NIDIS Intermountain West
Regional Drought Early Warning System
January 17, 2017


The images above use daily precipitation statistics from NWS COOP, CoCoRaHS, and CoAgMet stations. From top to bottom, and left to right: most recent 7-days of accumulated precipitation in inches; current month-to-date accumulated precipitation in inches; last month's precipitation as a percent of average; water-year-to-date precipitation as a percent of average.

Standardized Precipitation Index

Standardized Precipitation Index standardizes precipitation accumulations for a specified time period into percentile rankings. -1.0 to -1.5 is equivalent to a D1 to D2. -1.5 to -2.0 is equivalent to a D2 to D3. -2.0 and worse is equivalent to a D3 to D4. 30- and 60-day SPIs focus on short-term conditions while 6- and 9-month SPIs focus on long-term conditions. SPI data provided by High Plains Regional Climate Center.

Snotel and Snowpack

The top left image shows the Natural Resources Conservation Service's SNOTEL water-year-to-date precipitation percentile rankings. The top right image shows sub-basin averaged snow water equivalent accumulations as a percent of average. The images below show accumulated snow water equivalent in inches (green) compared to average (blue) and last year (red) for several different sub-basins across the UCRB (and were created by the Colorado Basin River Forecast Center).


The top left image shows 7-day averaged streamflows as a percentile ranking across the UCRB. The top right image shows 7-day averaged discharge over time at three key sites around the UCRB: The Colorado River at the CO-UT state line; the Green River at Green River, UT; and the San Juan River near Bluff, UT. All streamflow data provided by United States Geological Survey.

Surface Water

The top left image shows VIC modeled soil moisture as a percentile ranking. The top right image shows satellite-derived vegetation from the VegDRI product (which updates on Mondays).

The graphs shown below are plots of reservoir volumes over the past full year and current year to date (black). The dashed line at the top of each graphic indicates the reservoir's capacity, and the background color-coded shading provides context for the range of reservoir levels observed over the past 30 years. The data are obtained from the Bureau of Reclamation. Some of the reservoir percentiles don't line up at the new year due to differences in reservoir levels at the beginning of 1985 and the end of 2014.  Dead storage has been subtracted. Note: Lake Granby data are obtained from the Colorado Division of Water Resources, and only goes back to the year 2000.

Evaporative Demand

The above images are available courtesy of NOAA’s Evaporative Demand Drought Index (EDDI). Drought classification listed is a function of the depth of reference evapotranspiration accumulated over a given period of record with respect to a climatology of 1981-2010. The drought categories displayed are in line with the US Drought Monitor's Percentile Ranking Scheme. Data used to generate these maps come from the North American Land Data Assimilation System Phase-2 (NLDAS-2) project, which assimilates observations of temperature, wind speed, radiation, and vapor pressure deficit. The date indicates the last day of the period of record, and the week number indicates the window size for the period of record.


All images show temperature departures from average over different time periods (last 7 days on top left; month-to-date on top right; last full month on bottom). Temperature departure maps provided by HPRCC ACIS.


The top two images show Climate Prediction Center's Precipitation and Temperature outlooks for 8 - 14 days. The middle image shows the Weather Prediction Center's Quantitative Precipitation Forecast accumulation for seven days. The bottom left image shows the 3-month precipitation outlook from Climate Prediction Center, and the bottom right image shows the Climate Prediction Center's most recent release of the U.S. Seasonal Drought Outlook.

Summary and Recommendations

Above is the most recent release of the U.S. Drought Monitor map for the UCRB region. Below shows the proposed changes for this week, with supporting text.

Summary: January 17, 2017

Last week brought more precipitation to the Upper Colorado River Basin, mainly in western Colorado.  This area saw at least 0.50 inch with some areas seeing up to 4.00 inches of liquid.  Southwestern Wyoming saw less, with up to 0.50 inch in much of Sweetwater County, with a large area seeing between 0.10 and 0.25 inches.  Eastern Utah received between 0.25 and 1.00 inch over the last week.

East of the Divide, Colorado saw up to 1.00 inch along the Front Range.  Amounts decreased quickly with much of eastern Colorado seeing less than 0.25 inch last week.  Southeastern Colorado and eastern Cheyenne, Kit Carson and Yuma counties saw between 0.50 and 1.00 inches of precipitation.

SPIs for the past 30 days remain positive through the UCRB and Colorado, with many in western Colorado showing up in the +2 and greater range.  Longer-term SPIs in eastern Colorado are still dry with 90-day SPI in the 0 to -1.5 range and 6-month SPIs still showing the dry end to summer and fall.


UCRB:  It is recommended that the remaining D0 in Summit County, CO be removed.  This D0 removal also includes Chaffee County.  It is also recommended the D0 in Emery, Wayne, Garfield and eastern Sevier counties in southern Utah be removed.  SPIs out to 9-months are positive and snotel precipitation is above the median for these areas.  There seems to be no sign of abnormally dry in the UCRB at this time.

Eastern Colorado: Removal of D2 in Larimer and Kiowa counties is recommended.  With the past month of precipitation, SPIs for 30 and 90 days are now positive.  The recent precipitation in Larimer County does not make up for the dry late summer and fall, however it has helped, giving justification to improvement.