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Avalanche Forecast

Archived

Mar 22nd, 2014–Mar 23rd, 2014

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Wind slab avalanches should be less likely but still possible on lee aspects near and above treeline. Generally small wet loose avalanches are possible on solar aspects.

Detailed Forecast

Partial clearing should allow for a good refreeze Saturday night. Sunday should be a fair weather day with temperatures similar or a few degrees warmer than Saturday with more direct solar input. Sunshine is expected to be filtered at times with high clouds from the next approaching system. .    

Recent storm slabs instabilities should be settled out by now. However, continue to watch for lingering but likely isolated wind slab on lee north through easterly slopes near and above treeline. Watch for cracking or firmer wind transported snow in steep exposed terrain. A large cornice fall could provide the right natural trigger for a wind slab to release on a lee slope.  

The equinox has passed and we've officially moved into spring; wet loose avalanches remain possible on sun exposed terrain, especially mid and lower elevations in the late morning and afternoon hours. Watch for wet surface snow deeper than a few inches, pinwheeling of surface snow and small natural wet loose releases that usually precede more major wet loose snow avalanches.

Although temperatures and sunshine are only expected to be relatively warmer than Saturday, give cornices a wide berth during the heat of the afternoon and avoid travel on slopes directly below them. 

 

Snowpack Discussion

The last significant frontal boundary was stalled over the Olympics and north Cascades Saturday afternoon before finally sagging south last Sunday, with rain generally changing to snow in a north to south fashion across the area.  A favorable temperature trend with a gradual cooling occurred with this storm. The NWAC site at Hurricane picked up about 13 inches of snow late Saturday through Monday and produced wind slab layers on north through east aspects near tree line and allowed for one skier triggered soft slab Sunday afternoon that covered the road. 

The latest cold front crossed the Northwest on Wednesday. This system produced more snow in the Cascades with the Hurricane Ridge weather station recording only about 4 inches of new snow at low temperatures and with generally light winds.  On Friday afternoon NWAC observer Katy Reid reported a thin melt-freeze crust over this most recent storm snow and denser wind slab on N thru SE near treeline that was stubborn in stability tests and not noted in any recent avalanches.  She also observed widespread surface hoar from Thursday night (and probably Friday night) along with grapuel as being preserved under cool temperatures and light winds (see picture). This potential future weak layer may be destroyed by direct sun or winds, but is worth remembering if buried intact during future storms. See Katy's latest video here. 

3-21-14 Surface Hoar and graupel snow crystals, image Katy Reid, Steeple Rock, Olympics

Increasing clouds and periods of light rain or snow were seen on Saturday.  

Katy reported the lower and mid snowpack near treeline as generally well consolidated melt forms.  

Problems

Loose Wet

Loose Wet 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.

Wind Slabs

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.