THIS AVALANCHE ADVISORY EXPIRED ON February 23, 2019 @ 7:05 am
Avalanche Advisory published on February 22, 2019 @ 7:05 am
Issued by Dave Bingaman - Payette Avalanche Center
bottom line

The Avalanche Hazard is Moderate today. Natural Avalanches are unlikely and human caused Avalanches are possible.  Wind slab hazard exists on upper elevation, wind loaded, and exposed slopes.  Sluffing in the light density new snow is the biggest concern today and will be more likely in steep, rocky areas as the sun warms the surface of the snowpack.  Another series of storms will bring significant snowfall beginning tonight and will likely increase the hazard through the weekend.

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
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Wind slabs are still on our radar. The most recent crop of wind slabs vary from 3-6 inches deep. Over the last couple days we have seen calmer winds and light snow that has covered up any of the usual signs that would indicate a wind slab. Cornices are big, and overhanging right now, and are a good indicator of wind loaded terrain. Travel cautiously in and around wind loaded avalanche terrain and corniced ridge lines

Avalanche Problem 2: Loose Dry
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

We saw a lot of loose/dry activity or sluffing occurring Wednesday and Thursday.  Some of these were able to run long distances in steep terrain. Sluffing or point releases generally occur naturally in the new snow as it is warmed by the sun.  If you are skiing or riding in steep terrain you will likely be able to trigger good sized sluffs today and as we add more light density snow through the next few days.  Sluffs can entrain a surprising amount of snow and complex or confined terrain will make these more dangerous.

advisory discussion

PAC will issue 3 Advisories per week through the remainder of the winter as long as funding is available.

Don't forget about the FPAC fundraiser this Saturday at Banyans on the Green (McCall Golf Course).  Great folks and tunes by Jon Costa.

recent observations

We toured a lot of steep terrain yesterday in the Fisher Creek area and found a lot of very stable snow and heroic snowmobile conditions. At a pit site on a north aspect near 8000 ft yesterday we found 335 cm of snow or 10.9 feet of snow!

 Sluffing was the biggest concern on very steep terrain and was occurring naturally on sun warmed slopes.  Today will be another mostly sunny day with great conditions. Tonight will be another story, a series of storms will enter the area and begin piling up significant snowfall over the next few days. Storm slabs will become a concern especially where they are lying on surface hoar or near surface facets that have formed over the last 3 nights.  

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 6 deg. F.
Max. temperature in the last 24 hours: 17 deg. F.
Average wind direction during the last 24 hours: NE
Average wind speed during the last 24 hours: 5 mph
Maximum wind gust in the last 24 hours: 13 mph
New snowfall in the last 24 hours: NA inches
Total snow depth: NA inches
weather

.SHORT TERM...Today through Sunday...A weak upper ridge will slide
in from the northwest and maintain dry weather today. An upper
trough in western Canada will move south into the Pacific
Northwest this weekend. It will also tap into Pacific moisture
which will take aim on southeast Oregon and southwest Idaho. Snow
will develop across the far north this evening and spread
southward overnight through Saturday morning. Snow totals through
the period are expected to be up to an inch in the valleys, with
several inches in the mountains - especially in the mountains of
Baker County and central Idaho. The flow aloft will transition
from a colder northwesterly flow to westerly flow by Sunday as the
upper trough digs offshore. This subtle change will allow for
snow levels to rise to around 3000 feet by Sunday afternoon,
resulting in a rain/snow mix for the lower valleys. The moist flow
will continue to take aim in the mountains of Baker County and
central Idaho where additional significant snow accumulations are
possible. Also, the winds are expected to increase Sunday
afternoon and the breezy conditions could lead to areas of blowing
and drifting snow in the higher elevations. A Winter Storm Watch
is in effect for mountains this weekend through early next week.
Temperatures will trend a few degrees warmer each day.

.LONG TERM...Sunday night through Friday...Models during the
extended period are all in decent agreement initially by
indicating the flow aloft starts to back more southwest. Models
also indicating a good moisture plume undercuts the upper ridge,
located over the Gulf of Alaska, and moves into the region. This
all in turn allows the snow levels to rise (along with surface
temperatures) above the valley floors across the Snake River Plain
region Monday and Tuesday. Models diverge by midweek in the
strength of the brief upper ridge that builds ahead of the main
low thats off the PacNW coast Wednesday. Potentially more
precipitation expected by the end of the week as another moist
system from just north of Hawaii pushes into the west coast.
Temperatures at or above normal through the week with Monday
bringing potentially the warmest day.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Friday Friday Night Saturday
Weather: Partly sunny, with a high near 21. Calm wind becoming southwest around 5 mph in the afternoon. Snow likely, mainly after 11pm. Cloudy, with a low around 15. South wind 3 to 5 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible. Snow likely, mainly after 11am. Mostly cloudy, with a high near 25. Southwest wind 3 to 6 mph. Chance of precipitation is 60%. New snow accumulation of less than one inch possible.
Temperatures: 21 deg. F. 15 deg. F. 25 deg. F.
Wind direction: SW S SW
Wind speed: 5 3-5 3-6
Expected snowfall: 0 in. 1-3 in. 1 in.
Granite Mountain at 7700 feet.
  Friday Friday Night Saturday
Weather: Partly sunny, with a high near 12. Wind chill values between -5 and 1. Light and variable wind becoming south southwest 5 to 8 mph in the morning. Snow, mainly after 11pm. Low around 8. Wind chill values between -5 and zero. South southwest wind around 9 mph. Chance of precipitation is 80%. New snow accumulation of 3 to 7 inches possible. Snow likely. Mostly cloudy, with a high near 15. Wind chill values between -1 and 4. South southwest wind 7 to 9 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 3 inches possible.
Temperatures: 12 deg. F. 8 deg. F. 15 deg. F.
Wind direction: SSW SW SW
Wind speed: 5-8 7-9
Expected snowfall: 0 in. 3-7 in. 1-3 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.