Good Morning backcountry travelers, this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Thursday, February 12, 2009 at 7am. This will serve as a general backcountry avalanche advisory issued 5 days a week Wednesday-Sunday for the Turnagain Arm area (Turnagain Pass is the core advisory area). Local variations always occur.
MOUNTAIN WEATHER ROUND UP
In the last 24 hours…
-General Weather Observations-
Temps have continued to increase at all weather stations from Summit to Girdwood by an additional 4-11 degrees. Winds at all ridgetop weather stations have backed off a little this morning, but were strong yesterday afternoon.
–The DOT weather station near the crest the highway at Turnagain Pass at 1000 feet–
Is recording a temp of 23 degrees (5 degrees warmer than yesterday) with calm winds.
–The NRCS Center Ridge weather station at 1800 feet in Turnagain Pass–
Has a temp of 21 degrees (4 degrees warmer than yesterday). 0.2 inches of water and 2 inches of new snow has been recorded. Total snowpack depth is 66″.
–The Sunburst weather station at 3800 feet in Turnagain Pass–
Shows a temperature of 16 degrees (10 degrees warmer than yesterday). Winds have been moderate to strong averaging 7-34 mph out of the East with a max gust of 52 mph.
-Surface Analysis Maps-
Between 3am and 9pm yesterday, a weak low pressure moved into Prince William Sound and continued to get weaker (1000-1004mb). There is anCNFAIC Staff big storm building out in the Bering Sea (976-972mb).
Not much to report this morning. There is some moisture just outside of Prince William Sound. It must be the dregs of that low pressure from yesterday.
Primary avalanche concerns
-Surface wind slabs on slippery bed surface on alpine ridges above 3000 feet
Secondary avalanche concerns
-Rain crust from January hurricane below 3000 feet.
AVALANCHE AND SNOWPACK
Extra Caution is advised today. Avalanche hazards have increased since yesterday due to strong wind and some new snow. There will be pockets of considerable avalanche hazard. These are the types of conditions when most people get caught in avalanches because human overconfidence in the snow pack collides with deeper slabs.
We received anCNFAIC Staff report of a human-triggered avalanche from Girdwood Valley yesterday. Add that to the list in the general snow conditions at the bottom of the page, and you will see that people have been frequently triggering avalanches in: Girdwood Valley, Virgin Creek, Kern Creek, Placer River Valley, and Turnagain Pass. Our entire advisory area for the Turnagain Arm area has been having problems with human-triggered avalanches on that slippery wind hammered layer above 3000 feet, and on the rain crust below 3000 feet to sea-level.
*Yesterday’s strong wind and new snow have increased the chance of triggering larger, more destructive, and potentially deadly avalanches.*
Safe terrain management is essential today.
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST THU FEB 12 2009
…STRONG WIND EARLY FRIDAY MORNING THROUGH FRIDAY AFTERNOON
THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…
.TODAY…PERIODS OF SNOW…ESPECIALLY ALONG THE SOUND. SNOW
ACCUMULATION UP TO 2 INCHES. HIGHS IN THE MID 20S TO LOWER 30S.
LIGHT WINDS. NEAR SEWARD…NORTH WIND 15 TO 30 MPH BECOMING
LIGHT IN THE AFTERNOON.
.TONIGHT…SNOW SHOWERS LIKELY…ESPECIALLY ALONG THE SOUND. SNOW
ACCUMULATION UP TO 2 INCHES. LOWS IN THE LOWER 20S TO LOWER 30S.
EAST WIND 10 TO 15 MPH. THROUGH PORTAGE VALLEY AND TURNAGAIN
ARM…SOUTHEAST WIND 15 TO 25 MPH INCREASING TO 25 TO 40 MPH
.FRIDAY…SNOW SHOWERS LIKELY. SNOW ACCUMULATION 1 TO 5 INCHES.
HIGHS IN THE LOWER TO MID 30S. EAST WIND 10 TO 20 MPH EXCEPT
35 TO 50 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
TEMPERATURE / PRECIPITATION
SEWARD 28 27 36 / 40 40 60
GIRDWOOD 26 26 32 / 80 60 60
This concludes today’s avalanche advisory the next advisory will be on Friday, February 13th (ooga booga). Thanks and have a great day.