Category Archives: Weather Reports

Winter Storm Watch Feb 23, 11pm to Feb 24, 11pm

Yellow Pine Forecast

Winter Storm Watch

URGENT - WINTER WEATHER MESSAGE
National Weather Service Boise ID
311 AM MST Fri Feb 23 2018

...WINTER STORM MOVING INTO THE AREA FRIDAY NIGHT AND DEPARTING
SATURDAY EVENING...

.Another winter storm will move into the area from the northwest
Friday night, spreading snow initially to the mountains of Baker
County, the West Central Mountains, and the Owyhees. Saturday
morning, snow will rapidly spread south and east into the Boise
Mountains, all of Owyhee County, the northern portion of the
Upper Treasure Valley, the western Magic Valley, the Camas
Prairie, and southern Twin Falls County. Saturday evening, the
storm will end with snow in eastern Owyhee and southern Twin
Falls counties. Snowfall amounts of 1 to 3 inches in lower
elevations, 4 to 6 inches in mountain-valleys, and 8 to 12 inches
above 6000 feet are possible. In addition, northwest winds
averaging 10 to 20 mph Saturday will result in significant
reductions in visibility and potential blowing snow.

West Central Mountains-Boise Mountains-Upper Treasure Valley-
Southwest Highlands-Western Magic Valley-Camas Prairie-
Owyhee Mountains-Southern Twin Falls County-Upper Weiser River-
Baker County-
311 AM MST Fri Feb 23 2018 /211 AM PST Fri Feb 23 2018/

...WINTER STORM WATCH IN EFFECT FROM THIS EVENING THROUGH
SATURDAY EVENING...

* WHAT...Moderate snow likely. Blowing snow likely. Heavy snow
  possible. Plan on difficult travel conditions. Total snow
  accumulations of 1 to 3 inches below 3000 feet, 3 to 6 inches
  between 3000 and 6000 feet (including major mountain-valleys
  such as Long Valley), and 8 to 12 inches above 6000 feet, are
  possible.

* WHERE...Portions of northeast Oregon and south central,
  southwest and west central Idaho.

* WHEN...From this evening through Saturday evening.

* ADDITIONAL DETAILS...Significant reductions in visibility are
  possible.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Storm Watch means there is potential for significant
snow, sleet or ice accumulations that may impact travel. Continue
to monitor the latest forecasts.

 

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Avalanche Advisory Feb 18, 2018

Bottom Line

Strong winds and a combination of denser snow on top of light density snow has created Considerable wind slab avalanche hazard in lee terrain, and terrain exposed to the swirling mountain winds. Moderate to high W/SW winds hammered the upper elevations over the last 2 days forming sensitive wind slabs on leeward slopes. Slopes protected from the wind will be prone to storm slab avalanches. Steep, especially wind protected terrain may also be prone to loose sluffing.

Avalanche Problem 1: Wind Slab

Wind slabs are going to be the major concern today in the upper elevations.

West and Southwest winds hit the West Central Mountains over the last 2 days, and had plenty of light density snow to transport. Yesterday the wind slabs North of 8302 were sensitive to the weight of a skier, and were getting more consolidated and will likely be brittle and able to transmit energy given the warm cold temperature regime that they have seen over the last 24 hours. We were able to trigger a slab about a foot plus deep on an East facing ridge around 7500 feet. We also had cracking developing in the upper 15cm of snow that was denser.

Friday on the high ridges near Diamond Rock we observed cornices growing and becoming very sensitive to the weight of a skier. We also observed wind slabs growing in thickness and density through the day with gusts in the 25-30 mph range.

This problem should be mostly confined to North and East facing slopes BUT given smaller terrain features and undulations, you should expect wind slabs on any terrain with a North or East facing tilt, including gullies, small bowls and other natural catcher mitt features. These slabs are resting on a slick crust in some areas and will propagate and move quickly if triggered. As winds pick up later in the day, expect the wind slab hazard to rise as well.

Avalanche Problem 2: Loose Dry

On slopes over 35 degrees, that were protected from the last 2 days of winds, Loose/Dry avalanches or Sluffs are possible. Sluffs are an indicator of great ski and riding conditions but can also push you around especially in treed, or confined terrain. Below all of the new snow is a stout and in some areas slick crust which the new snow is not bonding to. Be extra careful if your line involves terrain traps such as benches or gullies where a little bit of moving snow can pile up quickly.

