Avalanche Forecast for Friday, February 1, 2019

This forecast was published 02/01/2019 at 7:06 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 02/01/2019 at midnight.


The Bottom Line

Wind transported snow has created our avalanche problem today. You’ll find these wind slabs in terrain that faces mostly east, beneath steep terrain features, and cross loaded into gullies and features in a wider portion of the compass rose. The slabs will appear smooth and chalky and will be firm but edgeable with boots or boards. They’ll also be hollow sounding and could crack and avalanche, especially at thin spots near the edges of thick slabs. The January 24th rain event that smoothed out all the earlier snow is now an exposed ice crust in many areas and makes a slick and planar sliding surface beneath these wind slabs. Crampons and an ice axe will be extremely useful in areas where wind scouring has exposed the crust but will give you options for avoiding wind slabs on the way up. Avalanche danger varies widely by aspect and elevation, but the possibility of human triggered avalanches tips the danger rating into the MODERATE range where medium to large size avalanches capable of burying a person exist.

2019-2-1 Printable

Forecast Area

Mountain Weather

Temperatures have remained cold in the past 24 hours with a high of -18 F and a low of -27. No new snow has fallen, though wind from the west, averaging 70 mph and gusting to 100, has resulted in blowing snow observations at every hour of the past 24. It is currently -22 F with wind from the west at 80 mph. Summit fog will begin to clear this morning with wind diminishing through the day, reaching a more tolerable 50 mph by dark. High temperature today will rise to around -10 F on the summit, 10F in the notches. Temperature will moderate some tonight and tomorrow though remain burly with new snow potentially challenging visibility and increasing avalanche danger tomorrow. At this time, Sunday looks like a warmer and less windy day for playing in the Ravines.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slabs, some of which will be large, are the main avalanche concern today. Strong winds have blown snow on the ground from the west to east facing terrain. These wind slabs are likely to be stubborn but should be approached with the kind of caution that this high consequence, low probability problem deserves. Smaller but potentially more reactive wind slabs may exist in sheltered areas.

What is a Windslab Avalanche?

  Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Snowpack and Avalanche Discussion

Fourteen inches of snow fell in the middle of the week. Cold temperature kept this snow dry and easy to transport into our easterly terrain and created touchy and reactive slabs that required staying on low angle slopes on Wednesday. The cold weather likely slowed the sintering and bonding process between layers formed this week. While natural avalanche potential is unlikely today, the recency of the new wind slabs, a steep, icy planar bed surface with few anchors remaining, and continued though minor loading could still tip the scales somewhere. Without field observations and assessment, it would be unwise to assume that avalanche danger is low in wind loaded terrain but it is almost certain that the specific areas mentioned in the bottom line create a high consequence, low probability avalanche problem. Easing into the terrain and careful travel techniques could yield some smooth turns and good booting and cramponing if you can withstand the cold and wind.

Additional Concerns

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch. The annual MWV IceFest this weekend draws climbers from all over New England to the mountains this weekend. The White Mountain Avalanche Education Foundation will be at the event on Saturday night and Frank will give a brief presentation about terrain management and avalanches in Huntington Ravine.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
03/26/19
05:30
0 CM 0 MM0CM245 CM-16.0 C-7.0 C-16.0 CClearNo precipitation
03/25/19
05:20
3 CM 1.7 MM 9%3CM249 CM-12.0 C-2.0 C-12.0 CBrokenNo precipitation
03/24/19
05:19
0 CM 4.0 MM32CM250 CM-10.5 C-5.0 C-13.0 CClearNo precipitationView
03/23/19
05:17
38 CM 38.6 MM 12%NC253 CM-5.5 C-2.5 C-5.5 COvercastSnowView
03/22/19
05:20
Trace Trace NC213 CM-4.0 C3.0 C-4.0 COvercastSnowView

Avalanche Log and Summit Weather

Daily Observations


Thank you Mount Washington Observatory for providing daily weather data from the summit of Mount Washington.

DateMax TempMin TempTotal (SWE)24H Snow & IceWind AvgWind Fastest MileFastest Mile DirAvalanche Activity
03/25/1911 F-3 F .15 in 1.7 in56.5 MPH86 MPH

270 (W)

03/24/1914 F1 F .21 in 3.4 in74 MPH123 MPH

310 (NW)

03/24/1918 F4 F Trace in 0.1 in63.2 MPH98 MPH

290 (WNW)

03/23/1914 F1 F 0.21 in 3.4 in74.4 MPH123 MPH

310 (NW)

03/22/1924 F12 F 1.09 in 15.2 in38.9 MPH79 MPH

330 (NNW)

View
03/21/1926 F15 F 0.02 in 0.3 in28.8 MPH60 MPH

160 (SSE)

03/20/1917 F1 F 0.0 in 0.0 in32 MPH58 MPH

270 (W)

03/19/194 F-4 FTrace Trace 43.4 MPH63 MPH

300 (WNW)

03/18/193 F-6 F 0.03 in 0 in52.1 MPH82 MPH

280 (W)

03/17/192 F-6 F 0.07 in .5 in61.5 MPH110 MPH

270 (W)

03/16/1925 F2 F 0.24 in 2.3 in67.5 MPH97 MPH

280 (W)

03/15/1941 F25 F 0.04 inTrace 54 MPH105 MPH

250 (WSW)

Please Remember:

Safe travel in avalanche terrain requires training and experience. This forecast 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.

Avalanche danger may change when actual weather differs from the higher summits forecast.

For more information contact the US Forest Service Snow Rangers, AMC visitor services staff at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or seasonally at the Harvard Cabin (generally December 1 through March 31). The Mount Washington Ski Patrol is also available on spring weekends.

Posted 02/01/2019 at 7:06 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest