NIDIS Intermountain West
Drought Early Warning System
June 19, 2018


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.


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.

Southeast CO

Very hot temperatures and windy conditions have been horrible on the land. I-70 near Highway 86, the grasses are showing a bluish-gray tint. The winter wheat harvest is expected to occur a couple of weeks early and will be less than average. There is no grazing available, so large numbers of cattle are being sold.  Crop losses are large, and prevented planting is occurring on many fields. There are no wet ponds. June 1 was a critical date for ranchers to see some moisture to keep cattle, but that didn't happen.  Precipitation can help green things up a little, but will not reduce impacts that are being experienced right now.

Southwest CO

San Juan National Forest has announced large-scale closures due to fires and drought. Right now, it is unclear what the impacts of that closure will be on the region.



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: June 19, 2018   

Last week the Intermountain West saw the remnants of Tropical Storm Bud roll through from southern Arizona, New Mexico and Colorado.  Utah and western Arizona remained dry for the week with less than 0.10" of precipitation.  New Mexico saw widespread precipitation amounts of at least 0.50" with isolated areas over 1.00".  Colorado was a mix of beneficial precipitation, and lack of precipitation.  Northwestern Colorado from Moffat to San Miguel counties were on the drier end with less than 0.25 inches.  Southwestern Colorado saw some of the best precipitation for quite a while, with amounts of 0.50" to over 1.00".  While this was above normal precipitation for this time of year and helped firefighting efforts, it was not enough to put out the fires or make up for the large precipitation deficits this area has seen over the last 9+ months.

Eastern Colorado saw a mix of precipitation amounts.  Northeastern Colorado saw widespread areas with at least 0.50" and isolated areas over 1.00".  Southeastern Colorado missed out on most of the precipitation with much of the Arkansas Basin seeing less than 0.25".  Extreme southeastern Baca and extreme eastern Prowers counties saw amounts of 0.25 - 1.00" last week.  This is near or just above normal for a week this time of year.  While this precipitation helped the area out, it isn't helping to fill the deficits that have accumulated this winter and spring.

Even with precipitation in southern Colorado SPIs remain low on all time scales, worsening on the longer times.  Snotel precipitation percentiles remain extremely low in the San Juan and Sangre de Cristo Mountains, still in the 0 - 3rd percentiles.  

Streamflows in the UCRB are continuing to fall and the majority of streamgages are reporting much below normal, including our three indicator sites.  Streamflows in eastern Colorado are slightly better, with gages in the mountains showing normal flows, but most gages on the plains are showing below normal flows.

Temperatures remained above normal for the entire IMW region, with the exception of northern Wyoming.  Higher temperatures mean higher evaporative demands, which means what rain did fall will be sucked out by the atmosphere faster.


UCRB: Status quo.  Despite the 0.50 to 1.00" that fell through southwestern Colorado, the accumulated deficits still warrant the current depiction.

Eastern CO:  The USDM Author is suggesting reduction of D3 in Baca, Prowers and Kiowa counties based on recent precipitation.  We are fine with reductions in extreme southeast Baca County, but not as far north and west as is suggested.  See change map on the right.  Since most of the precipitation that fell in eastern Colorado was near normal for a week in June, we don't feel it was enough to make up accumulated deficitsand improve conditions.

There is also a suggestion to trim D1 in Cheyenne County.  We are on board with this suggestion given the bullseye of precipitation where the improvements are being suggested.  Along with this improvement are reductions of D0 in Kit Carson County and reduction of D2 in Lincoln County.  While Kit Carson County hasn't see much precipitation this month, only 0.1 to 0.25", based on precipitation in May, D0 could be removed. 

We would like to hold off on the D2 reduction in Lincoln County.  There was beneficial precipitation, however it was not enough to recover the deficits accumulated this winter and spring.