Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Monday, November 22nd 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).
All areas designated for snowmachines are still closed. We are measuring the snow in these areas daily and will open them as soon as there is enough snow to protect the ground and vegetation from being torn up by the tracks of a snowmachine. Thanks for your patience.
Light rain and freezing rain started falling early this morning after 9 days without any form of precip in the Turnagain Arm area. Ridgetop winds were light yesterday, averaging 5-10mph out of the northwest, while a steep inversion kept mountain temperatures on the warm side for the fifth day in a row. Temps above 3000 feet elevation hit the low 40’s yesterday while sea level temps remained in the low 20’s. Steady rain continues to fall as of 6am morning while ridgetop winds remain light out of the south. Temperatures this morning range from 42F@3800′ to 38F@1800′ to 25F@sealevel. The inversion should break by midday today as a low pressure system displaces the ridge of high pressure. The freezing rain at the lower elevations will turn to all rain by late this morning and then taper off. Look for all rain at the higher elevations possibly turning to snow as temps cool off. Expect moderate to strong southerly ridgetop winds building later today to 20-25mph. The freeze line could then rise as high as 3000 feet by the end of the day.
Today the avalanche hazard will increase to MODERATE overall after 9 days at LOW. The combination of rain, moderate to strong southerly winds, and significant temperature swings will bump up the avalanche danger. As the rain line fluctuates today, natural avalanches may occur. Pockets of newly formed windslab above treeline may be sensitive to human triggers later today as the winds increase. Glide cracks continue to avalanche unpredictably and remain a secondary concern today. We saw a fresh glide avalanche yesterday morning on the west side of Pyramid.
Today is an extra challenging forecast for me due to all the weather variables. Precip today will be in the form of rain, snow, or freezing rain depending on elevation. Temperatures at the different elevations will flipflop by midday but still remain unseasonably warm. We can’t rule out the possibility of natural avalanches caused by rain at the middle and upper elevations this morning where temperatures are well above freezing. The absence of significant weak layers in the snowpack diminishes this possibility, but the chance is still there. On the bright side, rain at the lower elevations should melt the surface hoar that formed this past week and get rid of that future weak layer. Kevin and I will head up to the pass today to groundtruth this crazy weather.
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-
500 AM AKST MON NOV 22 2010
…FREEZING RAIN ADVISORY IN EFFECT UNTIL NOON AKST TODAY…
.TODAY…FREEZING RAIN…MIXING WITH RAIN AND THEN TAPERING OFF IN
THE AFTERNOON. HIGHS IN THE 30S. LIGHT WINDS. THROUGH PORTAGE
VALLEY AND TURNAGAIN ARM…SOUTHEAST WIND INCREASING TO 20 TO 35 MPH.
.TONIGHT…A CHANCE OF RAIN IN THE EVENING…THEN RAIN AFTER
MIDNIGHT. LOWS IN THE LOWER TO MID 30S. VARIABLE WIND 10 MPH
EXCEPT EAST 20 TO 35 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN
.TUESDAY…RAIN. HIGHS IN THE MID 30S TO LOWER 40S. VARIABLE WIND
10 MPH EXCEPT EAST 25 TO 40 MPH THROUGH PORTAGE VALLEY AND
TEMPERATURE / PRECIPITATION
SEWARD 34 33 40 / 100 100 100
GIRDWOOD 32 31 40 / 80 100 100
WEATHER STATION SUMMARY for Turnagain Pass:
-3800′ Sunburst Wx Station-
recorded light northwesterly winds yesterday averaging 5-10mph and temps ranging from 38-40F. The current temp is 42F with winds averaging 5mph out of the southwest.
-2600′ Seattle Ridge Wx Station-
recorded light and variable winds yesterday and temps ranging from 35-39F. The current temp is 40F with winds averaging 5mph out of the southeast.
-1800′ Center Ridge Wx Station-
recorded no new snow in the last 9 days. Temps yesterday ranged from 22-34F. The current temp is 38F with a total snowpack depth of 44 inches (minus 1 inch due to settlement in the last 24 hours).