Avalanche Forecast for Sunday, March 17, 2019

This forecast was published 03/17/2019 at 7:02 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 03/17/2019 at midnight.


The Bottom Line

Wind slabs sitting on top of a melt/freeze crust make up today’s avalanche hazard. These should be easy to identify by their smooth, white appearance when contrasted next to the dirty, textured, exposed melt/freeze surface. This melt/freeze surface presents a long, sliding fall hazard that makes bringing crampons, an ice axe, and the ability to use them effectively mandatory for travel today. Avalanche danger will be LOW at all aspects and elevations. Keep in mind the consequences of triggering even a small a avalanche would be a long, sliding fall with limited ability to self-arrest; be sure to factor this into decision-making today.

Printable 2019-03-17

Forecast Area

Avalanche Safety Information Study

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Mountain Weather

After a warm second half of the work week, temperatures began their plunge Friday night, falling from 32F midnight on Friday to 0F 24 hours later. Wind from the west blew in the 70 mph range Saturday, dropping slightly after dark to the 50 mph range. Snow showers delivered 2.3” of snow to the summit and 1.5” to Hermit Lake at 3800’. Today, light snow this morning may accumulate up to another inch (likely less) with a current W wind of 70 mph decreasing to 40-60 mph midday. Temperatures will increase slightly this afternoon, but expect a cold day overall. Monday should see skies clearing with temperatures staying around 0F.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Newly formed, isolated wind slabs can be found on slopes with an easterly aspect at mid and upper elevations. These will be stubborn to a trigger and small in size. Wind speeds yesterday were capable of scouring some locations, so expect a good amount of spatial variability of today’s avalanche problem. With good visibility, especially later in the morning or afternoon, it should be easy to identify and avoid the avalanche problem.

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

New snow that fell yesterday contained periods of graupel as well as experienced breaks in snowfall and slight dips in wind speeds. While some bonding at the interface of new and old snow may have taken place, interfaces in the new snow due to changing conditions as the snow arrived will likely be the culprit of an avalanche today should someone get a crack to propagate. The old snow is still in the process of refreezing after the thaw this past week. At mid-elevations yesterday, trails were supportable, but any off trail travel involved postholing. The continuing freeze today will lessen the amount of postholing, but also increase the hazard of long, sliding falls. Crampons and ice axes will be necessary for moving safely in avalanche terrain and flotation may be required to get to avalanche terrain. Despite the snowpack settling almost 7” at our snowplots during the thaw, no open holes were observed above 3500’ and stream crossings remain frozen.

Additional Concerns

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

Considering an avalanche airbag pack? Take advantage of our current auction for the Black Diamond Saga 40 airbag pack, ending at 8:00 pm this Monday. Increase your margin of safety AND support your avalanche center!

Don’t miss our last avalanche awareness presentation of the season, free to attend, this Tuesday evening at Plymouth State University.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
05/31/19
05:20
0 CMTrace 0CM0 CM8.0 C11.0 C0.5 CBrokenNo precipitation
05/30/19
05:25
0 CM 0.0 MM0CM0 CM7.5 C7.5 C1.0 CScatteredNo precipitation
05/29/19
05:25
0 CM 22.3 MM0CM0 CM1.5 C4.0 C0.0 COvercastNo precipitation
05/28/19
05:25
0 CM 0.0 MM0CM0 CM0.5 C11.0 C0.5 CClearNo precipitation
05/27/19
05:15
0 CM 0.0 MM0CM10 CM8.0 C15.5 C8.0 CClearNo precipitation

Avalanche Log and Summit Weather

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
05/30/1946 F36 F 0 in 0 in27.9 MPH55 MPH

290 (WNW)

05/29/1947 F33 F 0 in 0 in20 MPH48 MPH

290 (WNW)

05/28/1934 F28 F .71 in 3.7 in20 MPH48 MPH

290 (WNW)

05/27/1940 F27 FTrace 0 in38.9 MPH68 MPH

300 (WNW)

05/26/1948 F39 F .77 in 0 in48.7 MPH75 MPH

290 (WNW)

05/25/1947 F31 F .42 in 0 in17.7 MPH63 MPH

240 (WSW)

05/24/1942 F32 F .66 in 0 in44.8 MPH105 MPH

05/23/1944 F30 F .16 in 0 in26.8 MPH71 MPH

270 (W)

05/22/1934 F21 F 0 in 0 in36.2 MPH115 MPH

330 (NNW)

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)

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 03/17/2019 at 7:02 AM.

Helon Hoffer
USDA Forest Service
White Mountain National Forest