Good morning backcountry travelers this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday March 5th, 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).
AnCNFAIC Staff 3 inches of snow fell in the Girdwod Valley last night. No new snow in Turnagain Pass. Yesterday we measured 24 inches of snow in Turnagain Pass from the Tuesday – Wednesday night snow event. Winds were calm to moderate yesterday. Some wind transport was noted in the alpine. The big news is the current storm moving on shore this morning from Prince William Sound. Expect snow to start any minute now. The Middleton radar is packed full of precip. The NWS has a blizzard warning in effect this morning. The snow line will lift to approximately 400 ft today with 6-12 inches of snow down low and 12-18 inches at 1000 ft. Currently sea level temperatures are 29 deg F. AnCNFAIC Staff 3 to 8 inches is forecasted for tonight.
Today’s avalanche danger will start at CONSIDERABLE and increase to HIGH as the morning snow storm hits our advisory area. If the forecasted snow and wind materialize expect very dangerous avalanche conditions today. Natural avalanches will be likely and human triggered avalanches will be very likely.
Yesterday we climbed to ridgetop elevations in Turnagain Pass to find 24+ inches of 48 hour snow. Below 1500 feet the late Feb rain crust is still damp. From 1500 to 2000 that same layer is slightly refrozen, from 2000 and up that layer is not significant. We did not note any collapsing snow and limited shooting cracks. The winds have stiffened the surface snow in some alpine areas. Snow stability tests at 3000 ft showed moderate stability with failures at the snow event interfaces, 24 hour snow on top of 48 hour snow on top of 72 hour snow.
Although we saw an improvement in snow stability yesterday we are getting attacked by a very large 962 mb low currently. With an increased snow load today our avalanche danger will also increase. I expect to come out of this series of storms with a fairly good coastal snowpack. Our snowpack is already 117 percent of normal at Center Ridge in Turnagain Pass with a total snowpack of 119 inches.
Traveling on slopes steeper than 30 degrees will be dangerous today. Our current snowpack is starting to get tricky in a sense. With this deeper snowpack trigger points become a big deal. The trigger point may not be found by the 1st, 2nd, or 20th rider, but the person that does find the specific trigger point could trigger a deep avalanche that is too difficult to escape. A lot of times these trigger points are on steep rollovers, near rock outcroppings, or where the snow is shallower.
WEATHER FORECAST (National Weather Service)
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST FRI MAR 5 2010
…BLIZZARD WARNING NOW IN EFFECT UNTIL NOON AKST TODAY ALONG
TURNAGAIN ARM AND PORTAGE VALLEY AND SOUTH TO TURNAGAIN PASS…
.TODAY…SNOW AND BLOWING SNOW REDUCING VISIBILITY TO ONE QUARTER
MILE OR LESS TURNAGAIN PASS NORTHWARD. RAIN MIXED WITH SNOW AT SEA
LEVEL IN THE AFTERNOON. SNOW MAY BE HEAVY AT TIMES. SNOW ACCUMULATION
6 TO 12 INCHES. HIGHS IN THE LOWER TO MID 30S. SOUTH AND EAST WIND 15
TO 30 MPH WITH LOCAL GUSTS TO 45 MPH IN THE MORNING. THROUGH PORTAGE
VALLEY AND TURNAGAIN ARM…EAST WIND 70 TO 85 MPH DECREASING TO 35 TO
50 MPH IN THE AFTERNOON.
.TONIGHT…SNOW. AREAS OF BLOWING SNOW. SNOW ACCUMULATION 4 TO 8
INCHES. LOWS IN THE MID 20S TO LOWER 30S. SOUTHEAST WIND 10 TO 25 MPH
EXCEPT SOUTHEAST 30 TO 45 MPH THROUGH PORTAGE VALLEY AND
.SATURDAY…NUMEROUS SNOW SHOWERS. SNOW ACCUMULATION 1 TO
2 INCHES. HIGHS AROUND 30. SOUTHEAST WIND 10 TO 25 MPH EXCEPT
EAST 20 TO 35 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
.SATURDAY NIGHT…NUMEROUS SNOW SHOWERS. LOWS 5 TO 20 ABOVE.
VARIABLE WIND TO 10 MPH. NEAR SEWARD…NORTH WIND 10 TO 15 MPH.
.SUNDAY…MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS. HIGHS IN THE
LOWER TO MID 20S. VARIABLE WIND TO 10 MPH. NEAR WHITTIER…WEST WIND
10 TO 20 MPH SHIFTING TO THE EAST 10 TO 15 MPH IN THE AFTERNOON.
TEMPERATURE / PRECIPITATION
SEWARD 37 29 31 / 100 100 70
GIRDWOOD 36 30 31 / 100 100 70
WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS
3800′-Sunburst Wx Station
Current Temp: 15 (5 deg cooler than yesterday)
Winds: have just started rippin, with averages in the 60’s and gust near 90 mph out of the east.
2600′-Seattle Ridge Wx Station
Winds: have picked up with averages in the 40’s and gusts in the 70’s out of the southeast.
1800′-Center Ridge Wx Station
Current Temp: 23 degrees (4 degrees cooler than yesterday)
Precip: 0 new water, 0 new snow, total snowpack depth of 119” after 3 inches of settlement.
Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Saturday March 6th, 2010.