THIS AVALANCHE ADVISORY EXPIRED ON February 2, 2019 @ 6:36 am
Avalanche Advisory published on February 1, 2019 @ 6:36 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The Avalanche Hazard is Low.  Shallow wind slabs are possible near ridge tops and on exposed terrain.  Low hazard does not mean NO hazard.  Be smart, use safe travel protocols including 1 at a time on steep terrain and be aware of changes in the snow pack throughout the day on different aspects.  Watch for changing conditions over the next 72 hours as a series of storms move through the area.

How to read the advisory


  • Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
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Wind Slabs have stabilized for the most part, but should still be considered, especially if you are skiing or riding in steep, confined or consequential terrain where a small slab could push you into or over downhill hazards. 

Pay attention to wind stiffened snow near the ridge tops on the northern exposures today or places that show obvious wind effect in the form of ripples or small pillows. In addition, other steep slopes may produce small loose avalanches or sluffs.  As you move into shaded, sun protected, steeper terrain, keep in mind that you are likely to see dry snow moving with you.  Even small sluffs can steer you where you don't want to go especially in tight, confined terrain. 

Just because the snow pack is strengthening does not mean you should let your guard down, be smart, use safe travel protocols including 1 at a time on steep terrain and be aware of changes in the snow pack throughout the day on different aspects.

Many different  snow surfaces exist right now and a series of storms will begin to change the stability of the snowpack in the next few days.  As the new snow piles up pay attention to how the new snow is bonding to the old snow below.

advisory discussion

PAC will issue 3 Advisories per week through the remainder of the winter as long as funding is available.

Please be aware that there are areas that are CLOSED to motorized traffic in the McCall  and greater West Mountains area.  Just because there are tracks in some areas, does not mean they are open.  Please respect all users and closures.  See the Payette Winter Travel Maps for clarification.  Both the East and West maps can be downloaded on the Avenza app on your phone or are available at trailheads and local shops.   IT IS YOUR RESPONSIBILITY TO KNOW WHERE YOU ARE AND WHERE THESE CLOSURES EXIST.  

recent observations

We have had a great run of the high pressure, go anywhere conditions recently and the snowpack has done a great job stabilizing itself during this run.  Changes are on the horizon though, expect to see 12+ inches of new snow by Sunday afternoon. in the upper elevations.  

Storms are lining up for another blast of fresh snow and will affect the avalanche hazard through next week.   The most important factor is going to be how the new snow bonds to the variety of old snow surfaces below.  Yesterday we found very stiff, sculpted wind affected snow on most upper elevation Northerly slopes in the French and Little French Creek Headwaters.  Slopes that were tilted toward the sun had a variety of solar crusts that were very slick in some places.  As the new snow piles up, expect Storm Slab instabilities to be widespread and retune your avalanche receptors accordingly.

Wind affected NE aspect:

Slick solar crust on SE aspect 

 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 28 deg. F.
Max. temperature in the last 24 hours: 34 deg. F.
Average wind direction during the last 24 hours: SE
Average wind speed during the last 24 hours: 5 mph
Maximum wind gust in the last 24 hours: 19 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 66 inches
weather

SHORT TERM...Today through Monday Night...Approaching trough from
the Pacific will slow and split today, with the southern pieces
deepening into an upper low off the California coast by Saturday
morning. Expect some precipitation over the area tonight as the
weakening northern part of the trough moves in, but models have
trended a bit further south with the California low, so have
backed off slightly on precip amounts for tonight through
Saturday. The low lifts northeast across the area Saturday night
and early Sunday and this looks like the best period for
precipitation across much of the area. Snow levels are quite high,
around 5000-6000 ft, and models have trended even slightly higher
over the past day, so think that any snow impacts for this period
will be only at the highest mountain passes. A second upper low
then develops off the Washington coast later Sunday into early
Monday. This trough is trending deeper, and slower, in latest
model runs. This keeps the forecast area in broad, moist, west to
southwest flow Sunday into early Monday. Airmass during this
period is a little cooler, since it is behind the first low, with
snow levels starting out around 4500 feet, and slowly dropping to
3500 feet by Monday afternoon. Expect some snow impacts in the
populated mountain valleys during this time period, but might be a
bit limited since the trough off the coast is deepening and
slowing during this time. Finally, Monday night, the trough starts
to move inland, and pushes a cold front through the area, which
should bring snow to almost all valley floors. This could be the
most impactful period, but since it is still quite a ways out in
time, could easily see the track of the low shift a bit further
south, which would limit the amount of valley snowfall. Will hold
off on any winter storm watches for now - but the period Sunday
night through Monday should be watched closely for the mountains,
and the Monday night period watched closely for both the mountains
and the valleys.

.LONG TERM...Tuesday through Friday...Colder. An upper level trough
centered over the west coast on Tuesday will move inland on
Wednesday, bringing scattered snow showers mainly over the
mountains. As the trough exits to the east Wednesday night, showers
will decrease to isolated. Models show a second trough approaching
from British Columbia on Thursday and arriving over the northwest
states on Friday, with more snow showers, mainly over the mountains.
Temperatures will average 5 to 10 degrees below normal.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: Increasing clouds, with a high near 36. South southeast wind 3 to 5 mph. Rain and snow, mainly after 11pm. Low around 27. South wind 3 to 5 mph. Chance of precipitation is 80%. New snow accumulation of less than a half inch possible. Rain and snow. High near 36. South wind 3 to 5 mph. Chance of precipitation is 80%. New snow accumulation of less than a half inch possible.
Temperatures: 36 deg. F. 27 deg. F. 36 deg. F.
Wind direction: SSE S S
Wind speed: 3-5 3-5 3-5
Expected snowfall: 0 in. Trace in. Trace in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: A 20 percent chance of snow after 11am. Increasing clouds, with a high near 32. South wind 10 to 13 mph, with gusts as high as 22 mph. Snow. Low around 28. South wind 11 to 14 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible. Snow. High near 31. South wind 10 to 13 mph, with gusts as high as 23 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible.
Temperatures: 32 deg. F. 28 deg. F. 31 deg. F.
Wind direction: S S S
Wind speed: 10-13, Gusts to 22 11-14 10-13, Gusts to 23
Expected snowfall: 0 in. 2-4 in. 2-4 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 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.