Avoid traveling above your companions in steep terrain and keep your group corralled today; good travel practices, group and slope management as well as keeping eyes on all members of your group in steep terrain should be priorities.

Avalanche Problem 3: Storm Slab

The surface of the snow yesterday had grown denser than the snow below: a foot of light density, cold snow already on the crust and old snow layers below, the addition over the next 24 hours of another 8-16 inches of warmer higher density snow will help form a storm slab in the new snow. Rising temperatures created a layer of more dense snow and will be resting on the low density snow below which will make storm slab avalanches of between 1 and 2 feet more possible today.

Advisory Discussion

Don’t forget about the FPAC fundraiser at the McCall Golf Course next Friday 2/23 at 7pm. Admission includes raffle ticket with over $1000 worth of cool stuff, music by local bluegrass band Jughandle Parade and a short state of the snowpack address by the PAC staff.

Our website just went through a routine update and our email server is currently offline. No advisory emails will be sent out today or tomorrow. We are sorry for the inconvienience. The problem should be resolved by early next week.

Recent Observations

Yesterday we toured 8302 up the Lick Creek drainage and the wind slabs North of 8302 were sensitive to the weight of a skier, and were getting more consolidated and will likely be brittle and able to transmit energy given the warm cold temperature regime that they have seen over the last 24 hours. We were able to trigger a slab about a foot plus deep on an East facing ridge around 7500 feet. We also had cracking developing in the upper 15cm of snow that was denser.

https://payetteavalanche.org/tue-02132018-1900-wind-transport-upper-elevations

https://payetteavalanche.org/sat-02172018-1703-windloading-and-cracking-sargents

Weather

Area Forecast Discussion
National Weather Service Boise ID
243 AM MST Sun Feb 18 2018

.SHORT TERM…Today through Monday…Showers and wind gusts to 40
mph are accompanying a cold front, which is oriented west-east
just to the south of Boise. The front will continue to slowly
shift southward today. Showers will remain focused near the front
with snow levels falling to valley floors. Snow accumulations
near the ID/NV border warrant a Winter Weather Advisory for today.
Elsewhere, snow showers will accompany an upper trough as it
settles into the region. Bulk of the snow showers and accumulating
snows will be in the mountains. A Winter Weather Advisory remains
in effect for the West Central Mountains this morning. Another
cold front will cross the region from the north tonight and bring
modified arctic air to the region on Monday. Snow showers will
continue tonight through Monday, although additional snow
accumulations will be light and mainly in the mountains. Northwest
winds of 15 to 25 mph on Monday along with high temperatures only
in the 20s to lower 30s will create wind chills in the single
digits and teens.

.LONG TERM…Monday night through Saturday…Modified arctic air
will be with us Monday night through Tuesday night under strong
northerly flow aloft. Gusty northwest surface winds will produce
significant wind chill Monday night. Gradual moderation and less
windy thereafter but still colder than normal through Saturday.
Troughs in the northerly flow will bring a chance of snow to our
zones, especially Thursday and Saturday.

&&

.AVIATION…Cold front in south-central Idaho moving southeast
this morning. Areas of MVFR and mountain obscuration in showers
near the front and in the central Idaho mountains. Generally VFR
elsewhere. Snow level lowering to valley floors by 18Z with all
pcpn becoming snow. Surface winds west/northwest 15-25 kts, except
20-30 kts in southeast Oregon. Winds aloft at 10k ft MSL westerly
30-40 kts.

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.

source:
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Weather Reports Feb 11-17

Feb 11 Weather:

At 10am it was 19 degrees, cloudy and cold light breeze. At 150pm it was 33 degrees, overcast and light cold breeze. At 6pm it was 31 degrees and overcast. At 1030pm it was 27 degrees and snowing lightly. At 1am it was 24 degrees and clear.

