Wallowa Avalanche Center

Conditions Summary for November 6, 2009

Disclaimer: Wallowa Avalanche Center assumes no liability for the accuracy of the information contained in this summary. Information provided does not constitute or imply any type of forecast, advisory, or recommendation. Users are warned to use this information at their own risk.

The Bottom Line Synopsis:

After a little light rain on the snowpack even up high last Friday (10/30) there has been no measurable precipitation. Although this week has had a few cold nights, days have been into the low forties at 8000' and mostly sunny generally; causing much settlement, melting and melt/freeze type crusts to develop in the upper elevations.

Photo 1: Pete’s Point, E Aspect (SnowPilot  profile below is actually from a spot just below the 2 trees in the distance.)

Sunday, Wednesday and Thursday were substantial inversions up high. Snow line is 6800' +/- and spotty.  Hiking around up high on the snowpack does not require snowshoes (consider bringing your crampons) since I  was walking on top of the snow just about everywhere with only an occasional punch through. The surface is so hard that even with the warm temps, wet sloppy activity this week has not been an issue.

Photo 2: Aerial View from near Matterhorn Peak looking south. Taken on November 3.

Things to watch out for  is your footing. Should you slip up there on the icy supportable crust on any reasonable slope, you're gonna slide, and a long way at that! Most, but not all, of the surfaces are like facial pockmarks and abrasive. Other locations that saw much upslope wind activity directly after the storm of Oct. 26-27 or aspects that have gotten the sun this week either have uncovered that nasty shiny rain crust or have formulated a sun crust of the same slipperiness respectively. Either way, large slopes and other isolated areas  were this has occurred (especially upper parts of ridge lines and exposed summits) will not hold onto new snow when it finally comes. No new avalanche activity has been noted and the existing snowpack appears to be bonded well. Remember however, any major change in the weather, be it rain, warmth, snow, etc. can and will, change the existing stability.

Photo 3: Piece lying on shovel is result of a STH shovel shear (weak layer between the crusts). This photo on Dollar Ridge N aspect  @ 25 slope angle.

The Juicy, Techie Stuff:

My outing on Sunday the 1st yielded wind drifts and pillowing mimicking concrete. Sawing was the only way to penetrate the snowpack, using the shovel only to remove pieces of sawn chunks. I wandered around Aneroid Basin from near Aneroid Mtn. past Dollar Ridge to near Tenderfoot Pass, all the while jackhammering down to ground in 8 places on different aspects all pretty much at 8400'. I was always able to find the 3 mm rain crust deposited on Friday Oct. 23.  But I was surprised to find a 1.5 mm rc about an inch or so above the old one. This thinner rc was not always present but appeared to be more prevalent on N -> E aspects. I believe it was deposited at the beginning of a small precip event 10/27-29 but then changed to snow with a wet  1-2" accumulation before becoming a MF CR over last weekend. Surface temps from some residual solar on S -> W aspects could have prevented rc accumulation there. 4F hardness down near ground level and small faceting are now in development. Rock hard (P) snowpack exists up to within 3" of the surface where movement toward facets is causing concern both between the rc layers and directly under the lower rc. I found consistent STH shears directly above but not "on" the thicker rc. No stability tests were performed. Some spotty diurnal recrystallization was found on N aspects.

Photo 4: Piece lying behind block is  result of STH but weak layer on top of crust (only one crust detected, saw is  under crust). Photo 1/2 mile NE of Dollar Ridge on level ground.

Figure 1: SnowPilot plot for pit data. (Still having some software issues with the image)

Snowpack depths: Aneroid Basin (from observations)
No new, 10" @7400'  on Sunday 11-1
No new, 17" @8400'  on Sunday 11-1

Photo 5: Sometimes you can make a thin slice and hold up to sun to get a good look at the crust profile

Local Weather Forecast:
 

Today (Friday) expect rain up to about the 7000' level with wet snow above. The system moving in from the Pacific starting today will remain with us through the weekend. It will be cloudy for the duration with maybe as much as a few inches of snow accumulation in the high country. Much of the moisture from this system will be unloaded in the Cascades and won't make it here. Colder weather than we had this week is expected next week.

Recommend cautionary travel, once the precipitation begins,  above tree line in bowls (or crossing under them), ridges, & summit ascents due to the uncertain bonding of the new snow to these slick rain crust surfaces in many places.
 

General Announcements:

Be careful out there and keep looking at our Home Page Blog for updates during the week.

Photo 6: Knowledge Quiz!

This is a test of your knowledge (for the general public) . Which way was the wind coming from to cause these drifts?
a. from the left or right?
b. from behind the trees?
c. from in front of the trees?

Current Regional Weather Synopsis:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
255 AM PST FRI NOV 6 2009

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT...A COLD FRONT
MOVING THROUGH THE AREA WILL BRING RAIN TO NORTHEAST OREGON AND
SOUTHEAST WASHINGTON THIS MORNING. BEHIND THE FRONT...STRONG WINDS
ALOFT WILL MIX DOWN TO THE SURFACE CAUSING BREEZY TO VERY WINDY
CONDITIONS ACROSS THE REGION. AS SUCH...WIND ADVISORIES FOR NORTH
CENTRAL OREGON...THE EAST SLOPES OF THE SOUTHERN WASHINGTON
CASCADES...THE YAKIMA VALLEY...THE LOWER COLUMBIA BASIN AND THE BLUE
MOUNTAIN FOOTHILLS WILL REMAIN IN EFFECT THROUGH THIS EVENING. IN
THE LOWER COLUMBIA BASIN AND THE YAKIMA VALLEY...RAIN SHADOWING HAS
LIMITED PRECIPITATION...RESULTING IN DRY GROUND CONDITIONS THAT
COULD LEAD TO BLOWING DUST.

ANOTHER WEATHER SYSTEM WILL MOVE INTO THE PACIFIC NORTHWEST LATER
TONIGHT. ALTHOUGH MOST OF THE PRECIPITATION ASSOCIATED WITH THIS
DISTURBANCE WILL EITHER FALL WEST OF THE CASCADES OR NORTH OF THE
AREA....MOUNTAIN SHOWERS CAN BE EXPECTED. WITH SNOW LEVELS FALLING
TO NEAR 3000 FEET...SEVERAL INCHES OF SNOW MAY ACCUMULATE IN THE
HIGHER TERRAIN OF THE EASTERN SLOPES OF THE CASCADES.

BROAD TROUGHING OVER THE WESTERN U.S. WILL BRING YET ANOTHER
SHORTWAVE INTO THE REGION ON SATURDAY AFTERNOON. THIS SYSTEM IS
EXPECTED TO TRACK FARTHER SOUTH THAN FRIDAY NIGHTS
DISTURBANCE...THUS RAIN AND MOUNTAIN SNOW SHOWERS WILL BE LIKELY
ACROSS A LARGER PORTION OF THE AREA. THE BEST CHANCES FOR
PRECIPITATION WILL BE ALONG THE CASCADES...IN THE LOWER COLUMBIA
BASIN AND BLUE MOUNTAIN FOOTHILLS...AND IN THE BLUE MOUNTAINS. DRIER
CONDITIONS WILL RETURN BY SUNDAY MORNING.  82

.LONG TERM...SUNDAY THROUGH NEXT FRIDAY...WEAK HIGH PRESSURE WILL
BUILD BEHIND A DEPARTING WEATHER SYSTEM ON SUNDAY WHICH WILL
CONTINUE INTO EARLY NEXT WEEK. THE NEXT WEATHER SYSTEM AFTER THAT
WILL MOVE INTO THE PACIFIC NORTHWEST MONDAY NIGHT INTO TUESDAY WITH
THE ASSOCIATED COLD FRONT PASSING OVER THE CASCADES AROUND 06Z
TUESDAY AND THEN THE EASTERN MOUNTAINS OF OREGON/WASHINGTON AT ABOUT
12Z TUESDAY MORNING. THIS SYSTEM LOOKS TO BE SIMILAR TO THE CURRENT
SYSTEM MOVING ACROSS THE FORECAST AREA WITH PRECIPITATION AMOUNTS
ALONG WITH BREEZY TO WINDY CONDITIONS SIMILAR TO THE WEATHER SYSTEM
TODAY. AN UNSETTLED TROUGH LIKE PATTERN WILL THEN PERSIST OVER THE
REGION THROUGH AT LEAST THURSDAY OF NEXT WEEK WITH FREQUENT WEATHER
DISTURBANCES MOVING ACROSS THE AREA...EACH ONE BRINGING A CHANCE OF
LOWER ELEVATION RAIN SHOWERS AND HIGHER ELEVATION SNOW SHOWERS. HIGH
PRESSURE ALOFT WITH DRIER CONDITIONS ARE THEN EXPECTED TO RETURN ON
FRIDAY. 88