Turnagain Pass Avalanche Forecast

GENERAL ANNOUNCEMENTS

Good Morning backcountry travelers, this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday, February 20, 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 FOR THE LAST 24 HOURS

-General Weather Observations-

Say it isn’t so,,,anCNFAIC Staff storm misses us! Yesterday’s forecasted double digit storm missed the advisory area leaving us with only 1-2 inches of new snow. It looks like Hatcher Pass caught some of the system picking up 12 inches of new snow and 1.4 inches of water equivalent. Heads up, if you head north, that’s a large amount of new snow load.

A large upper level ridge is building in over much of the state today. This will push any chance of precip north or south of us over the weekend. Cooling temps and increasing outflow westerly winds are forecasted.

–The DOT weather station near the crest the highway at Turnagain Pass at 1000 feet–

Is recording a temp of 36 degrees (1 degrees cooler than yesterday) with light winds averaging 10mph out of the south.

–The NRCS Center Ridge weather station at 1800 feet in Turnagain Pass–

Has a temp of 22 degrees (7 degrees colder than yesterday). 0.1 inches of water and zero inches of new snow has been recorded. Total snowpack depth is 67″.

–The Sunburst weather station at 3800 feet in Turnagain Pass–

Shows a temperature of 17 degrees (4 degree colder than yesterday). Winds are increasing, averaging in the teens and gusting to 20 out of the west.

-Surface Analysis Maps-

The last low is only a 1023 and is hanging by Cordova. The rest of the area is under a high pressure ridge.

-Radar-

No green monsters left out there! Mostly clear!

AVALANCHE HAZARDS

Primary avalanche concerns

-Denser wind slab snow over lighter density snow with a weak layer exists on alpine slopes above 3000 feet. The size of these slabs has grown, up to 4 foot crowns reported!

-Denser snow on top of lighter density snow teetering on top of a weak rain crust layer below 3000 feet. (Avalanches have been common and widespread on this lower elevation instability. There is a layer of faceted snow on top of this rain crust. Areas of concern include but are not limited to: Placer Valley, Seattle Creek, and Girdwood Valley)

AVALANCHE AND SNOWPACK

Bottom Line

Extra Caution is advised today. There are pockets of considerable avalanche hazard at multiple elevations and aspects today. I have no doubt we will see human triggered avalanche activity all weekend. Managing your terrain will be key. Clear, blue bird skies will give false confidence that nothing can go wrong. That thought process could get you killed. Choosing terrain less than 30 deg, with smooth run outs and escape routes will be key. I don’t want to dig anyone out of a frozen hole this weekend!

Discussion

See photo gallery for some pictures of recent avalanches

Large natural avalanches occurred in Skookum, Peterson Creek, Portage Valley, and the northern end of Turnagain Pass earlier this week, just to mention a few. This northern edge of the advisory area received more snow load than did interior areas of Turnagain and Summit Passes. However, the same weak layers exist. This means that T. Pass has not yet hit the stress over strength point on the scale that an avalanche will occur at. A trigger is the something or someone that slides the scale to the tipping point and causes an avalanche. A trigger could be a skier, snowboarder, snowmachiner, or a wind driven snow flake. Use increased caution if these outflow winds pick up. Actively loading slopes will be areas of increased hazard.

Skier triggered avalanches were reported as recently as Wednesday. Check out the history and photo pages for the full skinny.

By definition, considerable avalanche hazard means conditions are dangerous. This has been proven by the natural, artillery, and human-triggered avalanches that have been observed/reported in the Girdwood Valley, Peterson Creek, Portage Valley, Skookum Valley, Placer Valley, and Turnagain Pass.

Safe terrain management is essential today. Stay away from slopes steeper than 30 degrees. A lot of times, we talk about the 24 hour rule, meaning that most avalanches occur during or within 24 hours of a storm. That is not the case with our current weak layers. These are persistant weak layers and will be with us for days if not weeks.

WEATHER FORECAST

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST FRI FEB 20 2009

…STRONG WIND NEAR SEWARD AND WHITTIER THROUGH SATURDAY MORNING…

.TODAY…MOSTLY SUNNY IN THE MORNING THEN BECOMING PARTLY CLOUDY.

HIGHS IN THE UPPER 20S TO MID 30S. NORTH TO WEST WINDS 10 TO 25 MPH.

GUSTS 35 TO 50 MPH NEAR SEWARD AND WHITTIER THIS AFTERNOON.

.TONIGHT…MOSTLY CLEAR. LOWS IN THE TEENS. NORTH TO WEST WINDS 10 TO

25 MPH. GUSTS 40 TO 55 MPH NEAR SEWARD AND WHITTIER.

.SATURDAY…MOSTLY SUNNY IN THE MORNING THEN BECOMING MOSTLY

CLOUDY. HIGHS IN THE UPPER 20S TO MID 30S. NORTH TO WEST WINDS 10 TO

20 MPH. GUSTS 40 TO 55 MPH NEAR SEWARD AND WHITTIER DIMINISHING 15 TO

25 MPH IN THE AFTERNOON BY AFTERNOON.

.SATURDAY NIGHT…MOSTLY CLOUDY. LOWS IN THE TEENS. LIGHT WINDS.

.SUNDAY…MOSTLY CLOUDY. HIGHS IN THE UPPER 20S TO MID 30S. LIGHT

WINDS.

TEMPERATURE / PRECIPITATION

SEWARD 33 23 31 / 0 0 0

GIRDWOOD 30 12 27 / 0 0 0

This concludes today’s avalanche advisory the next advisory will be on Saturday, February 21st. Thanks and have a great day.