Avalanche Forecast for Monday, March 11, 2019

This forecast was published 03/11/2019 at 7:02 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 03/11/2019 at midnight.


The Bottom Line

Wind drifted snow will dominate today and grow wind slabs quickly on slopes with an easterly aspect. These wind slabs should be reactive to a trigger and may entrain a large amount of snow due to the connected nature of avalanche paths on the east side of the Presidential Range. You will also be able to find newly formed wind slabs on slopes with a northerly aspect, though growth of these today will be limited to cross-loading and may become stubborn due to high wind speeds. Slopes that contain wind drifted snow will have CONSIDERABLE avalanche danger due to the likelihood of an avalanche and the size it could produce. Remember that wind can quickly turn inches of snowfall into feet of wind slab, particularly where the upwind fetch is largest.

2019-03-11 Printable

Forecast Area

Mountain Weather

A 12-hour period of steady snowfall yesterday that started late morning left around 4” on the east side of the Range, though less on the northwest side due to the location of the storm. During this time wind from the south decreased from 65 mph to the 40 mph range. Just as snow stopped, wind shifted to blow from the west and has increased to 75 mph where it should remain for the forecast period. Current temperatures on the summit are 14F and 23F at 3800’ which should gradually drop about 10F over the day. Conditions are ripe for upslope snow showers through the day and could deliver up to 3” by dusk. Snow showers may continue overnight into Tuesday, delivering another inch of two on steady high wind speeds from the NW.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slab that began building yesterday will continue to grow today with more snow and wind. These will likely be reactive to a human trigger. After northerly aspects saw direct loading yesterday, the shift in wind overnight will primarily load easterly aspects today. Those with a large fetch, such as the Tuckerman Headwall and main gullies in Gulf of Slides, are the areas that could produce a large avalanche, particularly in the unlikely but not impossible event of an avalanche stepping down into wind slab that formed last week.

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

Wind slab that formed early last week with a clear weak layer between the overlying slab and bed surface remained largely unreactive except for a small skier-triggered avalanche on Friday. Wind slab that built yesterday and will continue to grow today rests on top of this older wind slab in locations that see largest loading today. Though outside our forecast area, a human-triggered avalanche yesterday in Lincoln’s Throat demonstrated how quickly wind slabs can grow, particularly at the base of ice bulges where sluffing can contribute quickly to the mass of growing slabs. Wind speeds today will border on the verge of scouring in some locations, but with wind direction making a 90 degree swing last night, be prepared to find today’s avalanche problem around micro-features in many places of our terrain.

Additional Concerns

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

Join us next Tuesday evening, March 19th, for an Avalanche Awareness presentation at Plymouth State University! Details on our events page.

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 03/11/2019 at 7:02 AM.

Helon Hoffer
USDA Forest Service
White Mountain National Forest