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Logan area Avalanche Advisory

7:30, Thursday March 20, 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 Thursday March 20th, 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 Avalanchetools.com.

Current Conditions: It rained heavily in Logan for a few hours overnight, and I expect the snow at lower elevations to be saturated and slushy through and through this morning. Hopefully today’s colder temperatures will quickly solidify things. The Bear River Mountains picked up a good shot of snow overnight, with Beaver Mountain showing 9 new inches and the Tony Grove Snotel reporting 1.2 inches of water equivalent in the past 24 hours and close to 10 inches of accumulation in the last 6 hours. Radar is showing the cold front moving off to the south, but snowfall should continue into the morning and taper to showers this afternoon. Overnight winds at the CSI weather station on Logan Peak were from the west and northwest diminishing from hourly averages in the upper twenties yesterday evening to the mid teens overnight. The station shows recent 40 mph gusts from the northwest and its 19 degrees at 9400’. It’s currently 33 degrees in Logan, dropping from 44 at midnight.

Avalanche Conditions:

We noticed a handful of fresh natural wind slab avalanches yesterday morning after moderately strong westerly winds overnight Tuesday. Included on the list was more wind slab activity on east facing slopes in the Central Wellsville Range (photo from 3-18), a good sized release reported on Chicken Hill in Bunchgrass Canyon that was a foot or two deep and ~150’ wide, and other wind slabs in exposed upper elevation terrain. After an exceptionally warm day yesterday, large natural wet point-release type avalanches occurred in Logan Canyon in the evening. Tons of snow was dumped into the Logan River near Temple Fork with several wet slides gouging all the snow out to the ground. One such wet slide hit hwy 89 in the Dugway, burying the eastbound lane, (photos from 3-19).

Triggered storm snow avalanches are likely on steep upper elevation slopes with significant deposits of new or recently drifted snow. Sensitive drifts and wind slabs from yesterday are now buried and obscured by up to a foot of somewhat heavy new snow. Continuing snowfall today will also hide fresh drifts from overnight. I noticed easy failures on small sugary grains called near surface facets yesterday, and I fear that we are plagued by now buried persistent weak layers. Many avalanche slide paths in the area are well filled-in and smooth, so even relatively small avalanches might run far or fast.

Heavy rain and warmth at lower elevations overnight only exacerbated the wet avalanche problem. And significant wet avalanches are likely on steep slopes facing all directions this morning. Hopefully cooler temperatures today will solidify things, but any sunshine through the clouds will rapidly warm things up again. You may find even smallish wet avalanches entraining lots of mass and traveling far. Avoid and stay out from under steep low elevation slopes with saturated snow.

Bottom Line:

There’s a CONSIDERABLE avalanche danger in the backcountry, and you are likely to trigger avalanches on slopes steeper than about 35 degrees. The danger of storm snow avalanches is greatest at upper elevations and some natural slab releases are possible in drifted terrain. Natural wet avalanches are also possible at lower and mid elevations, and you should avoid and stay out from under steep slopes with saturated snow.

Mountain Weather: Expect the snowfall to taper to showers this afternoon with cooler temperatures. Another cold front and more snow is expected tomorrow. Continued productive zonal pattern will continue through the week and another vigorous storm is shaping up for early next 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.