THIS AVALANCHE ADVISORY EXPIRED ON January 26, 2018 @ 10:44 pm
Avalanche Advisory published on January 25, 2018 @ 10:44 pm
Issued by Eric Morgan - Idaho Panhandle Avalanche Center

Selkirks/Cabinets

bottom line

Recent natural, snowmobile and skier avalanches have been observed with the recent storm since Thursday in the forecast area.  Some areas are more reactive than others but we have consistent persistant weak layers in the snowpack across the board.  New storm snow has been reactive 1-2 feet deep with potential to trigger weak layers deeper in the pack.  

How to read the advisory

Selkirks/Cabinets

How to read the advisory

Recent natural, snowmobile and skier avalanches have been observed with the recent storm since Thursday in the forecast area.  Some areas are more reactive than others but we have consistent persistant weak layers in the snowpack across the board.  New storm snow has been reactive 1-2 feet deep with potential to trigger weak layers deeper in the pack.  

4. High

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Above Treeline
Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

3. Considerable

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Near Treeline
Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1: Storm Slab
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With over 2' of storm snow since Thursday in the mountains and some breezy winds, we are seeing frequent releases on top of last weekends storm snow interface which is still reactive and expected to be for most of the outlook through Sunday with the increasing snow accumulations, temperatures on the rise and breezy conditions.

Avalanche Problem 2: Persistent Slab
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There are numerous persistent weak layers within the pack with the upper 2 meters being the primary concern.  This is all ontop of the Thanksgiving crust which is a prime bed surface for large destructive slides.  The slabs above this crust could slide on the crust with a primary trigger on the upper storm snow that rattles and disturbes the deeper slabs which then could go big.  This is unlikely but the consequences are huge.

Avalanche Problem 3: Deep Slab
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With around 9 feet of snow in the mountains, near the Thanksgiving ice crust (1.5 feet from the ground) and to the ground there are some basal facets and facets surrounding the ice crust as it breaks down forming a sugarlike looseness (4 finger hardness) that is beneath meters of snow that is more dense with a pencil hardness.  One should monitor the crust layers that may become weaker over time.  

advisory discussion
 
Area Forecast Discussion
National Weather Service Spokane WA
517 AM PST Fri Jan 26 2018

.SYNOPSIS...
Today will be breezy across southeast Washington and the Idaho
Panhandle will experience snow showers throughout the day. A
vigorous low pressure system will bring accumulating snow to much
of the Inland Northwest late tonight into Saturday. Another round
of rain and snow is expected on Sunday.


&&

.DISCUSSION...

...ACCUMULATING SNOW EXPECTED FRIDAY NIGHT INTO SATURDAY ALONG AND
NORTH OF INTERSTATE 90...

Today: It will be another breezy day across the Palouse and West
Plains with southwest winds of 10 to 15 mph with occasional gusts
in the 20 to 25 mph range. Bands of convective snow are also
expected to produce accumulations across the Idaho Panhandle with
up to an inch in the valleys of Shoshone county this morning. The
high terrain around Sandpoint, Kellogg, and Deary will have a good
shot of 2 to 4 inches of accumulation by this afternoon. Motorists
going over Lookout Pass this morning may encounter winter driving
conditions mainly during the morning hours prior to increases in
road temperatures. The breezy conditions and snow showers will be
driven by a cold upper level disturbance moving across eastern
Washington into north Idaho this morning.

Tonight into Saturday: A vigorous low pressure system will spread
a shield of precipitation into Washington, Oregon, and Idaho
tonight. The tightly wound surface low is expected to reach the
Olympic Peninsula around sunrise on Saturday. Strong warm frontal
forcing is expected to produce 6 to 10 hours of light to moderate
snow for the East Slopes of the Cascades, Wenatchee area, Okanogan
Valley/Highlands, and Northeast Washington. At this time, it looks
like 3 to 5 inches of accumulation for Wenatchee, Chelan, Omak,
and Waterville. For the East Slopes including Leavenworth,
Stehekin, Mazama, and Winthrop contributions of east/southeast
upslope winds should contribute to 4 to 8 inch amounts.

Snow amounts for places like Colville, Deer Park, Sandpoint,
Spokane and CDA will be tougher. Precipitation is expected to
arrive several hours later putting some of the peak precipitation
intensity during the mid to late morning hours in Saturday. Low
level warm advection and rising ground temperatures may limit
accumulations especially below 2500 feet. At this time, it looks
like 1 to 3 inches for the Spokane/CDA metro with the highest
amounts on the Idaho side. For Colville, Deer Park, and Sandpoint,
2 to 4 inches falls close to the median of the SREF plumes for
tonight into Saturday afternoon.

Winds have the potential to become quite breezy Saturday afternoon
into the evening. As the compact surface low crosses the Cascades
near the WA/BC border, look for gusty south to southwest winds
across the Palouse, West Plains and Upper Columbia Basin. Gusts of
30 to 35 mph will have the potential to cause temperatures to
quickly spike into the 40s (near 50 for Lewiston) late in the day.

Saturday Night: Gusty post-frontal winds should diminish by late
evening on Sat. We should also see a break in precipitation Sat
evening before the next round of warm frontal precip develops
during the early morning hours on Sunday. /GKoch
 
recent observations

The past few days in the Selkirks from the southern areas north to Roman Nose Lakes we have seen natural avalanche activity and snowmobile triggered avalanches fracturing 200 feet.  Schweitzer had a significant slide triggered by explosives in control operations that ran beyond Colburn Lake on the Thanksgiving crust.  Other naturals and snowmobile triggered releases have been seen in the upper 2 feet in the storm snow interface between last weekends storm and the recent storms since Wednesday night.  Melissa observed some recent activity in the Lake Elsie are in the upper Big Creek drainage in the Silver Valley as well.  There has been a lot of rapid loading to the pack with many weak layers within.  

Weather and CURRENT CONDITIONS
weather summary
Schweitzer picked up an additional 4 inches of snow last night with temperatures in the mid 20's while Bear mountain snotel is showing 6 additional inches overnight.  Expect a bit of new snow with some breezy conditions and warming daytime temperatures as we get into the weekend.  
Weather observations from the Region
0600 temperature: 25 deg. F.
Max. temperature in the last 24 hours: 27 deg. F.
Average wind direction during the last 24 hours: 270
Average wind speed during the last 24 hours: 6 mph
Maximum wind gust in the last 24 hours: mph
New snowfall in the last 24 hours: inches
Total snow depth: inches
Disclaimer

Avalanche conditions change for better or worse continually. Backcountry travelers should be prepared to assess current conditions for themselves, plan their routes of travel accordingly, and never travel alone. Backcountry travelers can reduce their exposure to avalanche hazards by utilizing timbered trails and ridge routes and by avoiding open and exposed terrain with slope angles of 30 degrees or more. Backcountry travelers should carry the necessary avalanche rescue equipment such as a shovel, avalanche probe or probe ski poles, a rescue beacon and a well-equipped first aid kit.  For a recorded version of the Avalanche Advisory call (208)765-7323.