NOAA Weather report:

Observation time February 12, 2018 at 10:00AM
Mostly clear
Max temperature 34 degrees F
Min temperature 13 degrees F
At observation 15 degrees F
Precipitation Trace
Snowfall Trace
Snow depth 7.5 inch
— — — — — — — — — — — —

Feb 12 Weather:

At 10am it was 15 degrees and almost clear. At 245pm it was 36 degrees, clear and stiff cold breeze. At 650pm it was 25 degrees, clear and light cold breeze. At 1020pm it was 20 degrees, clear and windy.

NOAA Weather report:

Observation time February 13, 2018 at 10:00AM
Clear
Max temperature 36 degrees F
Min temperature 6 degrees F
At observation 9 degrees F
Precipitation 0.00 inch
Snowfall 0.0 inch
Snow depth 7 inch (est)
— — — — — — — — — — — —

Feb 13 Weather:

At 10am it was 9 degrees and clear. At 2pm it was 39 degrees and mostly cloudy. Mostly clear by 4pm. At 6pm it was 30 degrees, slight breeze and almost clear. At 8pm mostly clear, thin high haze and gusty breezes. At 1030pm it was 26 degrees, looks clear and gusty cold breezes. At 930am it was cloudy gusty breezes and lightly snowing.

NOAA Weather report:

Observation time February 14, 2018 at 10:00AM
Cloudy, windy, light snow
Max temperature 45 degrees F
Min temperature 9 degrees F <– Yesterday morning
At observation 31 degrees F
Precipitation Trace
Snowfall Trace
Snow depth 7 inch
— — — — — — — — — — — —

Feb 14 Weather:

At 10am it was 31 degrees, overcast, windy and light snow falling (sideways.) At noon, low clouds ridges socked in, steady light snow and gusty swirling breezes. At 2pm it was 34 degrees, snowing and blowing lightly, low overcast. Still snowing steady at 4pm, trace accumulation. At 6pm it was snowing lightly, about 1/4″ accumulation. At 8pm it was much calmer, probably snowing very lightly. At 1030pm it was 28 degrees, very low clouds – foggy to valley floor, steady light snow, another 1/2″ new, gusty light breezes. Looks like it snowed all night. Flaking snow at 930am.

NOAA Weather report:

Observation time February 15, 2018 at 10:00AM
Mostly Cloudy
Max temperature 34 degrees F
Min temperature 16 degrees F
At observation 23 degrees F
Precipitation 0.12 inch
Snowfall 1.8 inch
Snow depth 9 inch
— — — — — — — — — — — —

Feb 15 Weather:

At 10am it was 23 degrees and mostly cloudy. Light snow 1040am for about 10 minutes. Flaking snow at 1145am for less than 5 minutes. At noon bigger cracks in the clouds, occasional flake of snow, roofs starting to drip. At 150pm it was 34 degrees, partly clear to partly cloudy, gusty variable breezes, snow melting and dripping off roofs. At 4pm mostly cloudy. At 6pm it was 27 degrees, mostly cloudy, light cold breeze. At 8pm a few fuzzy stars showing. At 11pm it was 19 degrees, overcast (no stars) and slight breeze. At 6am it was 20 degrees (not snowing.) Snowing and trace at 930am.

NOAA Weather report:

Observation time February 16, 2018 at 10:00AM
Overcast, steady snow
Max temperature 36 degrees F
Min temperature 19 degrees F
At observation 25 degrees F
Precipitation Trace
Snowfall Trace
Snow depth 9 inch
— — — — — — — — — — — —

Feb 16 Weather:

At 10am it was 25 degrees, overcast and steady snow falling. Stopped snowing shortly after 12pm, some melting and dripping off roofs, occasional flake of snow. At 2pm it was 31 degrees and overcast, light cold breeze. At 430pm cloudy and a bit breezy. At 530pm a few flakes of snow started falling (sideways.) At 620pm it was 29 degrees, overcast and a few flakes falling. At 8pm steady light snow (trace), low foggy clouds. At 1015pm it was 27 degrees, snowing lightly (about 1/2″.) Not snowing at 1am.

