National Weather Service - NWS Salt Lake City

Cottonwood Canyons Forecast
This forecast, issued at: 02-13-2012 14:53:00 is for use in snow safety activities and emergency management.

Synopsis

A system passing to the south will bring some light snow to the northern mountains tonight through Tuesday. Another system passing to the west will bring a new threat of light snow on Wednesday.

1st Period: 12 Hour Forecast Beginning 5:00 PM

Weather: Occasional light snow.

1-3"	70%
4-5"	30%

0.1-0.3"	70%
0.4-0.5"	30%

Snow Rate (in/hr)	Average	Peak
	<1	1
Snow Rate Comment:

Wind (MPH)

9000' Ridgelines

5-15

<25

11000' Ridgelines

5-15

<25

Wind Comment

Chance of Lightning

0 %

2nd Period: 12 Hour Forecast Beginning 5:00 AM

Weather: SNOW SHOWERS

2-4"	70%
5-7"	30%

0.2-0.4"	70%
0.5-0.6"	30%

Snow Rate (in/hr)	Average	Peak
	<1	1
Snow Rate Comment:

Wind (MPH)

9000' Ridgelines

5-15

WNW

<25

11000' Ridgelines

5-15

WNW

Wind Comment

Chance of Lightning

0 %

Storm Details	Storm Duration	Total Storm Snow	Total Storm Water
	Begin - 2012-02-13 15:00 MST End - 2012-02-14 23:00 MST	4-8"	0.25-0.60"

Remarks

A drier northerly flow will be over the area Thursday. A very weak system could bring a little light snow on Friday. The next chance of significant accumulating snow comes over the weekend.

Salt Lake Avalanche Advisory

Monday, February 13, 2012

Created at 6:13 am

Forecaster: Bruce Tremper

SPECIAL ANNOUNCEMENT

The Utah Avalanche Center is holding a fund raising auction of donated gear to support forecasting and education. We have Black Diamond and Surface Skis, several OR jackets, a BCA airbag pack, and some Scarpa AT boots. Go to ebay and search for "Utah Avalanche Center” or click HERE.

We also still have discount lift tickets for Alta, Snowbird, Brian Head, Sundance, and Wolf Mountain. All proceeds go towards avalanche forecasting and education.

BOTTOM LINE

Danger by aspect and elevation on slopes approaching 35° or steeper.
(click HERE for tomorrow's danger rating)

Danger Rose Tutorial

Terrain I would avoid:

Deep, new snow makes you want to get onto steeper terrain than you should, so be disciplined about watching your steepness. Avoid slopes approaching 34 degrees or steeper. Avalanche problems are complex and unpredictable right now, so keep terrain choices conservative. Pay close attention to steepness and consequences.

Usually-safe terrain:

All slopes of 30 degrees of less not locally connected to steeper terrain.

Generally, the avalanche danger is Considerable.

CURRENT CONDITIONS

Yesterday's snow storm was much stronger than anticipated for Salt Lake and southward. Around a foot of new snow fell in the Cottonwood Canyons (with an inch of water weight). 15 inches fell at Brighton and Deer Valley . But life isn't fair, as we all know; Ogden and Logan got almost no snow. It felt strange to have a real snowstorm with light, fluffy snow without wind, which we haven't seen since....well...maybe last year.

This morning, temperatures are in the low 20's with continued light winds.

RECENT ACTIVITY

In the Salt Lake and Provo area mountains, there was a widespread avalanche cycle within the new snow yesterday morning from 6 am to 8 am when the precipitation intensity really spiked. During the day, backcountry travelers could trigger a few soft, sensitive, new snow avalanches especially where there was a solid crust underneath such as on the south facing slopes. Counter intuitively, the snow stayed in place better on the northerly facing slopes despite the presence of some pockets of surface hoar and some near surface faceted snow. One ski area reported a pocket in unskied terrain that likely broke into the deep layers of faceted snow near the ground but almost all the avalanches remained within the new snow.

Check out some good obs from Current Conditions such as Twin Lakes Pass, Emma Ridges, and No-No Name Bowl.

THREAT #1

WHERE

PROBABILITY

SIZE

TREND

Over the next 24 hours.

Although you are much more likely to trigger new snow avalanches today, the largest hazard is from the possibility of deep slab avalanches because they have much larger consequences. It's almost impossible to forecast these or know where they will break but here's one trick I think is handy in these conditions:

Combine two basic principles of avalanches 1) Thin snow means weak snow, and 2) snow does not like rapid change. So as far as deep slab avalanches, I am most suspicious of shallow snowpack areas because when you add a uniform blanket of an inch of additional water weight, it's the shallow areas that not only have the weakest snow, but they also receive a disproportionally high additional amount of weight on top of the buried weak layers. For instance, the Snowbird SNOTEL site, yesterday's snow increased the total snowpack water equivalent by a measly 5.6% while Timpanogos Divide and Sundance Mid Mountain was increased by 14% and a couple stations on the Manti Skyline increased by 17% and one by 25%.. Geeky, I know, but it's a handy way to evaluate deep slab potential.

What this means in the Salt Lake area mountains is that you should be suspicious of snowpacks that are less than about 3-4 feet deep such as slopes that slid during the last storm, or traditionally thin snowpack areas such as outside the Cottonwood Canyons.

THREAT #2

WHERE

PROBABILITY

SIZE

TREND

Over the next 24 hours.

Although much of the new snow avalanche activity will have settled out by this morning, you can still trigger avalanches about a foot deep on some of the steep slopes. I'm guessing that you could find some pockets with buried layers of persistent weak layers such as surface hoar and near surface faceted snow, which you will find on the wind and sun sheltered slopes (northerly-facing and out of the wind).

Be sure to jump on test slopes and use slope cuts today. See the Encyclopedia for tutorials on these.

MOUNTAIN WEATHER

It's not quite over yet. Another pulse of moisture will mostly dive into southern Utah today and tonight but there will be enough to give us light snowfall in northern Utah. Skies should be cloudy with a chance of a few more flakes today. Tonight and Tuesday, we should get about 3 more inches of snow. Ridge top temperatures will be in the lower 20's today with light winds from the south.

Low level moisture should linger into Wednesday but the extended forecast is for clear weather for the next week or so.

GENERAL ANNOUNCEMENTS

If you trigger an avalanche in the backcountry - especially if you are adjacent to a ski area – please call the following teams to alert them to the slide and whether anyone is missing or not. Rescue teams can be exposed to significant hazard when responding to avalanches, and do not want to do so when unneeded. Thanks.

Salt Lake – Alta Central (801-742-2033)

Ogden – Snowbasin Patrol Dispatch (801-620-1017)

Provo – Sundance Patrol Dispatch (801-223-4150)

Dawn Patrol Forecast Hotline, updated by 05:30: 888-999-4019 option 8.

Twitter Updates for your mobile phone http://utahavalanchecenter.org/twitter)

Daily observations are frequently posted by 10 pm each evening.

Subscribe to the daily avalanche advisory e-mail click HERE.

UDOT canyon closures UDOT at (801) 975-4838

Wasatch Powderbird Guides does daily updates about where they'll be operating on this blog http://powderbird.blogspot.com/ .

You have the opportunity to participate in the creation of our own community avalanche advisory by submitting avalanche and snow observations. You can also call us at 801-524-5304 or 800-662-4140, or email by clicking HERE

Donate to your favorite non-profit –The Friends of the Utah Avalanche Center. The UAC depends on contributions from users like you to support our work.

We will update this forecast tomorrow morning. Thanks for calling.

This information does not apply to developed ski areas or highways where avalanche control is normally done. This advisory is from the U.S.D.A. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.

This advisory provided by the USDA Forest Service, in partnership with:

The Friends of the Utah Avalanche Center, Utah Division of State Parks and Recreation, Utah Division of Emergency Management, Salt Lake County, Salt Lake Unified Fire Authority and the friends of the La Sal Avalanche Center. See our Sponsors Page for a complete list.