Avalanche Forecast for Sunday, March 3, 2019

This forecast was published 03/03/2019 at 7:09 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

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


The Bottom Line

Wind slabs remain our primary avalanche problem today. LOW avalanche danger exists throughout the forecast area though the potential for small avalanches remains in isolated areas. Human triggered avalanches in these wind slabs are unlikely but not impossible. Normal precautions in your terrain management as well as in the gear that you carry is advised. The firm slabs in steep open terrain present a long sliding fall hazard so crampons, an ice axe, and an honest assessment of the consequences of a slip will also be useful today.

2019-3-3 Printable

Forecast Area

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Mountain Weather

Around an inch of low density snow fell on the summit overnight and early this morning on moderate (40’s mph) summit winds from the WNW. Temperatures are starting in the single digits above zero and will rise to the teens on the summit and around freezing in Crawford Notch. Skies will clear and winds will diminish further today as high pressure passes by before tonight’s storm. Snow will begin shortly after dark tonight. Though most weather models show the low pressure tracking far enough off shore to keep snow totals on the modest side, between the storm and the upslope snow that follows we will have elevated avalanche danger tomorrow, especially as the west and northwest winds increase.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slabs may also be found at lower elevation locations and have presented clean shears though no sign of propagation has been evident since their formation in the extreme wind event on Feb 25th. At mid elevation areas, most of these wind slabs are firm and unreactive. There have been multiple observations of an upside down snow structure, particularly at lower elevations or some wind sheltered locations, but with no reports of significant cracking or collapsing. Wind sheltered terrain may contain softer wind slabs that are more stubborn than unreactive, so be increasingly cautious where hollow sounding snow and steep terrain intersect.

  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

Snow that fell at higher elevations last night, like the light snowfall on Wednesday night, is unlikely to improve skiing conditions. The softest snow is found either at lower elevations or wind sheltered areas. Snow coverage has improved on the west side with an avalanche observation in the main gully of the Ammo recently which helped to fill in and cover some obstacles. The snowpack there remains thin with open water and the typical terrain traps in place. Lots of lines have been skied this week throughout the range, though no huge, soft snow induced grins have been observed. Technical ski mountaineering with careful crampon and ice axe equipped ascents, followed by cautious, short radius turns on the way down paints a clearer picture of what’s been happening. It’s not even close to spring yet at any elevation with a dynamic snowpack that continues to demand respect. Crowds of people on the Lion Head winter route are being reported so factor in wait times on the steep sections into your itinerary or consider an alternate route.

Additional Concerns

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch. Thanks to those who have been submitting observations this week. These are very helpful to our forecast and the community so please keep them coming. Some issues involving iPhone photo uploads have been resolved so the sideways photo problem is no longer a problem.

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 03/03/2019 at 7:09 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest