Avalanche Forecast for Friday, March 1, 2019

This forecast was published 03/01/2019 at 7:19 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

Cold temperatures have slowed settlement of the large wind slabs formed during Monday’s snow & wind storm. Generally speaking, these wind slabs are firm enough to support the weight of a skier or climber and triggering an avalanche is unlikely. The avalanche danger is LOW in all forecast areas today. However, unlikely does not mean the same as impossible so it is worth considering today that our steepest and most sheltered areas hold thick, wide wind slabs that push the upper end of the LOW rating due to their size. You’ll find the largest of these slabs in the usual east facing places including the Headwall of Tuckerman Ravine and the Gulf of Slides.

 

Danger Rating by Zone

Tuckerman Ravine 2/27/2019. Wind slabs appear smooth and pillowy in some areas, heavily wind textured in others.

Be mindful that our deep snowpack has allowed the normally smaller snowfields to grow in size and should be on your radar. If you’re out today, enjoy the nice weather but don’t let your guard down. Also, bear in mind that the snow is really firm so the potential for long sliding falls should have you thinking about crampons, and an ice axe. Moving carefully and assessing obstacles in your fall line will reduce your risk to this hazard.

2019-3-1 Printable

Mountain Weather

Today is forecast to be another pleasant day with light W winds of 20-30mph and a summit high temperature of 10F, a nice increase from yesterday’s high of 3F. A low pressure system to our south will slide in, increasing overhead clouds through the day with the summits expected to remain in the clear. Tomorrow will be slightly warmer with temperatures in the teens, continued low wind speeds and increasing clouds leading to a chance of light snow in the afternoon.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slabs formed from the three days of high of wind following Monday’s snow are generally firm in middle and upper elevations. Expect them to be unreactive to a human trigger, but look for exceptions to help guide your terrain choices. Be especially careful of smooth slabs that sound hollow or are soft underfoot. These slabs vary in size and are quite large in some terrain, particularly the Headwall of Tuckerman Ravine. This avalanche problem should be generally absent on the western half of the compass rose. In lower elevations you’ll find pockets of snow with a poor structure that may be more reactive to a human trigger though smaller in size.

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

Lower Snowfields. 2/27/19. Snow sloughing from Dutchess collecting under the gully on the left side of the Lower Snowfields. Sections of the crown from a recent natural avalanche in the Lower Snowfields still visible.

Some say that wind is the architect of the snowpack, and nowhere is this more true than on Mount Washington.  The 8” of new snow on Monday has been ravaged by consistent wind as high as 171 mph. In the aftermath we find areas of smooth and hard (1F – P) wind slab, heavily wind textured snow, and scouring. When we see wind speeds this high, the slabs tend to form much lower on the slopes and this was evidenced by crown lines remaining from natural avalanches in the Lower Snowfields and a very low snow slope on the north side of Raymond’s Cataract. Interestingly, field observations did not show signs of natural avalanches from the usual performers. With plump slabs below many of our large avalanche paths it appears more likely that they continually sluffed snow throughout the storm, possibly due to such high wind speeds.

Additional Concerns

Wind sculpted sastrugi in the drainage as you exit the floor of Tuckerman Ravine.

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch. The Little Headwall filled in during the storm though it is guarded by large and aggressive sastrugi snow in the drainage.

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
05/22/19
05:25
Trace 6.2 MMTrace60 CM0.5 C2.0 C-1.0 CClearNo precipitationView
05/21/19
05:25
0 CM 4.2 MM0CM60 CM2.0 C15.0 C2.0 COvercastNo precipitation
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

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
05/21/1934 F23 F .57 in 1.9 in73 MPH135 MPH

330 (NNW)

05/20/1951 F33 F 0.57 in 0.0 in48 MPH82 MPH

250 (WSW)

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)

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 03/01/2019 at 7:19 AM.

Jeff Fongemie
USDA Forest Service
White Mountain National Forest