Avalanche Forecast for Tuesday, April 2, 2019

This forecast was published 04/02/2019 at 6:58 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 04/02/2019 at midnight.


The Bottom Line

Small wind slabs formed since late Sunday could still produce a human triggered avalanche, and large areas of hard, refrozen snow make long, sliding falls a crucial risk to manage. The recently formed wind slabs should be avoidable in most terrain. Look for any new wind drifted snow in the alpine as the avalanche problem. While human triggered avalanches are unlikely today due to the isolated and avoidable nature of our current wind slabs, they are not impossible and you may be drawn to travel on these areas of softer snow. All forecast areas have LOW avalanche danger. A small avalanche or stumble on today’s hard refrozen crust could cause a high consequence, long sliding fall. Bring crampons, an ice axe, and your ability to use them to prevent a fall.

2019-4-2_printable-pdf

Forecast Area

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Mountain Weather

A trace of new snow yesterday morning was followed by clearing through the day. Wind on the summits decreased and shifted slightly from WNW at 70 mph to W at 40 mph. Temperatures remained below freezing in all of our terrain, with the Summit hovering around 0F. Today should be 15-20 degrees warmer at all elevations, increasing towards 20F on the summits and 35F at 3,500’ elevations. Decreasing wind may drop below 30 mph by this afternoon while shifting S. Below freezing temperatures tonight should refreeze any melting that occurs at middle and low elevations before tomorrow brings temperatures similar to today. Clouds move in overnight and will bring a chance of light precipitation tomorrow which should fall as snow at high elevations but as mixed precipitation and rain at middle and low elevations. Wind will increase significantly late tomorrow.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slabs from the 1-3” of snow since Sunday can be found in the terrain and especially on the eastern half of the compass rose. These small slabs can likely be avoided in many areas by travelling on the hard, refrozen crust. While we expect these pockets of wind slab are becoming stubborn to a human trigger, human triggered avalanches are not impossible and could cause a high consequence sliding fall. Variable recent snowfall across the range, with the Northern Presidentials receiving a little more snow, means that your evaluation of actual location and size of these wind slabs will be important today.

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

Small amounts of snow fallen since Sunday has been affected by wind and presents the only distinct layer of concern in our present snowpack. Warming over the weekend thoroughly moistened the pre-existing upper snowpack which has since refrozen. Expect to find a snow surface of this robust melt freeze crust with areas of wind slab that formed in the past 24 hours. We expect the largest, though still relatively small, wind slabs to be in areas with a significant upwind fetch like the Headwall of Tuckerman Ravine and possibly in the Northern Presidential Range which has received slightly more new snow since Sunday. These wind slabs are gaining stability but should be respected and possibly avoided in high consequence terrain. Exposed melt freeze crust may see a little softening on sun exposed slopes this afternoon at middle and low elevations, but this softening is unlikely to be enough to for wet loose sluff to become a problem. Our lowest elevations like Crawford Notch are losing snow rapidly and some areas lack sufficient snow to have any avalanche problem.

Additional Concerns

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

Details on daily snowfall totals, precipitation type, total depth of snow and other information can be found on our page devoted to snow study plot data. Click here to check it out.

Recent snowpack and avalanche observations can be found here and on Instagram. Your observations help improve our forecast product. Please take a moment and submit a photo or two and a brief description of snow and avalanche information that you gather in the field.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
04/24/19
05:20
0 CM 1.7 MM0CM146 CM4.5 C7.0 C2.0 COvercastNo precipitation
04/23/19
05:22
0 CM 10.4 MM0CM152 CM3.0 C12.0 C1.0 COvercastRain
04/22/19
05:20
0 CM 0.0 MM0CM156 CM1.0 C10.0 C1.0 CFewNo precipitation
04/21/19
05:15
0 CM 28.0 MM0CM160 CM6.5 C11.0 C6.5 CBrokenNo precipitation
04/20/19
05:15
0 CM 16.5 MM0CM175 CM9.5 C12.0 C6.5 COvercastRain

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
04/23/1946 F33 F .18 in 0.0 in25.8 MPH60 MPH

240 (WSW)

04/22/1942 F33 F .15 in 0.0 in18.1 MPH54 MPH

50 (NE)

04/21/1945 F36 F 0.21 in 0 in23.8 MPH66 MPH

170 (S)

04/20/1949 F43 F 1.11 in 0 in42.6 MPH96 MPH

240 (WSW)

04/19/1947 F41 F 0.23 in 0 in46 MPH95 MPH

240 (WSW)

04/18/1942 F18 F .23 in .2 in39.4 MPH98 MPH

240 (WSW)

04/17/1925 F15 F 0 in 0 in28.8 MPH82 MPH

330 (NNW)

04/16/1916 F12 F .28 in 1.5 in82.2 MPH142 MPH

290 (WNW)

04/15/1945 F12 F .97 in 1.6 in55.6 MPH133 MPH

290 (WNW)

04/14/1945 F24 F 0.22 in 0 in53 MPH85 MPH

290 (WNW)

04/13/1941 F28 F 0.09 in 0 in55.8 MPH86 MPH

280 (W)

04/12/1941 F20 F 0.15 in 0.0 in47 MPH106 MPH

240 (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 04/02/2019 at 6:58 AM.

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