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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, April 15th, 2011 - 7:00AM
Expires
Sat, April 16th, 2011 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

Good morning backcountry travelers. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Friday, April 15th at 7am. 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

*Tomorrow, Saturday April 16th, will be the final official advisory for the 2010/2011 season.

*Throughout the remaining two weeks of April, periodic updates will be posted as avalanche conditions warrant.

BOTTOM LINE

Today the avalanche danger is MODERATE and will rise to pockets of CONSIDERABLE throughout the day for wet avalanche activity. This will be first on east then south then west facing slopes at all elevations. Expect wet loose snow sluffing as well as a possibility for larger and more dangerous wet slab avalanches. Also, there is a MODERATE danger for lingering wind slabs in areas with new snow on mid to upper elevation northerly aspects.

AVALANCHE DISCUSSION

It was nice to see a fresh coat of white on the mountains yesterday. By midday snow showers put down 4-8” in the Turnagain Pass area, Johnson Pass looks have done a little better with around 10”, likely more at the higher elevations, and Girdwood Valley less with a few inches. Winds picked up as well and some exposed northerly slopes are now a bit wind scalloped.

The sun broke through in the afternoon and did it’s damage dampening the new snow on southerly aspects quickly. Wet loose snow sluffing as well as a few 30′ shallow new snow soft slabs pulled out on the steeper southerly terrain.

Wet slab activity is starting to show signs of getting interesting. Two glide avalanches have released (east facing in Placer and south facing on Eddies) as well as a wet slab avalanche (south facing east of Girdwood). These all are thought to have been in the past few days.

Today the primary concern is wet avalanches. The snowpack will see temperatures close to, or warmer than, what it has seen this season. This along with direct sun and calm winds will likely get wet snow suffing, with a potential for wet slabs, going in the afternoon and peaking near 3-5pm. Areas developing a sun crust yesterday had a fair refreeze overnight but these will soften today. Remember, once the snow softens to boot high it is high time to leave that aspect for a cooler one. These avalanches are easy to avoid by staying clear of east then south then west facing slide paths as they become mushy over the course of the day. These often release naturally and can entrain quite a bit of snow so watch what kind of slopes and gullies you are hanging out under in the afternoon.

Those venturing to the colder snow on northerly aspects at higher elevations will want to keep in mind easterly winds accompanied the new snow yesterday and plums were seen off the peaks. Though the winds have died down, watch for lingering wind drifts and slabs that could still be touchy. Also, there is a possibility surface hoar lies under the recent storm snow, most concerning where more significant new snow accumulations or wind loading has occurred.

Lastly, there is still a chance to trigger a slab avalanche that fails deeper in the pack, lingering weak layers and crusts still exist. The increasingly warm temperatures and sun can help to reactivate these layers.

Encyclopedia of avalanche terms.

WEATHER ROUNDUP

Late morning snow showers kicked in yesterday and by midday 4-6” of snow fell around 2500′ with 6-8” near 3500′ in Turnagain Pass. Johnson Pass faired a little better with around 10”, likely more at the higher elevations, and Girdwood Valley less with a few inches. Winds also kicked in midday with over 40mph gusts on ridgetops from the East. By the afternoon the sun broke through and winds subsided while temperatures climbed into the mid 20’s at 3500′ and low 40’s at 1800′.

Overnight, skies were clear dropping temperatures to the upper 20’s at 1000′ and mid 20’s at 3500′. Winds have been light from the east. Today the sun should be out in full force with the easterly winds remaining light. Temperatures may feel tropical with mid 40’s at 1000′ and near 30F at 3500′.

I will issue the next advisory tomorrow morning at 7am. If you get out in the backcountry give us a call at 754-2369 or send us your observations using the button at the top of this page. Thanks and have a great day.

The NWS weather forecast for:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKDT FRI APR 15 2011

.TODAY…MOSTLY SUNNY. HIGHS IN THE MID 40S TO LOWER 50S. NORTH WIND

10 MPH NEAR SEWARD. WEST WIND 10 TO 15 MPH NEAR WHITTIER. LIGHT

WINDS ELSEWHERE.

.TONIGHT…MOSTLY CLEAR. LOWS IN THE LOWER 20S TO LOWER 30S.

VARIABLE WIND TO 10 MPH. NEAR SEWARD…NORTH WIND 10 MPH.

.SATURDAY…MOSTLY SUNNY IN THE MORNING THEN BECOMING PARTLY

CLOUDY. HIGHS IN THE 40S. LIGHT WINDS EXCEPT NORTH 10 MPH NEAR

SEWARD.

.SATURDAY NIGHT…PARTLY CLOUDY. LOWS AROUND 30. LIGHT WINDS.

.SUNDAY…MOSTLY SUNNY. HIGHS IN THE MID 40S TO LOWER 50S. VARIABLE

WIND TO 10 MPH. NEAR WHITTIER…WEST WIND 10 TO 15 MPH.

TEMPERATURE / PRECIPITATION

SEWARD 47 29 47 / 0 0 0

GIRDWOOD 45 25 47 / 0 0 0

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

25 degrees. ENE wind 5mph gusting to 10mph.

-2600′ Seattle Ridge Wx Station-

28 degrees. ESE wind 3mph gusting to 3mph.

-1800′ Center Ridge Wx Station-

27 degrees. Around 3″ new snow with .4″ of water equivalent.

Fri, April 15th, 2011
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
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This is 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.