Avalanche Forecast for Tuesday, February 26, 2019

This forecast was published 02/26/2019 at 7:09 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 02/26/2019 at midnight.


The Bottom Line

New wind slabs that are possible to trigger should be your primary avalanche concern if you brave the extreme wind and frigid temperatures today. Continued wind loading on these new slabs should also keep natural avalanches initiating in steep overhead terrain on your radar. While unlikely, recent snow and loading make it prudent to assume a natural avalanche could occur in locations with the greatest upwind fetch until you can determine otherwise. Wind affected snow can be found at lower elevations where you’re most likely to find reactive wind slabs today. MODERATE avalanche danger exists for all forecast areas. Make careful observations of our variable upper snowpack to guide your terrain decisions today.

2019-2-26_printable_pdf

Forecast Area

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Mountain Weather

Snowfall yesterday and last night ended around midnight, totaling over 8 inches at the summit with less at lower elevations. Wind from the W and NW has been sustained at over 100 mph on the summit for all but a few hours since late Sunday night. Several hours last night were in the 120-140 mph range with a peak gust of 171 mph. Today and tonight wind should remain NW around 80 mph with temperatures in the teens below 0F. A trace to one inch of snow is forecast as clouds decrease today. Expect no snowfall tomorrow as wind speeds finally drop significantly.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Fresh wind slabs are the primary avalanche problem for all elevations today. You’re most likely to find them on the eastern half of the compass rose, with stubborn slabs at middle elevations and the potential for reactive but smaller wind slabs at lower elevations. No recent visual observations of higher terrain combines with wind continuing to affect the upper snowpack to provide a healthy dose of uncertainty today. Look for smooth wind drifted snow to identify the avalanche problem wherever you travel today and expect great variability in the wind’s effect on the snow surface.

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

The notable wind event that is tapering slightly but continuing today will make for varied upper snowpack conditions of hard wind slab, heavily wind textured snow, and scouring to old crusts. You can also expect to find wind affected snow at low elevations which is also where you’re most likely to find reactive wind slab today. The unique recent weather factor was continued snowfall with significant accumulation on the extreme wind yesterday and last night. This somewhat rare occurrence of significant snowfall through peak wind speeds of a storm lends uncertainty to today’s forecast. We will undoubtedly have an interesting aftermath of this snow and wind event when visibility returns. Continued wind loading today should couple with potentially wide spatial variability in motivating you to carefully and continually assess snowpack if you venture into steep terrain.

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 02/26/2019 at 7:09 AM.

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