NOAA Weather report:

Observation time February 17, 2018 at 10:00AM
Overcast and Windy
Max temperature 34 degrees F <–this morning
Min temperature 24 degrees F
At observation 34 degrees F
Precipitation 0.03 inch
Snowfall 0.3 inch
Snow depth 9 inch
— — — — — — — — — — — —

Feb 17 Weather:

At 10am it was 34 degrees, overcast and quite windy. Snowed sideways pretty good for a couple hours, then lightly flaking at noon (trace.) At 130pm it was 34 degrees, breezy and just a few flakes falling. Probably quit snowing around 2pm. Windy and cloudy at 4pm. Light rain then rain/snow mix (and windy) started just after 450pm, for about 10 minutes. At 535pm it was 37 degrees, dark overcast, very windy and starting to sprinkle lightly. Snowing pretty good at 8pm, trace, 33 degrees. Not snowing at 1030pm and 33 degrees. Not snowing at 1am or 3am. Snowing at 930am.

NOAA Weather report:

Observation time February 18, 2018 at 10:00AM
Overcast and snowing
Max temperature 38 degrees F
Min temperature 23 degrees F
At observation 26 degrees F
Precipitation 0.40 inch
Snowfall 3/4 inch
Snow depth 9 inch
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Winter Weather Advisory Feb 17, 11am to Feb 18, 11am

Yellow Pine Forecast:

Winter Weather Advisory

URGENT - WINTER WEATHER MESSAGE
National Weather Service Boise ID
944 AM MST Sat Feb 17 2018

...Snow to Impact the Central Mountains of Idaho...

.A Pacific weather system will usher in the threat of snowfall for
the central mountains of Idaho through Sunday. Snow levels will
hover near 5000 feet early in the event, with wet snow impacting
valley areas initially. Overnight the snow level will drop
allowing for faster accumulation. Mountain areas above 6000 feet
will see a significant snow with this system.

West Central Mountains-
944 AM MST Sat Feb 17 2018

...WINTER WEATHER ADVISORY IN EFFECT UNTIL 11 AM MST SUNDAY...

* WHAT...Snow expected. Plan on slippery road conditions. Total
  snow accumulations of 3 to 6 inches, with amounts in excess of
  12 inches above 6000 feet.

* WHERE...Valley County, including McCall and Cascade.

* WHEN...Until 11 AM MST Sunday.

* ADDITIONAL DETAILS...Be prepared for reduced visibilities at
  times along with slippery roads.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Weather Advisory for snow means periods of snow will
cause primarily travel difficulties. Be prepared for snow covered
roads and limited visibilities, and use caution while driving.
The latest road conditions can be obtained by calling 5 1 1.

 

Avalanche Advisory Feb 11, 2018

Bottom Line

The risk of triggering an avalanche is generally Low throughout the PAC advisory area today. Warm temperatures and a lack of significant snow accumulations have allowed the snowpack to strengthen over the last two weeks. High elevation ridgelines and other features may still harbor scattered windslabs that are sensitive enough to trigger especially where they are resting on firm snow or crusts below. Use normal caution while traveling and good group management. Remember, Low Hazard does not mean No Hazard.

Avalanche Problem #1: Wind Slab

Wind slabs have been our main problem for a good portion of the winter this year. We have not seen or had reports of natural or human caused avalanches for several weeks in the PAC advisory area. Warmer than normal day time temperatures and light precipitation over the last 2-3 weeks have allowed the snowpack, including the windslab problem to strengthen quite a bit. With cooler temperatures in store this week, this snowpack will continue to strengthen.

We have been seeing winds over the last few days gusting into the mid to upper 20 mph range but there is generally very little soft snow available for transport, so any new slabs that have formed are likely to be relatively thin.

Don’t let your guard down though if you are skiing or riding in high consequence terrain, plan for and anticipate the presence of thin windslabs especially on northerly and east facing aspects. Any windslabs that are lingering are likely resting on a firm old snow surface below and if triggered will want to run fast. Small, fast moving sluffing will also be a concern on very steep terrain. Remember, just because the hazard is Low doesn’t mean that it is 100% safe. Low hazard means that you may still find small avalanches in isolated areas or extreme terrain.

Advisory Discussion

The Friends of the Payette Avalanche Center is hosting a night of Bluegrass and gear raffles at the the McCall Golf Course on Friday, Februrary 23 at 7pm. Cost at the door is $10 which includes a raffle ticket and admission for music. The proceeds of this event will help support the Payette Avalanche Center and the future of its programs in the McCall area.

