Friday January 17, 2020

Sunday January 19, 2020
Saturday January 18, 2020
Friday January 17, 2020
Confidence: Moderate - Forecast models all agree on high precipitation amounts and rising freezing levels.

Main Concerns

Wind Slab, Storm Slab, Loose Dry - view Avalanche Problems for detailed information.

Travel & Terrain Advice

Careful and selective route finding combined with conservative decision making is essential as storm snow settles.

Seek sheltered and low angle terrain during the incoming storm events, ensure avoidance of overhead hazard.

During periods of high hazard, travel in avalanche terrain is not recommended.

Avalanche Summary

Thursday am avalanche control at Mount Washington reported a few explosive triggered size one very soft slabs avalanches. Ski cutting produced widespread loose dry avalanches to size one. No other reports or observations.

Avalanche Problems

Wind Slab

Touchy wind slabs will continue to build and will be found on all aspects, but predominantly North. Found in both alpine and treeline terrain, triggering of this avalanche problem is likely to very likely from light loads such as skiers. If triggered expect these avalanches to be large, up to size two and on specific terrain features very large, size 3.

Storm Slab

New snowfall expected to continue over the forecast period will form new and touchy storm slab avalanches. The chance of this avalanche problem being trigger is very likely to certain ,especially during periods of warming. Expect to find this new problem widespread and at all elevations and on all aspects. If triggered, expect avalanches to be large, size two and in specific terrain very large, size 3.

Loose Dry

New loose dry avalanches due to unconsolidated new snow can be found on all aspects, but predominately in areas protected from the wind. Found at all elevations, triggering of this avalanche problem is likely to very likely from light loads such as skiers. If triggered expect these avalanches to be small to large, up to size two .

Expect Sunday loose dry to transform to loose wet as freezing levels rise and precipitation continues in the form of rain below 1500 m.

Snowpack Summary

New snow and cold conditions with plenty of wind 60 plus centimeters in all the forecasts region areas. Old exposed hard crust surfaces in exposed alpine terrain has now been buried as the wind had intensely transported the available new upper snow. Freezing levels remained low, but early Thursday morning an upper warm front brought increasingly warm temperatures and continued and sustained south west wind. These conditions supported the development of both new storm slabs and wind slabs on North aspects. South aspects, endured a period of warming with the upper surface snow becoming moist, all terrain protected from the sun remained preserved.

Mid pack, a coupe of melt freeze crusts, with embedded facets and surface hoar, both are settling and becoming less reactive.

The lower snow pack is predominantly well settled and dense, with the exception of upper alpine terrain in isolated features that are exposed to wind and unsupported. Theses features continue to harbor a basal instability that is dormant but may wake after an extreme loading event of spring warm up.

Snowpack Details

SurfaceNew low density snow and a variety of surfaces from a stiffening slab to exposed crust.
UpperMoist and settling.
MidA variety of melt freeze crusts can be found.
LowerDense and settled with a faceted basal instability found on isolated features in the upper alpine.

Past Weather

A period of intense snowfall and strong south wind.

Weather Forecast

Friday all is quite on the storm front and the freezing levels will maintain at sea level. Weather is expected to ramp up for Saturday and Sunday as a strong southwest flow continues bring to the forecast area moderate to heavy precipitation amounts. Freezing levels at 500 m Saturday morning and will begin to rise to above 1500 m by Sunday.

Friday 5 to 10 cm snow , Winds Moderate from the South , Freezing levels at sea level.

Saturday 40 to 60 cm snow, Winds Strong from the South, Freezing levels 900 meters.

Sunday 40 to 60 mm precipitation , Winds Strong from the South, Freezing levels 1700 meters.

Posted on Friday January 17, 2020 by Jesse Percival

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