THIS AVALANCHE ADVISORY EXPIRED ON February 3, 2018 @ 8:03 pm
Avalanche Advisory published on February 2, 2018 @ 8:03 pm
Issued by George Halcom - Payette Avalanche Center
bottom line

The Avalanche Hazard is Moderate today. Rain on snow is possible below 6,000 feet which increases the wet avalanche hazard. Freshly formed and lingering wind slabs exist in upper elevation exposed terrain. The upper 4 inches of the snowpack is not well bonded to the crust. Travelers should avoid areas with recent evidence of wind loading, and watch for wet avalanches and saturated steep slopes. 

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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Around 4 inches of new snow fell Thursday night. At upper elevations, winds have formed slabs that may have trouble bonding to the melt-freeze crust that formed just before the snow fell. Skiers and riders should look for signs of recent loading and should pay additional attention to lingering wind slabs that formed during last week's wind events. These slabs may be found in steep terrain near ridges or exposed areas, and may be large enough to injure and bury a person. 

 

Avalanche Problem 2: Loose Wet
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Rain on snow is possible below 6,000 feet today. Temperatures have been trending warmer which may weaken some of the layers in the snowpack. Keep off of steep slopes that are saturated. Rollerballs and pinwheels are going to be abundant, as will loose wet natural avalanches near rocks and slopes above 35 degrees.

advisory discussion

Area Forecast Discussion
National Weather Service Boise ID
316 AM MST Sat Feb 3 2018

.SHORT TERM...Today through Sunday...Persistent large scale
pattern will keep northwest flow over the region through the
weekend. The orographic flow will keep at least a slight chance of
showers in the east-central Oregon and west-central Idaho
mountains. Passing upper waves will enhance precipitation
development in these areas early today and again on Sunday. Snow
levels hold around 6k feet today, rising to around 7k feet on
Sunday, thus limiting accumulations to higher peaks. Liquid totals
will of 0.10-0.25 are possible across the central Idaho mountains
and higher terrain of Baker county on Sunday. Southeast Oregon
and the Snake Plain the NV border are dry and breezy today, with a
slight chance of showers Sunday over northern Malheur and the
lower Snake Plain. Temperatures remain well above normal through
Sunday with some near record highs forecast (especially across
southeast Oregon). Have issued a PNS detailing these sites.

.LONG TERM...Sunday night through Friday...Northwest flow aloft
dominates the long term forecast as the upper level ridge sits
offshore. A series of disturbances will push up and over the ridge
axis impacting northern areas, especially Baker county and the
central Idaho mountains. Friday evening the GFS has continued to
want to bring a trough down through our CWA bringing showers and
cooler temperatures to the area. The ECMWF holds off on this
feature keeping us in the northwest flow aloft. Added a chance of
showers to the forecast for the central Idaho mountains with this
possible feature on Friday. Temperatures will continue to be above
normal for much of the period except Friday and Saturday
depending on what comes of the upper level flow.

&&

.AVIATION...Mostly VFR. Showers push into the northern zones in and
around KBKE and KMYL after 11z staying mostly confined to the higher
elevations. Surface winds, light and variable in the Treasure
Valley, west-northwest 10-15kts elsewhere. Winds aloft to 10k feet
MSL, northwest 25-35kts.

Sunday Outlook...Northwesterly flow aloft will continue the threat
for MVFR showers across the West Central Mountains.

recent observations

Yesterday, we toured in the Boulder Lake area. The visibility was challenging as the fog left a mist on goggles and lower elevation snow surfaces. We found just over 6 feet of snow in our pit on Boulder near 8200 feet. The new 4 inches of snow that fell overnight showed poor bonding to the melt freeze crust that it is resting on.  

The past week provided a roller coaster of snowpack and avalanche conditions. Last weekend, heavy snowfall and winds created tender slabs that produced several avalanches and resulted in a partial burial. Warming temperatures stabilized many of the layers in the upper snowpack. Cold temperatures followed and left most of the zone with a melt/freeze crust at or just below the surface.

 

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 25 deg. F.
Max. temperature in the last 24 hours: 25 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 3 mph
Maximum wind gust in the last 24 hours: 20 mph
New snowfall in the last 24 hours: 3 inches
Total snow depth: 62 inches
Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: Rain and snow showers likely before 11am, then scattered rain showers. Patchy dense fog before 11am. Otherwise, mostly cloudy, with a high near 39. Calm wind becoming south southwest around 5 mph in the afternoon. Chance of precipitation is 60%. Little or no snow accumulation expected. Rain likely, mainly after 11pm. Cloudy, with a low around 35. Calm wind becoming southwest around 5 mph after midnight. Chance of precipitation is 60%. Rain likely. Cloudy, with a high near 40. South wind around 5 mph becoming calm in the morning. Chance of precipitation is 70%.
Temperatures: 39 deg. F. 35 deg. F. 40 deg. F.
Wind direction: South Southwest Southwest South
Wind speed: 5 mph 5 mph 5mph-Calm
Expected snowfall: 0 in. 0 in. 0 in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: Snow showers likely, mainly before 11am. Mostly cloudy, with a high near 31. West wind 7 to 14 mph. Chance of precipitation is 70%. New snow accumulation of less than a half inch possible. Snow likely, mainly after 11pm. Cloudy, with a low around 29. West wind 8 to 11 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible. Snow. High near 33. West wind 7 to 9 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible.
Temperatures: 31 deg. F. 29 deg. F. 33 deg. F.
Wind direction: West West West
Wind speed: 7-14 mph 8-11 mph 7-9 mph
Expected snowfall: Less than one half in. 1-3 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.