Avalanche Forecast for Thursday, February 27, 2020

This information was published 02/27/2020 at 6:54 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 02/27/2020 at midnight.


The Bottom Line

A winter storm will bring 8-14” of new snow with extreme, shifting winds to the mountains. Avalanches could occur without a human trigger, starting this afternoon, particularly in places like Tuckerman Ravine and Gulf of Slides. Avalanche conditions could develop later this morning in west facing terrain and mid-elevations like Crawford Notch due to a strong east wind and heavy snowfall. Avalanche danger will be CONSIDERABLE today. Dangerous avalanche conditions will develop today.

2020-2-27 Printable forecast


Mountain Weather

Yesterday, around an inch of new snow fell through the day on very light wind. The summit temperature reached 23F and dropped to 19F overnight. Generally calm and foggy throughout the day. 

Today, a storm system will pass over the area and gain strength as it reaches the coast. Temperatures will fall and the snow that began around 5am at middle and upper elevations will intensify through the day. Winds are currently blowing well into loading speed, (90 mph, gusting to 129 mph), even considering the heavy, wet snow, from the E and ESE. Wind will shift quickly early this afternoon, blowing from the south for a couple of hours before shifting to the west. Wind will remain in the prime wind loading range of 50-70 mph through the day. If forecasts play out accurately, 6” snow should be available by mid-day prior to the time the wind shifts west, with 8-14” total in the forecast for today and tonight.

Tomorrow’s weather will bring a return to our standard pattern of cold temperatures and strong to extreme wind from the west. The storm system is leaving a lot of moisture in its wake with even more available from the unfrozen Great Lakes. Another 4” should fall Thursday night with another 4” possible by Saturday. Wind from the west at 50-70 mph will dump this snow into eastern facing terrain.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slabs will develop on multiple aspects and beneath steep terrain as snow accumulates today. Wet snow will form cohesive slabs quickly that will grow in size and become increasingly sensitive through the day. Though snow will start out wet and dry as temperatures cool, don’t expect the snow to be “right-side up” since wind effect will counter that occurrence. Natural avalanches will become possible by mid-day with avalanches potentially becoming dangerously large by afternoon after the wind shifts west.

  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 – Storm Slab

Storm Slab

Aspect/Elevation

Likelihood

Size

Wind sheltered areas will develop storm slabs as snow accumulates through the day. Be wary of steep wind sheltered terrain and check small, steep test slopes for signs of slab formation. Heavy snow can pack a punch so don’t underestimate the ability of a 6-8” slab to push you someplace you don’t want to go.

  Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

Forecast Discussion

The powder hounds among us may be tempted to cheat the avalanche problems today to find the goods. The high wind and low visibility will hopefully lead you to the trees or resorts. Not only is wind currently hammering near treeline, the visibility will make it challenging to use visual cues to assess risk. Swirling localized winds and rapidly accumulating snow will change things rapidly today. If you do attempt to thread the needle today, keep the angle low (30 degrees or less) and avoid avalanche paths and their runouts. Timing of the wind shift and the length of time the wind blows from each cardinal point will change conditions significantly. Banking on hourly wind forecasts is a significant gamble today and probably a bet worth passing up. Seems like a good day for lift served skiing or tours in the woods.

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
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
03/20/20
05:05
0 CMTrace 0CM154 CM7.0 C8.5 C-4.5 CClearNo precipitation
03/19/20
05:10
0 CM 0.0 MM0CM156 CM-1.5 C3.0 C-7.5 CClearNo precipitation
03/18/20
05:41
1 CM 3.0 MM1CM157 CM-8.0 C-2.5 C-10.0 CFewNo precipitationView

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 02/27/2020 at 6:54 AM.

Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest