Avalanche Forecast for Sunday, March 10, 2019

This forecast was published 03/10/2019 at 7:20 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 03/10/2019 at midnight.


The Bottom Line

Snow falling today will combine with wind to create new unstable slabs and increasing avalanche danger through today and tonight. Wind from the south today will load terrain on the northern half of the compass rose. After dark, wind shifting to the westwill transport snow from our largest fetch zones into easterly terrain and continue to enlarge new slabs. Watch for quickly developing wind slabs today and realize that the size of new wind slabs depends on the amount of snow we actually receive.. Avalanche danger will rise to MODERATE today as human triggered avalanches in these growing slabs become possible. If you’re in the mountains late today, be aware that a wind shift to W and increasing speeds may result in avalanche danger reaching CONSIDERABLE due to the increased chance of natural avalanches in wind loaded terrain.

2019-3-10_printable_pdf

Forecast Area

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Mountain Weather

Temperatures slowly climbed to the upper teens F on the summit yesterday under clear skies and decreasing NW wind. New snow today should total 2-4 inches and fall on S wind that will increase this morning from under 30 mph to the 50-60 mph range. Snowfall may taper slightly  after dark as wind ultimately shifts W and increases. A period of mixed precipitation, particularly sleet, may occur tonight though forecasts are trending towards all snow and totaling at least another inch. Consistently W wind around 70 mph is forecast tomorrow and we may receive an additional trace to 2” of snow.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

New snow on increasing southerly wind will build new wind slabs though the day that will become possible to human trigger as they grow in size. Expect the largest wind slabs to develop on northerly aspects but watch for cross loadinging to also build slabs on easterly and westerly aspects. The wind shift to W is forecast to occur around midnight tonight, but if you’re out late today, watch for an earlier shift in wind and corresponding wind loading of easterly terrain from our large fetch zones. Additionally, a remote possibility does exist for an avalanche to entrain existing snow in isolated areas and contribute to overall size.

  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.

Secondary Avalanche Problem – Dry Loose

Dry Loose

Aspect/Elevation

Likelihood

Size

Steep, wind sheltered terrain will be prone to dry loose sluffing as new snow accumulates today. While small in size, always remember that a small loose snow avalanche in the wrong place can knock you off your feet and be a big deal. Additionally, sluff tends to pile relatively low in terrain, especially below ice climbs, and ultimately helps to build cohesive slabs in these locations.

   Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

Snowpack and Avalanche Discussion

The wind slabs that formed over the past week have finally had time to gain stability; today’s avalanche problem is primarily based on inbound snow and wind. In the past two days with many skiers and climbers in the terrain, just one human triggered avalanche has been reported. These older wind slabs do seem to have a firm over soft structure but have become largely unreactive to a human trigger. Today starts with low avalanche danger for most terrain. As new slabs build and avalanche danger increases today, it’s important to remember that today’s moderate avalanche danger rating is based fully on the forecast of incoming weather. Watch for snowfall totals and wind direction that differ from the forecast if you’re playing in or around avalanche terrain today.

Additional Concerns

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

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 03/10/2019 at 7:20 AM.

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