Avalanche Forecast for Thursday, April 23, 2020

This information was published 04/23/2020 at 7:36 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 04/23/2020 at midnight.


The Bottom Line

More new snow fell yesterday with howling west and west-northwest winds dumping all of it onto eastern aspects. You’ll find a mix of scoured and impenetrable hard snow and thick wind slabs at and above treeline today. Wind slabs are likely to be stubborn to a human-trigger but large in size. The avalanche danger today in MODERATE. Assess these slabs for soft, weak layers beneath the stiffer slabs on the surface and manage your terrain carefully.

Rescuers should respond with a surgical mask or high quality homemade mask for themselves along with hand sanitizer and/or wipes. Due to wide community spread of the virus, every patient and rescuer may be a coronavirus carrier so act accordingly. In the Cutler River Drainage, we have an extremely limited supply of N95 masks which will be reserved for the patient care provider(s) and the patient. Continue to maintain your distance from other rescuers and use a mask when forced to work closely together or ride in a vehicle together. Surface contact remains an equal or greater threat than airborne spread so know what your hands are doing at all times. 

As always, rescuers without PPE will be turned away or reassigned. This includes beacon, shovel and probe. Also, like a beacon, a mask is just one tool to help keep you safe during a rescue. Also like a beacon, a mask requires training and experience to use properly. N95 masks should be reserved for close quarters and inside work.

If you would like other people on your SAR team to receive this email product, please email us at forecasters@mountwashingtonavalanchecenter.org  with names and email addresses. Thanks for your help.


Mountain Weather

Yesterday, another 3” snow fell, adding to the 3” that fell the day prior. Winds howled all day from the west in the 65-85 mph range and gusting to 110mph. Temperatures remained below normal with temperatures in the single digits.

Today, wind will diminish through the day from 60-80mph this morning to 35-50 mph later in the day. Temperatures will rebound to the high teens on the summit and continue to rise overnight. Fog will begin to lift with partly sunny skies above leading to improved visibility later in the day.

Tomorrow, low pressure brings clouds and rain showers with freezing rain possible if cold air remains pooled in place. Temperatures will rise to the low 30’s on the summit. Winds will be generally light from the southwest.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

6-8” of new snow has fallen over the past 48 hours with winds blowing at speeds prime for transporting this snow for nearly 36 hours. These wind slabs grew on top of a hard, refrozen crust. Remember that large stubborn wind slabs can be triggered from thin spots. Travel carefully and one at a time when exposed to this hazard.

  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.

Forecast Discussion

As time wears on and the public grows weary of staying at home, we have seen an uptick in attempts to enter the closure area both from Route 16 and the west side. A large majority of the public do not have the skills or wisdom necessary to adequately gauge the risks they are taking or have a sense of what “dialing it back” means. Local trends indicate that large crowds are not necessarily an accurate indicator of the likelihood of an incident or accident. Please stay prepared for winter conditions rescues that could range from searches to avalanche rescue. Winter remains in full force above tree-line with spring hazards on the back-burner for a while longer. May is only a week away and the waterfall hole and glide cracks in Tucks have barely begun to appear, though they are now fully filled in with new snow. 

Additional Information

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch.

The Lion Head Winter Route remains the easiest route to the summit from Pinkham Notch but requires an ice axe, crampons (not just micro-spikes) and possibly a rope. This is a mountaineering route and requires solid skills for a safe, timely ascent.

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
04/13/20
06:15
0 CM 0.1 MM0CM206 CM-3.5 C7.5 C-7.0 COvercastRain
04/12/20
06:20
Trace 1.8 MMTrace216 CM-7.0 C-4.0 C-7.0 CFewNo precipitation
04/11/20
06:20
14 CM 23.1 MM 14%62CM222 CM-8.0 C-6.0 C-8.0 COvercastNo precipitation
04/10/20
06:30
53 CM 49.5 MM 12%NC200 CM-6.0 C-2.0 C-6.5 COvercastSnowView
04/09/20
06:25
0 CM 0.0 MM0CM158 CM-1.0 C8.0 C-4.5 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
05/21/2053 F38 F 0.0 in 0.0 in29.4 MPH59 MPH

280 (W)

05/20/2050 F34 F 0.0 in 0.0 in29.4 MPH59 MPH

280 (W)

05/19/2041 F27 F 0.0 in 0.0 in15.3 MPH36 MPH

100 (E)

05/19/2050 F34 F 0.0 in 0.0 in11.4 MPH25 MPH

30 (NNE)

05/18/2045 F30 F 0.0 in 0.0 in14.7 MPH36 MPH

70 (ENE)

05/17/2040 F30 F 0.0 in 0.0 in17 MPH35 MPH

270 (W)

05/16/2037 F28 F .16 in 0.0 in38.8 MPH101 MPH

310 (NW)

05/15/2042 F32 F .95 inTrace 31.5 MPH95 MPH

250 (WSW)

05/14/2035 F19 FTrace 0.1 in42.8 MPH85 MPH

300 (WNW)

05/13/2022 F9 F 0.0 in 0.0 in66.3 MPH98 MPH

300 (WNW)

05/12/2018 F12 F .51 in 3.5 in58.5 MPH100 MPH

310 (NW)

05/11/2034 F18 F .65 in 5.1 in35.1 MPH73 MPH

280 (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 04/23/2020 at 7:36 AM.

USDA Forest Service
White Mountain National Forest