THIS AVALANCHE ADVISORY EXPIRED ON January 3, 2019 @ 7:05 am
Avalanche Advisory published on January 2, 2019 @ 7:05 am
Issued by George Halcom - Payette Avalanche Center
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Moderate Avalanche hazard exists throughout the West Central Mountains.  It is possible to trigger an avalanche. The snow pack is widely variable right now.  Wind Slabs may be found in exposed, upper elevation terrain.  Human triggered avalanches are also possible in wind protected areas where buried weak layers exist within the snow pack.  Your safest option is to avoid steep terrain, especially areas where the snow pack is still thin enough to trigger the sugary, faceted layer near the ground.

How to read the advisory


  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Wind Slab
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Some things never change? The wind in the mountains has just started winding down after over a week of action. The combination of light, dry snow and winds from multiple directions over the week has been perfect for creating soft, thin wind slabs on upper elevation, wind exposed slopes.  You will notice two layers of wind slabs that are not bonding well, and the upper slab is showing some cracking through the surface from our skis...more load this weekend may bring some natural avalanches. These slabs may be found on all slopes that have seen winds over the last week, especially the above treeline exposed slopes . These relatively thin slabs also have the possibility of triggering or "stepping down" into  the deeper weak layers within the snowpack.   

Wind slabs are relatively easy to spot and recognize, look for sculpted snow surfaces, cornices and drifted pillows of snow, or areas where the snowpack is more firm and supportive to the weight of a skier or snowmobiler.  

We witnessed a natural wind slab avalanche on Rain Peak on December 31st. Check out the obvervation

 

Avalanche Problem 2: Persistent Slab
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Our snowpack continues to show us reasons not to venture into steep terrain right now.  Despite the fact that we have not seen any new avalanches throughout the local mountains in almost 2 weeks, we still have a VERY unusual and atypical snowpack for the West Central Mountains.  Avalanche Professionals to our East and West are echoing the same themes in both the Sawtooth area and in the Wallowas.  Cautious travel is advised, the weak layers that continue to get deeper in our snowpack are refusing to go away quickly this year.  While the upper snowpack continues to gain strength and depth, the weakest layer of Basal Facets(near the ground) continues to show the ability to both initiate and propagate avalanches that would run to the ground.  A weak layer in the middle of the snowpack continues to produce failures in our pit tests too.  This is a layer of Surface Hoar and Near Surface Facets that are getting stronger in most cases but remain well preserved in others. 

In many areas, the snowpack is still relatively thin and the lack of snowpack is allowing skiers and snowmobilers to affect this layer resulting in collapsing or whumphing as this layer fails or is triggered by our weight.  We experienced several of these yesterday in wind protected areas including one that displaced the snow in the flats, reverberated away from us for several hundred feet and shook snow out of nearby trees.

The skiing and riding is getting better by the day with the addition of light, dry snow but unfortunately, until we have a large snowfall event coupled with warmer temperatures our buried weak layers are going to be a problem.  Your best and safest bet is to avoid slopes steep enough to produce avalanches, especially where the snowpack is still thin and the weak layers are more likely to be influenced by your weight.

Variability is the name of the game right now, check out the pictures and pit profiles from our day out yesterday in the observations section of the advisory or on the observations page.

advisory discussion

Due to the partial government shutdown, avalanche forecasting will be limited.  We expect to forecast 3 times a week until the shutdown has ended.

Your observations are very helpful to the PAC staff and help create a better picture of the complex terrain in our advisory area.  You can click on the add observations link and add as little or as much detail as you have.  It is easy to navigate and will also upload pictures easily.  Please contribute to your local forecast by sharing what you see or experience even if it is just good snow. or a trip report.

recent observations

In the Lick Creek drainage near Duck Lake, on December 31st, we witnessed some impressive wind plumes coming off of the peaks and ridges, and emptying trees into the air. There was also a natural avalanche on the Eastern Face of Rain Peak just above the Lake. The wind has helped push snow into places between rocks and logs and has gained some strength and density that inspires winter travel much more, but be careful as there is still a lot of buried treasure out there to hit. 

The avalanche problems will likely lurk through January, and vary depending on location and elevation. While they may be difficult to trigger, they still deserve respect and cautious travel protocols in avalanche terrain.  The skiing and riding continues to get better, you really couldn't ask for better quality snow. The Sun gave us a crust in some spots on the surface on the last day of 2018, and the wind also made its mark.  See the photos from the last day of the year near Duck Lake.

 

   

 

 

 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 22 deg. F.
Max. temperature in the last 24 hours: 25 deg. F.
Average wind direction during the last 24 hours: NW
Average wind speed during the last 24 hours: 8 mph
Maximum wind gust in the last 24 hours: 25 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: NA inches
weather

 

 

Area Forecast Discussion
National Weather Service Boise ID
258 AM MST Wed Jan 2 2019

.SHORT TERM...Today through Friday...Ridge along the West Coast
will weaken and move inland through Friday. Flow aloft will shift
from cold northerly today, to more westerly flow Thursday, and
southwest on Friday. Deep, but weak, inversion today will get
shallower on Thu/Fri as heights/temperatures cool aloft, and low-
level flow from southeast increases. This leads to more mixing and
a warming trend in most valley areas through Friday. But with
increased southeast surface winds, and increasing clouds in the
Snake River Plain, it won`t really feel all that much warmer. For
the most part, the forecast area should remain dry through the
short term - with precipitation mainly north and west of the
forecast area. Slight chance for some mountain snow showers in
northern Baker and Valley counties both Thu and Fri afternoons as
weak waves pass by to the north in the increasing southwest flow
aloft.

.LONG TERM...Friday night through Wednesday...Models are finally
in good agreement showing an upper trough pushing into the Pac NW
and into Idaho Sunday morning. This should bring generally snow to
most locations except a mix of precip for the Treasure Valley.
This trough weakens as it slides through the forecast area Monday
morning. The next system rapidly moves toward the west coast but
amplifies the ridge out ahead of it and therefore keeping precip
west and north of the forecast area. This brings warm and breezy
conditions to all zones Tuesday.

Models begin to diverge Wednesday with the GFS/ECM indicating the
upper ridge sliding eastward allowing whats left of the upper
trough to slide into the region. The Canadian keeps the upper ridge
axis over the desert SW northward into Idaho which destroys the
trough as it pushes over the region. For now, chance pops looks good
for that period.
&&

.AVIATION...VFR, except IFR/LIFR in the vicinity of KMYL due to low
clouds and fog through sunrise. Surface winds variable 10kt or less.
Winds aloft near 10KFT MSL: NW 10-20kt shifting W to SW after
02/18z.
&&

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Wednesday Wednesday Night Thursday
Weather: Mostly sunny, with a high near 24. Calm wind. Partly cloudy, with a low around 11. Calm wind. A 20 percent chance of snow after noon. Mostly sunny, with a high near 28. Light south southeast wind.
Temperatures: 24 deg. F. 11 deg. F. 28 deg. F.
Wind direction: Calm Calm SE
Wind speed: 0 0 Light
Expected snowfall: 0 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Wednesday Wednesday Night Thursday
Weather: Mostly sunny, with a high near 21. South wind 5 to 7 mph. Mostly cloudy, with a low around 14. South wind around 8 mph. A 20 percent chance of snow after 11am. Mostly sunny, with a high near 23. South wind around 9 mph.
Temperatures: 21 deg. F. 14 deg. F. 23 deg. F.
Wind direction: S S S
Wind speed: 5-7 8 9
Expected snowfall: 0 in. 0 in. 0 in.
Disclaimer

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.  This advisory applies only to backcountry areas outside established ski area boundaries. and describes general avalanche conditions.  Local variations always occur. and should be expected. This advisory expires at midnight on the posted day unless otherwise noted