Good morning backcountry travelers. This is Jon Gellings with the Chugach National Forest Avalanche Information Center on Tuesday, February 22nd 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).
We would like to send out a big THANK YOU to everybody who submitted their useful opinions on our Friends survey! This information will help decide how our program operates and potentially expands in the near future.
Here is anCNFAIC Staff one for you, which would hopefully involve all backcountry skiers in North America. The focus is on the differences between all male, all female, and mixed gender ski groups, and is actually being conducted by a local APU student. Please fill it out, which should take about 10 minutes.
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Today, the avalanche danger is MODERATE, with pockets of CONSIDERABLE. The strong winds from yesterday afternoon and overnight have made wind loaded slopes near ridgelines the most dangerous, and are likely to be triggered by people travelling in this terrain; some spots could possibly pop out naturally as well. Slopes that have not received a wind load still contain a MODERATE danger for deep slabs, which are still possible to trigger on slopes steeper than 30 degrees in areas with a relatively shallow snowpack (less than 2 meters deep).
We have a few new avalanches that failed between Saturday night and Monday afternoon to report, as well as several new photos. Several natural avalanches were observed near Twin Peaks on NE aspects and down in Johnson Pass on E and SW aspects, as well as two long-running soft slabs which failed south of the snowmachine route up Seattle Ridge on SE aspects. It is unclear whether the Seattle Ridge slides were triggered naturally or by humans.
The winds from yesterday and last night transported large amounts of low density snow, and there is still plenty left to get blown around… Multiple parties reported seeing snowy plumes onto usually windward slopes, which is concerning because previously windward slopes inherently have relatively shallow snowpacks, and may now hold sensitive wind slab as well. We are unable to place a specific aspect and elevation to these new slabs, because they were being created on multiple aspects of the same mountains at the same time. This picture shows Magnum being heavily wind loaded to its North side, even though the Sunburst weather station (off left side of photo) presently showed winds blowing from the Northwest at a slower speed. As a side note, please keep in mind at all times that live data from telemetry sites is provisional, and has not been verified for accuracy.
Signs that you are travelling on a wind slab include seeing shooting cracks, and hearing hollow sounds on hard snow. Triggering one of these wind slabs is probably easiest near convex rollovers and/or ridgelines. Also, if one of these wind slabs is triggered, the possibility exists for a step-down to deeper weak layers, creating a larger avalanche.
Deep slab avalanches are still a concern, and the slab near Twin Peaks is the most recent one observed. It propagated fairly wide, and slid down to the ground in most areas. These deep slabs can possibly be triggered in regions with a snowpack generally less than two meters deep, and conditions are not likely to improve until we get a large storm with lots of water which causes these layers to fail and eventually strengthen. Until then, know the snow you are on to avoid this hazard.
Encyclopedia of avalanche terms.
Winds are still our major contributor to instability today, as they are currently ramping up again with a recorded 68mph gust on Seattle Ridge at 4am. Temperatures are forecast to increase into the upper 20’s today, so we could start seeing sun affected snow very soon. New precipitation is unlikely today, as radar, satellite, models and forecasts all show clear to partly cloudy weather. However, snow blowing from one side of a mountain to the CNFAIC Staff is just like getting a new snow storm as far as avalanches are concerned.
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 TUE FEB 22 2011
…HIGH WIND WARNING IS CANCELLED…
.TODAY…SUNNY. HIGHS IN THE LOWER 20S TO LOWER 30S. VARIABLE
WIND 10 MPH EXCEPT WEST 35 TO 50 MPH WITH GUSTS TO 60 MPH NEAR
WHITTIER. NEAR SEWARD…NORTH WIND 15 TO 25 MPH INCREASING TO 35 MPH
.TONIGHT…MOSTLY CLEAR. LOWS 5 BELOW TO 20 ABOVE…COOLEST INLAND.
VARIABLE WIND TO 10 MPH. NEAR WHITTIER…WEST WIND 25 TO 40 MPH WITH
GUSTS TO 55 MPH IN THE EVENING. NEAR SEWARD…NORTH WIND 20 TO 35
MPH DIMINISHING TO 10 TO 20 MPH AFTER MIDNIGHT.
.WEDNESDAY…PARTLY CLOUDY. HIGHS IN THE MID 20S TO LOWER 30S.
LIGHT WINDS EXCEPT NORTH 10 TO 15 MPH NEAR SEWARD.
TEMPERATURE / PRECIPITATION
SEWARD 30 13 29 / 0 0 0
GIRDWOOD 27 5 27 / 0 0 0
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
Temperature 5 F. Northwest winds 13 mph gusting to 41mph.
-2600′ Seattle Ridge Wx Station-
Temperature 10 F. Northwest wind 27 mph gusting to 50mph.
-1800′ Center Ridge Wx Station-
Temperature 14 F. 0″ new snow. 87” total snow depth.