Advisory Archive

Since yesterday morning a trace to one inch of snow fell in most areas with the exception of the Bridger Range which picked up an additional 3-5 inches between 7 am and noon yesterday. Winds have been decreasing over the past 24 hours and are currently blowing 5-15 mph out of the SSE.  Temperatures are in the single digits under mostly cloudy skies.  Today, temperatures will warm into the low twenties F and winds will gradually shift to the SW blowing 5-15 mph.  Skies will be partly cloudy in the north, but a weak weather disturbance in the south will produce a chance of snow showers for the mountains around West Yellowstone and Cooke City, 1-2 inches is possible by this afternoon.  An unsettled weather pattern will remain over the southern mountains through tomorrow, but the north will stay mostly dry.

                                         AVALANCHE WARNING

ISSUED ON FEBRUARY 26 2012 AT 5:00 am

 The Gallatin National Forest Avalanche Center is issuing a Backcountry Avalanche Warning for the Bridger Range, southern Madison and southern Gallatin Ranges, the Lionhead area near West Yellowstone and mountains around Cooke City.  Heavy snowfall, high winds and an extremely weak snowpack are causing unstable conditions.  Today the avalanche danger is HIGH on all slopes. Natural and human triggered avalanches are likely.  Avalanche terrain including avalanche runout zones should be avoided.

You are urged to contact the Gallatin National Forest Avalanche Advisory for more detailed information.

Website: www.mtavalanche.com/advisory

Avalanche Hotline: 406-587-6981

Mountain Weather: 

Over the past 24 hours the Bridger Range and mountains near west Yellowstone picked up 8 inches of new snow, 5-7 inches fell elsewhere.  Winds blew 30-40 mph out of WNW during the storm, but have decreased to 20-30 mph out of the WNW.  The exception is the Bridger Range where ridgetop winds are still blowing 30-40 mph.  Mountain temperatures are ranging between 5-10 degrees F under cloudy skies.  Today, temperatures will warm into the mid to high teens and winds will gradually decrease to 15-25 mph out of the west.  Lingering snow showers could produce 1-2 inches of new snow by this afternoon, but conditions will dry out by this evening.  

Since yesterday a few places near Cooke City and West Yellowstone received a trace of new snow.  This morning ridgetop temperatures were in the mid teens F and W/SW winds were blowing 20-30 mph with gusts up to 60 mph. Today will be cold, windy, and snowy. Temperatures may climb a few degrees this morning before cold air moves into the area. Winds will blow mostly from the W at 25-40 mph. Snow will start falling early this morning. By tomorrow morning 4-6 inches will accumulate near Cooke City and West Yellowstone. Further north near Bozeman and Big Sky, 2-4 inches will accumulate.

Lingering snowfall yesterday produced 2-3 inches in most areas. Last night winds increased blowing 20 mph and gusting to 40 mph from the W. This morning winds calmed and were blowing 10-15 mph with gusts of 25 mph.  Temperatures were in the single digits to low teens F. A short-lived, upper level ridge will bring dry weather today with a mix of sun and clouds and temperatures near 20 degrees F. Winds will remain about the same speed but shift to the SW as a trough of low pressure approaches tonight. Snowfall will begin tomorrow morning.

In the last 24 hours the heaviest snowfall occurred in the Bridger Range and the mountains near Cooke City. Yesterday’s snow was wet and heavy while snow that fell late last night had a much lower density because temperatures dropped into the low teens and single digits F. The exact amount of snow is hard to gauge, but the snow water equivalent (SWE) is measured exactly and tells how much weight was added to the snowpack:

• Near Cooke City 1 inch of SWE (5-10” of snow)
• In the Bridger Range 0.5 - 0.9 inches of SWE (3-5” of snow)
• Near Big Sky, Hyalite, and West Yellowstone 0.4 to 0.6 inches of SWE (2-4” of snow)
• Near the Taylor Fork 0.2 inches of SWE (1-2” of snow)

Further complicating snowfall totals is yesterday’s extreme winds which averaged 50 mph from the W with gusts of 60-90 mph. This morning winds were blowing 15-20 mph from the WNW with gusts of 40 mph. Today will be mostly cloudy with an additional 2-4 inches of snow falling. Temperatures will warm into the high teens F.

During the last 24 hours snow fell, winds blew and temperatures warmed.  Since yesterday morning the mountains got 4 to 10 inches of new snow with varying densities.  The Bridger Range has gotten 6” of 20% density snow (1.2” Snow Water Equivalency or SWE); the northern Gallatins, Big Sky area and West Yellowstone received about 5” of new (.7-.9” SWE) and Cooke City has about 10 inches (1.4” SWE).  Higher elevations were colder than the measuring stations.  Colder air makes lower density powder with the same water equivalency, so expect substantially more snow the higher you go.  Winds are blowing out of the west at 30-60 mph with mountain temperatures in the mid to high 20s.  The storm will continue today and drop another 6-10 inches in the mountains (.6-.8” SWE) with strong winds and falling temperatures.

At 6 a.m. seven to nine inches of new snow has fallen throughout southwest Montana.  A moist Pacific storm is driving through on a northwest flow.  Mountain temperatures are in the teens and ridgetop winds are blowing west to northwest at 25-35 mph.  The storm is expected to pick up later this morning and last through Wednesday.  Today winds will pick up to 30-40 mph and more snow will fall.  By morning I expect 10-12 inches in the mountains.  

Over the past 24 hours quiet weather has been in place over southwest Montana.  This pattern should continue through much of today.  Currently, mountain temperatures are ranging from the single digits to low teens and winds are blowing out of the WNW at 15-25 mph.  Today, temperatures will climb into the twenties and winds will gradually increase out of the WNW blowing 25-35 mph. Skies will remain mostly clear through the morning, but an approaching front will produce increasing clouds by this evening.   A warming trend will allow temperatures to rise to above seasonal averages by tomorrow.