Good morning backcountry travelers this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Saturday, February 6th 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).
Plenty to report this morning. I’ve been staring at weather models this morning since our roof avalanched and woke me up at 3am. This is about the time winds picked up and snow changed to rain in the Girdwood Valley. Since this time ridge top weather stations have reported easterly gusts to 68 mph. Approximate overnight snow fall and water equivalent totals: Girdwood 10″,1.27″; Alyeska midway 14″, 1.23″; Alyeska top ~20+”, 1.9″; Turnagain Pass 10-12″,.9″; and Summit Lake 8″,.3. These numbers are increasing by the hour. Very heavy precip at this time. It looks like more precip fell in the Girdwood Valley and Chugach State Park than did in Turnagain Pass. Weather models and the NWS forecast the precipitation to continue until mid morning. Some models have anCNFAIC Staff 1″ of water predicted. Expect precip to stop later today with a good chance of it returning again tomorrow.
Today’s avalanche danger for the Turnagain Arm area has increased to HIGH . Natural avalanches likely and human triggered avalanches very likely. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
With 10 to 20 inches of new snow in the mountains, today is a no brainer. This snow fell in 24 hours and has added a lot of stress to the snowpack. This storm snow has fallen on a snowpack with a significant weak layer associated with a rain crust formed one month ago. This weak crust has just been buried 3-4 ft deep. Much deeper in wind deposition areas. Winds have been very strong overnight with averages in the 20’s and gusts in the 60’s. Natural or human triggered avalanche could be large in nature, 3-6+ feet deep. I think you will also see some smaller new snow instabilities.
Areas of most concern include slopes steeper than 30 degrees below 2500 feet. Elevations below 2500 ft are where we saw the above mentioned weak layer most reactive. From 2500 ft to ridge tops you will find newly formed wind slabs on leeward aspects.
A key to the elevated avalanche hazard today is the unfortunate nature of this storm. This storm started with calm winds and temperatures in the teens. This storm is ending with very strong winds and above freezing temps. Bottom line is we have very dense wind driven snow over very light density snow. This is a bad setup. Today is a resort day, stay off and away from steep backcountry slopes. We need to give the mountains time to adjust to the new snow load. Snowmachiners, it’s a good day to explore Johnson Pass or CNFAIC Staff low angle terrain.
Always remember that safe backcountry travel requires training and experience. You control your own risk by choosing where, when, and how you travel.
WEATHER FORECAST (National Weather Service)
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST FRI FEB 6 2010
…BLIZZARD WARNING IS CANCELED…
…STRONG WIND THIS MORNING THROUGH PORTAGE VALLEY AND TURNAGAIN
.TODAY…RAIN AND SNOW BECOMING SCATTERED SNOW AND RAIN SHOWERS BY
MIDDAY. SNOW ACCUMULATION UP TO 3 INCHES. HIGHS IN THE MID 20S TO
UPPER 30S. SOUTH TO EAST WIND 10 TO 20 MPH. THROUGH PORTAGE VALLEY AND
TURNAGAIN ARM…SOUTHEAST 30 TO 50 MPH DIMINISHING TO 25 MPH IN THE
.TONIGHT…MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS. LOWS 5 TO 25
ABOVE…COLDEST INLAND. SOUTHEAST WIND 10 TO 15 MPH EXCEPT SOUTHEAST
15 TO 30 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
.SUNDAY…SNOW LIKELY. SNOW ACCUMULATION UP TO 4 INCHES. HIGHS IN THE
MID 20S TO MID 30S. SOUTH WIND 15 MPH.
.SUNDAY NIGHT…SNOW LIKELY. LOWS IN THE LOWER TEENS TO LOWER
30S…COLDEST INLAND. VARIABLE WIND 10 MPH EXCEPT NORTH 15 MPH
.MONDAY…BECOMING PARTLY CLOUDY. HIGHS IN THE MID TEENS TO MID
30S…COLDEST INLAND. LIGHT WINDS EXCEPT NORTH 10 MPH NEAR SEWARD.
.MONDAY NIGHT…CLOUDY WITH A CHANCE OF SNOW. LOWS IN THE TEENS.
TEMPERATURE / PRECIPITATION
SEWARD 31 20 35 / 40 40 60
GIRDWOOD 34 22 31 / 100 20 60
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
Strong easterly winds continue averaging 37-47 with gusts of 52-68. The current temp is 26F (8 degrees warmer than yesterday).
-2600′ Seattle Ridge Wx Station-
Strong easterly winds continue averaging 23-29 with gusts of 38-52.
-1800′ Center Ridge Wx Station-
10-12 ” of new snow and .9 inches of water equivalent recorded. The current temp is 32 deg F.
Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Sunday, February 7th.