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RegisterJan 9th, 2017–Jan 10th, 2017
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New wind slab is most likely on Monday on northwest to southeast slopes mainly in the near and above treeline. Avoid slopes above terrain traps in the below treeline where recently formed weak layers may have been buried by new snow.
Several inches of new snow or more should be seen along the east slopes by Monday morning. Temperatures will be cooler by Monday morning.
Southwest winds aloft should decrease on Monday. Light snow showers mainly at higher elevations along the east slopes should decrease on Monday with further cooling.
If you travel into the back country Monday watch for new wind slab mainly on northwest to southeast slopes mainly in the near and above treeline. Previous wind slab may linger on other slope aspects also mainly in the near and above treeline. Watch for firmer wind transported snow.
New storm slab is possible Monday on sheltered slopes where there was more than several inches of rapidly accumulating snowfall.
New wind and storm slab layers should be more stable by the end of the day on Monday.
Remember that recently formed surface hoar and surface faceted snow has been seen lately in the below treeline. It will be a good plan to avoid slopes above terrain traps in the below treeline where these weak layers may have been buried by new snow.
Continue to identify the 12/17 buried PWL in snowpits and avoid areas where the overlying snowpack is shallower where affecting this layer would be more likely.
Weather and Snowpack
A cold dry Arctic air mass was over the Northwest last week. The main weather event last week was a day or so of nuclear east winds on Wednesday that went on a powder wrecking rampage, scouring windward slopes, re-distributing it to lee slopes and building sastrugi in other areas.
Reports indicate the winds eliminated most of the faceted surface snow and surface hoar that formed in the near and above treeline during the cold weather. But these weak surface crystals are still reported below treeline.
A warm front is moving south to north over the Northwest on Sunday eroding and replacing the Arctic air mass and causing warmer temperatures. Southeast winds aloft on Sunday will shift to southwest by late Sunday and Monday.
Recent Observations
There haven't been many recent observations from the east slopes.
On New Years Day reports from multiple snow pits by the the Mission Ridge pro-patrol indicated that basal facets remained intact but were showing signs of rounding and bonding.
Th Mission Ridge ski patrol had their hands full on Monday morning after an unusual reverse orographic flow with about 34 inches of new snow and strong northeast winds. It was not possible for them to visit lee S-W slopes where new, deep wind slab was expected.
The NCMG were in the Cutthroat drainage near Washington Pass area on Wednesday and found cold temperatures and evidence of stubborn wind slab up to size 1.5 in the near and above treeline.
A report for Friday via the NWAC Observations page for Red Mountain in the central east zone indicated a 10-20 cm deep surface layer of faceted surface snow and surface hoar in the below treeline band. A wind slab also gave a triggered collapse on a ridge top.
The Mission Ridge pro-patrol on Saturday reported that the deep low density heavy snow from early last week had greatly consolidated and stabilized.
The NCMG were out again on Delancey Ridge on Saturday and found that snow from a week ago had settled and stabilized. Weak surface layers were noted with surface hoar in the below treeline. Small wind slab was noted in the near and above treeline which was not reactive.