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 13, 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 again today. Winds at all ridgetop weather stations have also increased dramatically overnight. Snow and strong winds are forecasted for today.

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

Is recording a temp of 32 degrees (9 degrees warmer than yesterday) with NE winds from 10 to 14mph.

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

Has a temp of 26 degrees (5 degrees warmer than yesterday). Turnagain Pass did receive 2 inches of snow Wednesday night, no new snow last night. Total snowpack is 65 inches.

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

Shows a temperature of 19 degrees (3 degrees warmer than yesterday). Winds have increased from the east with averages in the 30 ‘sand gusts in the 40’s.

-Surface Analysis Maps-

A 972 mb low is moving into the Cook Inlet this morning from the east bringing with it precip. A 1038 mb high is to our NE. The pressure gradient between these two systems is responsible for strong winds present and forecasted today.

-Radar-

Only scattered showers on the PWS radar. The Kenai radar shows a cell heading for Homer. The big news is the precip that’s forecasted for today and tonight can be seen heading our direction on the King Salmon radar.

AVALANCHE HAZARDS

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

Bottom Line

Extra Caution is advised today. The avalanche hazard will increase today if we see the 4-10 inches forecasted and strong winds. Winds are already gusting in the 50’s. Expect moderate avalanche hazard in most areas today with pockets of considerable near ridge tops. Human triggered avalanches are probable and natural avalanches are possible in these wind loaded pockets near ridge tops or side loaded gullies.

Discussion

We have been watching a trend of human triggered avalanche activity over the last 10 days. The weak layer resonsible for these avalanches has not gone away. It is just getting deeper under new snow. A rain crust from 800 to 1800 feet is faceted with weak snow and will continue to be effected by human triggers. This low elevation instability has llimited consiquenses unless above a terrain trap. The instability of more concern to me exists where wind has created slabs over a slick sliding surface in the alpine. Yesterday’s 2 inches of snow along with current wind and forecasted snow will push these alpine slabs closer to the failure point.

Yesterday we found stiffer wind effected snow from 1000 to 3600 feet on Sunburst in T.Pass.

WEATHER FORECAST

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST FRI FEB 13 2009

…STRONG WIND THROUGH LATE THIS EVENING THROUGH PORTAGE VALLEY

AND TURNAGAIN ARM…

.TODAY…SNOW AND BLOWING SNOW. SNOW ACCUMULATION 2 TO 4 INCHES.

HIGHS IN THE 30S. SOUTH TO EAST WIND 15 TO 30 MPH EXCEPT EAST

30 TO 45 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

.TONIGHT…SNOW AND BLOWING SNOW. SNOW ACCUMULATION 2 TO 6 INCHES.

LOWS IN THE MID 20S TO LOWER 30S. SOUTH TO EAST WIND 15 TO 30 MPH

DECREASING TO 5 TO 15 MPH AFTER MIDNIGHT. THROUGH PORTAGE VALLEY

AND TURNAGAIN ARM…EAST WIND 35 TO 45 MPH DECREASING TO 20 TO 30

MPH AFTER MIDNIGHT.

.SATURDAY…SNOW LIKELY IN THE MORNING…THEN A CHANCE OF SNOW

SHOWERS IN THE AFTERNOON. SNOW ACCUMULATION UP TO 2 INCHES. HIGHS

IN THE LOWER TO MID 30S. SOUTH TO EAST WIND 10 TO 15 MPH.

.SATURDAY NIGHT…SNOW SHOWERS LIKELY. LOWS IN THE MID 20S TO

LOWER 30S. SOUTH TO EAST WIND 10 TO 15 MPH.

.SUNDAY…SNOW AND RAIN LIKELY. HIGHS IN THE 30S. SOUTH TO EAST

WIND 10 TO 20 MPH EXCEPT EAST 25 TO 40 MPH THROUGH PORTAGE VALLEY

AND TURNAGAIN ARM.

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 Saturday, February 14th. Thanks and have a great day.