Greetings from Silverton on Tuesday afternoon, April 14, 2015
As has been very well advertised by the National Weather Service, a potent, synoptic-scale weather system is approaching western Colorado this afternoon with a strong, pre-frontal wind field developing over the Colorado Plateau. A High Wind Warning has been issued for strong SW’ly winds (SSW to WSW) and blowing dust is in the forecast this afternoon and this evening at several locales throughout the Plateau, from Leupp, AZ to Moab, UT. As of 1:16 PM this afternoon airborne dust was beginning to obscure visibility from the USGS Abajo Peak webcam.
This potential D3 event is likely to be virtually dry and would be deposited directly onto the now-merged D1 and D2 dust depositions at the snowpack surface here at Senator Beck Basin. Those two comparatively minor dust-on-snow events are presently exposed and readily, if weakly, apparent in the alpine terrain of Senator Beck Basin. However, because of the very small amounts of dust mass contained in those two events, effects on snow albedo have been small and snowmelt discharge has shown no major surging in response to the exposure of the merged D1 and D2 dust. In the scheme of the CODOS classification of dust intensity, we remain in the “Min(imal) Dust” category at this hour.
Unfortunately, a significant D3 event deposited later today (and tonight) onto and merged with D1/D2 could result in much more significant reductions in snow albedo, as and when those three merged layers are exposed at or near the snowpack surface. Snowmelt rates could then accelerate substantially. Even a single, major dust deposition could push our dust-on-snow intensity here at Senator Beck Basin into the “Avg Dust” category.
The CODOS team’s planned circuit of all eleven CODOS sites that was to begin today is now on ‘pause’ to allow this potential D3 event to play out and for the subsequent winter storm behind the dust to conclude. We will then proceed with the circuit to verify the presence/absence of dust events D1 and D2, and this potential D3, at all CODOS sites. An Update will follow, reviewing current conditions in the context of the CODOS Dust Enhanced Runoff Classification’s most similar prior seasons.