Wallowa Avalanche Center

Conditions Summary for February 5, 2010

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:

Look for soft turning snow measuring about 6 inches deep in areas completely away from any place wind can sneak in and disturb it. The thicker trees have great snow! The warmer, but just below freezing temperatures of this week at 8000 ft have not adversely effected the snow surface in these areas. On steeper terrain, even in non-wind effected terrain, and on wind exposed areas are found sensitive weaknesses in the top foot of snow. Where wind slabs are developing, they are not sticking (bonding) very well at all to the snow just under them. Most of these slabs are thin, about 3 inches or less and cover larger than expected areas. Not just at rollovers on ridges for instance. Many are found over large, open, wind exposed areas. These are actually skiable but rather funky and tend to trip you up. The other weakness is a poor bond of the most recent snow of last weekend (where there isn’t wind slab action) to the older snow surface below.

Photo 1: Climbing ridge before entering into 2nd Basin on Wing Ridge. Still some varying snow depths, eh? Photo taken 2-3-10

Last weekend we received about 8” of new snow which has since been blown around a bit with the strong winds of early this week from the south. January weather otherwise has been about 3 degrees (F) temperature above average and the snowpack averages in the Northern Basins are about 63% of average according to our SNOTELs and the National Weather Service.

In the Southern Wallowas: Look for 2 sensitive weak layers. One, a possible surface hoar (frost) deposit is buried down approximately 4 inches as of Monday 2-1 and appears to be mostly prevalent on northerly aspects below treeline. The other is a persistent troublesome rain crust with weakness underneath it at about 15 inches below the surface. This rain crust is found primarily between 5000 and 8000 feet on all aspects. Besides these weaknesses the snowpack is well bonded all the way to the ground. Some wind board slabs are found in the southern reaches as well that are moderately sensitive to movement.

Photo 2: Outing of WAC Observers on Traverse Ridge 2-1-10, note the winds at the summit.

Recent activity: None reported this week from our observers.

Breaking news: Late yesterday received info about possible natural on the west face of Redmont seen from the trail into McCully Basin. No further details.

Concern #1: Wind slabs and the newest snow bonding to the older surfaces. Most of the wind slabs this week have been thin but the bond is poor and likely will trip you in your travels. Areas with 6 to 8 inches of snow, which are areas that haven’t seen wind on NW -> SE aspects, maintain a very poor bond to the surface below. It is unclear what the cause of this poor bond is (crusting?) and as of 2-3-10 hand shears worked quite well to give you an indication of what you’re getting into. Continue to bear in mind where wind loading of the last two weeks has occurred and adjust your travel accordingly.

Concern #2: This past week has seen another round of strengthening of the persistent lower snowpack weakness since last weeks report. Places where the snowpack is deep (greater than 1.5 meters) show more strength than the shallower areas. The weak crystals in the lower one third of the snowpack nearest the ground are continuing to get smaller and are less sugary and loose. Bottom line is: there still remains a possibility of triggering an avalanche in a shallower snowpack area with the result simply: BAD NEWS.

Acknowledge and evaluate these concerns with sufficient understanding when venturing into avalanche terrain.

Photo 3: Keith studying change in weak layer crystals above the melt-freeze layer @7800 feet, N aspect, Aneroid Basin on 1-30-10.

Average snowpack depths at 8000 feet:

Northern and Eastern Wallowas: 6 in new, still about 50 in. €� total depth
Southern Wallowas: Rain and some snow, still about 100 in total depth
 

Photo 4: WAC interns, Victor and Brian, assisting in analysis of snowpack in 2nd Basin of Wing Ridge. ESE aspect, 7900 feet. photo taken 2-3-10.

The Juicy, Techie Stuff:

WAC is seeing a metamorphosis of the persistent weakness in the facets/depth hoar down below. The bottom of the layer is still running larger 2 mm less rounded facets. The upper part of the layer is in the 1 - 1.5 mm range with no noticeable striations any longer and far better rounding. Now we’re talking only a distance between these samples of 3 or 4 inches. Sintering is a different story. But the hardness is increasing ever so slowly and we would assume the bonding as well. Consistent CT22’s Q2 or Q3 this week within that layer on aspects N -> ESE at the mid level elevations. The mid part of the snowpack now is becoming very uniformly bonded with hardnesses ranging from at least 1F to almost P.

Figure 1:: Located @ UTM 0484900E 5005400N NAD27. Pit data of photo with Keith in pit

Figure 2: Generalized profile diagram

General Announcements

Don’t forget our Wallowa Avalanche Center biggest fun event of the year on February 11 (Thursday) 6pm at the OK Theater in Enterprise!!  Cool movies!! The event will feature pizza from Embers in Joseph and beer from Terminal Gravity, as well as a raffle and a drawing for items that include a backcountry safety package consisting of a backpack, shovel, probe and electronic beacon. Proceeds from the event will purchase additional educational materials to be offered free to the public; instrumentation for better wind data from the top of Mt. Howard; additional Web site enhancements; and support for WAC’s Observers Network.

