GNFAC Avalanche Advisory for Wed Apr 3, 2013

Not the Current Forecast

Good morning. This is Mark Staples with the Gallatin National Forest Avalanche Advisory issued on Wednesday, April 3 at 7:30 a.m. Montana Ale Works in partnership with the Friends of the Avalanche Center sponsors today’s advisory. This advisory does not apply to operating ski areas.

Mountain Weather

This morning temperatures in most areas were at or slightly above freezing following high temperatures yesterday in the high 40s/low 50s F. Winds were averaging 10 mph from the W with gusts of 15-20 mph. Clouds will keep today a bit cooler than yesterday with high temperatures in the low to mid 40s F. Winds should ease a bit as cloud cover increases this afternoon when a few rain drops or snowflakes may fall.

Snowpack and Avalanche Discussion

Bridger Range   Madison Range   Gallatin Range   

Lionhead area near West Yellowstone   Cooke City

More wet loose and wet slab avalanches occurred yesterday at Big Sky (photo1, photo2) and nearby in Beehive Basin (photo). Watch this video from mid-March to see how quickly wet avalanches can slide and gain volume. Ski patrols at Bridger and Moonlight did not have similar activity but closely monitored the snow has it warmed, became wet, and lost strength.

Today will be tricky. The snowpack should teeter on the edge of producing wet avalanches or not. Air temperatures this morning did not drop below freezing in many places, and the snowpack probably did not refreeze overnight; however, clouds will limit warming today thus limit the production of liquid water in the snowpack. Liquid water breaks bonds between snow crystals, decreases strength of the snowpack and leads to avalanches.

For today the avalanche danger is rated MODERATE but could rise higher if clouds don’t block the sun or rain falls.

Looking ahead: Be especially watchful for wet snow avalanches anytime the snowpack doesn’t refreeze the previous night. In this scenario, it doesn’t take much sunshine, warm weather, or rain to get water flowing in the snowpack and cause unstable conditions. Eventually the snowpack will establish drainage channels for melt water and the potential for wet snow avalanches will drop, but this process will take a month or more to occur.

I will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations drop us a line at mtavalanche@gmail.com or call us at 587-6984.

Avalanches can happen anywhere. You can never be too safe Check out this video from a Cooke City regular working in North Dakota.

Take Note:

Our 136th and last avalanche advisory will be on Sunday, April 7th.

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