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.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 03/01/2019 at midnight.


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.

 

Forecast Area

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.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
03/22/19
05:20
Trace Trace NC213 CM-4.0 C3.0 C-4.0 COvercastSnowView
03/21/19
05:23
0 CM 0 MM0CM213 CM-1.5 C0.0 C-11.5 COvercastNo precipitation
03/20/19
05:28
0 CM 0 MM0CM214 CM-11.0 C-4.5 C-14.0 CClearNo precipitation
03/19/19
05:25
0 CM 0.0 MMNC215 CM-13.0 C-9.5 C-15.0 CFewNo precipitation
03/18/19
05:20
Trace 0.1 MMNC216 CM-15.5 C-13.0 C-15.5 CBrokenSnowView

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
03/20/1917 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)

03/14/1940 F17 F Trace in Trace in27.7 MPH75 MPH

200 (SSW)

View
03/13/1924 F11 F .07 in .8 in29 MPH52 MPH

290 (WNW)

03/12/1911 F-1 F 0.14 in 1.9 in65 MPH104 MPH

280 (W)

03/11/1917 F6 F 0.35 in 4.4 in77 MPH114 MPH

280 (W)

03/10/1925 F4 F .35 in 3.7 in47.2 MPH94 MPH

150 (SSE)

View
03/09/1919 F0 F 0 in 0 in36.1 MPH70 MPH

290 (WNW)

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