Good morning backcountry travelers this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday March 19th, 2010 at 7 am. 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).
A significant shot of precip is moving through the advisory area this morning. The radar and satellite show more moving our way. The snowline dropped to near sealevel last night. Look for that to lift up again today to approximately 600 ft. Winds have been moderate to strong with ridgetop averages in the teens to twenties. Ridgetop gusts have been 30 – 50 mph. All winds have been east to southeast. Snowfall totals range from 0 at sealevel to 16 inches at Grandview. Alyeska midway got 6-9″, Alyeska top got 15 plus, and Turnagain Pass (1800) got 15″. It’s hard to say how much fell at the highway elevation of 1000 ft in T-Pass. Less than 15 but probable 10-12″
Today’s avalanche danger level is CONSIDERABLE with pockets of HIGH on south to southwest alpine slopes.
Considerable means natural avalanche are possible and human triggered avalanches are likely. Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision making essential.
The pockets of HIGH avalanche danger will exist where suncrusts were formed over the last week. South to southwest slopes steeper that 35 degrees that have this crust will see this higher hazard.
We received over an inch of water and up to 16 inches of snow above 1000 ft in the last 24 hours. Winds have been significant. Add this to the many weak layers we had present and we see our avalanche danger jump up a notch. It looks like the weather will settle down this afternoon with less chance for rain and snow tonight.
Proof of the weak layers present lie in the multiple human triggered avalanches we saw over the last week. See a full detailed list by checking the 03-18-2010 advisory in the archive. In the spring we start to see many layers in our snowpack. Wind, sun, rain, snow, faceting, all form funky layers in the snow. These layers will be harder and harder to track. You will have to rely less on reports and advisories and more on your ability to interpret the snow in front of you. Spacial variability becomes common place in the spring. One slope may have great stability and 100 ft that way on a westerly aspect the stability may be death on a stick.
Take time to evaluate conditions this weekend. This little (not so little) storm of snow will increase our hazard all weekend. Time to dial it back for a couple days and see how this layer sets up. My biggest concern lies in those alpine south to southwest aspect where buried sun crusts exist.
Glide cracks are secondary concern today. These crevasse like features that are cracks that go all the way to the ground appeared to have opened up a bit more over the past 2-4 days. Glide cracks are like cornices in that they are wild cards that are very difficult to predict. Stay far away from these cracks today since they are actively moving right now.
WEATHER FORECAST (National Weather Service)
WESTERN PRINCE WILLIAM SOUND-
500 AM AKDT FRI MAR 19 2010
…STRONG WIND THIS MORNING THROUGH PORTAGE VALLEY AND ALONG
.TODAY…SNOW AND RAIN. SNOW ACCUMULATION UP TO 6 INCHES AT HIGHER
ELEVATIONS…LITTLE ACCUMULATION ELSEWHERE. HIGHS AROUND 40. NORTH TO
EAST WIND 10 TO 20 MPH. GUSTS TO 30 MPH THIS MORNING. THROUGH PORTAGE
VALLEY AND TURNAGAIN ARM…EAST WIND 15 TO 30 MPH. GUSTS TO 45 MPH
.TONIGHT…MOSTLY CLOUDY. A CHANCE OF SNOW AND RAIN IN THE
EVENING…THEN A CHANCE OF SNOW AFTER MIDNIGHT. LOWS IN THE MID
20S TO LOWER 30S. NORTH TO EAST WIND 15 MPH.
.SATURDAY…MOSTLY CLOUDY. A SLIGHT CHANCE OF SNOW SHOWERS IN THE
MORNING…THEN A CHANCE OF RAIN SHOWERS AND A SLIGHT CHANCE OF
SNOW SHOWERS IN THE AFTERNOON. HIGHS IN THE MID 30S TO LOWER 40S.
VARIABLE WIND 10 MPH.
.SATURDAY NIGHT…MOSTLY CLOUDY IN THE EVENING THEN BECOMING
PARTLY CLOUDY. A CHANCE OF SNOW SHOWERS. LOWS IN THE LOWER TO MID
20S. VARIABLE WIND TO 10 MPH.
.SUNDAY…PARTLY CLOUDY WITH A SLIGHT CHANCE OF SNOW SHOWERS.
HIGHS IN THE MID 30S TO LOWER 40S. LIGHT WINDS EXCEPT WEST 10 TO
20 MPH NEAR WHITTIER.
TEMPERATURE / PRECIPITATION
SEWARD 42 29 41 / 80 30 40
GIRDWOOD 42 25 41 / 80 30 0
WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS
3800′-Sunburst Wx Station
22 degrees F, average east winds in the 20’s with gust in the 30’s to 40’s.
2600′-Seattle Ridge Wx Station
26 degrees F, with average southeast winds in the single digits and gust into the teens.
1800′-Center Ridge Wx Station
29 degrees F, 1.3 inches of water equivalent and up to 15 inches of snow.
I will update this advisory tomorrow morning Saturday March 19, 2010 by 0700. Thanks and have a great day.