Avalanche Forecast for Tuesday, February 25, 2020

This information was published 02/25/2020 at 7:24 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 02/25/2020 at midnight.


The Bottom Line

All forecast areas have LOW avalanche danger today.  Use normal caution for avalanche terrain and remember that Low does not mean no avalanche danger.

South facing aspects warmed from the sun over the last two days may be re-frozen in steep terrain creating a sliding fall hazard, requiring crampons and the ability to self arrest to travel safely. 

2020-2-25 Printed Forecast


Mountain Weather

Yesterday was unseasonably warm with clear skies and wind from the west at 35-45 mph. Highs from around the Presidential Range yesterday:

Today warm temperatures continue with summit high temperatures in the upper 20sF. Scattered clouds this morning will thicken through the day limiting/eliminating the effects of the sun on southern aspects. Light precipitation is expected in the afternoon as snow or freezing drizzle with a trace to less than an inch expected. Wind will be from the west at 5-20 mph.

Tomorrow, 1-3” of snow is possible with summit temperatures in the mid 20sF and cloudy skies. Wind from the west at 15-30 mph will increase to 25-40 mph. Avalanche danger will increase if we see snow totals at the upper end of the forecast.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Cloudy skies today and slightly cooler temperatures will limit the amount of warming the week-old wind slabs at mid and upper elevations will receive today. This should limit or even eliminate the instability concerns due to surface warming experienced over the last two days. What still remains, is a firm wind slab over an ice crust and a thin layer of weak facets. Triggering a wind slab today is unlikely though not impossible should you find a thin spot. With a trace to under an inch of new snow in the forecast, it’s worth keeping an eye out for new wind slab development, though with such little snow and light wind this will be unlikely.

  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 – Wet Loose

Wet Loose

Aspect/Elevation

Likelihood

Size

Wet loose avalanches are a concern today at mid and lower elevations due to warm temperatures and the chance of precipitation that will fall as rain or freezing rain, depending on elevation. These will likely be small in size, and more likely on steep terrain where even a small avalanche can have consequences.

  Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Forecast Discussion

The Moderate avalanche hazard over the last two days was driven by the warm air temperatures and bright sun working to warm surface snow, weakening the strength of the wind slab. Today, clouds should eliminate solar radiation from the equation, leaving us with ambient air temperature as the primary weather factor affecting snow stability. Today will be warm, but slightly cooler than yesterday, and air temperatures in the mid and upper elevations will likely remain just below freezing through the day. The second weather factor today is the chance of snow or freezing rain. Precip should fall as snow at upper elevations, and likely mid elevations. Lower elevations will see some light rain, which will add some degree of instability to the snowpack. With temperatures hovering around the freezing mark and with little QPF for precip we don’t expect these subtle factors to have a significant effect on the snowpack today. 

Additional Information

The Sherburne and Gulf of Slides 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
04/03/20
05:10
4 CM 30.6 MM 37%NC168 CM-1.0 C-0.5 C-1.0 COvercastRain
04/02/20
05:25
Trace 0.1 MMTrace165 CM-0.5 C0.0 C-11.5 COvercastSnow
04/01/20
05:30
0 CM 0.0 MMTrace166 CM-10.5 C6.5 C-11.0 CClearNo precipitationView
03/22/20
05:07
0 CM 0 MM0CM145 CM-18.0 C-5.0 C-18.0 CClearNo precipitation
03/21/20
05:10
Trace 1.6 MMNC145 CM-9.5 C12.0 C-9.5 COvercastSnow

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
03/20/2043 F20 F 0.31 in 0.2 in66.5 MPH145 MPH

260 (W)

03/19/2036 F14 F 0.02 in 03 in26.5 MPH50 MPH

180 (S)

03/18/2021 F9 F 0.03 in 0.5 in39.7 MPH94 MPH

290 (WNW)

03/17/2021 F6 F 0.25 in 2.1 in52.4 MPH109 MPH

280 (W)

03/16/2014 F1 F 0 in 0 in21.3 MPH50 MPH

240 (WSW)

03/15/207 F-3 F 0.0 in 0.0 in42.1 MPH71 MPH

300 (WNW)

03/14/2014 F6 F 0.09 in 0.7 in76.9 MPH117 MPH

270 (W)

View
03/13/2032 F12 F .43 in 1.4 in64.3 MPH94 MPH

270 (W)

03/12/2022 F14 F .02 in .2 in27.4 MPH48 MPH

210 (SSW)

03/11/2024 F9 F 0.02 in 0.2 in47.3 MPH85 MPH

300 (WNW)

03/10/2035 F24 F 0.45 in 0.5 in52.1 MPH97 MPH

260 (W)

03/09/2034 F21 FTrace Trace 57 MPH84 MPH

270 (W)

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 02/25/2020 at 7:24 AM.

Jeff Fongemie
USDA Forest Service
White Mountain National Forest