Good morning backcountry travelers. This is Jon Gellings with the Chugach National Forest Avalanche Information Center on Wednesday, April 6th 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).
The avalanche danger today is MODERATE with pockets of CONSIDERABLE. Recent wind slabs on steep leeward terrain could still possibly be triggered by a skier or snowmachiner. The pockets of elevated danger will become increasingly obvious as the sun begins to warm this surface layer of previously non-sun-affected snow, if the sun acts as forecast.
We will hopefully be able to see the extent of recent avalanches today, pending whether or not the obscure skies lift for once. I suspect a new layer of surface hoar has formed last night due to clear skies, low temperatures, moist snow, and light breezes. If the approaching storm comes in overnight and drops a significant amount of snow on this, expect anCNFAIC Staff increase in avalanche activity.
The weak layers of surface hoar and small facets from the end of March are currently the most concerning layer in our snowpack. Steep alpine slopes facing North which lack crusts in upper snow layers have a more concerning setup than lower elevations which now have a rain crust, and alpine South aspects which have sun crusts from previously sunny days last week.
The secondary concern, which may become a higher concern in the afternoon dependent on sun, is that South aspects will start shedding snow in the form of point releases near rock outcroppings. As these roll down the slope, they could naturally start pulling out wet and/or soft slabs further downhill. Clues to this instability include increasing temperatures, which manifest in seeing roller balls, as well as upper layers of snow settling and creeping, and becoming saturated with water.
If you hear any “whumpf” sounds, see shooting cracks, feel collapses, or see any recent avalanches, please let us know about them by submitting an observation at the top of this page. These clues help us determine what type of instability we are dealing with, and where more concerning areas are located. Plus, you get entered to win a beacon of your choice on April 15th!
Encyclopedia of avalanche terms.
For the next 12 hours, the winds are not forecasted to be strong enough to transport snow, therefore will not increase the avalanche danger. Temperatures are not going to be as warm as they were yesterday, which has already started freezing up the recently saturated snow at lower elevations. Expect a surface crust… Precipitation will likely not be falling at a significant rate today, as radar, satellite, models and forecasts all point to semi-clear skies. Winds and precipitation rates will increase later on tonight, affecting tomorrow’s avalanche danger.
Kevin 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 THE CITIES OF…WHITTIER…SEWARD…GIRDWOOD…
546 AM AKDT WED APR 6 2011
…HIGH WIND WATCH IN EFFECT FROM THURSDAY MORNING THROUGH
THE NATIONAL WEATHER SERVICE IN ANCHORAGE HAS ISSUED A HIGH WIND
WATCH…WHICH IS IN EFFECT FROM THURSDAY MORNING THROUGH THURSDAY
SOUTHEAST WINDS WILL INCREASE TO 65 MPH WITH POSSIBLE GUSTS TO 90
MPH THURSDAY MORNING. WINDS ARE EXPECTED TO DIMINISH TO 50 TO 65
MPH BY LATE THURSDAY AFTERNOON AFTER FRONTAL PASSAGE.
A HIGH WIND WATCH MEANS THERE IS THE POTENTIAL FOR A HAZARDOUS
HIGH WIND EVENT. PEOPLE ARE ENCOURAGED TO CLOSELY MONITOR THIS
WEATHER SITUATION. PREPARATION FOR THIS POTENTIALLY DANGEROUS
WEATHER EVENT SHOULD BEGIN NOW.
WESTERN PRINCE WILLIAM SOUND-
500 AM AKDT WED APR 6 2011
…HIGH WIND WATCH EARLY THURSDAY MORNING THROUGH THURSDAY AFTERNOON
THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…
.TODAY…PARTLY CLOUDY. HIGHS IN THE MID 30S TO LOWER 40S.
NORTHWEST WIND 10 TO 15 MPH. NEAR WHITTIER…NORTH WIND 15 TO 25 MPH
BECOMING 10 MPH IN THE AFTERNOON.
.TONIGHT…CLOUDY. SNOW AFTER MIDNIGHT. AREAS OF BLOWING SNOW WILL
REDUCE VISIBILITIES TO LESS THAN A MILE AT TIMES AFTER MIDNIGHT. SNOW
ACCUMULATION UP TO 5 INCHES. LOWS 10 TO 20 ABOVE. LIGHT WINDS
BECOMING SOUTHEAST 15 TO 30 MPH AFTER MIDNIGHT. THROUGH PORTAGE
VALLEY AND TURNAGAIN ARM…VARIABLE WIND 10 MPH INCREASING TO EAST 35
TO 50 MPH AFTER MIDNIGHT.
.THURSDAY…AREAS OF BLOWING SNOW IN THE MORNING WILL REDUCE
VISIBILITIES TO LESS THAN A MILE AT TIMES. SNOW IN THE
MORNING…THEN SNOW AND RAIN IN THE AFTERNOON. SNOW MAY BE HEAVY
AT TIMES IN THE MORNING. SNOW ACCUMULATION UP TO 10 INCHES OVER
HIGHER ELEVATIONS. HIGHS IN THE LOWER 30S TO LOWER 40S. SOUTHEAST
WIND 20 TO 35 MPH. THROUGH PORTAGE VALLEY AND TURNAGAIN ARM…EAST
WIND 65 WITH POSSIBLE GUSTS TO 90 MPH DECREASING TO 50 TO 65 MPH IN
.THURSDAY NIGHT…NUMEROUS SNOW SHOWERS. LOWS IN THE MID 20S TO
MID 30S. SOUTH WIND 10 TO 20 MPH EXCEPT SOUTHEAST 15 TO 30 MPH
THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
TEMPERATURE / PRECIPITATION
SEWARD 40 29 42 / 0 100 100
GIRDWOOD 36 30 39 / 0 100 100
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
16 degrees. N wind 4mph gusting to 13mph.
-2600′ Seattle Ridge Wx Station-
26 degrees. Winds are not being recorded due to an iced-up anemometer. This should correct itself when the winds pick up tonight.
-1800′ Center Ridge Wx Station-
23 degrees. 2-3 inches new snow.