Avalanche Advisory for Wednesday February 27, 2013

Expires at Midnight Wednesday 2-27-2013

Tuckerman and Huntington Ravines will have CONSIDERABLE avalanche danger today.  Natural avalanches are possible and human triggered avalanches are likely.  Dangerous avalanche conditions will develop making conservative decision making essential.  The only exception to this is the Lower Snowfields and the Little Headwall which will have Moderate avalanche danger where natural avalanches are unlikely and human triggered avalanches are possible.

Another storm is beginning to consume the region as snow has enveloped the higher summits over the past couple of hours.  Snow is expected to increase today, falling heavy at times, from the ESE at 35-50mph (55-80kph) increasing to 60+mph (96kph) later today.  Total accumulations should reach 12-16″ (30-40cm) by the time the system moves out later on Thursday.  Today’s wind velocities will likely be the highest we have seen over the past 6 days.  Currently winds are from the SSE gusting to 47 mph (75kph).  This is generally causing some loading to begin on slopes with a N and NW facing aspect.  This includes the upper start zones of Hillman’s and Left gully in Tuckerman, and the Escape Hatch, South and Odell in Huntington.  Based on winds shifting slightly today through the SE to the ESE, occasionally flirting with the E, these N and NW pointing slopes will reach the Considerable rating first.  Although the 10″ (25cm)of snow from the weekend storm has been sitting above treeline and bonding, increasing resistance to transport from wind, the 60+ mph forecast should begin moving these old crystals mixing them in with today’s storm snow.  This additional snow and perfect loading wind velocities from 40-60mph (64-96kph) will place new unstable slabs in the deposition of many protected lee areas today.

Many forecasted areas will develop instabilities much slower than the aforementioned locations above.  Slopes pointing directly into the expected winds today like the Lip and Yale gullies shouldn’t see rapid loading from new snow through most of today.  They also don’t have alpine zones with waiting snow to load into them from the SE.  As winds move to the ESE and perhaps the E, slopes pointing S and N will see additional cross loading with some old alpine zone snow mixing in.  To sum up all the nuances today here are some bull’s-eye points to remember:

**Slopes with a northerly component will see the most loading today and should be the first aspects to reach the Considerable rating due to a shifting, increasing, wind from the SSE, SE, and ESE with heavy snow.

**As winds arrive at their expected ESE/E direction crossloading of S and N facing slopes should be at their maximum.  Effecting locales like the Lobsterclaw, Right, North, and Damnation gullies in addition to those already discussed that face N.

**Instabilities on forecasted slopes facing E and SE such as portions of the Sluice, Lip, Center Bowl, Yale and Central gully will likely linger just a bit behind S aspects, but do have larger bed surfaces to consider.  I would anticipate all forecasted areas posted at Considerable to have natural avalanche potential by later this afternoon. 

**As the storm intensifies overnight with more heavy snow the avalanche danger will increase pushing to a “High” rating likely sometime after midnight.  You should be prepared for elevated avalanche danger ratings tomorrow. 

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.Posted 7:45 February 27, 2013.A new advisory will be issued tomorrow.

Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2013-02-27 Print Version