Recent Observations

We toured a lot of country Thursday and Friday, in the Granite, Goose and Fisher Creek areas on Thursday and near Green Mountain and Rapid Creek Friday. The quality of the snow varies quite a bit by elevation with a breakable crust being the highlight. Above 7400 feet the crust is less noticeable and there is 2-3 inches of new snow on the old firm snow below that made for good riding and sidehilling. Below 7400 feet it is a mixed bag of somewhat supportable to supportable crusts that make for go anywhere sled conditions…just don’t plan on sticking a sick sidehill on the way. The snowpack has done a great job consolidating after the last round of warm precip last weekend and lacks any notable instabilities in the upper 3-4 feet. We found a few buried crusts that failed in compression but lacked the ability to propagate across our test blocks. Wind transport was noticeable on the highest peaks Frirday afternoon but with only a few inches of fluff to move around, we did not see signs of significant loading or new wind slab formation. A major cool down occurred as a cold front blew in Friday afternoon which kept the snow pretty firm throughout the day except for in very low elevation areas. See the crust picture below, notice the snowmobile ski penetration is very shallow. This was on a south facing slope at 1:00 pm Friday afternoon. The next picture is of a northerly pit from Thursday with several crust layers visible that are slowly breaking down in an otherwise very stable snowpack.

Weather

Area Forecast Discussion
National Weather Service Boise ID
316 AM MST Sun Feb 11 2018

.SHORT TERM…Today through Monday…A northwesterly flow aloft
will turn briefly west, and then southwest as a trough drops
south from the Gulf of Alaska and into the Pacific Northwest.
Light snow showers will begin across southeast Oregon as early as
this evening, and spread across the region tonight and into early
Monday morning as the trough continues its journey to the south
and east. A reinforcing shortwave circling through the trough will
continue light snow showers across east-central Oregon and west-
central Idaho mountains overnight. Snow showers will remain
across the Nevada border and north through the Magic Valley Monday
as the trough digs farther south and east into Utah. Snow levels
will reach valley floors overnight. However, snowfall totals will
be generally light through the period. Highest snowfall amounts
(2 to 4 inches) will occur across the higher elevations along the
Idaho-Nevada border where a deformation zone may set up; of
course, any adjustment to this boundary location will
significantly alter the forecast in these locations. Dry
conditions return to all areas by Monday evening. Breezy northwest
winds are expected Monday as the trough axis exits to the
southeast, especially along the I-84 corridor, Baker City through
Mountain Home. Temperatures will remain near normal through the
period.

.LONG TERM…Monday night through Saturday…Cold and dry Tuesday
with clear skies and light surface winds and northeast flow aloft.
Min temps Tuesday have been lowered several degrees. Not as cold
Tuesday night. Next upper trough from the north will bring a
chance of snow showers Wednesday (rain below 3000 feet) with a cold
front midday, followed by windy cooler weather Wednesday afternoon.
High temps Wednesday may occur in the morning. Thursday looks dry
with temps similar to Wednesday, although models disagree with ECMWF
noticeably colder than GFS. For now will go with a blend.

.AVIATION…VFR. Increasing clouds from west to east. Snow showers
developing over the mountains after 20Z with terrain obscuration
developing after 12/00Z. Light surface winds. Winds aloft at 10
kft MSL westerly 20 kts.

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.

source:
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Weather Reports Feb 4-10

Feb 4 Weather:

At 10am it was 36 degrees, overcast, light fog and light sprinkles. Not raining at 12pm. Starting to sprinkle around 145pm and 41 degrees. Sprinkling an occasional drop at 4pm. Very light sprinkles at 5pm. Steady light rain at 520pm and 37 degrees. Very light sprinkle at 545pm and 36 degrees. Raining pretty hard at 7pm, loud long clap of thunder at 708pm! Barely sprinkling at 725pm. At 11pm it was 33 degrees and clear, lots of stars. Little skiff of snow fell before sunrise.

