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“keeping you on top”
December 27, 2006 7:30 am
Good morning, this is Bruce Tremper with the
An inch of snow has
fallen at Alta with 3 inches at
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
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 ˝ 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
Bottom Line for the
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.
I’m expecting more
snow today north of
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.
The Wasatch Powderbird Guides will not fly today because of weather.
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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.