frost crystals or surface hoar.   Of course, the danger this afternoon will be highest in areas that receive the most snow and wind, with slabs building up on steep slopes and in avalanche starting zones.  Although most wind slabs will be fairly small today, they could well be long running and quite fast moving on well smoothed out and slick run-outs or avalanche paths…

Last week slabs formed on a few slopes plagued by buried persistent weak layers and although now fairly unlikely, there’s still a possibility that you might trigger a dangerous hard slab avalanche in places.  I’m still leery of lower elevation slopes with generally shallow and hence, weaker snow.  The recent avalanche on the Richmond Bench may fit into this category. 

   Bottom Line:  During today’s storm, the danger will rise to MODERATE on steep drifted slopes in the backcountry, and you might trigger wind slab avalanches.  More than expected snowfall and/or sustained strong winds may cause the danger to rise to CONSIDERABLE in a few upper elevation pockets by late afternoon.  Avoid obvious drifts on steep slopes and use good snow assessment and safe travel techniques to minimize your risk.

   Mountain Weather:   Radar returns depict a band of precipitation moving into Cache Valley and the surrounding mountains as I write.  Expect a period of intense snowfall, possible lightning and strong northwest winds.  6 to 10 inches will accumulate in the mountains during the day today.  The storm will depart the region, heading south this evening, and a high pressure system will build in for the weekend.

General Announcements:  This advisory will expire in 24 hours from the posting time.

Check out the images page for photos of some of last week’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.

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.