http://wwa.colorado.edu Snowpocalypse A 2019 feast after a 2018 famine 2019 Annual Seminar Colorado River District Grand Junction, CO – September 18, 2019 Jeff Lukas, Western Water Assessment CIRES, University of Colorado Boulder Image: Shaune Goleman http://wwa.colorado.edu US Drought Monitor for Upper Colorado River Basin October 2, 2018 Source: US Drought Monitor; https://droughtmonitor.unl.edu/ http://wwa.colorado.edu CBRFC modeled antecedent soil moisture – Nov 2018 • Much below normal almost everywhere in Upper Basin • Near-record-low in San Juan and Gunnison basins Source: NOAA CBRFC; https://www.cbrfc.noaa.gov/ http://wwa.colorado.edu CBRFC forecast evolution plot – Lake Powell Apr-Jul inflows 10.40 maf 9.20 maf 4.55 maf Source: NOAA CBRFC; https://www.cbrfc.noaa.gov/wsup/ http://wwa.colorado.edu February – persistent trough, favorable flow http://wwa.colorado.edu March 1st-15th – persistent trough, favorable flow http://wwa.colorado.edu Rank of Feb-Mar 2019 precip at SNOTEL sites Source: NRCS Interactive Map; https://www.nrcs.usda.gov/wps/portal/wcc/home/quicklinks/imap http://wwa.colorado.edu “Historic” avalanche cycle in early March in CO mts From February 28th - March 10th: • 10-15 feet of snow • 6”-12” of SWE • Avalanche activity not seen since 1950s Conundrum Creek slide down Highlands Ridge, Aspen Source: Colorado Avalanche Information Center, from Telluride Helitrax http://wwa.colorado.edu Feb-Mar Upper Basin precip, 1900-2019 2019 Source: NOAA NCEI Climate at a Glance; https://www.ncdc.noaa.gov/cag/ http://wwa.colorado.edu May – very deep trough, favorable flow http://wwa.colorado.edu Rank of May 2019 precip at SNOTEL sites Source: NRCS Interactive Map; https://www.nrcs.usda.gov/wps/portal/wcc/home/quicklinks/imap http://wwa.colorado.edu Oct-May Upper Basin precip: 2019 2nd highest since 1900 2019 Source: NOAA NCEI Climate at a Glance; https://www.ncdc.noaa.gov/cag/ http://wwa.colorado.edu Oct-May Upper Basin temps: 2019 coolest since 2010 2019 Source: NOAA NCEI Climate at a Glance; https://www.ncdc.noaa.gov/cag/ http://wwa.colorado.edu WY 2019 SWE plot –Lake Powell 104 Group 130% of median peak SWE Source: NOAA CBRFC; https://www.cbrfc.noaa.gov/station/sweplot/snowgroup.php http://wwa.colorado.edu US Drought Monitor for Upper Colorado River Basin October 2, 2018 July 2, 2019 Source: US Drought Monitor; https://droughtmonitor.unl.edu/ http://wwa.colorado.edu Schematic of typical winter El Nino effects on U.S. Source: NOAA; https://www.climate.gov/news-features/ http://wwa.colorado.edu CPC seasonal outlook for Feb-Apr, issued Jan 17th http://wwa.colorado.edu CPC seasonal outlook for Mar-May, issued Feb 21st http://wwa.colorado.edu Upper Basin Feb-May precip vs. ENSO state, 1979-2019 2019 75th Median Average of 25th all years Precipitation, inches El Niño La Niña Neutral http://wwa.colorado.edu Jun-Aug Upper Basin precip: 2019 8th driest 2019 Source: NOAA NCEI Climate at a Glance; https://www.ncdc.noaa.gov/cag/ http://wwa.colorado.edu July-Aug Upper Basin temps: 2019 6th warmest 2019 Source: NOAA NCEI Climate at a Glance; https://www.ncdc.noaa.gov/cag/ http://wwa.colorado.edu Lees Ferry water-year natural flows: 2019 looking good, but not great 30 25 20 2019 est. 15 17.5 maf (118% of average) 10 5 0 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 http://wwa.colorado.edu UCRB Oct-May precip vs. Lees Ferry flows, 1900-2019 30 R2 = 0.67 25 maf 20 2019 15 est. 10 2018 5 Lees Ferry WY natural flow, natural flow, Lees Ferry WY 0 0 5 10 15 20 UCRB Oct-May precip, in. http://wwa.colorado.edu UCRB Oct-May precip vs. Lees Ferry flows, 1900-2019 30 25 maf 20 1906-1999 15 10 2000-2019 5 Lees Ferry WY natural flow, natural flow, Lees Ferry WY 0 0 5 10 15 20 UCRB Oct-May precip, in. http://wwa.colorado.edu Increasing hydroclimatic variability and volatility? • Upper Basin interannual precipitation variability has increased ~10% since 1980 • Consistent with expectations from climate models: more warming = more precip variability • Individual storms will tend to be ”juicier” in a warmer climate • And: Warmer summer temperatures will dry out land surface faster http://wwa.colorado.edu Lessons from Snowpocalypse • The snowpack and runoff outlook can turn around in a month, given the right weather pattern • El Niño tilts the odds towards a wet late winter-spring in the Upper Basin, but randomness does the rest • Extreme seasonal conditions will always be hard to forecast • There is such a thing as too much snow http://wwa.colorado.edu Lessons from Snowpocalypse • Near-record precipitation and snowpack does not necessarily translate into near-record annual runoff • We will likely see more frequent feast-after-famine years (and the reverse) • As well as more within-season volatility http://wwa.colorado.edu Colorado River Basin Climate and Hydrology report Volume I. Background • Introduction • Current understanding of basin hydroclimate • Primary operations and planning tools Volume II. Informing all time scales • Observations – Weather and climate • Observations – Hydrology • Hydrologic models Volume III. Short-term and mid-term • Weather and climate forecasting • Streamflow forecasting Volume IV. Long-term • Historical hydrology • Paleohydrology • Climate-change-informed hydrology Scheduled release: December 2019 http://wwa.colorado.edu Comments? Questions? Please contact me at [email protected].