Turnagain Pass

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Thursday April 1st, 2010 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).

ANNOUNCEMENTS

Skookum Valley and Skookum Glacier are closed to motorized vehicles (snowmachines, helicopters, ATVs) except for subsistence uses.. This closure is directed in the current Chugach National Forest Land and Resource Management Plan. Placer River Drainage remains open for motorized use to Spencer Glacier.

WEATHER ROUNDUP

-The winds are still light to strong this morning averaging 10-27mph on ridge tops with extreme gusts up to 39mph

-The snotel sites have recorded:

-1.4 inches of water and 16 inches of new snow at 1800′ at Turnagain Pass

-1.3 inches of water and 16 inches of new snow at 1100′ at Grandview

-0.1 inches of water and 0 inches of new snow at 1400′ at Summit Creek.

-This morning’s (5am) radars show scattered precip moving west over PWS directly toward the Kenai Mountains

-Temps have cooled off at most weather stations by 2-4 degrees compared to yesterday. Above freezing temps made it up to 33 degrees at 1800′ yesterday. This morning’s range from 32 degrees F at sea-level and 20 degrees F at 3800′.

AVALANCHE DISCUSSION

Today’s avalanche danger will remain at CONSIDERABLE, due a complex snowpack consisting of buried weak layers of surface hoar and suncrusts. Newly formed windslabs and buried surface hoar will be the primary avalanche hazards today.

The National Weather Service forecast does not call for sunshine today, but the NWS discussion mentions, “Precipitation should stay confined to coastal areas while inland portions of South Central Alaska should see a decent amount of sunshine this afternoon.”

The sun is a critical “watch out” situation this time of year. Avalanche danger can increase rapidly during periods rapidly warming temps and direct sunlight.

CNFAIC Staff than sunny slopes, the buried surface hoar is a serious concern today. A party reported a large collapse on the ridge near the top of Sunburst 2 days ago. In the past week, there have been several human-triggered avalanches that have occurred on one of the MULTIPLE layers of buried surface hoar that are currently buried 2-4 feet deep in our snowpack. The pre-cooked surface snow can still act as a slab on top of this surface hoar which is protected further down in the snowpack.

Terrain management is the key right now. Keep your slope angles below 35 degrees. AVOID traveling on any sunny slopes IF the sun comes out and get out of avalanche terrain immediately if it does. Remember that most of the avalanches that failed on the surface hoar have occurred on northern aspects.

Glide cracks are secondary concern today. These crevasse like features are those cracks that go all the way to the ground. Avoid traveling underneath these cracks. A full depth climax avalanche occurred on lower Goat Ridge in Girdwood Valley on 3/30/2010.

WEATHER FORECAST (National Weather Service)

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKDT THU APR 1 2010

.TODAY…SNOW SHOWERS…MIXING WITH RAIN AT TIMES. SNOW ACCUMULATION

UP TO 2 INCHES. HIGHS IN THE UPPER 30S TO LOWER 40S. VARIABLE WIND 10

MPH EXCEPT EAST 15 TO 30 MPH THROUGH PORTAGE PASS AND TURNAGAIN ARM.

.TONIGHT…NUMEROUS RAIN AND SNOW SHOWERS IN THE EVENING. NO SNOW

ACCUMULATION. LOWS IN THE UPPER 20S TO MID 30S. NORTHEAST WIND 10 MPH

EXCEPT EAST 15 TO 25 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

.FRIDAY…NUMEROUS SNOW AND RAIN SHOWERS. NO SNOW ACCUMULATION. HIGHS

IN THE 40S. VARIABLE WIND 15 MPH.

TEMPERATURE / PRECIPITATION

SEWARD 42 32 45 / 100 70 60

GIRDWOOD 40 29 46 / 100 50 60

Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass

Sea-level: temps are forecasted between 29-40 and between 0.1-0.25” of water forecasted

3000′: temps are forecasted in the range of 23-32 degrees F with winds 25-30 mph

6000′: temps are forecasted in the range of 14-23 degrees F with winds 30-40 mph

WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS

3800′-Sunburst Wx Station

Temp (5am): 20 (4 degrees colder than yesterday morning)

Winds: In last 24 hours winds have been moderate to extreme averaging 25-38mph with an extreme max gust of 59mph

2600′-Seattle Ridge Wx Station

Temp (5am): 23 (4 degrees colder than yesterday morning)

Winds: In last 24 hours winds have been light to extreme averaging 10-39 mph with an extreme max gust of 61mph

1800′-Center Ridge Wx Station

Temp (5am): 27 (2 degrees colder than yesterday morning)

Precip: 1.4 inches of water and 16 inches of new snow

HIGH TEMP 33 at 2pm

Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Friday April 2nd, 2010.