Good morning backcountry travelers this is Kevin Wright with the Chugach National Forest Avalanche Information Center on Wednesday, November 24th 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).
Turnagain Pass and Johnson Pass North Trail Head motorized use areas will open for snowmobile use starting today Wednesday, November 24th. Adequate snow is present to prevent resource damage. These areas consist of the lands on the west side of the Seward Highway between the Turnagain Arm and Sixmile Creek and the drainage Southwest of Bench Creek adjacent to the Johnson Pass North Trailhead south to Bench Lake. Center and Divide Creek Drainages are closed to snowmachine use.
All CNFAIC Staff areas of the Chugach NF are closed to motorized use until December 1st or adequate snow to prevent resource damage.
Weather has remained unseasonable warm. The rain line is quite high at 2000-3000 ft. Remote stations recorded up to .8 inches of water in Girdwood and .7 inches in Turnagain pass. Wind was mostly moderate overnight except for sites exposed to the southwest flow, which recorded gusts to 64mph.
Today the avalanche hazard will be MODERATE with pockets of CONSIDERABLE.
It is safe to say that this storm will have a significant effect on the snowpack. Identifying the nature of the changes is a moving target at the moment. Yesterday we toured up tincan ridge to 3000 feet. The surface hoar that we saw last week had been obliterated by the rain. The rain crust that replaced it was thick near the road, gradually became thinner as we climbed, then started getting thicker again. We still don’t know how high the crust goes, but it is safe to say that it goes to ridge-tops in Turnagain pass, well into common avalanche start zones.
Last night the weather changed again, staying warm and dumping a significant amount of rain. Somewhere up high that rain becomes snow… Probably around 2000-3000 feet.
This is going to affect our stability in a couple of ways. My primary concern is new snow on top of the old rain crust. It will have a hard time sticking to this surface, but may hang on just enough until triggered by a skier or rider. I’m guessing you could find 1-2 foot wind slabs on top of a slippery rain crust near the ridge-tops. Until we get out and take a close look it will be difficult to place a rating on that danger.
AnCNFAIC Staff concern is the rain and continued warm temperatures on the glide cracks. In theory the rain will get into the ground/snow interface and add lubrication to increase the glide rate. We could be seeing an increase in these avalanching today.
This is a fairly complicated cycle when assessing the weather and related snowpack stability. Use good judgement in the backcountry and look for signs that may not be consistent with what you are reading in this advisory.
Matt 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:
625 AM AKST WED NOV 24 2010
…STRONG WIND THROUGH LATE THIS MORNING IN PORTAGE VALLEY AND
ALONG TURNAGAIN ARM…
.TODAY…RAIN. HIGHS IN THE MID 30S TO LOWER 40S. SOUTH TO EAST
WIND 10 TO 20 MPH EXCEPT EAST 30 TO 45 MPH THROUGH PORTAGE VALLEY
AND TURNAGAIN ARM…DIMINISHING TO 30 MPH IN THE AFTERNOON.
.TONIGHT…RAIN…CHANGING TO SNOW AT HIGHER ELEVATIONS AFTER
MIDNIGHT. SNOW ACCUMULATION UP TO 2 INCHES AT HIGHER ELEVATIONS.
LOWS IN THE MID 20S TO MID 30S. NORTHEAST WIND 15 MPH. THROUGH
PORTAGE VALLEY AND TURNAGAIN ARM…EAST WIND 15 TO 30 MPH
DECREASING TO 10 TO 15 MPH AFTER MIDNIGHT.
.THANKSGIVING DAY…SNOW LIKELY. SNOW ACCUMULATION UP TO
2 INCHES. HIGHS IN THE 30S. VARIABLE WIND 10 MPH EXCEPT NORTH
10 TO 25 MPH NEAR SEWARD.
.THURSDAY NIGHT…MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS. LOWS
IN THE LOWER 20S TO LOWER 30S. NORTHWEST WIND 10 TO 15 MPH EXCEPT
NORTH 10 TO 25 MPH NEAR SEWARD.
.FRIDAY…PARTLY CLOUDY. HIGHS IN THE LOWER 20S TO LOWER 30S.
NORTHWEST WIND 10 TO 20 MPH.
.FRIDAY NIGHT…MOSTLY CLOUDY WITH A CHANCE OF SNOW. LOWS IN THE
.SATURDAY AND SATURDAY NIGHT…CLOUDY WITH A CHANCE OF SNOW.
HIGHS IN THE 20S. LOWS IN THE TEENS.
.SUNDAY THROUGH MONDAY…CLOUDY WITH A CHANCE OF SNOW. HIGHS IN
THE TEENS. LOWS 5 TO 15.
.MONDAY NIGHT AND TUESDAY…MOSTLY CLOUDY WITH A CHANCE OF SNOW.
LOWS 5 TO 15. HIGHS IN THE TEENS.
TEMPERATURE / PRECIPITATION
SEWARD 40 33 36 / 90 80 70
GIRDWOOD 42 25 33 / 80 70 70
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
Light wind from the east. Temperatures in the high 20s.
-2600′ Seattle Ridge Wx Station-
Recorded the strongest wind speeds in the area with SE wind up to 64mph. Temperatures were 29-30 all day.
-1800′ Center Ridge Wx Station-
Showed .7 inches of water yesterday. Most if not all of that was in the form of rain. Temperatures stayed just above freezing for the second half of yesterday and into today.