Apr 172015
 

Spring has been in the air!  Last weekend, the snowpack went isothermal and people feasted on mashed potatoes and corn snow.  Four out of the past five days, the Mount Washington Observatory recorded the weather as “In the clear under clear skies.”  Talk about a harbinger of A-frames, coolers, and beacon tans.  Unfortunately, all good things must come to end.  This was all too obvious as I drove to Pinkham this morning and turned my windshield wipers in order to see the dense cloud encasing the mountains.

A weak cold front passed through today, delivering mostly rain to Mount Washington.  The summit hovered at the freezing mark all day while the temperature steadily increased down the vertical temperature profile to the mid-40s at Pinkham.  Steady precipitation ended late morning and it looks as if the next cold front will arrive late Saturday morning.   Rain, sleet, and snow are terms all being thrown around by various forecasters.  It looks as if the colder air will move in after precipitation starts, transitioning to snow by early afternoon.  By the time the front passes late on Saturday, we are expecting 2-6” of snow.  Winds on Saturday will be increasing to hurricane force during the night and then decreasing to the 30-45mph range on a possibly sunny Sunday.

Two to six inches… sounds like ankle-deep powder in April!  Almost.  Remember, this is The Whites, where if you don’t like the weather, wait two minutes and it will change.  Colder temperatures following a rain event will lock up the snow into cement in places.  Once this happens, add a few inches of snow transported on hurricane force winds and we may see heightened avalanche danger.  Most likely, we will see a fine display of extreme spatial variability.  Although the Mount Washington Avalanche Center is a micro-scale forecast center, even we do not get as detailed as a safe traveler will need to be over the next 48 hours.  Expect scoured cement next to pockets of potential touchy wind slab that are insulating areas of rain-saturated snow, next to dust on crust, next to sheltered spots containing actual skiable snow that is stable.  I’m starting to exhaust my vocabulary in thinking of conditions you could find if you go into avalanche terrain this weekend.  Have I mentioned long, sliding falls, crevasses, falling ice, or undermined snow yet?

It’s about this time of year when I feel like I transition from an avalanche forecaster into a spring hazard forecaster.  Do you have crampons and an axe in your mountain kit?  These tools can make that ascent of the headwall feel much more secure.  Have you bought your “Ice-Out” ticket for when the Sluice ice will come crashing into Lunch Rocks?  Make sure your lunch spot of choice is not directly underneath that hanging cleaver.  While on that topic, you should realize that Lunch Rocks is more accurately “Icefall Rocks” and has been the site of dozens of significant icefall caused injuries.  It is not a good place to hang out as we transition into the middle of icefall season.  Who will be first to take the leap of faith over the waterfall hole currently opening in the Lip?  Now is the time, more than ever, to ascend the line you plan to ski.  It’s much easier to assess how big those crevasses are as you work your way up the boot-pack, rather than as you fly by on your descent.  Do you think that snow-bridge on the Little Headwall is strong enough to hold your weight?  Perhaps you should buy that Dynafit race suit just to keep you weight to a minimum.  As you climb up to the Bowl from Hermit Lake, be sure to look to your left.  Plot on your mental map where those open holes are on the Little Headwall.  Talk to a Snow Ranger or ski patroller in the Bowl to get the best advice on whether it’s better to ski or walk down.  Walking or skiing with maybe a swim in the Cutler River, it’s a tough answer that will change by the minute this weekend and into this coming week.

The John Sherburne Ski Trail is still completely open.  It will remain so for this weekend.  Looking ahead at the coming week with inches of rain in the forecast, we will begin closing the bottom sections of the trail.  Please respect this closure when it happens as the trail is not built for foot traffic.  Crossing over to the Tuckerman Ravine Trail helps prevent erosion on the ski trail, making early and late-season skiing possible.  As to the current conditions, you will encounter large moguls, rocks, grass, and open partially flooded water bars.  Classic spring skiing.  The Tuckerman Ravine Trail still has snow coverage from Pinkham to Hermit Lake.  Skinning is possible the entire way with some careful navigation exposed rocks down low.

Be sure to read the tomorrow’s Avalanche Advisory for the latest update.  See you in the morning.

-Helon

 Posted by at 5:37 pm
Apr 172015
 

This advisory expires at 12:00 midnight.

Tuckerman Ravine has Low avalanche danger. Natural and human-triggered avalanches are unlikely. Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when traveling in avalanche terrain in Huntington. A danger of falling ice exists, and will persist until it all comes down.

AVALANCHE PROBLEM: Wet loose avalanches continue as an unlikely threat today as temperatures hover just above freezing. Steep slopes that have seen a lot of ski traffic generally have less of this type of problem. Areas without recent ski traffic have the greatest potential for a larger sluff. The hazard of these heavy, wet piles of snow moving downhill comes from their ability to bulldoze you into bushes, rocks or over cliffs or to push your boards in expected directions.

OTHER HAZARDS: The typical spring hazards are showing themselves.  Numerous areas of large ice have horizontal cracks forming and the Sluice ice, above Lunch Rocks, is already missing some chunks. Be aware of what is above you on a warm day and realize that eating lunch at Lunch Rocks puts you directly in the runout of large pieces of falling ice. Today’s warm temperatures and rain showers will increase the likelihood of this annual hazard. During this period of falling ice every year we do not recommend sitting at Lunch Rocks even though it may have a long tradition for you. The vast majority of icefall injuries over the past 50 years have occurred at Lunch Rocks also dubbed, “Icefall Rocks”. Reduced visibility due to summit fog will challenge navigation as well as your ability to identify and manage other objective hazards. The snowpack is slowly moving downhill as a unified mass and is pulling away from cliffs, creating crevasses. These may change quickly, so anticipate them growing in size. Undermined snow is creating challenges for exiting the Bowl. While the Little Headwall is still skiable, there is open water both above and below. The best exit from the Bowl may involve walking to Connection Cache and possibly farther.

WEATHER: The weaker of two cold fronts arrived this morning, bringing light rain and mixed precipitation showers depending on elevation, along with moderate to strong summit winds and fog. The amount of rain and precipitation associated with this front is minimal, and won’t change our snowpack much. Tonight, temperatures will drop as the next cold front arrives, bringing 2-4” of snow on Saturday. Northwest winds with the potential for 2-6” (5-15 cm) total of snow by the end of the storm Saturday afternoon will change things quite a bit. After the warm spell of sunny corn skiing, followed by rain, we will return to wintry conditions Saturday and Sunday with an icy snowpack beneath fresh wind slab.

 SNOWPACK: The near freezing conditions over the past couple of day helped to firm up and preserve our snow at ravine elevations after last Friday’s rain and thaw. In Tuckerman Ravine, plenty of ski traffic Wednesday and Thursday tested and compacted our slopes and helped to ease our minds about wet slab avalanches. Being a generally cautious person, I wouldn’t leave my beacon, probe and shovel behind for lots of reasons.  Most of these are unlikely, but consider a large icefall or a subsurface meltwater blowout as an unusual, but not impossible, potential trigger. These are just of couple of reasons why we will continue to wearing our avalanche PPE through late spring.  As our snowpack melts, thin spots develop and firm or icy surfaces are exposed so be aware that an ice axe or self-arrest ski pole and crampons may be worthwhile weapons in your quiver.

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 Mount Washington Volunteer Ski Patrol, or the AMC at the Pinkham Notch Visitor Center and Hermit Lake.
  • Posted 7:45 a.m. Friday, April 17, 2015. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2713

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