Avalanche Forecast for Sunday, January 13, 2019

This forecast was published 01/13/2019 at 6:56 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 01/13/2019 at midnight.


The Bottom Line

High wind speeds have deposited wind slabs that will be stubborn to human triggers today, but could produce a large avalanche. Hard wind slabs like those that exist in much of our terrain are difficult to evaluate for stability, but can be easily navigated by avoidance. Today’s avalanche problem often produces no avalanches until an unlucky skier or climber ventures to find the particular weak spot in the slab. The potential size and destructiveness of an avalanche today is keeping our danger ratings elevated at MODERATE. Locations with a LOW rating (Tuckerman’s Left Side and Boott Spur as well as Huntington’s Northern Gullies) do contain snow that could produce an avalanche and will still require careful terrain selection.

2019-01-13 Printable

Forecast Area

Mountain Weather

The last recorded snowfall in our terrain was Thursday evening. Since that time, NW winds blew in the 70-100 mph range until midday yesterday. A sharp drop in wind speed took place overnight with wind currently WNW 15mph. Today, wind will be light and variable with some high level clouds. Expect sunshine for much of the day with temperatures on the summits cresting at 10F.  No new snow is forecast tonight or tomorrow.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slab exists primarily on the eastern half of the compass. Most of these formed on high wind speeds after a widespread avalanche cycle Wednesday night and Thursday. Most existing wind slabs will be stubborn to human triggers. Areas with a large upwind fetch at mid-elevations have the potential to produce a large avalanche should you find the thin spot of the slab. Lower elevations or wind-sheltered locations may harbor softer pockets of wind slab that may be possible to produce an avalanche, but the overall size will be smaller.

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 effect of Mount Washington’s notorious wind combined with last week’s 26” of snow should finally reveal itself today as blowing snow and fog finally subside. Ravines with a larger upwind fetch such as Tuckerman and the Gulf of Slides both saw significant avalanche activity, likely Wednesday into Thursday, while other ravines with a similar aspect but smaller fetch saw much less loading of wind transported snow. Wind slabs that remain in east-facing terrain will be variable in size and distribution due to terrain, the timing of recent avalanche cycles, and reloading. Making good observations of distribution while moving in the field and basing travel decisions off this will go much further than conducting stability tests while in the avalanche problem today.

Debris below Hillman’s Highway. Photo taken Friday, January 11.

Avalanche debris at base of Gully #1 in Gulf of Slides. Photo taken Saturday, January 12.

Additional Concerns

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch. Thanks to those who submitted observations on our website. These are invaluable to the avalanche center and we hope to see more submissions as the season progresses.

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 01/13/2019 at 6:56 AM.

Helon Hoffer
USDA Forest Service
White Mountain National Forest