Greetings from snowy Silverton on Monday morning, April 28th.
We're catching up with recent events before, during, and after our Wednesday-Saturday CODOS circuit last week. This Alert will revise our previous "D6 Averted" email and update you on our subsequent seventh event of the season - D7-WY2014, deposited on Saturday, April 26.
Upon arriving at Swamp Angel Study Plot last Wednesday morning, to begin the CODOS circuit, we did, in fact, observe a trace of the much anticipated event D6-WY2014 dust at the snowpack surface, apparently delivered in rain on the afternoon of April 22nd. This can be seen as a patchy stain in the snow surface in the photo on the right. D6 was only very thinly separated from merged layers D5/4/3 by a cleaner crust of melt/freeze snow at SASP and we did capture a discrete 0.5 m2 sample of D6. Similar evidence of D6 dust was not observed at any other CODOS site in subsequent days except, perhaps, at our Wolf Creek Pass site where it may have fallen directly onto exposed D4/3 dust, also as dust-in-rain. In any case, D6 had only very minor impact on snow albedo.
More recently, a much more substantial D7 dust layer was deposited at Senator Beck Basin on Saturday afternoon, April 26, in association with very intense SSW'ly winds as the current and ongoing winter Storm #23 arrived. This D7 event occurred during a short time window, with clean snow preceding the 'wet' dust deposition, creating a clear separation from the underlying merged D6/5/4/3 layer, and a very abrupt 'top' boundary in the fairly thick layer of snow containing the dust layer. Since the end of the dust event, some 15" of clean snow containing 1.4" of water fell on top of the D7 layer. The photos below show the depth of burial of the D7 layer during collection of the standard 0.5 m2 sample on Sunday afternoon - several inches more snow have fallen since then.
More soon about our recent CODOS circuit findings,