Good morning backcountry travelers. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Sunday, February 20th at 7am. This will serve as a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).
The avalanche danger today is MODERATE for wind slabs on any steep slope with recent wind deposited snow. There are also pockets of CONSIDERABLE danger on slopes with more significant wind loading overnight. Triggering a wind slab is possible near ridgelines, well off ridgelines and in cross loaded terrain. In addition, there remains a MODERATE danger for avalanches to break, or step down, into the deeper weaknesses, producing a potentially large slide.
Well, the winds seemed to have ruled the roost yesterday. The 8-12 inches of ‘champagne powder’ blew in plumes off many of the peaks and ridgelines, as well as funneling through drainages. Countless point release loose snow sluffs were seen in the entire region with some natural wind slab activity as well. These slides were generally shallow, soft and manageable yet they did run fast and far. In fact, yesterday was a good day to watch live natural new snow sluffs. Kevin caught a photo of a natural wind slab in action on the east side of Seattle Ridge (click HERE ). There were also a few larger and more dangerous wind slabs in the higher terrain that broke naturally around 100-200′ wide.
Due to the ramped up southwest through northwesterly winds overnight, the main concern for today will again be wind slabs in areas with recent wind deposited snow. These areas are likely on steep slopes on the north through east through south side of the compass and could be well off ridgelines or in cross loaded terrain. Click HERE for a photo of a natural wind slab just south of Turnagain Pass on Silvertip Peak. Significantly loaded steep slopes pose a more dangerous situation and from what we have seen lately, natural triggers in these pockets are possible today with a likely chance for a human trigger. Watch for smooth ‘wind whales’ and ‘hollow’ feeling drifts in the steep terrain. I am expecting these drifts to be stiffer today and less easily managed if one pops out.
Several photos from yesterday’s activity were sent in to us last night so make sure and check them out in the photo gallery.
Last, we can’t forget that even with these last few snow falls slowly adding to our snowpack, deeper weakness still exist. Most suspect areas are where the total snow depth is less than 2 meters. This is mainly in the Crow Pass/Raggedtop area above Girdwood and the interior Kenai south of Turnagain Pass. Triggering this type of deeper avalanche is possible by a human, snowmachine or the weight of a wind slab running over it and could have high consequences. Avoiding steeper slopes in these shallow snow cover areas is advised.
Encyclopedia of avalanche terms.
Although the sun was out in full force yesterday, the single digit temperatures and gusty westerly winds kept things quite cold. The 8-12 inches of fluff remains on any relatively wind sheltered aspect but many areas, especially ridgelines, have seen quite a bit of wind damage. Just before midnight the winds ramped up, with gusts in the 50’s from the northwest through southwest, but have backed down this morning and are in the 10mph range with gusts in the 20’s. Temperatures continue to hover in the single digits at all elevations this morning. Today skies will be mostly cloudy with a chance for light snow showers, expecting only a trace to an inch. Temperatures should warm into the teens with the westerly winds remaining light and gusting into the 20-30’s on the peaks.
The Forest Service is installing winter use bridges across Granite creek in Turnagain Pass. Be aware of an ice road from the Lyon creek bridge south towards Johnson Pass on the West side of the highway. Heavy equipment will also be used in the area.
This is the LAST day to fill out the survey for the Friends of the CNFAIC (FCNFAIC)! With a new staff of forecasters and a list of previously completed goals, the program is growing and potentially heading in new directions. The FCNFAIC wants to know what you have to say about YOUR avalanche center. Thank you in advance for taking it!
Click here to take survey
or cut and paste the address directly:
I will issue the next advisory tomorrow morning at 7am. If you get out in the backcountry give us a call at 754-2369 or send us your observations using the button at the top of this page. Thanks and have a great day.
The NWS weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST SUN FEB 20 2011
…STRONG WIND MONDAY NEAR WHITTIER…
.TODAY…MOSTLY CLOUDY. ISOLATED SNOW SHOWERS IN THE AFTERNOON. HIGHS
IN THE MID 20S TO LOWER 30S. NORTH AND WEST WIND 10 TO 20 MPH EXCEPT
WEST 20 TO 35 MPH NEAR WHITTIER.
.TONIGHT…MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS. LOWS 15 TO
25…COOLEST INLAND. NORTH AND WEST WIND 10 TO 20 MPH EXCEPT WEST
25 TO 35 MPH NEAR WHITTIER.
.WASHINGTONS BIRTHDAY…PARTLY CLOUDY IN THE MORNING…THEN MOSTLY
SUNNY IN THE AFTERNOON. HIGHS IN THE UPPER 20S TO MID 30S. NORTH AND
WEST WIND 10 TO 20 MPH EXCEPT WEST 30 TO 45 MPH NEAR WHITTIER.
.MONDAY NIGHT…MOSTLY CLEAR. LOWS ZERO TO 20 ABOVE…COOLEST
INLAND. NORTHWEST WIND 10 TO 15 MPH EXCEPT WEST 20 TO 35 MPH NEAR
.TUESDAY…MOSTLY SUNNY. HIGHS IN THE MID 20S TO LOWER 30S.
NORTHWEST WIND 10 TO 15 MPH EXCEPT WEST 10 TO 25 MPH NEAR WHITTIER.
TEMPERATURE / PRECIPITATION
SEWARD 32 26 34 / 20 0 0
GIRDWOOD 25 20 30 / 20 40 30
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
Temperature 4F and should increase. Recent max gust around 20mph from the WNW.
-2600′ Seattle Ridge Wx Station-
Temperature 0F and should increasing. Max gust before midnight 59 from the NW.
-1800′ Center Ridge Wx Station-
Temperature 6F and should increase. No new snow.