Wasatch Cache National Forest

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Avalanche advisory

WEDNESday, FEBRUARY 21, 2002 7:30 AM

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Good afternoon, this is Bruce Tremper with the Forest Service Utah Avalanche Center with your backcountry avalanche and mountain weather advisory. Today is Wednesday, February 20, 2002, and it’s 4:00 p.m.

Current Conditions:

It’s been snowing hard all day through most of the Wasatch Range and storm totals are around a foot in the Salt Lake and Provo-area mountains and about 8 inches in the Ogden-area mountains. The snow is dense and heavy—around 14 percent water--with the rain-snow line around 6,000 feet. This snow is falling on top of about 6 inches of very light density snow that fell on Sunday, making the snow seem what we call “inverted, upside down, or slabby.” Ridgetop winds have been blowing around 25 mph all day long and ridgetop temperatures are around 20 degrees.

Avalanche Conditions:

Many of the ski resorts have reported soft slab avalanches today ranging from localized to widespread with both explosives and ski cuts. Several backcountry observers have reported stubborn, dense slabs about a foot deep on slopes with recent wind drifts. On non-wind loaded, steep slopes, the new snow is sluffing easily on hard, old bed surfaces. On the sun exposed slopes the new snow is sliding on yesterday’s sun crust and on the more shady slopes, the snow is sliding on the old, hard snow surface with the Sunday’s light density snow as the weak layer. The winds seem to have drifted the new snow only in the upper elevation wind exposed areas and they haven’t gotten down too far into the mountain valleys.

Although most of this avalanche activity will remain just within the new snow, there’s always the possibility that they may step down into the old, weak sugary snow. The most recent example of this persistent deep slab instability occurred on Monday, where a snowmobiler triggered an avalanche and was buried with one hand out of the snow in the Wolf Creek area of the Uinta Mountains (avalanche photograph). He was the only member of the party wearing an avalanche rescue beacon, but fortunately his friends saw his hand and dug him out uninjured.

I imagine that many of these new snow slabs will settle out by Thursday morning and become less sensitive, I’m sure you can still find a number of places where you can still trigger avalanches. Also, if we get some sun on Thursday, we can expect lots of wet or damp sluffs on the sun exposed slopes. In the mean time….

Bottom Line:

The danger of human triggered avalanches will vary dramatically with location, elevation and wind exposure. The danger of human triggered avalanches is CONSIDERABLE on all slopes about 35 degrees and steeper, above about 8,000’ with recent deposits of wind drifted snow. You’ll find these mostly in upper elevation wind exposed terrain. On non-wind loaded slopes, above 8,000’ there is a MODERATE danger.

(Provo Area Mountains)

The danger of human triggered avalanches may be CONSIDERABLE in the upper elevation areas of the Provo Mountains especially on steep wind loaded slopes, and MODERATE in lower elevations.

(Ogden Area Mountains)

The danger of human triggered avalanches may be CONSIDERABLE in the Ben Lomond Peak Area especially on steep wind loaded slopes and MODERATE in lower elevations.

Mountain Weather:

The moist westerly flow will slowly dry out late this afternoon with some lingering snow showers in the Cottonwood Canyons this evening. Ridgetop winds will continue to blow around 25 mph from the west and northwest with ridgetop temperatures around 20 degrees. Partly cloudy skies tonight with some higher clouds on Thursday. On Thursday, ridgetop winds should diminish to around 5 mph from the northwest with ridgetop temperatures continuing around 20. Friday, we should see a dramatic warming with sun and ridgetop temperatures reaching into the upper 30’s and 8,000’ temperatures reaching into the mid 40’s. Then, we have one more shot of snow before the Olympics are over with some moisture coming in on a northwest flow on Saturday night into Sunday.

General Information:

To report backcountry snow and avalanche conditions, especially if you observe or trigger an avalanche, you can leave a message at (801) 524-5304 or 1-800-662-4140. Or you can e-mail an observation to uacobs@avalanche .org, or you can fax an observation to 801-524-6301.

During the Olympics, we will issue both morning and afternoon advisories. We’ll use the 364 -1591 line for more detailed or additional avalanche information.

Wasatch Powderbird Guides will not be flying during the Olympics.

We have a new icon-based, short advisory posted each day at www.avalanche.org. We would appreciate any feedback on this new product.

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.

Tom Kimbrough will update this advisory by 7:30 on Thursday morning.

Thanks for calling!

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For more detailed weather information go to our Mountain Weather Advisory

National Weather Service - Salt Lake City - Snow.

For an explanation of avalanche danger ratings:

http://www.avalanche.org/usdanger.htm