Monday, March 17, 2014

CODOS Update on Large Snowpacks, Lack of Dust, Runoff Patterns

From CODOS update:



Given the north and northwesterly bias of this winter’s active storm track and winds, and corresponding lack of southwesterly flow, most of Colorado’s mountain watersheds have already developed well-above-average snowpacks.  The San Juan Mountains and most associated watersheds are the exception to that trend in snowcover.  The southern San Juan Mountains may also have the only snowpack containing significant dust, as of event D1, February 16.  If, in fact, the remainder of the state’s snowpack remains dust-free, then snowpack ‘ripening’, toward snow temperatures of 0° C throughout, is proceeding without the extra energy provided when desert dust contained in or near the snowpack surface absorbs solar radiation.  However, the majority of dust-on-snow events (and dust mass) logged by CODOS for Water Years 2005-2013 occurred after mid-March.  Given current snowpack conditions, and the likelihood that many Snotel sites have not yet recorded Peak SWE, even in the absence of dust-on-snow Spring 2014 snowmelt runoff is going to release large amounts of water and flooding hazards are emerging in some watersheds.   Should dust be deposited in the Colorado snowcover over the next several weeks, that dust will be positioned high within the snowcover and, in conjunction with April and May weather, influence the timing and rate of the high-volume snowmelt runoff.  That potential interaction of very high SWE, potential dust forcing, and spring weather conditions is captured within a 3x3x3 dust-enhanced snowmelt runoff behaviors “space”.  


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