THIS AVALANCHE ADVISORY EXPIRED ON February 26, 2019 @ 6:16 am
Avalanche Advisory published on February 25, 2019 @ 6:16 am
Issued by George Halcom - Payette Avalanche Center
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The Avalanche Hazard is Considerable. Natural Avalanches are Possible and Human Triggered Avalanches are likely. Warmer and heavier snow is sitting on top of older loose snow. Strong South winds have created Wind slab hazard on wind loaded, and exposed slopes.  Storm slabs are likely in sheltered areas.  Travel cautiously in Avalanche terrain, and avoid wind loaded slopes.

How to read the advisory


  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
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Wind slabs have formed and some have failed from the continuous wind and snow.  Warming temperatures and more snow and wind today will add stress to the heavier wind slabs that are hanging on. New slabs will form this evening under Gusty winds upwards of 20 MPH. Wind loaded terrain should be approached with cation if not completely avoided Today!

Avalanche Problem 2: Storm Slab
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The warmer denser snow has created Storm Slabs. Storm slabs are going to be hanging in areas protected from the wind. The slabs are much heavier, and denser than the snow below them and are going to take some time to bond. Steep sheltered rollovers should be avoided.

 

Avalanche Problem 3: Cornice
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The size of some of the cornices lately has been impressive. The warmer temperatures and more snow load will increase the likely hood of Cornice growth and failure today, and especially this evening as the winds pick up.

Stay far away from cornices as they may be sensitive, and may be very hard to distinguish exactly where they start and the Earth ends?

advisory discussion

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

We had a great turnout at the FPAC fundraiser this Saturday at Banyans on the Green (McCall Golf Course).  Great folks and tunes by Jon Costa. Thanks to everyone that came and supported the Friends of the Payette Avalanche Center.

 

recent observations

Yesterday, in the Granite Mountain/ Twin Lakes area we got to see the effects of the latest winter storm. Our weatherstaion on Granite has about 11 feet of snow, and may get buried this winter? Crown lines from avalanches that failed naturally during the latest storm were present on most NE and East (leeward) slopes above 35 degrees, and ranged from 2-4 feet in depth. So much weight created a glide crack near the Goose Lake Road visible in the last photo above...Check out the observations page for other similar avalanche observations that were submitted. Our warmer storm made a dense, "upside down" layer on top that has some lighter snow on it now. This denser snow was not able to grab onto the blower snow below it, and a brief cooldown after extensive loading likely made the slabs brittle and fail.  We were still able to find great riding conditions with deep, unconsolidated, good soft snow that produced face shots in protected areas that still had a bit more density to it than one would order up.

CURRENT CONDITIONS Today's Weather Observations From the Granite Weather Station at 7700 ft.:
0600 temperature: 28 deg. F.
Max. temperature in the last 24 hours: 28 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 8 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
weather

 

 

Area Forecast Discussion
National Weather Service Boise ID
347 AM MST Wed Feb 27 2019

.SHORT TERM...Today through Friday...A large upper level low off
the coast continues to help advect moisture into the region. As
of 3 am MST, this moisture was falling to the ground in the forms
of rain, freezing rain, snow, and ice pellets. Thankfully, the
freezing rain is falling on yesterday`s snow, and therefore is
not causing the types of problems we typically get with freezing
rain. Latest guidance indicates that warming is working its way
to the ground, and we expect most of the freezing rain to end by 6
am MST. This will occur thanks to a warm front that will push
through the entire CWA by midday. Snow levels will rise to near
6500 feet in the south, and 4000 feet in the far north, this
afternoon. The warm air will have a hard time scouring out the
last of the cold air in isolated or protected valleys, so those
will be the last places to change from freezing rain over to rain.
Precipitation will continue through the morning over most of the
area, and then push north and east into the Idaho mountains this
afternoon. Showers will still be possible this afternoon south and
west of a line from Burns, to Ontario, to Boise, to south of Twin
Falls. Tonight, another shortwave moves out of the main upper low
and passes over the area, bringing a new round of precip to most
of the area. This will push a cold front through the region, and
return snow levels to the lowest valleys. We will see a break in
precip Thu night as our upper flow becomes westerly. The main low
will begin to move onto the coast Friday, and we will see showers
mainly in the south.

We will continue the winter weather advisories for now, and
monitor for areas where freezing rain persists. We may have to
extend the advisories beyond 12Z in some areas.

.LONG TERM...Friday night through Tuesday...Finally some fairly
quiet weather expected during the first part of the extended
forecast. Models indicating that the upper low that is now forming
out north of Hawaii begins to lift to the east-northeast and into
the Northern Ca border area by Saturday morning and across
northern Nevada through the reminder of the weekend. Elsewhere,
the omega block that has resided over the Gulf of Alaska the last
several days slides to the east. This brings more nw-ly flow
aloft into the PacNW keeping the moisture associated with this low
generally south of the region. Have limited pops in the forecast
for the end of the weekend and first part of next week. Models
keeping dry weather into the first part of next week, before yet
another upper low from near Hawaii ejects to the NE and moves
inland across most of the west coast Wednesday. Temperatures are
expected to remain at or slightly below normal for the extended
period.

&&

.AVIATION...MVFR/IFR conditions with snow in the higher terrain
and mixed rain and freezing rain across the lower terrain. VFR
conditions across the KJER/KTWF expected through the afternoon.
Conditions expected to improve through the day. Surface wind east
through south 5 to 15 kts except 15 to 25 kts across eastern
Oregon. Winds near 10KFT southwest 15 to 30 kts through the
forecast period.

Two-Day Mountain Weather Forecast Produced in partnership with the NOAA-NWS
McCall Airport at 5021 feet.
  Monday Monday Night Tuesday
Weather: Snow before 11am, then rain and snow. High near 35. South wind around 6 mph. Chance of precipitation is 100%. Total daytime snow accumulation of around an inch possible. Rain and snow, mainly after 11pm. Low around 30. South wind around 6 mph. Chance of precipitation is 80%. New snow accumulation of less than a half inch possible. Snow, mainly before 11am. Temperature falling to around 25 by 5pm. West wind around 6 mph. Chance of precipitation is 80%. New snow accumulation of around an inch possible.
Temperatures: 35 deg. F. 30 deg. F. 25 deg. F.
Wind direction: S S W
Wind speed: 6 6 6
Expected snowfall: 1 in. Less than one half in. 1 in.
Granite Mountain at 7700 feet.
  Monday Monday Night Tuesday
Weather: Snow. High near 26. South southwest wind 11 to 13 mph, with gusts as high as 22 mph. Chance of precipitation is 100%. Total daytime snow accumulation of 3 to 7 inches possible. Snow. Steady temperature around 25. South wind 11 to 13 mph, with gusts as high as 22 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible. Snow. Temperature falling to around 15 by 4pm. West southwest wind 8 to 11 mph, with gusts as high as 22 mph. Chance of precipitation is 90%. New snow accumulation of 2 to 4 inches possible..
Temperatures: 24 deg. F. 14 deg. F. 15 deg. F.
Wind direction: S SW SW
Wind speed: 11-13 Gusts 22 MPH 11-13 Gusts 22 MPH 8-11 Gusts to 22 MPH
Expected snowfall: 3-7 in. 2-4 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.