Avalanche Advisory published on January 16, 2019 @ 7:02 am
Issued by George Halcom - Payette Avalanche Center
bottom line

The Avalanche danger is Low today.  Thursday, the wind and snow will pick up from the South and begin to form new Wind Slabs and Cornice avalanche danger.  

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 ?
    Very Likely
  • Size ?
    Very Large

While the hazard is low Today, keep in mind that New wind Slabs will be growing, especially starting Thursday morning when the snow and Southern wind is forecasted to really pick up.

Older wind slabs are resting on a layer of Graupel that has lacked propagation recently in our tests and our Persistent Weak Layer of Basal Facets are still damp, and may take a bit more time to fully freeze.  


advisory discussion

Due to the partial government shutdown, avalanche forecasting will be limited.  We expect to forecast 3 times a week until the shutdown has ended.

Your observations are very helpful to the PAC staff and help create a better picture of the complex terrain in our advisory area.  You can click on the add observations linkand add as little or as much detail as you have.  It is easy to navigate and will also upload pictures easily.  Please contribute to your local forecast by sharing what you see or experience even if it is just good snow. or a trip report.

recent observations

Yesterday, near Trail Lake, we observed a fairly strong snow pack. Inverted temperatures did a good job of making our snow pack stronger and covered up some of the beautiful forest we are definitely getting above the anchors and have a pretty good base above 6,500'. Snowmobile and ski travel is "hero", or very predictable, putting people higher in the snow pack. Soft, good snow conditions are still out there to be had.

The basal facets are still damp, and the mid pack is dense. Buried surface hoar is still present in some areas, and has gained a lot more strength, but unfortunately we have just buried a major crop of surface hoar: Much of it has been destroyed by the wind, warm temps up high from the inversion, and the Sun, but there may be some places where the giant Doritos sized feathers will persist?  The warmer temperatures and the Sun have also created some crusts that we will be watching over the next couple of days to see how well the new snow bonds to them. 


CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 20 deg. F.
Max. temperature in the last 24 hours: 21 deg. F.
Average wind direction during the last 24 hours: SE
Average wind speed during the last 24 hours: 6 mph
Maximum wind gust in the last 24 hours: 21 mph
New snowfall in the last 24 hours: na inches
Total snow depth: na inches


Area Forecast Discussion
National Weather Service Boise ID
301 AM MST Wed Jan 16 2019

.SHORT TERM...Today through Friday...Patchy dense fog noted across
portions of the Lower Treasure Valley this morning. Fog will
continue through the early-mid morning hours before diminishing.
An unsettled pattern remains through the forecast period. The next
push of moisture will spread snowfall across the southern third of
the forecast area early this morning, with the system moving north
through the day. Activity is favored to impact the valleys with
periods of light snow through the morning commute. By the
afternoon, the system will have generally moved into the central
mountains, and temperatures will have risen. Warmer temperatures
are anticipated today, with many areas seeing values above normal.
This will also help snow levels to rise, with the valleys seeing
4000-5000 ft snow levels by Wednesday evening. Yet another push of
moisture will impact the area late Wednesday. Increased snow
levels across the area will leave snow confined to the mountains,
with rain anticipated across the valleys. Moisture will be
plentiful with this system, with mountain snowfall of 3 to 7
inches with locally higher amounts by Thursday evening. Periods of
gusty wind will also be possible through Thursday afternoon with
gusts to 25 mph across and south of portions of the Magic and
Upper Treasure Valleys, and across the southern portions of
Malheur and Harney counties in Oregon.

.LONG TERM...Friday night through Tuesday...Extended
models are in excellent agreement in showing as the next system
approaches the coast...the ridge ahead of it amplifies northward.
This puts the ridge axis around 120W (or the Id/Ore border region).
Therefore the best chance of precipitation gets pushed northward in
to the northern zones of Baker county and Idahos central mountains
Saturday. Snow levels rise to around 5000 ft in the north to 6000
feet along the Nd border.

The next system (currently at 35n180 as of this morning) is poised
to move into the forecast area Sunday is a little more worrisome.
The timing of the system is in good agreement, but the ECM is
hinting that it may show signs that it may want to split as it moves
into the Great Basin and mainly head south. Models are very moist
and are indicating that PWAT values maybe around the 90th
percentile. This gives the forecast area high chances of
precipitation and accumulating snow above about 5000 ft Sunday
through Monday. The upper ridge rebuilds along the coastline Tuesday
morning as the system quickly ejects to the east allowing drier
conditions to the region. Temperatures remaining slightly above
normal through the extended period.


.AVIATION...MVFR/LIFR conditions in fog across the lower mtn valleys
along with the lower Treasure Valley including KONO-KMAN through the
early morning hours. Otherwise, snow and mtns obscd begins to spread
northward bringing another round of IFR/LIFR aft 11z in the south
and 18z in the north thru 18z. Improving conditions mid afternoon
but more rain/snow spreading into KREO by 20z. Surface winds
southeast around 10 kts shifting s-ly 10-20 kts by 15z. Winds alft
nr 10kft s- ly to sw-ly 10 to 20 kts.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Wednesday Wednesday Night Thursday
Weather: Snow likely. Mostly cloudy, with a high near 32. Light and variable wind. Chance of precipitation is 60%. Total daytime snow accumulation of less than a half inch possible. Snow likely, mainly after midnight. Cloudy, with a low around 27. Southeast wind 3 to 5 mph. Chance of precipitation is 60%. New snow accumulation of less than a half inch possible. Rain and snow. High near 35. South wind around 5 mph. Chance of precipitation is 80%. New snow accumulation of less than one inch possible.
Temperatures: 32 deg. F. 27 deg. F. 35 deg. F.
Wind direction: Light SE S
Wind speed: Variable 3-5 5
Expected snowfall: less than one half in. Less than one half in. Less than one in.
Granite Mountain at 7700 feet.
  Wednesday Wednesday Night Thursday
Weather: Snow likely. Mostly cloudy, with a high near 24. South wind 8 to 11 mph. Chance of precipitation is 70%. Total daytime snow accumulation of less than one inch possible. Snow likely, mainly after 11pm. Cloudy, with a temperature rising to around 27 by 5am. South southeast wind 13 to 18 mph. Chance of precipitation is 70%. New snow accumulation of less than one inch possible. Snow. High near 28. Breezy, with a south wind 17 to 22 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible.
Temperatures: 24 deg. F. 27 deg. F. 28 deg. F.
Wind direction: S SSE S
Wind speed: 8-11 13-18 17-22
Expected snowfall: Less than one in. less than one in. 2-4 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.