Avalanche Forecast for Saturday, January 12, 2019

This forecast was published 01/12/2019 at 7:01 AM.
A new forecast will be issued tomorrow.

The Mount Washington Avalanche Center will no longer issue daily avalanche forecasts for the 2018/19 season. Read more

The Mount Washington Avalanche Center will no longer issue daily avalanche forecasts for the 2018/19 season. Instead, we will post an updated General Bulletin as needed, in case of significant snow or weather events that might vary from the typical daily changes that come with spring weather. We will also keep you informed about the official closure of the portion of the Tuckerman Ravine Trail from Lunch Rocks through the Lip and Headwall as well as the switch from the Lion Head Winter Route to the summer trail. Observations from the field will continue to be a valuable resource, so please keep submitting photos, videos and observations here and we will do the same. Check the Forecast page for update on Sherburne Trail closures, which are imminent as spring snowmelt continues.

The switch to a General Bulletin does NOT mean that the mountains are now a safe place to ski. The hazards which emerge in the spring are significant and require careful assessment and strategic management. If you have never skied Tuckerman, peruse our Incidents and Accidents page for spring related incidents involving avalanches, long sliding falls, icefall, crevasse and moat falls, and other incidents related to diurnal changes in the snowpack. These will help you understand and plan for these hazards.


The Bottom Line

Human triggered avalanches remain possible in the wind slabs formed late this week, but they have become stubborn and firm in most areas. You should continue to respect these hard slabs which can be tricky to assess due to their stubborn nature. The Presidential range and a majority of our forecast areas have MODERATE avalanche danger today. The Left Side and Boott Spur areas of Tuckerman Ravine as well as the Northern Gullies of Huntington Ravine have LOW avalanche danger. These Low rated areas may have pockets of unstable snow on isolated terrain features, so remember that Low does not mean no avalanche danger.

2019-1-12_printable_pdf

Danger Rating by Zone

Mountain Weather

Sustained NW wind from 70-90 mph with gusts to near 100 has been the dominant weather factor affecting our snowpack in the past 36 hours. No significant precipitation was recorded over the same period. The current summit temperature of -20F will rise towards 0F by this evening, with wind slackening to under 50 mph. Partial and variable cloud cover is forecast with summit fog generally decreasing. Wind should continually decrease to 20 mph by tomorrow evening while remaining from the NW. Expect mostly clear skies and slightly warmer temperatures tomorrow.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slabs built from the recent extreme wind speeds are variable across our terrain and mostly located found on the eastern half of the compass rose. We generally expect these relatively new slabs to be quite firm and stubborn to a human trigger. Even across similar aspects and elevations, expect a great deal of spatial variability today. Avalanche activity, upwind fetch zones, and degree of scouring all vary across the Presidential range and have created this spatial variability.

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

Continuous wind loading both during and after the recent storm produced a number of natural avalanches. Our terrain illustrated the effect of what 20” of snow in a large upwind fetch area can do, with a widespread natural avalanche cycle in Tuckerman Ravine. Huntington Ravine, with it’s much smaller fetch zone, experienced little if any natural avalanche activity and appears much more scoured. It’s notable that these ravines of similar aspect and elevation can vary significantly due to upwind fetch. We have yet to make observations in other east facing terrain, though we expect similar variability in recent avalanche activity and wind affect due to upwind fetch variability. We expect remaining wind slabs to be stubborn and potentially even unreactive, but spatial variability will challenge your ability to extrapolate stability observations across terrain. If you see evidence of avalanches from the recent storm or have any pertinent snowpack information, please use our observations submission option.

Additional Concerns

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

Avalanche Safety Information Study

Please contribute to the effort to improve backcountry avalanche forecasts! Researchers in Canada devised a study to better understand how we communicate the avalanche risk, and we need your help. Please fill out this survey. It will take a few minutes, but it will help us as we work on new ways to give you the most important avalanche information.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
05/20/19
05:30
0 CM 20.4 MM0CM68 CM11.0 C12.0 C3.5 CObscuredNo precipitation
05/19/19
05:25
0 CM 0.0 MM0CM72 CM4.0 C6.0 C2.0 COvercastNo precipitation
05/18/19
05:20
0 CM 7.6 MM0CM80 CM1.0 C6.0 C1.0 COvercastNo precipitation
05/17/19
05:25
0 CM 0.8 MM0CM84 CM4.0 C10.0 C0.0 CClearNo precipitation
05/16/19
05:20
0 CM 0.0 MM0CM84 CM1.0 C1.5 C0.0 CFewNo precipitation

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
05/19/1951 F34 F .6 in 0 in34.2 MPH66 MPH

250 (WSW)

05/18/1934 F26 F 0.06 in 0.5 in39 MPH74 MPH

300 (WNW)

05/17/1940 F28 F .22 in .05 in37 MPH81 MPH

300 (WNW)

05/16/1932 F25 F .03 in 04 in22.8 MPH40 MPH

310 (NW)

05/15/1926 F20 F .05 in .4 in32.1 MPH67 MPH

330 (NNW)

05/14/1928 F17 F .2 in 2 in19.1 MPH57 MPH

100 (E)

05/13/1928 F19 F .07 in 0.9 in34.6 MPH67 MPH

100 (E)

05/12/1931 F17 F 0 in 0 in20.5 MPH47 MPH

330 (NNW)

05/11/1932 F18 F .1 in 0 in53.6 MPH84 MPH

300 (WNW)

05/10/1944 F27 F .85 in 0 in50.1 MPH88 MPH

220 (SW)

05/09/1942 F20 F .04 in 0 in18.6 MPH44 MPH

190 (S)

05/08/1927 F18 F 0 in 0 in38.3 MPH65 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 01/12/2019 at 7:01 AM.

Ryan Matz, Snow Ranger
USDA Forest Service
White Mountain National Forest