Avalanche Advisory published on February 18, 2019 @ 7:08:
This advisory is valid for 24 hours
Issued by George Halcom -
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How to read the advisory

The Avalanche Hazard is Considerable today. Natural Avalanches are possible and Human caused Avalanches are likely.  Strong winds and heavy snow have created wind slabs on upper elevation, exposed slopes that may be hidden under the latest snow.  The Sun may produce some loose wet Avalanches on solar aspects today.

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Natural avalanches possible; human-triggered avalanches likely. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.



Area Forecast Discussion
National Weather Service Boise ID
257 AM MST Mon Feb 18 2019

.SHORT TERM...Today through Wednesday...A slow-moving upper trough
will continue to support snow showers over the higher terrain of
southwest Idaho today, mainly along the ID/NV border where an
additional inch or two of new snow is expected this morning. A
Winter Weather Advisory is in effect this morning for southern
Twin Falls County and eastern Owyhee County where roads may be
slick and snow-covered. Northerly flow aloft will bring drier air
into southeast Oregon. The trough will move east tonight with a
dry northerly flow aloft across the entire area through Tuesday.
An upper trough in western Canada will spread snow into our area
Tuesday night and Wednesday as it moves into the northwestern U.S.
Snow accumulations are likely, with preliminary estimates of 1-3
inches in the valleys and 3-6 inches in the mountains.
Temperatures will continue around 10-15 degrees below normal.

.LONG TERM...Wednesday night through Monday...The low is centered
over eastern Oregon to begin the period with lingering snow
showers for all areas. Additional accumulations will be generally
less than an inch for lower valleys. Snow showers will start to
diminish by late Thursday night. A small break Friday as we sit in
between systems. The weekend system looks more and more
interesting with each new model run. Models have been in fairly
good agreement on placement for this system with long range models
showing some decent accumulations for all elevations through the
start of next week. Temperatures remain below normal for the
entire period.


MSL, southwest 30-40kts.

recent observations

Yesterday we toured the No Business and Granite Basin area. Deep, unconsolidated, punchy conditions were a challenge for our 600's. Visibility was intermittent and allowed us to see some of the ridge line just North of Council Mtn that has some sharp overhanging cornices on the NE aspect that had fresh debris from wind slabs that had ran naturally during the latest round of snow and wind. There is a lot of dry snow that came down yesterday without much wind. The new dry snow is now covering up some firm surfaces,wind slabs, and a generally punchier upside down layer that formed during Thursday's warm-up that laid down one of the 3 feet that we received in the last week. 

Avalanche Problem #1: Wind Slab

We have been seeing a lot of wind and snow for multiple storm cycles that have created wind slab problems that over the last  day or so have been getting covered up with the new snow under light wind influence. This will make wind slabs difficult to recognize. Shooting cracks or hollow, sculpted snow are warning signs of wind slabs.Travel cautiously in and around wind loaded avalanche terrain and corniced ridge lines.  



Avalanche Problem #2: Loose Wet

A lot of wind and snow has glued up some of our mountains that will get a good dose of solar effect over the next day or so we hope? Without having seen much Sun, like us lately, the mountains are gonna fry, and likely shed some snow in the form of wet-loose rollerballs and point releases. Steep South and South-West slopes will be most prone to avalanches, especially in the afternoon. 

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, Goose Lake 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. 

CURRENT CONDITIONS  Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 7 deg. F.
Max. temperature in the last 24 hours: 26 deg. F.
Average wind direction during the last 24 hours: NW
Average wind speed during the last 24 hours: NA mph
Maximum wind gust in the last 24 hours: NA mph
New snowfall in the last 24 hours: inches
Total snow depth: NA inches
Two-Day Mountain Weather Forecast  Produced in partnership with the Reno NWS
For 7000-8000 ft.
  Monday Monday Night Tuesday
Weather: Isolated snow showers before 11am. Partly sunny, with a high near 23. North northwest wind 5 to 7 mph. Chance of precipitation is 20%. Mostly clear, with a low around -1. North northwest wind 5 to 7 mph becoming light and variable in the evening. Increasing clouds, with a high near 20. Light and variable wind.
Temperatures: 23 deg. F. -1 deg. F. 20 deg. F.
Wind direction: NNW NNW Variable
Wind speed: 5-7 5-7 becoming Light Light
Expected snowfall: 0 in. 0 in. 0 in.
For 8000-9000 ft.
  Monday Monday Night Tuesday
Weather: Isolated snow showers. Partly sunny, with a high near 13. Wind chill values between -1 and -8. North wind around 9 mph. Chance of precipitation is 20%. Partly cloudy, with a low around -1. Wind chill values between -6 and -11. North northeast wind 7 to 9 mph. Increasing clouds, with a high near 12. Wind chill values between -1 and -11. North northeast wind 5 to 7 mph becoming west southwest in the afternoon.
Temperatures: 13 deg. F. -1 deg. F. 12 deg. F.
Wind direction: N NNE NNE becoming West
Wind speed: 9 7-9 5-7
Expected snowfall: 0 in. 0 in. 0 in.

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.