Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Tuesday March 9th, 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).
-The winds have backed off at all ridge top weather stations since the height of the storm yesterday. Average winds speeds are light this morning between 3mph-14mph with strong gusts up to 26mph.
-In the last 24 hours (5am-5am), the snotel sites recorded: 2.3 inches of water and 22 inches of new snow at Grandview, and 0.7 inches of water and 11 inches snow at Summit Creek, Turnagain Pass is not working right now, but I measured 22” of new snow in the motorized parking lot yesterday at 3pm.
-The current radar shows some precip over Prince William Sound heading toward Cordova, but the Kenai radar shows light to moderate precip directly over Turnagain Pass and Girdwood heading toward Anchorage.
-Temps have cooled off at all wx stations this morning by 4-6 degrees since the height of the storm yesterday. Current temps are 24 degrees F at sea-level and 14 degrees F at 3800′.
Today’s avalanche danger will decrease to CONSIDERABLE due to a less intense weather forecast for the next 24 hours, but DANGEROUS avalanche conditions still exist.
According to the weather stations, the majority of the precip from this storm had already hit our area by yesterday afternoon to early evening. Looking out the window, I’m seeing about a foot of new snow on my truck in Girdwood this morning. The Kenai Mountain snotel sites, however, look like they are recording less precip than Girdwood with only 0.1-0.6 inches of water since yesterday at 3pm at Summit and Grandview compared to 1.2 inches in Girdwood in that same time frame. It’s too bad that the Turnagain Pass snotel site is not working today, but I checked all the parking lot snow stakes yesterday at 3pm and found 22” of new snow on the northern end of Turnagain Pass and 15” new snow at the southern end of the Pass. I’m sure the storm total exceeds 2 feet of new snow at Turnagain Pass this morning. Winds have backed off at all ridge top weather stations this morning, and temps are cooling off as well.
The structure of the snowpack right now is a big glob of storm snow and wind slabs without persistent buried weak layers. There will be weak interfaces within the old snow/new snow and within the new storm snow that could be reactive to human triggers today and create dangerous avalanches. This was a BIG storm that RAPIDLY loaded the snowpack with lots of new weight. These are two big red flags waving in your face. You have to give the snowpack time to adjust after a storm like this. Remember that 90% of all avalanches occur during storms and within 24 hours following storms. We are still in that time frame, do not take your chances on steep slopes today.
Terrain steeper than 35 degrees will be dangerous today. Although the weather has backed off, natural avalanches are still possible today, however, human triggered avalanches are the main danger today. The danger rating of CONSIDERABLE is the most dangerous rating for the human factor. When the avalanche danger is high or extreme, most people do not travel in the mountains. Now that the weather has backed off, this is the time when people start to venture out into the mountains. This is when people’s goals and objectives intersect with unstable snow. Most avalanche fatalities occur when the danger scale reads CONSIDERABLE, just like today. Simply waiting a day or two for the snowpack to adjust could mean the difference between life and death. Don’t get lured into the “I love big dumps” syndrome. Don’t put yourself on steep terrain today.
WEATHER FORECAST (National Weather Service)
WESTERN PRINCE WILLIAM SOUND-
500 AM AKST TUE MAR 9 2010
.TODAY…SNOW SHOWERS. SNOW ACCUMULATION 1 TO 4 INCHES…HIGHEST
AMOUNTS NORTH OF MOOSE PASS. HIGHS IN THE MID 20S TO LOWER 30S.
VARIABLE WIND 15 MPH. NEAR WHITTIER…WEST WIND 15 TO 30 MPH SHIFTING
TO THE EAST 15 TO 20 MPH BY NOON.
.TONIGHT…SNOW SHOWERS. SNOW ACCUMULATION UP TO 2 INCHES EXCEPT 2 TO
4 INCHES NORTH OF MOOSE PASS. LOWS 5 TO 20 ABOVE. VARIABLE WIND 15
MPH. NEAR SEWARD…NORTH WIND 20 TO 30 MPH.
.WEDNESDAY…NUMEROUS SNOW SHOWERS. SNOW ACCUMULATION 1 TO 2 INCHES.
HIGHS 15 TO 20. VARIABLE WIND 10 MPH EXCEPT NORTH AND WEST 20 TO 35
MPH NEAR SEWARD AND WHITTIER.
Temperature / Precipitation
SEWARD 28 9 19 / 100 70 20
GIRDWOOD 26 10 17 / 100 100 60
Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass
Sea-level: temps are forecasted between 10-26 and between 0.25” of water forecasted
3000′: temps are forecasted in the range of 5-14 degrees F with winds 10-15 mph
6000′: temps are forecasted in the range of -4-5 degrees F with winds 10-30 mph
WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS
3800′-Sunburst Wx Station
Current Temp: 14 (2 degrees warmer than yesterday; although cooling off since last night)
Winds: In last 24 hours winds have been light to extreme averaging 3-63mph with extreme gusts up to 94mph
2600′-Seattle Ridge Wx Station
Winds: In last 24 hours winds have been calm to strong averaging 0-36mph with an extreme gust of 58mph
1800′-Center Ridge Wx Station
Current Temp: not working
Precip: not working
Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Wednesday March 10, 2010.