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Daily Winter Weather Report

Date: Thursday - December 15, 2011

Station Max Temp Min Temp Pres Temp New Snow Depth Sky Present Conditions

East Entrance 26 7 7 .5 18 BC Calm
Grant Village 22 14 17 1 22 OC Calm
Lake 22 12 13 2 16 OC Lt Snow

Madison 18 -4 14 1 12 OC Calm

Old Faithful 23 18 18 T 13 SC Calm

Snake River

Soda Butte

Thumb Divide

Tower 28 14 18 .7 10 OC Lt Snow
West Entrance 24 14 18 T 14 OC Calm / Lt Snow
T=Trace / BC=Broken Clouds / OC=Overcast / SC=Scattered Clouds
All Temperatures are in °F ~ All Snow Depths are in Inches

* * * Road Conditions * * *
Road Section Status Conditions Public Access / Info
Gardiner to Mammoth YR Good STR
Mammoth to Tower YR Good STR
Tower to NE Entrance YR Good STR
Beartooth Highway CLOSED * CLOSED * CLOSED *
Firehole Canyon Drive CLOSED CLOSED CLOSED
Grant to South Entrance Open   Rubber tracked oversnow concession vehicles
Junction to Chief Joseph Hwy CLOSED * CLOSED * CLOSED *
Lake to East Entrance CLOSED CLOSED CLOSED
Madison to Old Faithful Open   Rubber tracked oversnow concession vehicles
Madison to West Yellowstone Open   Rubber tracked oversnow concession vehicles
Mammoth to Norris Open   Rubber tracked oversnow concession vehicles
Norris to Canyon Open   Rubber tracked oversnow concession vehicles
Norris to Madison Open   Rubber tracked oversnow concession vehicles
Old Faithful to Grant Open   Rubber tracked oversnow concession vehicles
Tower to Canyon CLOSED * CLOSED * CLOSED *

YR=Year Round / NR=No Restrictions / STA=Snow Tires Advised / STR=Snow Tires Required


# Poor road conditions - bare spots and melting snow - Restricted to Snowcoaches Only.

The park service plowing schedule for roads for the spring season.

******** FOR CURRENT ROAD INFORMATION PLEASE CALL 307-344-2117 ********


Yellowstone Forecast on December 15, 2011
by the National Weather Service Riverton, WY

Today: A 40 percent chance of snow with a high near 30°F and low around 14°F. South southwest wind around 9 mph. New snow accumulation of less than one inch possible.

Friday: Mostly sunny, with a high near 28°F and low around 17°F. South southeast wind between 3 and 6 mph.

Saturday through Tuesday: Sunny, with highs in the mid 30°F and lows in the high teens and low 20°F.

Snowflake Hazardous Weather Snowflake Gibbon Falls Forecast Snowflake Mammoth Forecast Snowflake Midway Forecast Snowflake Norris Forecast Snowflake Old Faithful Forecast Snowflake

* * * Snow Depth Totals as reported at SNOTELs * * *
Station Depth (inches) Station Depth (inches)
Black Bear 34 Parker Peak 33
Blackwater 37 Snake River Station 20
Canyon 18 Sylvan Lake 27
Evening Star 35 Sylvan Road 17
Fisher Creek 41 Thumb Divide 20
Grassy Lake 27 Two Ocean Plateau 43
Lewis Lake Divide 29 West Yellowstone 14
Madison Plateau 23 Whiskey Creek 19
Northeast Entrance 11 Wolverine 13

Avalanche Information
from the Gallatin National Forest Avalanche Center - December 15, 2011 - this report is by Mark Staples. This advisory does not apply to operating ski areas.

Mountain Weather

Yesterday an additional 1-2 inches of snow fell. Not much, but a little snow is better than none at all. This morning winds were blowing 15-20 mph from the Southwest with temperatures in the low teens Fahrenheit. Today will be mostly cloudy and temperatures will be in the high teens Fahrenheit. Winds will increase and blow 15-30 mph from the West. Late this afternoon some moisture should arrive from the north but only produce 1-2 inches of snow. Long range models indicate more snow for the rest of December. Keep your fingers crossed.

Snowpack and Avalanche Discussion:

The Bridger, Gallatin and Madison Ranges, the Lionhead area near West Yellowstone and mountains around Cooke City:

New snow and avalanches: Mountains near Bozeman and Big Sky received the most snow yesterday with a 48-hour snowfall of 6-8 inches while further south the 48-hour snowfall was 4-6 inches. This storm provided just enough snow for local ski patrols to ski cut soft slab avalanches, loose snow avalanches, and a few wind pillows. The Bridger Bowl Ski Patrol noted that yesterday's avalanche activity provided a small "taste of what our future looks like" because there will be significant avalanche activity once more snow falls.

A new problem: Prior to yesterday's snowfall, a combination of clear cold nights and warm sunny days significantly weakened upper layers of the snowpack. This weather metamorphosed (changed) this snow from old, broken snowflakes to weak faceted crystals, otherwise known as "near-surface facets." To compound the problem, a layer of surface hoar, formed on top of these facets in most areas (photo). Yesterday, Doug and I found this combination throughout the Taylor Fork area in the southern Madison Range (photo). Often surface hoar is destroyed by sun or wind, but yesterday's snowfall covered and preserved it. Right now these layers of near-surface facets and surface hoar make great riding conditions because the powder seems deeper than it is.

An old problem: At the bottom of the snowpack, old snow from October metamorphosed into big, depth hoar crystals. Avalanches in late November and early December occurred on this layer which hasn't gone away. It is waiting to be stressed by a load of new snow which hasn't come.

The current situation: You can find two basic snowpack structures. In some places the snowpack is greater than 2 ft deep with depth hoar at the bottom, a slab in the middle, and facets on top. On these slopes and any recently wind loaded slope, the Avalanche Danger is rated MODERATE. Other slopes have a snowpack less than 2 ft deep with depth hoar at the bottom, more facets in the middle, and near-surface facets on top (video). These slopes have a LOW Avalanche Danger if not wind loaded.

I will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations, drop us a line at or call us at: 406-587-6984.


1. We've recently uploaded more photos and snowpits to our web site, more than what are linked in the advisory.

2. We're creating a series of "How To…" stability test videos. So far we've got clips on performing a CT and ECT. There are located under Stability Tests on the Resources page.

Information provided by Doug Chabot, Mark Staples, and Eric Knoff from the Gallatin National Forest Avalanche Center. For Photos and Videos, please visit the Avalanche Centers Website!

If you have any snowpack or avalanche observations, drop them a line at or call: 406-587-6984.

For detailed Avalanche Terms utilized here, please see the Avalanche Glossary.

Avalanche Danger Scale

Back to the Yellowstone Daily Winter Reports or the Yellowstone Weather Page

Information provided by Yellowstone National Park, National Weather Service and Gallatin National Forest Avalanche Center

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