Wasatch Cache National Forest
In partnership with: Utah Division of State Parks and Recreation, The Friends of the Utah Avalanche Center, Utah Department of Emergency Services and Homeland Security and Salt Lake County.

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AVALANCHE ADVISORY

Wednesday, December 27, 2006 7:30 am
Good morning, this is Bruce Tremper with the Forest Service Utah Avalanche Center with your backcountry avalanche and mountain weather advisory. Today is Wednesday, December 27, 2006 and it’s 7:30 in the morning.

Current Conditions:

An inch of snow has fallen at Alta with 3 inches at Brighton on a strong southwest flow. The Ogden area mountains have accumulated 4 inches of dense snow with a half inch of water weight. Temperatures are warm again this morning, around freezing at 8,000’ and the ridge top winds are blowing 20 gusting to 40 from the southwest and on the highest peaks they are blowing 30, gusting to 55 with temperatures in the mid to lower 20’s. Even though temperatures started out warm, the new snow is 7-8 percent water weight.

The pre-existing snow surfaces were a wide variety with sun crusts on south facing slopes, hard wind slabs above tree line and soft, moist, recrystallized snow on the wind and sun sheltered north facing slopes.

Snowpack and Avalanche Conditions:

I did not hear about any avalanches yesterday except for in the Logan area mountains where our forecaster intentionally dropped a cornice and triggered a wind slab 2 feet deep and 150 feet wide.

Yesterday’s temperatures were very warm with daytime highs in the mid 40’s. This really helped to settle the very weak faceted snow that was on the surface and most of the old snow was damp below about 9,000’. Above about 9,000’ the old snow surface was mostly hard, old, wind slabs. So what I’m trying to say is that the new snow falling today will likely bond fairly well to the old snow surfaces with the exception of fresh wind drifts. Today, your main concern will be the new snow as fresh wind slabs accumulate on downwind terrain. These will occur mostly on south through east facing slopes above about 9,000’ and near exposed ridge tops but this morning the winds are drifting snow as low as 8,000’. I’m expecting about 3-6 inches of snow to accumulate this morning before we get a break this afternoon and the winds will likely drift the new snow into 6 inch to a foot deep wind slabs, especially along the exposed ridges.

The second problem you may find today is in the shallow snowpack—say less than about 2 ½ feet deep—where the entire snowpack is a mess of rotten, faceted snow. If we get more than about an inch of water weight, it may overload this weak snow and produce some deeper, more dangerous avalanches. I don’t think we will get more than an inch of water weight out of this storm, but if I am wrong, you can expect deeper, more dangerous avalanches in places where the snowpack is only a couple feet deep. The Ogden area mountains will likely get more snow today than the Salt Lake and Provo area mountains, so the danger may be higher there. (Click here for December Weather Chart)

Bottom Line for the Salt Lake, Park City, Provo area mountains:

If we get less than about 6 inches of new snow today, the danger will be MODERATE on any slope steeper than about 35 degrees with recent deposits of wind drifted snow. The danger will be LOW elsewhere. If we get more than 6 inches of new snow, you can bump those danger ratings up one notch.

Ogden area mountains:

I’m expecting more snow today north of Salt Lake City and this will cause the avalanche danger to rise to CONSIDERABLE in the Ogden and Logan area mountains on steep slopes with recent wind drifts and in shallow snowpack areas.

Mountain Weather:

This is a problematic storm and it doesn’t look like the big dump we were hoping for. Today, we will have fairly dense snow on a southwest flow and it should accumulate about 3-6 inches this morning. Then, most of the energy from the storm is diving south of us and we will have a bit of a break this afternoon and then the trough will arrive this evening and the ridge top winds will drop to near zero and suddenly turn northerly. We may get another 3-6 inches of lighter density snow overnight. Then, on Thursday, the ridge top winds will be from the northeast and pick up to 35 mph. This may quickly ruin what little snow we can squeeze out of this storm. Today, temperatures will fall from near freezing this morning to the teens tonight and bottom out around 15 degrees on Thursday morning. It looks like snow will end around Thursday by noon.

The extended forecast calls for clear weather through the weekend with another chance for snow on about Tuesday and again on Friday.

Announcements:

The Wasatch Powderbird Guides will not fly today because of weather.

The Rescue Training Center at the Canyons Resort is up and running now at the top of the gondola.

Listen to the advisory. Try our new streaming audio or podcasts

Our new, state wide tollfree hotline is 1-888-999-4019.
(For early morning detailed avalanche activity report hit option 8)

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We appreciate any snowpack and avalanche observations you have, so please leave us a message at (801) 524-5304 or 1-800-662-4140, or email us at [email protected]. (Fax 801-524-6301)

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.

I will update this advisory by 7:30 on Thursday morning, and thanks for calling.