Greetings from Silverton,
As it started raining early last night and continued throughout the evening here in Silverton (this morning it is slowly turning to wet snow) I could not avoid the feeling that spring is really trying to rush things a bit. Add the scant snowcover and muddy streets and it definitely feels like late May and not late March. These conditions lead me to think of snow melt and streamflow and what could unfold this runoff season. In many areas of Colorado this snow season is being compared to the notorious low snowpack of WY2002, and indeed considering the graphs below WY2018 is tracking WY2002 snow conditions very closely. With this shot of precipitation we are currently receiving, and a bit going into next week, it is looking like we may be slightly be above WY2002 conditions statewide by April 1. Keeping a similar train of thought as in the March 9 CODOS Update the cumulative streamflow plots below show what unfolded in WY2002, and may give a sense of what we could see this year. In our CODOS report last week we included a table of snowpack temperatures from our March 14-17 tour. Results were generally comparable to the last four out of five years.
The one-month forecast remains boring. Colorado saw some decent storms this past week as we issued two storm reports for Senator Beck, and the 7-day outlook indicates ~1” of potential precipitation in the mountains, but the one-month outlook still calls for warms temperatures and below average chance of precipitation. See forecast images below.
DUST: High winds in Utah on a couple different occasions this week had us wondering if we would see dust in the Colorado mountains. The snowpack at SASP did not reveal any new dust and D2 is still at least 12" below surface. We will keep an eye out and report any new developments ASAP. It will be interesting to see how these next couple of months develop in terms of spring weather, dust conditions, and resultant streamflow. Will we see some gains in snowpack going into April? If spring is warm and dry, how early will snowmelt begin? To what degree will dust conditions advance an already potentially early melt season?
Streamflow timing indices were calculated based on cumulative flow from March 1 thru June 30, this time period captures the dominant snowmelt portion of the hydrograph for most rivers in Colorado. WY2002 was compared to the median for the San Juan, Animas, Rio Grande, Taylor, and Uncompahgre rivers. Indices calculated are Q20, Q50, and Q80, corresponding to 20%, 50%, and 80% of cumulative flow having passed the stream gauge. These values approximate the beginning, middle, and end of the snowmelt period. From left to right, the red and black vertical lines indicate Q20, Q50, Q80, respectively, for WY2002 (red) and the median (black)