NOAA Weather report:

Observation time February 05, 2018 at 10:00AM
Overcast, occasional flake of snow
Max temperature 45 degrees F
Min temperature 29 degrees F
At observation 33 degrees F
Precipitation 0.11 inch
Snowfall Trace
Snow depth 8 inch
— — — — — — — — — — — —

Feb 5 Weather:

At 10am it was 33 degrees, overcast and occasional flakes of snow falling. At 230pm it was 38 degrees and cloudy. Flaking snow 315pm until 4pm, no accumulation. At 5pm overcast. At 6pm it was 34 degrees and overcast. At 8pm dark and cloudy. At 10pm it was 32 degrees and cloudy – it had snowed a tiny skiff some time earlier. Snowed early morning before sunrise.

NOAA Weather report:

Observation time February 06, 2018 at 10:00AM
Overcast, lightly snowing
Max temperature 39 degrees F
Min temperature 30 degrees F
At observation 32 degrees F
Precipitation 0.04 inch
Snowfall 3/4 inch
Snow depth 9 inch
— — — — — — — — — — — —

Feb 6 Weather:

At 10am it was 32 degrees, overcast and light snowfall. Not snowing at 12pm. Brighter sunlight just before 1pm. At 2pm it was 41 degrees and mostly cloudy (cracks in the clouds, bit of blue, occasional sunshine.) At 6pm it was 37 degrees and partly clear. At 8pm mostly cloudy, a few stars. At 11pm it was 29 degrees and overcast, no stars visible. A few flakes of snow fell before sunrise.

NOAA Weather report:

Observation time February 07, 2018 at 10:00AM
Overcast, breezy
Max temperature 44 degrees F
Min temperature 28 degrees F
At observation 36 degrees F
Precipitation Trace
Snowfall Trace
Snow depth 8 inch
— — — — — — — — — — — —

Feb 7 Weather:

At 10am it was 36 degrees, overcast and breezy. At 2pm it was 41 degrees and overcast, slight breeze. At 4pm breaks in the clouds. At 6pm it was 36 degrees, high thin haze. At 830pm it was cloudy. At 11pm it was 31 degrees and cloudy (no stars.)

NOAA Weather report:

Observation time February 08, 2018 at 10:00AM
Dark clouds, light breeze
Max temperature 47 degrees F
Min temperature 30 degrees F
At observation 33 degrees F
Precipitation 0.00 inch
Snowfall 0.0 inch
Snow depth 8 inch
— — — — — — — — — — — —

Feb 8 Weather:

At 10am it was 33 degrees, dark clouds and light breeze. Light short sprinkle at 1015am. At 1230pm it was 44 degrees, cloudy and stronger breezes. At 2pm it was 43 degrees, cloudy and breezy. At 6pm it was 40 degrees, thinner clouds and breezy. At 1030pm it was 31 degrees and clear, lots of stars, milky way visible.

NOAA Weather report:

Observation time February 09, 2018 at 10:00AM
Cloudy
Max temperature 47 degrees F
Min temperature 27 degrees F
At observation 33 degrees F
Precipitation Trace
Snowfall Trace
Snow depth 8 inch
— — — — — — — — — — — —

Feb 9 Weather:

At 10am it was 33 degrees and cloudy. A few flakes of snow fell at 1030am. A few more flakes around 1120am. Breaks in the clouds at 12pm, scattered sunshine. At 2pm it was 41 degrees, partly clear, light breezes. Spit flakes of snow 330pm – 4pm and mostly cloudy. At 430pm breaks in the clouds. At 6pm it was 33 degrees and partly cloudy. At 1050pm it was 26 degrees, clear and a stiff cold breeze. A scant skiff of snow (graupel) fell sometime early morning.

NOAA Weather report:

Observation time February 10, 2018 at 10:00AM
Partly clear
Max temperature 44 degrees F
Min temperature 18 degrees F
At observation 24 degrees F
Precipitation Trace
Snowfall Trace
Snow depth 7.5 inch
— — — — — — — — — — — —

Feb 10 Weather:

At 10am it was 24 degrees and partly clear. A few snowflakes drifting down at 1105am, lasted a few minutes. At noon it was partly cloudy and breezy. At 145pm it was 35 degrees and clear, light cold breeze. Sunny at 4pm. At 620pm it was 26 degrees and clear. At 1045pm it was 19 degrees, clear and flag flapping breezy.

