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RegisterDec 5th, 2017–Dec 6th, 2017
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Watch for small areas of firmer, wind-transported snow on isolated, lee terrain features. Watch for loose-wet snow avalanches releasing from sun exposed rock faces or below cliffs or rock bands.
Tree well hazard may still exist: Travel with a partner and keep them in sight and in communication in areas where there has been recent heavy snowfall.
Continued sunny and mild weather is expected Wednesday with some moderate to strong crest level easterly winds.
This should allow for further settlement of the recent storm layers and cause an overall slowly decreasing danger.
Small wind slabs may exist on a variety of aspects, mainly on exposed lee slopes receiving any transported snow. The warming surface snow should limit or end further transport. Any remaining wind slabs are expected to be stubborn or difficult to trigger. Watch for small areas of firmer, wind-transported snow on isolated, lee terrain features.
Continue to watch for isolated, small, loose wet avalanches on steep sun exposed terrain during the late morning or afternoon, especially on unsupported slopes or near rocks.
Early season terrain hazards still exist, such as poorly covered rocks, vegetation and creeks, particularly at lower elevations.
Travel with a partner and keep them in sight and in communication in areas where there has been recent heavy snowfall due to tree well danger.
Warm, very wet weather before Thanksgiving caused wet snow and glide avalanches as well as snowpack consolidation, leaving a strong crust as a gift. There are no snowpack concerns below the Thanksgiving crust and in general new snow received post-Thanksgiving has reportedly bonded well.
A series of frontal systems produced snow over the week following Thanksgiving at all stations in the Cascades: Locations on the west side of the Cascade crest received 1.5' to 4.5' with the most at Mt. Baker.
This includes the most recent 2 day total snowfall ending Sunday morning along the Cascade west slopes, ranging from 5-27" with the most again at Mt. Baker.
The recent storm cycle ending early Sunday with 3-6 inches of snowpack settlement by Tuesday afternoon.
Observations
North
Storm slabs were sensitive early Saturday, however, by Sunday, the Mt. Baker ski patrol reported many folks were skiing in the backcountry with no avalanches reported. Additionally, a private report to NWAC indicated small, thin wind slab high on north-facing slopes near the Mt. Baker ski area. Otherwise, no signs of instability. Plenty of point releases on S-facing slopes during sun breaks.
On Sunday, a Professional Guide was skiing in the Bagley Lakes area and despite many back-country skiers, saw only one small triggered shallow wind slab in a steep, loaded location. Layers from Friday were less reactive and healing.
Central
On Sunday, NWAC observer Jeremy Allyn was in the Alpental/Source Lake area. A lot of recent storm snow hasn't fully settled and there were still some storm layers giving moderate RP results in snow pit tests. Pockets of wind affected snow seen on high terrain. The low-density snow was deep and tree wells were a major hazard.
By Tuesday, observations in the Alpental valley indicated sun and warming were quickly creating moist surface snow with several small loose-wet slides releasing from rock or unsupported features exposed to direct sun.
South
NWAC Pro Observer, Dallas Glass was out on Saturday in the Paradise area. On W-S-E aspects he found 8” new of new snow, well-bonded to 2 feet of previous snow on the Thanksgiving crust. He found 5400-6000’ W-SW-S-SE-E. He did not find evidence of storm or wind slab.
On Sunday, Crystal Mountain Ski Patrol reported 10” of new snow in the last 24 hours. The upper snowpack is generally right-side up and well-bonded to the Thanksgiving day crust. Winds on Saturday night also created a shallow surface layer of higher density snow giving minor cracking and likely small, shallow areas of wind slab.
Another Pro Observer was at Paradise on Sunday where the main story was the 9-10" of new snow that fell at slightly higher densities and precipitation rates, giving small storm slab on varied aspects. Several small loose-dry avalanches were observed in the near tree-line.
NWAC observer, Ian Nicholson, travelled in the Crystal back country Tuesday, finding new shallow wind slabs that had formed overnight from increasing easterly crest level winds. These were small and isolated to features near ridges, causing terrain choices to be altered to avoid exposure to obvious wind loaded pockets. By afternoon, surface snow had become moist on any solar facing slopes, from E-SW, ending further wind transport.