Avalanche Forecast for Thursday, March 21, 2019

This forecast was published 03/21/2019 at 6:55 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 03/21/2019 at midnight.


The Bottom Line

Hard, icy, old snow makes up the majority of our surfaces with areas of softer but firm wind slab on mostly east facing slopes and behind terrain features. Light wind and summit temperatures increasing to the low 20’s F may warm these wind slabs for the first time since their formation last weekend. Larger east facing slopes and gullies like the Headwall in Tuckerman and the Gulf of Slides contain the largest areas of this stubborn wind slab. The hard and barely edgeable bed surface that is exposed in other areas is a very difficult, if not impossible, surface on which to arrest a fall. Consider your runouts and the consequences of a fall carefully. LOW avalanche danger exists today with human triggered avalanche unlikely. The likelihood may increase towards possible on sunny aspects or lower elevations where the snow warms to the point that it becomes wet.

2019-3-21 Printable

Forecast Area

Avalanche Safety Information Study

Please contribute to the effort to improve backcountry avalanche forecasts! Researchers in Canada devised a study to better understand how we communicate the avalanche risk, and we need your help. Please fill out this survey. It will take a few minutes, but it will help us as we work on new ways to give you the most important avalanche information.

Mountain Weather

Summit temperatures have remained in the high teens F since yesterday afternoon and will rise a bit more to 21F later today. West and southwest summit wind seem on track to remain moderate through the day at around 30 mph. Clouds will begin to gather this afternoon with summit fog descending late in the day as a low pressure system makes its way up the east coast. Snowfall should begin after dark and increase in intensity through tomorrow morning. Total snowfall amounts are uncertain as the freeze line rises to somewhere near ravine and summit elevations bringing mixed sleet and rain with it. Storm snow at higher elevations followed by upslope snowfall should bring more than enough snow to result in another avalanche cycle at ravine elevations starting tomorrow and continuing into Saturday.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Consider the consequences of a small wind slab avalanche or sluff causing you to take sliding fall into the terrain below you. Change objectives if the snow on your intended route becomes wet. Shady aspects may remain frozen with lesser concerns about the older stubborn wind slabs but greater concerns for slide-for-life conditions. Wind slabs may weaken further if they warm in the sun today.

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

Crampons were needed for safe travel up HIllmans yesterday. Note the well developed snowpack, read slide paths, that are primed for large and far running avalanches if the coming storm plays out as snow up high.

Signs of the thaw that occurred last week remain visible in many areas despite the new snow that fell and blew in over the weekend. Glide cracks in Oakes Gulf, chunks of fallen ice beneath Odell Gully and refrozen, wet loose debris piles serve as reminders of the emergence of spring hazards. Over the weekend, we will shift gears again back to avalanches being the primary concern. The incoming storm has plenty of water associated with it and will create prime upslope snowfall potential as well. The freeze line and temperatures aloft remain a wild card making tomorrow a good day to have flexible plans. The wind shift and increase Friday night may set the stage for peak natural avalanche activity due to wind loading on Saturday morning. The spring weather and the hazards it creates will be dynamic for the next few days.

Additional Concerns

The Gulf of Slides and Sherburne Ski Trails are snow covered to Pinkham Notch.

Details on daily snowfall totals, precipitation type, total depth of snow and other information can be found on our page devoted to snow study plot data. Click here to check it out.

Recent snowpack and avalanche observations can be found here and on Instagram. Your observations help improve our forecast product. Please take a moment and submit a photo or two and a brief description of snow and avalanche information that you gather in the field.

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 03/21/2019 at 6:55 AM.

Frank Carus
USDA Forest Service
White Mountain National Forest