NOAA Weather report:

Observation time February 11, 2018 at 10:00AM
Cloudy, cold light breeze
Max temperature 38 degrees F
Min temperature 13 degrees F
At observation 19 degrees F
Precipitation Trace
Snowfall Trace
Snow depth 7.5 inch
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Avalanche Advisory Feb 4, 2018

Bottom Line

The Avalanche Hazard is Moderate today. Lower elevation slopes are saturated and with a rain line near 7000 feet today, expect an increase in loose/wet avalanches. Wind slabs are the primary concern on upper elevation, exposed slopes that have been affected by SW, W and NW winds. Avoid traveling on steeper slopes with stiff or hollow feeling snow, watch for obvious texture changes and wind deposited snow. Cornices are starting to grow and will become less stable as temperatures warm.

Avalanche Problem #1: Wind Slab

Wind slabs have formed over the last week on several aspects. Winds have been consistent enough to create slabs of varying thickness on exposed upper elevation terrain. Some of these slabs may be resting on crusts or weaker layers of snow below them. Temperatures in the mid 30’s and rain to near 7000 feet today will make these slabs more touchy and more dense today and until we see a cooling of the snowpack. Pay attention to changing snow conditions as you approach exposed, wind affected terrain today whether you are traveling uphill or downhill. Watch for obvious signs of textured, pillowed or drifted snow as well as hollow sounding or feeling snow. Cornices are also starting to grow large and with increasing temperatures and the addition of heavy snow or rain, they will likely become more unstable as well. Avoid traveling on or under areas of large overhanging cornices.

Avalanche Problem #2: Loose Wet

Temperatures will continue to warm well into the 30’s as we receive more moisture through the day today. Below 6000 feet expect mostly rain with a mix of wet snow and rain in the upper elevations. Warm temps combined with rain will increase the potential for wet/loose avalanche activity on steep lower elevation slopes especially near rocks, road cuts and on slopes over 35 degrees today. Roller balls and pinwheels are great indicators of rising wet/loose avalanche activity.

Recent Observations

Winds were gusting out of the NW and W yesterday throughout the advisory area. Granite Mt. weather station saw gusts over 25mph yesterday and it sounds like the West Mountains in the Southern portion of the advisory area have seen W winds for several days as well.

Yesterday PAC forecasters toured in the Victor Trail area near Trail Lake and found a similar snowpack structure to what we found near Boulder Mt. on Thursday. The upper snowpack has several crusts that are starting to degrade. The older Thanksgiving crust is still present but the faceted layer has been diminished over time and is not reactive. The dirty layer between 40 and 60cm down is showing some consistent fracture results in our pit tests but lacks the ability to propagate. The exception right now is the thin rain/humidity crust near the surface, earlier in the week it showed the ability to collapse suddenly and propagate through our test pits.

Monumental Summit
https://payetteavalanche.org/fri-02022018-1237-monumental-summit

Boulder ESE
https://payetteavalanche.org/fri-02022018-1304-boulder-ese

Above Trail Lake
https://payetteavalanche.org/sat-02032018-1130-above-trail-lake

Weather

[?] to yesterday, with showers continuing across the central Idaho
mountains and well above normal temperatures across the region.
Record temperatures are again possible across southern areas where
more breaks in the cloud cover are expected. Precipitation chances
increase late this afternoon into tonight ahead of an upper short
wave trough entering the Pac NW. As with recent disturbances the
southern edge of precipitation will skirt northern Malhuer county
and the Snake Plain with a slight chance of showers through Monday
morning. Snow levels remain at or above 7k feet across the region
into Monday morning which will limit accumulations to higher
peaks. All areas trend drier during the day Monday as the wave
quickly exits the region. Will also see slight cooling in its
wake, which means well above normal temperatures, but not quite
reaching record territory. Have updated the PNS product for sites
forecast to approach records for today.

.LONG TERM…Monday night through Saturday…Northwest flow aloft
continues through much of the extended forecast. Moisture pressing
up and over the ridge axis stationed offshore will provide chances
of showers for the central Idaho mountains through the entire
extended period. The GFS has now come in alignment with the ECMWF
for Friday keeping the moist northwesterly flow and slight chance
of showers for the West Central Mountains. After Friday, models
diverge and confidence lowers. Temperatures remain above normal
throughout the period.

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.

source:
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