Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Wednesday April 14th, 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).
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.
-The winds are moderate this morning averaging 16-21mph with some strong gusts up to 31mph down on Seattle Ridge
-The 24 hour snotel sites are reporting:
-0.1 inches of water, 4” of melting/settlement at 1800′ at Turnagain Pass
-0.1 inches of water, 3” of melting/settlement 1100′ at Grandview
-0.1 inches of water, 2” of melting/settlement at 1400′ at Summit Creek.
-This morning’s (5am) radars are full of precip with the majority missing our location and heading east of Cordova
-Temps are starting off about the same this morning at most weather stations as they did yesterday morning. Above freezing temps made it up to 33 degrees at 2600′ yesterday. This morning’s temperature range is 33 degrees F at sea-level and 22 degrees F at 3800′.
Today’s avalanche danger is LOW with pockets of MODERATE. Small human-triggered avalanches will be possible on isolated wind slabs sitting on top of a crust with buried surface hoar/facets on top of that crust.
Surface hoar was observed on Tincan, Pastoral, Twin Peaks, and Pete’s North, and Cornbiscuit at the end of last week. On Sunday we found this surface hoar buried and standing up on a small wind lip on Tincan. This small pocket was very reactive to human triggers. Monday, we tried to confirm this same layer of buried surface hoar on Sunburst, but could not find it. We did, however, find facets on top of the most recent sun crust instead of the surface hoar. Recent observations have described this surface hoar as large above 3200′ (up to 1cm).
Yesterday’s sun pre-cooked a lot of the surface snow. We observed lots of small point release avalanches on sun affected slopes. Only a couple of spots entrained enough snow to become medium sized avalanches. Some new glide crack avalanches were reported in Placer Valley.
The sun is the critical “watch out” situation this time of year. April sun and temps can change the snowpack much more drastically than January or February sun. Avalanche danger can increase quickly during periods of rapidly warming temps and direct sunlight; especially, when the sun hits fresh snow.
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. Glide cracks and full depth release avalanches have been occurring on warm sunny days. We are seeing more and more of these glide cracks form everyday.
WEATHER FORECAST (National Weather Service)
WESTERN PRINCE WILLIAM SOUND-
500 AM AKDT WED APR 14 2010
.TODAY…SNOW AND RAIN. SNOW ACCUMULATION 1 TO 4 INCHES. HIGHS IN THE
30S TO NEAR 40. SOUTH TO EAST WINDS 10 T0 20 MPH.
.TONIGHT…SNOW IN THE EVENING…THEN A CHANCE OF SNOW SHOWERS AFTER
MIDNIGHT. SNOW ACCUMULATION UP TO 1 INCH. LOWS IN THE LOWER 20S TO
LOWER 30S. LIGHT WINDS EXCEPT SOUTH 15 MPH NEAR SEWARD IN THE
.THURSDAY…SKIES BECOMING PARTLY CLOUDY. A CHANCE OF SNOW SHOWERS IN
THE MORNING. HIGHS AROUND 40. LIGHT WINDS EXCEPT WEST 10 TO 15 MPH
TEMPERATURE / PRECIPITATION
SEWARD 41 28 42 / 100 70 0
GIRDWOOD 40 26 40 / 100 90 20
Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass
Sea-level: temps are forecasted between 26-40 and between 0.1-0.25” of water forecasted
3000′: temps are forecasted in the range of 23-32 degrees F with winds 5-10 mph
6000′: temps are forecasted in the range of 14-23 degrees F with winds 5-10 mph
WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS
3800′-Sunburst Wx Station
Temp (5am): 22 (same as yesterday morning)
Winds: In last 24 hours winds have been light-moderate averaging 6-20mph with a strong max gust of 37mph
HIGH TEMP of 29 at 1pm
2600′-Seattle Ridge Wx Station
Temp (5am): 25 (same as yesterday morning)
Winds: In last 24 hours have been light to moderate averaging 5-21 mph with a strong max gust of 31mph
HIGH TEMP of 33 between 4-5pm
1800′-Center Ridge Wx Station
Temp (5am): 29 (1 degrees warmer than yesterday morning)
Precip: 0.1 inches of water, 4 inches melting/settlement
HIGH TEMP 43 between 4-6pm
Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Thursday April 15th, 2010.