AVALANCHE WARNING IN EFFECT. The avalanche danger is HIGH. The current storm has added substantial weight to a snowpack that consists of a variety of weak layers. Both natural and human triggered avalanches are likely. Travel in avalanche terrain is not recommended. Stay off of and out from underneath slopes steeper than 30 degrees. Avalanches may run long distances and can reach into mature forests.
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Above 6500 ft.
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5000-6500 ft.
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3500-5000 ft.
Snowfall rates have tapered off overnight but air temperatures at all elevations have risen. These warm temperatures will be responsible for a more cohesive storm slab than what we saw yesterday. The bountiful new snow that we have received over the past 48 hours was deposited onto a weak snowpack structure consisting of near surface weak layers and crusts along with deeper instabilities. An avalanche that initiates at the snowpack surface may step down to a deeper weak layer producing a much larger slide. Cracking in the snow surface is an obvious sign of storm slabs. It is recommended to avoid recreating in avalanche terrain today including runout zones.
We currently have an abundance of snow on the snow surface available for transport. Winds increased overnight and have finally swung back to a southwest flow for all mountain locations. Expect to find fresh wind slabs on the usual leeward slopes today which will continue to form and thicken throughout the day. Be aware that this storm started with northerly winds in many locations and therefore expect to find wind slabs on all aspects. Today's wind slabs should be easy to identify by cracking in the snow surface and newly created pillows of snow. An avalanche that initiates in a wind slab may step down to a deeper weak layer producing a much larger slide. Due to the poor snowpack structure that these slabs are being deposited on it is best to avoid wind loaded slopes today.
Substantial new snow fell at all elevations over the past 48 hours. This snow has fallen on a variety of surfaces including low density surface snow and crusts. I anticipate that this snow will not adhere to the underlying layer and sluff easily on terrain steeper than 30°. These loose slides may be small but could knock you off your feet or machine and push you into trees or gullies and easily ruin your day.
After a dismally dry January this current storm is a great way to start February! The sheer magnitude of this storm has elevated the avalanche danger but unfortunately this storm is being deposited onto a weak snowpack structure which is making current conditions even more dangerous. We all have powder fever but now is not the time to charge and ski or ride aggressive terrain. Most avalanche accidents occur during or immediately following a storm cycle and therefore give our snowpack a few days to adjust to the load being deposited onto it. Enjoy this storm snow on low angle terrain that is not connected to avalanche terrain.
We have received word of an avalanche incident in the Lost Johnny area of the Swan Range that occurred yesterday. Initial unconfirmed reports involve a party of 5 riders with 2 of them ending up being partially buried in an avalanche . Fortunately no injuries were reported. We will release more details concerning this incident as we receive them.
Saturday: We received several reports from riders in the Lost Johnny area of the Swan Range. In one instance 2 riders were partially buried in an avalanche that fortunately resulted in no injuries. We also heard of natural avalanche activity that possibly deposited debris onto the road. WMR ski patrol reported good results with both ski cutting and explosive use. They noted that most of their wind slabs were the result of northerly winds. BNSF Avalanche Safety reported small slab avalanche activity on low elevation steep cutbanks.
Friday: Guy and Mark travelled to the Skyland area of the Flathead Range. A layer of buried surface hoar was found approximately 6" below the surface in both north and south facing pits. This layer was reactive in stability tests but did not propagate due to the lack of a slab above. Soft surface snow conditions were found at mid and upper elevations.
See below for all observations this season.
Storm snow and water totals from the past 48 hours are impressive. 18-24" of new snow is common with snow water equivalents (SWE) of around 2" at Noisy Basin, Flattop, Pike Creek and Stahl Peak. A valley floor weather station near Devil Creek in John F. Stevens Canyon is reporting 1.33" of water. New snow in the past 24 hours varied from 4-11" with light winds and moderate gusts out of initially the northeast which then shifted to the southwest. Currently, temperatures above 6000 feet range from 22-32º F with winds out of the southwest at 10-21 mph with gusts of 23-29. Light to moderate snow will continue through this morning before an even more impressive surge of moisture enters our area this afternoon.
| 0600 temperature: | 22-32 deg. F. |
| Max. temperature in the last 24 hours: | 22-32 deg. F. |
| Average wind direction during the last 24 hours: | Northeast shifting to SW |
| Average wind speed during the last 24 hours: | 3-21 mph |
| Maximum wind gust in the last 24 hours: | 23-34 mph |
| New snowfall in the last 24 hours: | 4-11 inches |
| Total snow depth: | 67-82 inches |
| Sunday | Sunday Night | Monday | |
|---|---|---|---|
| Cloud Cover: | Light to moderate snow this morning followed by heavy snow this afternoon. | ||
| Temperatures: | 26-38 deg. F. | deg. F. | deg. F. |
| Wind Direction: | Southwest | ||
| Wind Speed: | 9-12 mph with gusts to 33 | ||
| Snowfall: | 6-10 in. | in. | 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.
