THIS AVALANCHE ADVISORY EXPIRED ON February 11, 2018 @ 6:31 am
Avalanche Advisory published on February 10, 2018 @ 6:31 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 day time temperatures and light precipitation over the last 2-3 weeks have allowed the snowpack, including the windslab problem to strengthen quite a bit.  With cooler temperatures in store this week, this snowpack will continue to strengthen.

We have been seeing winds over the last few days gusting into the mid to upper 20 mph range but there is generally very little soft snow available for transport, so any new slabs that have formed are likely to be relatively thin.

Don't let your guard down though if you are skiing or riding in high consequence terrain, plan for and anticipate the presence of thin windslabs especially on northerly and 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 have seen a lot of country the last two days, in the Granite, Goose and Fisher Creek areas on Thursday and near Green Mountain and Rapid Creek yesterday.  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 our  test blocks.  Wind transport was noticeable on the highest peaks  again yesterday afternoon but with only a few inches of fluff to move around, we did not see signs of significant loading or new wind slab formation. A major cool down occurred as a cold front blew in yesterday afternoon which kept the snow pretty firm throughout the day except for in very low elevation areas.   See the crust picture below, notice the snowmobile ski penetration is very shallow.  This was on a south facing slope at 1:00 pm yesterday afternoon.   The next picture is of a northerly pit from Thursday with several crust layers visible that are slowly breaking down in an otherwise very stable snowpack. 

 

                                                               

 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 12 deg. F.
Max. temperature in the last 24 hours: 22 deg. F.
Average wind direction during the last 24 hours: NW
Average wind speed during the last 24 hours: 9 mph
Maximum wind gust in the last 24 hours: 19 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 62 inches
weather

.SHORT TERM...Today through Sunday...A weak upper trough and its
associated cold front will slowly pass through the region this
morning. Little is expected in the way of precipitation with this
passing system, except for isolated (and light) snow showers
south and east of Twin Falls and Jerome. The main impacts will be
cooler temperatures, down to a few degrees above normal, and
increased winds. The strongest winds will be along the Snake River
Plain, centered around Mountain Home. Winds are expected to peak
just after noon MST to near advisory levels, and become calm by
midnight. The next trough will approach the region from the
northwest Sunday, with increasing cloud coverage throughout the
day. Snow showers will begin as early as Sunday afternoon across
the mountains, north of a Baker City to McCall line. Temperatures
will remain just above normal through the weekend.

.LONG TERM...Sunday night through Friday...Upper trough digging
southward through the Intermountain Region will bring scattered snow
showers to our CWA Sunday night. Snow showers continuing Monday
in the southern Sawtooths, but clearing elsewhere from the north.
Dry northwesterly flow aloft Tuesday and Tuesday night, then
moistening Wednesday as a new trough carves out over Vancouver
Island. The trough will bring a chance of light snow to
northern mountains Wednesday while southern areas stay dry.
Tuesday will be the coldest day of the period with temperatures
slightly below normal, but not as cold as MOS products suggest.
The really cold air will stay east of the Continental Divide.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Saturday Saturday Night Sunday
Weather: Sunny, with a high near 32. North northwest wind around 8 mph. Mostly clear, with a low around 16. West northwest wind around 5 mph becoming calm in the evening. Increasing clouds, with a high near 33. South southeast wind around 6 mph.
Temperatures: 32 deg. F. 16 deg. F. 33 deg. F.
Wind direction: NNW NNW SE
Wind speed: 8 5 6
Expected snowfall: 0 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Saturday Saturday Night Sunday
Weather: Sunny, with a high near 20. Wind chill values between -9 and 1. North wind 9 to 15 mph. Mostly clear, with a low around 12. North northwest wind 5 to 7 mph becoming light and variable. A 20 percent chance of snow showers after 11am. Increasing clouds, with a high near 20. South wind around 11 mph
Temperatures: 20 deg. F. 12 deg. F. 20 deg. F.
Wind direction: N NNW S
Wind speed: 9-15 5-7 11
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 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.