Good morning backcountry travelers. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Monday, February 21th 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).
There is a MODERATE avalanche danger today for soft and hard wind slabs on and off ridgelines and in cross loaded terrain. Triggering a fresh wind drift as well as lingering stiffer drifts formed over the weekend is a possibility. A MODERATE danger remains for triggering a deeper avalanche that breaks into the older weak layers in shallow snow cover areas.
One human triggered soft slab avalanche was reported yesterday in the Turnagain Pass area. This was on the south face of Corn Biscuit and was estimated to be 20′ wide and 4-5” deep. The slide was initiated while a skier was traversing away from a thin rocky area and noticed a large, 20 foot, shooting crack. CNFAIC Staffwise, we have not heard, or seen (albeit limited visibility), of any CNFAIC Staff avalanche activity from Sunday.
It seems as though the winds had their way with much of the snow over the weekend. Everything from soft settled powder, wind crusts with variable thicknesses, large drifts and sastrugi cover the surface. The main concerns for today are any new fresh wind drifts that may have recently formed or lingering wind slabs which developed over the weekend. Overnight, the winds remained fairly light with moderate gusts however, if they do increase as forecast, watch for developing sensitive fresh wind drifts on leeward steeper slopes. There is still plenty of snow for transport even though the surface has already seen a couple windy days. The older wind slabs, formed over the past couple days, are expected to be stiffer, more stubborn and harder to trigger today, most dangerous in steep rocky terrain. Also, any new drifts may be on slopes different than those loaded over the weekend considering the main flow has switched around to a more northerly direction. Keep an eye out for firm hollow-feeling snow and cracking around, or shooting from, your skis/board/sled.
It has been 7 days now since the last avalanche we know of broke into the deeper weak layers near the ground. However, we are still concerned with the poor structure we keep seeing in shallow snow cover areas (less than 2 meters in general). Until we get a large enough storm with significant water weight to stress these layers to the point of failure, we cannot expect them to heal anytime soon. It is a ‘spooky’ MODERATE – lower probability, higher consequence. Steering clear of steep slopes in these areas is wise.
Encyclopedia of avalanche terms.
Yesterday clouds and flurries covered most of our region and temperatures were in the teens with west to north winds gusting into the 20’s. Overnight, the northwest winds remained light gusting into the 20’s and temperatures slightly dropping into the low teens. Today winds are forecast to increase from predominantly the northwest, gusting into the 40’s or more on the higher ridgelines. It looks like we’ll have party cloudy skies with temperatures climbing into the 20’s for the first time in several days.
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.
Jon 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 MON FEB 21 2011
…STRONG WIND THROUGH TUESDAY EVENING NEAR WHITTIER…
.TODAY…PARTLY CLOUDY IN THE MORNING THEN BECOMING MOSTLY SUNNY.
HIGHS IN THE 20S. NORTHWEST WIND 15 TO 30 MPH EXCEPT WEST 40 TO
55 MPH NEAR WHITTIER.
.TONIGHT…MOSTLY CLEAR. LOWS 5 BELOW TO 15 ABOVE…COOLEST
INLAND. NORTHWEST WIND 15 TO 30 MPH EXCEPT WEST 30 TO 45 MPH NEAR
.TUESDAY…SUNNY. HIGHS IN THE LOWER TO MID 20S. NORTHWEST WIND
10 TO 25 MPH EXCEPT WEST 40 TO 55 MPH NEAR WHITTIER.
.TUESDAY NIGHT…MOSTLY CLEAR. LOWS 10 BELOW TO 15 ABOVE…COOLEST
INLAND. NORTHWEST WIND 15 MPH. NEAR WHITTIER…WEST WIND 30 TO 45
MPH DECREASING TO 15 TO 30 MPH AFTER MIDNIGHT.
.WEDNESDAY…PARTLY CLOUDY IN THE MORNING THEN BECOMING MOSTLY
CLOUDY. HIGHS IN THE MID 20S TO MID 30S. LIGHT WINDS. NEAR
WHITTIER…WEST WIND 10 TO 15 MPH IN THE MORNING BECOMING LIGHT.
TEMPERATURE / PRECIPITATION
SEWARD 28 17 24 / 0 0 0
GIRDWOOD 29 10 27 / 0 0 0
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
Temperature 11F and increasing. North wind 5-10mph gusting to 20.
-2600′ Seattle Ridge Wx Station-
Temperature 13F and increasing. North wind 5-10 gusting to 20.
-1800′ Center Ridge Wx Station-
Temperature 16F and should increase. No new snow.