Recent wind deposited snow is slowly gaining strength but there still remains instability associated with wind slabs. The avalanche danger is MODERATE above 5000 feet. Human triggered avalanches are possible, especially in recently wind loaded areas and areas where weak snow deeper in the snowpack exists. This warrants careful snowpack evaluation and conservative terrain choices. The avalanche danger is LOW below 5000 feet.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Winds have moderated over the past couple of days allowing for recently formed wind slabs to gain a bit of strength. However, in favored locations, wind speeds have been strong enough to transport the low density surface snow. These areas are generally in the upper elevation on leeward and crossloaded slopes. Unfortunately, we have limited field observations from the true alpine terrain of our forecast area where wind slabs have continued developing. Windslabs in these areas have increased in size and thickness and can easily be 2-3 feet thick. Cross loaded slopes have also developed thick wind slabs as Erich found Monday (video). Windslabs can take up to a week to gain strength. In some areas expect to find fresh windslabs 2-3 feet thick that will remain sensitive to human triggers. Wind loaded slopes are easy to identify. Look for smooth, rounded features and convex pillows on leeward slopes. Carefully evaluate wind loaded terrain before committing to a slope.
Persistent slabs, including those sitting on weak snow above the late January crust as well as below the January 12 rain crust and around the January 17 rain crust are getting more difficult to affect in stability tests. They are gaining strength but in some areas they continue to fracture and propagate in these tests illustrating that it is still possible to trigger an avalanche on these layers. BNSF avalanche safety noted clean Q1 shears in tests performed Monday. The failure layer was on top of a melt freeze crust 30 inches below the snow surface (video). As these layers get buried deeper and the probability of triggering an avalanche on one of them lowers the consequence remains severe. The only way to know if these layers are present and reactive is to dig into the snow and perform stability tests. Where these weak layers exist consider how you may trigger them like in areas with shallow snow where they are closer to the surface, and in steep, rocky terrain. A rapid stress to these layers like cornice fall, smaller avalanches, or multiple machines on a slope could also awaken them.
In many locations recent low density snow was deposited onto a rain crust. This snow has not bonded well to the crust and loose snow avalanches may still be triggered in steep terrain. These avalanches could entrain a lot of snow and pack a big punch. Remember that even small avalanches can have severe consequences if you are caught while traveling in or around terrain traps like narrow gullies, trees, or cliffs.
Though not wide spread across the advisory area, there are locations where large cornices have been observed with some of these failing (photo). If you encounter large cornices give them a wide buffer as they are likely recently formed and sensitive. Remember that cornices can pull out behind the ridgeline and take you with them. Aside from the danger of being hit by a large mass of consolidated snow they are the "bombs of the backcountry" and can trigger deep and dangerous avalanches.
The final report for the 1/23/2016 avalanche fatality in Swede Creek in the Whitefish Range is complete and located here: http://www.flatheadavalanche.org/sites/default/files/20160124_swedecreekavalaccidentreport_final.pdf.
Yesterday, BNSF avalanche safety traveled to a high elevation (7250 feet) starting zone in John F. Stevens Canyon. No wind transport of snow nor recent avalanche activity was observed. The main concern in their snowpit was the interface at a melt freeze crust 101 cm from the snow surface (observation)..
Also on Tuesday, skiers in the northern Swan Range found a deep snowpack on a west-northwest aspect. Stability tests and ski cutting showed instabilities confined to the surface snow (observation).
Monday, I traveled to Wahoo Creek in the Flathead Range. We found low density surface snow that was not adhering well to a rain crust formed January 28 (observation).
Erich and Guy went to the northern Mission Mountains Monday (outside of our advisory area). On their snowmobile tour they found evidence of recent crossloading (photo, video, observation).
Also on Monday, BNSF avalanche safety reported Q1 shears with hard force in their stability tests. The failure layer was facets/decomposing surface hoar resting on a melt freeze crust buried approximatley 30 inches below the snow surface (video, observation). Skiers in Rescue Creek in the Flathead Range noted evidence of avalanche debris covered by recent snowfall.
A skier triggered avalanche was reported in Noisy Basin in the Swan Range Sunday. There were no other details, but no one was caught.
Also on Sunday, a party of snowbikers and snowmobilers were in McGinnis Creek in the southern Whitefish Range and triggered a small windslab (observation). Skiers in the Ghoulie Point area in the southern Whitefish Range dug a snow pit and found a crust buried buried 20 inches deep with weak, faceted snow on top. Stability tests produced fractures on top of this crust that did not propagate and fractures below the recent storm snow (observation).
Saturday, snowmobilers reported natural avalanche activity in McGinnis Creek in southern Whitefish Range.
Guy and I were in the Skyland area in the Flathead Range Saturday. We observed a recent natural avalanche thought to be a wind slab triggered by loose snow (photo). He noted wind drifting the snow on the ridgelines, as well as mid slope level.
BNSF Avalanche Safety reported a large cornice failure in their program area that occured on January 29. The debris slid an estimated 800 vertical feet (photo *observed 1/30).
For more information on the recent avalanche fatality in Swede Creek, Whitefish Range (1/23/2016) please view the final report here.
Visit our Observations page and our You Tube channel for more observations from the entire season.
Thanks to everyone for submitting observations. They are extremely useful and could help save lives.
HOW TO SUBMIT OBSERVATIONS:
Email: [email protected]
Call and leave a message: 406.387.3821
You can also submit quick observations via text: 406.241.4571 (FAC mobile)
OR
Submit Snowpack Observations: http://www.flatheadavalanche.org/node/add/snowobs
Submit Avalanche Observations: http://www.flatheadavalanche.org/node/add/avyobs
Weak high pressure has moved into our area early this morning allowing for clearing skies and plummeting temperatures. Over the past 24 hours scattered snow showers have produced up to 2 inches of snow, light winds with moderate gusts blew out of the west-southwest and ridgeline temps ranged from the mid teens in John F. Stevens Canyon to the mid twenties elsewhere. Currently, temperatures range from 8º-18º F, and winds are 2-11 mph out of the west-southwest. Today, temperatures will rise to the low to mid 20s and winds will be light out of the west-southwest with moderate gusts in the Flathead Range. Partly cloudy skies can be expected before another storm system moves into our area later today.
| 0600 temperature: | 8-17 deg. F. |
| Max. temperature in the last 24 hours: | 16-25 deg. F. |
| Average wind direction during the last 24 hours: | W-SW |
| Average wind speed during the last 24 hours: | 4-18 mph |
| Maximum wind gust in the last 24 hours: | 6-24 mph |
| New snowfall in the last 24 hours: | 0-2 inches |
| Total snow depth: | 68-99 inches |
| Wednesday | Wednesday Night | Thursday | |
|---|---|---|---|
| Cloud Cover: | Weak high pressure. | Pacific storm enters our area. | Snow tapering throughout the day with gusty winds. |
| Temperatures: | 21-30 deg. F. | 17-24 deg. F. | 26-35 deg. F. |
| Wind Direction: | W-SW | W-SW | W-SW |
| Wind Speed: | 6-9 gusts 29 | 7-11 gusts 29 | 11-16 gusts 38 |
| Snowfall: | 0 in. | 1-3 in. | 1-2 in. |
| Snow Line: |
This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires at midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.
