THIS AVALANCHE ADVISORY EXPIRED ON February 29, 2016 @ 7:19 am
Avalanche Advisory published on February 28, 2016 @ 7:19 am
Issued by Dave Bingaman - Payette Avalanche Center
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The avalanche danger is MODERATE  above 6,000 feet today. Rain up to 7,000 feet yesterday, and above normal temperatures again today give us the possibility of loose/wet avalanches and cornice failures. S/SW and W winds gusting over 40 MPH today will add new wind slabs on leeward terrain. Older wind slabs still remain on some E,N and W facing slopes. Terrain below 6, 000 feet will have LOW danger today. 

How to read the advisory


  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
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Temperatures in the upper elevations have been above or close to freezing for most of the last 24 hours and rain fell all the way up to 7,000 feet yesterday.  Last night temperatures just barely slipped below freezing at our local Snotel sites. The high today is expected to be near 40 in the mountains so as the temperatures warm today expect to see more activity as the snow surface begins to soften and destabilize. Wet, loose activity in the form of rollerballs and point releases are possible, and so are human triggered wet, loose slides in terrain steeper than 35 degrees. The snow surface will begin to stabilize and refreeze as temperatures cool down this evening and through tomorrow.

 

Avalanche Problem 2: Wind Slab
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Wind slabs have been a concern all week even as the storm snow and older instabilities have stabilized.  High winds last weekend and again over the last 24 hours have created some stiff but shallow wind slabs throughout our leeward terrain. Watch for signs of sculpting on the snow surface, hollow or drummy feel, or stiffer snow. South and Southwest winds will be steady in the mid 20 MPH range through the day today with gusts in the mid 40's.  Winds are expected to shift to the West tonight with gusts close to 40. The good news is that the new wind slabs won't have get too deep as their just isn't that much loose snow available for transport on the windward sides.  Look for crossloading and micro terrain feature loading lower down on the Northerly aspects or anywhere that still has soft snow.  Keep your eyes on heavily corniced areas today as well as we have been seeing some big pieces failing through the week with the warming temperatures.

The East/Northeast face of Bruin Mt. shows some of the crossloading and Mid elevation micro loading that we saw last week.

recent observations

Yesterday was a high humidity, foggy and unfortunately soggy day in the mountains. Rain fell close to 7000 feet.  Winds are going to have a big impact on the snow right now with solid windboard on windward aspects and a fresh crop of new windslabs on the leeward aspects. Based on the limited amount of snow available for transport, new windslabs should be pretty thin today. Some soft snow still remains on the Northerly aspects for those willing to look for it. Large cornices continue to fail and have triggered some decent sized wind slab avalanches in leeward terrain.

Big cornices in the  Mac Han Lake basin. We observed a natural avalanche below this ridge where a chunk of cornice fell into old windslab last week.

weather

Expect fog in the valleys today with increasing clouds  later this morning and a 40% chance of snow showers in the upper elevations. Little to no accumulation is expected. Temperatures are expected to remain 10 degrees above normal today but will drop to near normal tomorrow. Winds are going to be the story today with S/SW winds in the 20-30 range with gusts near 44 MPH forecasted.  Winds will remain strong tonight and shift to the West.  Overnight temperatures will drop well below freezing and remain near normal tomorrow.  

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Sunday Sunday Night Monday
Weather: A 40 percent chance of showers after 11am. Patchy fog before 11am. Otherwise, cloudy, with a high near 43. South southwest wind 6 to 11 mph. Rain showers likely before 11pm, then a chance of rain and snow showers. Mostly cloudy, with a low around 22. West southwest wind 7 to 9 mph. Chance of precipitation is 70%. New snow accumulation of less than a half inch possible. A 20 percent chance of snow showers before 11am. Partly sunny, with a high near 37. West southwest wind around 7 mph.
Temperatures: 43 deg. F. 22 deg. F. 37 deg. F.
Wind direction: S/SW W/SW W/SW
Wind speed: 6-11 7-9 7
Expected snowfall: 0 in. Trace in. 0 in.
Granite Mountain at 7700 feet.
  Sunday Sunday Night Monday
Weather: A 40 percent chance of snow showers after 11am. Cloudy, with a high near 40. Windy, with a south southwest wind 22 to 31 mph, with gusts as high as 44 mph. Total daytime snow accumulation of less than a half inch possible. Snow showers, mainly before 11pm. Low around 18. Breezy, with a west wind 23 to 28 mph decreasing to 16 to 21 mph after midnight. Winds could gust as high as 39 mph. Chance of precipitation is 80%. New snow accumulation of less than one inch possible. A 20 percent chance of snow showers before 11am. Partly sunny, with a high near 33. West wind 8 to 15 mph.
Temperatures: 40 deg. F. 18 deg. F. 33 deg. F.
Wind direction: S/SW W W
Wind speed: 22-31, gusting to 44. 16-21, gusting to 39 8-15
Expected snowfall: Trace in. Trace 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.