Avalanche Forecast for Thursday, January 31, 2019

This forecast was published 01/31/2019 at 6:55 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 01/31/2019 at midnight.


The Bottom Line

Frigid temperatures and wind will make for challenging travel while you sort through deep drifts, wind scoured ice and stubborn but potentially large wind slabs that exist in our forecast area. Wind has had time to build these wind slabs from the 14” of snow which has fallen in the past 36-48 hours. These slabs may be above a weak layer of soft snow and many will be resting on an icy bed surface. It will be possible for a climber or skier to trigger an avalanche today in steep, predominantly east facing, mid-elevation avalanche terrain which has MODERATE avalanche danger. While natural avalanches are unlikely today, it is not impossible as wind continues to move some snow and stress the slabs on steep slopes. Lower elevation areas may have some easily avoided areas of wind slab and have LOW avalanche danger. The icy snow surface that is exposed or barely covered creates the potential for a long sliding fall were new snow has been scoured away.

2019-1-31 Printable

Forecast Area

Mountain Weather

Two to three inches more snow fell yesterday and overnight. That brings the 48 hour total at east side snow study plots, as well as Gray Knob to 14”, with only about half that amount captured in the precipitation can on the summit. Wind early yesterday shifted from the SE before becoming variable in the 35-45 mph range. It then shifted SW through the NW before settling into a W and WNW direction. West wind overnight increased to the 60-70 mph range. Expect cold temperatures and wind in the 50-70 mph range today. The current low temperature is -27 F and will remain in the -20’s through today and overnight. High pressure will build in tonight with west wind approaching 100 mph, driving out snow showers that may deliver another inch of snow this afternoon.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Recent snowfall and strong wind has created wind slabs in mostly east facing terrain as well as  beneath steep terrain features. Crossloading of slopes and gullies is almost always a factor so be looking for accumulated snow behind natural drift fences like alpine trees and shrubs or behind small terrain features. Piles of sluff debris, such as develops beneath the first pitch of Pinnacle Gully and across the Headwall of Tuckerman, are the type of wind slabs that grow well beyond the amount of snow accumulated on the ground and produce larger than expected avalanches.

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

The timing of recent snowfall, wind speed and direction make it likely that we passed through peak instability late yesterday or overnight. Reactive to touchy wind slabs were present during our field time early yesterday afternoon in Huntington Ravine though wind speeds had only reached into the 50 mph range on the summit for a few hours at that time. Wind speeds have ramped up quite a bit since that time and have likely blown most, but not all, available snow from the fetch. The icy crust that you may find in lower elevation or wind protected areas may be breakable with near-crust faceting that does not exist in most of our larger, mid-elevation avalanche terrain where the snow is either a knife hard mass to the ground or has the kind of bridging power that reduces deeper instability concerns to near zero for the time being.  

Additional Concerns

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
02/18/19
05:22
Trace Trace NC201 CM-14.5 C-9.0 C-16.5 COvercastSnow
02/17/19
05:24
Trace Trace Trace204 CM-16.5 C-9.5 C-16.5 CClearNo precipitation
02/16/19
05:22
13 CM 10.7 MM 12%13CM205 CM-10.0 C-2.0 C-10.0 COvercastNo precipitation
02/15/19
05:22
Trace 0.1 MM30CM195 CM-7.0 C-5.0 C-15.0 COvercastNo precipitation
02/14/19
05:24
11 CM 6.5 MM 10%NC196 CM-14.0 C-6.0 C-15.0 COvercastSnow

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
02/17/1914 F-3 F 0.00 in 0 in37 MPH74 MPH

310 (NW)

View
02/16/198 F-5 F .05 in .8 in52.4 MPH84 MPH

310 (NW)

02/15/1925 F7 F .37 in 2.7 in45.3 MPH84 MPH

240 (WSW)

02/14/1919 F-4 F .13 in 1.1 in56.2 MPH90 MPH

280 (W)

02/13/1916 F0 F .87 in 5.1 in46.3 MPH92 MPH

280 (W)

View
02/12/1912 F2 F .54 in 3.3 in37.5 MPH76 MPH

130 (SE)

02/11/196 F-9 F 0 in 0 in59.0 MPH86 MPH

330 (NNW)

02/10/19-4 F-13 F 0 in 0 in65.3 MPH101 MPH

290 (WNW)

02/09/19-7 F-14 F .01 in .2 in87.5 MPH148 MPH

280 (W)

02/08/1937 F-8 F .20 in .2 in71 MPH124 MPH

230 (SW)

02/07/1934 F22 F .04 in .2 in32.2 MPH56 MPH

250 (WSW)

02/06/1932 F17 F .23 in .4 in30.9 MPH68 MPH

330 (NNW)

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 01/31/2019 at 6:55 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest