NIDIS Intermountain West
Drought Early Warning System
August 13, 2019


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. Colors match the different drought categories with the U.S. Drought Monitor. 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.


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 of reference evapotranspiration (ET) from CoAgMET sites across Colorado. Reference ET assumes the amount of water that will evaporate from a well-irrigated crop. Higher ET rates occur during hot, dry, and windy conditions. Lower ET rates are more desirable for crops. See a map of locations for the above ET sites.

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.

Condition Monitoring and Impacts

Map of current condition monitoring reports submitted to CoCoRaHS in the last week overlaid on the current U.S. Drought Monitor depiction. Specific impacts reports from local experts listed below.

Weld County:  Driving through central Weld County, the native grasses are looking good with a lot of green showing up.  The crops are looking great and most of the hay has just been cut.


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: August 13, 2019

The last week the Intermountain West region saw a west-east division for precipitation.  The western portion of the region from the Continental Divide west was mostly dry with less than 0.10" over most of the region.  East of the Divide saw a decent week with much of the area receiving at least 0.50" of precipitation, higher amounts near the eastern border.  

The 30 and 60 day SPIs are showing the lack of moisture through most of the region, especially western Colorado and eastern Utah with the lack of monsoonal moisture.  Once the wet spring comes into play in May and earlier, SPIs turn around quickly.

Despite the recent dryness, Evaporative Demand remains low or near normal in the UCRB.  Since streamflows are still high and water supply is still in good shape, the recent dryness is not causing major alarm yet, however it's an area to keep a close eye on and slight expansions of D0 will be recommended as a warning for developing dryness.  

The next few weeks are looking like the same pattern of wetter on the eastern portion of the IMW region and dry on the western portion will continue.  This means there will likely be more drying out of the UCRB and expansion of D0 will continue. 


UCRB: An expansion of D0 through San Juan County, Utah into western Colorado connecting to the D0 in the Four Corners is recommended.  SPIs in this area are showing quite a bit of drying with the lack of monsoonal moisture.  The San Juan Mountains in Colorado saw some moisture last week, so we are limiting these recommendations to the lower elevations and keeping the D0 south of Mesa County.

Eastern CO: Status quo.  Despite 1-2" in Baca County last week, the Walsh NWS Coop station is still over 2" below normal for the past 30 days.  With this being the case, the D0 should stay put.  There are some dry spots showing up in Central Colorado, Summit, Lake and Chaffee counites, however this area received a decent shot of precipitation last week holding off any degradations.  There's also a dry spot in Weld and Larimer County.  I drove through Weld County last week and noticed the native grasses are still looking good with some green and the crops are looking fantastic, so no degradations in this area either.