Avalanche Advisory published on March 23, 2018 @ 7:16 am
Issued by Dave Bingaman - Payette Avalanche Center
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Loose/wet avalanches are possible on all slopes steep enough to slide today.  The Avalanche Hazard is Considerable. Over the last 48 hours snow and rain fell at all but the highest elevations, adding weight to the snowpack and significantly reducing stability.  Natural wet avalanches were occurring on multiple aspects yesterday especially where a stout melt freeze crust was present 10-12 inches down.  Play it safe and avoid steep slopes until a solid refreeze has occurred. 

How to read the advisory

  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Loose Wet
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Very Likely
  • Size ?
    Very Large

Wet avalanches or wet slab avalanches were occurring throughout the West Central Mountains yesterday as the rain line crept up towards 8000 feet. Wind loaded slopes and heavily corniced ridgelines had already released and steep slopes from close to the valley floor up to nearly 8000 ft. were shedding snow.  On steep slopes where the melt freeze crust from early last week was present we were able to easily trigger wet, slablike avalanches with ski cuts.  In the upper elevations, the slightly cooler snow was more cohesive and more slablike.  In the lower elevations, roller balls and loose/wet slides were prevalent.

Temperatures dropped early this morning into the upper 20's around 6500 feet and will begin to refreeze the snowpack from the top down, but this is going to take a little time to stabilize the snowpack.  Expect the instabilities to persist through today especially in the mid to lower elevations where it is going to take longer to refreeze.  As the snowpack cools back down over the next couple of days, expect stability to improve. 

Rain on snow events create unusual conditions and extra caution should be taken to avoid exposure on or near slopes steep enough to slide.  These are the kind of events that create large, destructive avalanches in steep canyons, gullies, confined avalanche paths and other lower elevation terrain.


recent observations

Local Snotel sites picked up quite a bit of moisture over the last 24 hours.  With day time temperatures in the high 30's yesterday that moisture was nearly all rain.  Secesh Summit picked up just about .75 inches of Snow Water Equivalent yesterday with Brundage Reservoir topping 1 inch.  Winds were also gusting yesterday and last night and probably made for some more weird conditions in the heavy, wet snow that was falling in the upper elevations. 

We toured up Lick Creek canyon to Hum Saddle yesterday and saw some debris on steep, avalanche prone terrain in the morning as we sledded up towards the Duck Lake trail head.  We found a saturated snowpack that was loosing cohesiveness and some challenging ski conditions.  Throughout the day the visibility gave us glimpse of slopes that were littered with fresh, loose, wet avalanche debris and some older debris from earlier in the week on wind loaded slopes.  Pit tests showed easy initiation of the wet slab above last week's melt freeze crust but a general lack of propagation in the wet slab. On our way down canyon, most of the big slide paths had wet debris in them although visibility  was poor and still didn't give us a clear picture of size.

Also,  having seen older debris on Northerly slopes near Hum Lake, we were reminded of the natural cycle that occurred last Sunday.  Skiers reported triggering 10-12 inch soft slab avalanches that propagated easily on a layer above the crust.  Natural, shallow avalanches release on many northerly aspects. Tuesday, we received a second hand report of a skier that was partially buried in the Lick Creek Canyon but no further information about that incident.

If you are involved in an incident in the West Central Mountains or anywhere in the West. PLEASE, take the time to share incidents and your observations on the PAC or your local avalanche center website.  You can fill out an observation and remain anonymous if you choose.  There are several questions and easy to fill out fields to describe what you saw or what occurred.  Gathering this information helps not only the local avalanche center and its audience but the incident information gets logged in a national database and studied to help snow scientists gather more knowledge about the human and environmental factors as well as the decision making processes that contribute to avalanche accidents and incidents.  

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 19 deg. F.
Max. temperature in the last 24 hours: 32 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 7 mph
Maximum wind gust in the last 24 hours: 31 mph
New snowfall in the last 24 hours: 4 inches
Total snow depth: 60 inches

SHORT TERM...Today through Saturday...A drier and colder air mass
has filtered into the region behind Thursday`s strong cold front.
More than 50 cloud-to-ground lightning strikes occurred with the
front`s passage, with many striking the Lower Treasure Valley.
The associated upper level trough, anchored offshore, will send a
shortwave trough inland across southeast Oregon Friday night, and
southwest Idaho Saturday morning; this will bring a chance of
rain and snow showers and a brisk southwesterly wind across
southeast Oregon and along the NV-ID border. Snow levels will vary
between about 3000-4500 feet Friday. Behind the shortwave trough and
its associated cold front, snow levels will drop to valley floors
for a cooler than normal Saturday; temperatures will drop to
about 10 degrees below the norm. Snow showers will bring about
1-3 inches of accumulation to the higher elevations late Friday
and Saturday; valleys will see little to no accumulation.

.LONG TERM...Saturday night through Friday...An upper level
trough will move onshore into the PacNW Saturday night, and cross
the area Sunday into Sunday evening, spreading snow showers as it
moves through. Residual moisture will result in mountain showers
again Monday. Ridging will build in behind the trough, with just
enough moisture reaching the West Central Mountains to maintain a
slight chance of showers there Tuesday and Wednesday. We expect
Thursday to be dry. By late Friday, moisture returning on
northwest flow aloft warrants a slight chance of showers in the
mountains once again. Temps will start out around 10 degrees below
normal Sunday and Monday. As the ridge moves in, readings will
rise to near normal Wednesday, and become slightly above-normal
Thursday and Friday.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: A 30 percent chance of snow showers, mainly before noon. Mostly cloudy, with a high near 38. South southwest wind 9 to 15 mph. Total daytime snow accumulation of less than a half inch possible. Snow showers likely, mainly after midnight. Mostly cloudy, with a low around 26. South wind 10 to 14 mph. Chance of precipitation is 70%. New snow accumulation of around an inch possible. Saturday Snow showers likely, mainly before noon. Mostly cloudy, with a high near 34. Southwest wind 11 to 13 mph. Chance of precipitation is 60%. New snow accumulation of less than one inch possible.
Temperatures: 38 deg. F. 26 deg. F. 34 deg. F.
Wind direction: SSW S SW
Wind speed: 9-15 10-14 11-13
Expected snowfall: Trace in. 1 in. Trace in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: A 30 percent chance of snow showers. Mostly cloudy, with a high near 24. Breezy, with a south southwest wind 14 to 22 mph. Total daytime snow accumulation of 1 to 2 inches possible. Snow showers. Low around 17. Breezy, with a south wind 20 to 23 mph. Chance of precipitation is 80%. New snow accumulation of 2 to 4 inches possible. Snow showers, mainly before noon. High near 21. Wind chill values between -1 and 4. Breezy, with a southwest wind 16 to 21 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 3 inches possible.
Temperatures: 24 deg. F. 17 deg. F. 21 deg. F.
Wind direction: SSW S SW
Wind speed: 14-22 20-23 16-21
Expected snowfall: 1-2 in. 2-4 in. 1-3 in.

This avalanche advisory is provided through a partnership between the Payette National Forest and the Payette Avalanche Center. This advisory covers the West Central Mountains between Hard Butte on the north and Council Mountain on the south. 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.