THIS AVALANCHE ADVISORY EXPIRED ON February 10, 2018 @ 5:54 am
Avalanche Advisory published on February 9, 2018 @ 5:54 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The risk of triggering an avalanche is generally Low throughout the PAC advisory area today. Warm temperatures and a lack of significant snow accumulations have allowed the snowpack to strengthen over the last two weeks. High elevation ridgelines and other features may still harbor scattered windslabs that are sensitive enough to trigger especially where they are resting on firm snow or crusts below. Use normal caution while traveling and good group management.  Remember, Low Hazard does not mean No Hazard.

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
    Large
    Small

Wind slabs have been our main problem for a good portion of the winter this year.  We have not seen or had reports of natural or human caused avalanches for several weeks in the PAC advisory area.  Warmer than normal temperatures and light precipitation over the last 2-3 weeks have allowed the snowpack, including the windslab problem to strengthen quite a bit.  We have been seeing winds over the last week gusting into the mid to upper 20 mph range but there is generally very little soft snow available for transport.  Yesterday we did see some plumes on the high peaks and ridges near South Bruin Mountain but with only a few inches of soft snow on last weekend's rain and melt freeze crust, we did not see significant building of new windslabs.   

Don't let your guard down though if you are skiing or riding in high consequence terrain though, plan for and anticipate the presence of thin windslabs especially on slopes facing the top half of the compass and including east facing aspects.  Any windslabs that are lingering are likely resting on a firm old snow surface below and if triggered will want to run fast.  Small, fast moving sluffing will also be a concern on very steep terrain.  Remember,  just because the hazard is Low doesn't mean that it is 100% safe.  Low hazard means that you may still find small avalanches in isolated areas or extreme terrain.

advisory discussion

The Friends of the Payette Avalanche Center is hosting a night of Bluegrass and gear raffles at the the McCall Golf Course on Februrary 23 at 7pm.  Cost at the door is $10 which includes a raffle ticket and admission for music. The proceeds of this event will help support the Payette Avalanche Center and the future of its programs in the McCall area.  

recent observations

We toured on sleds yesterday from Granite Mt through Twin Lakes and areas north to Duck Lake and the Fisher Saddle area.  The quality of the snow varies quite a bit by elevation with a breakable crust being the highlight.  Above 7400 feet the crust is less noticeable and there is 2-3 inches of new snow on the old firm snow below that made for good riding and sidehilling.  Below 7400 feet it is a mixed bag of somewhat supportable to supportable crusts that make for go anywhere sled conditions...just don't plan on sticking a sick sidehill on the way.    The snowpack has done a great job consolidating after the last round of warm precip last weekend and lacks any notable instabilities in the upper 3-4 feet.  We found a few buried crusts that failed in compression but lacked the ability to propagate across the  test blocks.  Wind transport was noticeable on the highest peaks yesterday afternoon but with only a few inches of fluff to move around, we did not see signs of significant loading or wind slab formation.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 23 deg. F.
Max. temperature in the last 24 hours: 31 deg. F.
Average wind direction during the last 24 hours: W
Average wind speed during the last 24 hours: 10 mph
Maximum wind gust in the last 24 hours: 22 mph
New snowfall in the last 24 hours: 2 inches
Total snow depth: 54 inches
weather

.SHORT TERM...Today through Saturday...Periods of a gusty wind
will continue as a cold front approaches the area. The cold front
will move through the area through early Saturday, resulting in
cooler temperatures both days. Moisture remains fairly limited
with this system, with showers remaining confined the the higher
elevations of the West Central Mountains of Idaho and into the
higher elevations of Baker County in Oregon on Friday. The front
will generally move south of the area by Saturday afternoon with a
building, dry northwesterly flow, though gusty to strong wind may
remain across portions of the Treasure Valley.

.LONG TERM...Saturday night through Thursday...No changes in the
extended as an upper ridge remains out near 140W. This upper ridge
keeps a north-northwest flow across the Pacific Northwest
allowing several systems to brush through the region through the
end of next week. The first system drops through the region Sunday
evening with a secondary disturbance dropping out of Canada and
into Eastern Oregon Monday morning. This system splits with a
portion forming a cutoff low across Nevada with another portions
exiting to the east. This complex system continues to be the best
chance of light snow across the forecast area. Yet another system
drops from the Bering Sea and into the region by Wednesday.

No big changes to the current extended forecast, only minor changes
to cool temperatures closer to normal through the weekend.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: A 20 percent chance of snow showers. Partly sunny, with a high near 37. West northwest wind 3 to 7 mph. Partly cloudy, with a low around 16. North wind around 6 mph Sunny, with a high near 32. North wind around 7 mph.
Temperatures: 37 deg. F. 16 deg. F. 32 deg. F.
Wind direction: WNW N N
Wind speed: 3-7 6 7
Expected snowfall: 0 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: A 30 percent chance of snow showers, mainly before 11am. Partly sunny, with a high near 23. Northwest wind around 9 mph. Total daytime snow accumulation of less than a half inch possible. A 20 percent chance of snow showers. Mostly cloudy, with a low around 8. Wind chill values between -5 and 4. North wind 8 to 11 mph Sunny, with a high near 22. Wind chill values between -8 and 2. North wind 9 to 13 mph
Temperatures: 23 deg. F. 8 deg. F. 22 deg. F.
Wind direction: NW N N
Wind speed: 9 8-11 9-13
Expected snowfall: Trace in. in. 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.