The avalanche danger above 6000 feet on steep wind-loaded terrain is MODERATE and human triggered avalanches are possible. On all other slopes the avalanche danger is LOW. Remember, LOW danger does not mean NO danger. An avalanche can still be triggered during periods of LOW danger. Treat recently wind loaded terrain as suspect and carefully evaluate the snowpack and terrain before committing to any slope. Continue to use proper travel techniques in avalanche terrain.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
It is possible to trigger lingering, stiff wind slabs as well as new, shallow, soft wind slabs in steep, exposed terrain. You are most likely to find this problem near ridgelines and cross-loaded gullies in the alpine. Models suggest wind gusts today could be strong (up to 25-30 mph) so pay attention for potentially increasing winds this afternoon. Over the past few days the wind has flip-flopped numerous times from the west/southwest to the north/northeast, thus making wind slabs potentially present on numerous aspects in the alpine. The wind has been mostly light to moderate (with some strong gusts three days ago), but there is plenty of low density snow to redistribute and form shallow slabs on more southerly aspects as well as hard wind slabs on more northerly aspects. These harder wind slabs will sound hollow or "drummy" and typically sit on less dense snow. Softer wind slabs will look more smooth, pillowy, and rounded. With high pressure entering the region, blue skies and ample sunshine in the alpine will be inviting. Though most locations currently harbor a stable snowpack it's still important to carefully assess each and every slope. Even a small wind slab in high consequence terrain can ruin the New Year.
There are currently two deeper layers in the snowpack that aren't necessarily problems, but are still concerns. We haven't observed or received reports of avalanches on these layers (even during or after last week's storms) or reactiveness in stability tests, but they are easily identifiable and worthy of investigation in your snowpit due to their variablity.
1. The December 9 rain crust still lurks throughout most of the advisory area. A layer of softer facets (weak, sugary snow) below the crust has shown no signs of instability (fracture or propagation) in our snowpits for two weeks, but it's still there. It is unlikely you'll trigger an avalanche on this layer, but not impossible. It is still worth taking the time to dig into the snow and see how it is reacting in the areas that you are skiing or riding.
2. In some locations throughout the advisory area we noted and have received observations of weak, sugary snow (facets) near the ground. This layer has not been reactive in stability tests in over three weeks, but in shallow areas (snowpack less than 3-4 feet deep) this layer may be more developed and could be more reactive. It is best to avoid areas of shallow snowpack where this layer exists (like steep, rocky slopes).
Two skiing parties (observation 1, observation 2) in the Apgar Range reported good skiing with minimal slab formation. Though one party, in their stability test, was able to initiate fracture with hard force on a layer about 2 feet from the surface (suspected wind slab near the ridge) that propagated across the column. Though, they could not repeat this result on subsequent tests. Another party yesterday on Sub-Shields in southern Glacier Park reported a thin snowpack in their pit with weak snow near the ground and wind slabs on easterly aspects (observation).
On Tuesday, my partner and I traveled to Elk Mountain in southern Glacier Park. We observed reactive thin wind slabs on southerly aspects above 6000 feet from north through east winds (photo) as well as dense hard wind slabs that formed on northerly and easterly aspects during recent wind events (video, observation).
Tuesday, BNSF Snow Safety reported no notable results in stability tests on a southeast aspect at 6000 feet in John F. Stevens Canyon. At this location, the December 9th rain crust was a 6+ inch thick, knife hard, ice mass with weak depth hoar below (observation). On Monday, skiers in the Middle Fork reported the recent storm snow as being right side up and the Dec 9th rain crust as decomposing (observation).
Last weekend, we received numerous reports from the southern Whitefish Range of deep, cohesionless surface snow on non-wind loaded slopes with no obvious signs of instability except sluffing on steep slopes during the storms. Also last weekend, Todd and Mark headed into Noisy Basin in the Swan Range. The snow was deep and unconsolidated (photo), and they observed several natural loose, dry avalanches that had recently occurred in steep terrain as well as evidence of recent wind-loading at higher elevations on surrounding peaks.
Thanks to everyone for submitting observations. They are extremely useful for everyone.
Visit our Observations page and our You Tube channel for more information from the entire season.
Please let us know what you are seeing out there. Your observations are important and valued.
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
Winds have been light over the past 24 hours with a few moderate gusts. Currently, temperatures above 6000 feet range from 0º-12º F and winds are out of the southwest though northwest at 5-7 mph with gusts up to 15 mph. Today, high pressure begins to build over the region with chilly valley temperatures (mid- to upper teens F) and warming mountain temperatures (up to the mid-20s F). Winds should be out of the southwest at 5-10 mph with gusts to 25 mph near the Continental Divide.
| 0600 temperature: | 0 to 12 deg. F. |
| Max. temperature in the last 24 hours: | 10 to 19 deg. F. |
| Average wind direction during the last 24 hours: | Southwest shifting to Northwest |
| Average wind speed during the last 24 hours: | 5-7 mph |
| Maximum wind gust in the last 24 hours: | 11-18 mph |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 50-64 inches |
| Thursday | Thursday Night | Friday | |
|---|---|---|---|
| Cloud Cover: | Very light snow flurries this morning with clearing skies today. | High pressure builds. Clear. | Sunny. Warming mountain temperatures. |
| Temperatures: | 10 to 24 deg. F. | -5 to 10 deg. F. | 18 to 29 deg. F. |
| Wind Direction: | West-Southwest | Southwest | Southwest |
| Wind Speed: | 3-6 mph with gusts to 16 mph. | 4-6 mph. | 2-4 mph. |
| Snowfall: | 0 in. | 0 in. | 0 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.
