Avalanche Forecast for Monday, December 31, 2018

This forecast was published 12/31/2018 at 7:16 AM.
A new forecast will be issued tomorrow.

NOT THE CURRENT FORECAST

This is an archived avalanche forecast and expired on 12/31/2018 at midnight.


The Bottom Line

All forecast areas have LOW avalanche danger today. Areas of wind slab can be found, but these have proven unreactive and can be avoided in most terrain by traveling on the exposed melt-freeze crust. The potential for long, sliding falls should be as much or more of a concern today. Bear in mind that crampons and ice axes are tools for fall prevention and will be of little use after a slip due to the firm nature of the current snowpack.

Tonight’s inbound storm may produce significant snowfall on increasing wind before this forecast expires at midnight. Avalanche danger will exceed our current low rating once this takes place. Watch for the red flags of heavy snowfall and wind blown snow to guide cautious route-finding if you are out late today.

2018-12-31 Printable PDF

Forecast Area

Mountain Weather

On Sunday, temperatures remained in the single digits with broken and overcast cloud cover for most of the day. Shifty wind in the morning with speeds less than 20 mph became NW around 40mph in the evening. A trace of snow fell in the morning followed by 0.4” overnight. Today, summits will be in and out of the clouds with temperatures increasing to the teens F by dusk. Wind will remain in the 30-50 mph range from the W and SW for daylight hours with up to an inch of snow falling during the day. Once nighttime arrives, the storm will begin with up to 5” falling by midnight on shifting and increasing wind. Snow continues into tomorrow morning with high wind speeds, bringing a storm total of up to 12” of snow by the end of Tuesday. Warm temperatures may mix in sleet at high elevations with rain likely down low.

Primary Avalanche Problem – Wind Slab

Wind Slab

Aspect/Elevation

Likelihood

Size

Wind slabs formed during a period of extreme NW wind on Saturday in the lee of terrain features. Areas in the lee of our largest fetch contain the largest and thickest wind slab, but in most of our terrain they are isolated and can be avoided. These firm wind slabs have been unreactive to human triggers and appear well bonded to the melt-freeze crust.

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

Currently, our snowpack has very good stability. A robust melt-freeze crust that formed December 22 and 23 exists on all aspects and elevations with recently formed, firm wind slab in isolated locations. The melt-freeze crust offers excellent climbing as well as providing the opportunity for long sliding falls. This surface snow will also provide a smooth bed surface for avalanches to occur as snow arrives tonight into tomorrow.

Additional Concerns

The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch. If you’re interested in giving your brain a workout, check out the list of upcoming events on our website. You can find the calendar on our home page or the full list here. These are all free and hosted in part by the White Mountain Avalanche Education Foundation and Friends of Tuckerman Ravine.

Snow Plot Information

DateHN24HN24W
(SWE)
Density (%)HSTTotalAir TT MaxT MinSkyPrecipComments
03/21/19
05:23
0 CM 0 MM0CM213 CM-1.5 C0.0 C-11.5 COvercastNo precipitation
03/20/19
05:28
0 CM 0 MM0CM214 CM-11.0 C-4.5 C-14.0 CClearNo precipitation
03/19/19
05:25
0 CM 0.0 MMNC215 CM-13.0 C-9.5 C-15.0 CFewNo precipitation
03/18/19
05:20
Trace 0.1 MMNC216 CM-15.5 C-13.0 C-15.5 CBrokenSnowView
03/17/19
05:26
4 CM 3.7 MM 9%4CM218 CM-14.5 C-2.5 C-15.0 CBrokenNo precipitation

Avalanche Log and Summit Weather

Daily Observations


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
03/20/1917 F1 F 0.0 in 0.0 in32 MPH58 MPH

270 (W)

03/19/194 F-4 FTrace Trace 43.4 MPH63 MPH

300 (WNW)

03/18/193 F-6 F 0.03 in 0 in52.1 MPH82 MPH

280 (W)

03/17/192 F-6 F 0.07 in .5 in61.5 MPH110 MPH

270 (W)

03/16/1925 F2 F 0.24 in 2.3 in67.5 MPH97 MPH

280 (W)

03/15/1941 F25 F 0.04 inTrace 54 MPH105 MPH

250 (WSW)

03/14/1940 F17 F Trace in Trace in27.7 MPH75 MPH

200 (SSW)

View
03/13/1924 F11 F .07 in .8 in29 MPH52 MPH

290 (WNW)

03/12/1911 F-1 F 0.14 in 1.9 in65 MPH104 MPH

280 (W)

03/11/1917 F6 F 0.35 in 4.4 in77 MPH114 MPH

280 (W)

03/10/1925 F4 F .35 in 3.7 in47.2 MPH94 MPH

150 (SSE)

View
03/09/1919 F0 F 0 in 0 in36.1 MPH70 MPH

290 (WNW)

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 12/31/2018 at 7:16 AM.

Helon Hoffer
USDA Forest Service
White Mountain National Forest