Tickets are available for only $5.00, while children under 6 are free. Purchase tickets at the Bookloft, Central Copy and Shipping, and The Sports Corral. More information is available by calling Penny at 541-263-1454 or emailing info@wallowaavalanchecenter.org

February 21st (Sunday) is our beacon practice day up on the Salt Creek Summit. Please sign up at info@wallowaavalanchecenter.org and also let us know if you need a loaner beacon.

Quiz!

Photo 5: Quiz: Around the base of these small trees are _______ cones. What do they help tell you about the snowpack?

Wallowa Mountain Weather Briefing:

We are working directly with the National Weather Service in Pendleton through special briefings to provide you with applicable local mountain weather information. You should always obtain a weather forecast from National Weather Service before undertaking any winter outdoor activities.

The weather pattern of the past week is expected to continue through the weekend, with a series of weak frontal systems approaching the Pacific Northwest and then splitting and shearing as they move eastward. None of these systems will carry much energy as they make their way across our region. As of this morning, today’s system appears to carry the highest probability of snow in the mountains, as the splitting flow is further weakening the next system. NWS provided models indicate that Friday will see mostly cloudy conditions through the day with a valley rain and mountain snow possible. Snow amounts should be minimal, with less than a couple of inches in most areas. Friday night should see drying conditions, before another week system approaches Saturday, again producing a possibility of valley rain and mountain snow showers. Snow levels should hold in the 4000 -5000 ft range through the weekend.

This morning’s models indicate that our next possibility for a potent storm will be the middle of next week.

Current Regional Weather Synopsis:

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
337 AM PST FRI FEB 5 2010

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH SUNDAY...A FRONT EXTENDS FROM THE
KITTITAS VALLEY TO GRANT COUNTY OREGON. THERE WILL BE WIDESPREAD
RAIN AND MOUNTAIN SNOW AS IT MOVES THROUGH THE AREA THIS
MORNING...WITH SCATTERED SHOWERS BEHIND IT THIS AFTERNOON. EASTERN
WASHINGTON AND OREGON WILL DRY OUT TONIGHT AS A TRANSITORY RIDGE
MOVES THROUGH. SATURDAY SPLIT FLOW WILL DEVELOP AS A CUTOFF LOW
MOVES INTO CENTRAL CALIFORNIA. THIS IS MUCH FARTHER SOUTH THAN
YESTERDAY SO REDUCED POPS OVER THE AREA...PARTICULARLY IN EASTERN
WASHINGTON. A WEAK UPPER LEVEL LOW WILL MOVE THROUGH EASTERN OREGON
SATURDAY NIGHT AND SUNDAY...BUT THE SPLIT FLOW WILL CONTINUE WITH
MOST OF THE ENERGY REMAINING WITH THE LOW IN CALIFORNIA. HOWEVER...A
FEW SHOWERS ARE POSSIBLE IN OREGON AS THE WEAK LOW MOVES THROUGH.
COONFIELD

.LONG TERM...SUNDAY NIGHT THROUGH THURSDAY...HAVE REMOVED MENTION OF
POPS FOR SUNDAY NIGHT AND MONDAY AS THE REGION REMAINS UNDER THE
INFLUENCE OF A STABILIZING SPLIT FLOW ALOFT. HAVE LESS CONFIDENCE
MONDAY NIGHT THROUGH WEDNESDAY AS THE SPLIT POINT EDGES CLOSER TO
THE COAST WHILE CONTINUING TO SEND MOST OF THE ENERGY SOUTHWARD. DID
KEEP LOW END MENTION WITH LIGHT QPF AMOUNTS EXPECTED, BUT WOULD NOT
BE SURPRISED IF THE SHARP RIDGING HELD IN PLACE LONGER THAN MODELS
EXPECT THUS KEEPING THE MOISTURE SOUTH AND THE REGION DRY. MODELS
CONTINUE TO AGREE ON BRINGING ANOTHER POTENT STORM ACROSS THE REGION
MAYBE LATE WEDNESDAY AFTERNOON, BUT MORE LIKELY WEDNESDAY NIGHT AND
THURSDAY. STILL SEE SNOW LEVEL BEING RATHER HIGH WITH THE CASCADES
PICKING UP THE BRUNT OF THE PRECIPITATION. IT`S STILL EARLY TO HAVE
SIGNIFICANT CONFIDENCE IN THE DETAILS, BUT QPF AMOUNTS BEGINNING
THURSDAY AND LASTING THOUGH THE FOLLOWING WEEKEND MAY BE RATHER
SIGNIFICANT. /JBONK