NIDIS Upper Colorado River
Regional Drought Early Warning System
July 19, 2016


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.

 

 

Additional Precipitation Links: (will take you to an outside website)
AHPS Precipitation
High Plains Regional Climate Center's ACIS Maps


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).

Additional SNOTEL and Snowpack Links: (will take you to an outside website)
CBRFC Snow Conditions Map
NOHRSC Regional Snow Analyses: Central Rockies


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.

Additional SPI Links: (will take you to an outside website)
WestWide Drought Tracker SPI Maps
HPRCC's SPI Maps



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.

Additional Streamflow and River Links: (will take you to an outside website)
USGS Streamflow Drought
CBRFC Peak Flow Forecast Conditions Map

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The top left image shows VIC modeled soil moisture as a percentile ranking. The top right image shows satellite-derived vegetation from the VedGRI 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.


Additional Surface Water Links: (will take you to an outside website)
NLDAS Drought Monitor



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 http://droughtmonitor.unl.edu/AboutUs/ClassificationScheme.aspx. 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 3 months Precipitation outlook. The bottom left image shows the Weather Prediction Center's Quantitative Precipitation Forecast accumulation for the seven days between Tuesday 12Z and ending Tuesday 12Z. The bottom right image shows the Climate Prediction Center's most recent release of the U.S. Seasonal Drought Outlook.

Short Term: (7/19)

  • Rainfall totals may be generous across southwest and central Colorado between now and Tuesday with subtropical moisture being funneled into the region. Rainfall totals of over 0.50" are expected for the region between now and Friday morning. The southern Wasatch Range is likely to see over 0.25" of precipitation. Some light precipitation is likely for eastern Colorado. 
  • This weekend the west side of the basin will be dry. Afternoon thunderstorms will still be possible for most of the state of Colorado. These storms will be isolated and likely low precipitation cells. The San Juan Range continues to be the wettest anticipated location. 
  • Longer Term:
  • The 8-14 day precipitation outlook shows increased chances for below average precipitation for the Upper Green River Basin and extreme southeast Colorado. The rest of the basin and eastern Colorado are forecast equal chances of above and below average precipitation.  
  • The 8-14 day temperature outlook shows increased chances for above average temperatures for the entirety of the UCRB and eastern Colorado. These chances are highest in the southwest corner of the basin. 
  • The Climate Prediction Center July through September outlook shows equal chances of above an below average precipitation for the entirety of the UCRB and eastern Colorado. 
  • The seasonal drought outlook for Colorado and the UCRB shows no likely drought development over the next three months.


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: July 19, 2016

Over the past week southerly flow developed over south and central Colorado bringing in subtropical moisture. There were afternoon and evening thunderstorms somewhere in eastern Colorado every night of the week except Saturday. Most of the eastern plains picked up at least 0.25" of precipitation from these storms. The highest totals were over an inch in central and eastern Lincoln County, western Cheyenne County, southwest Kit Carson County, and central Yuma County. Conditions were dry over the Upper Colorado River Basin as the moisture did not extend far enough west. 

Despite being dry, temperatures were cooler than average for the UCRB over the past week generally by only 0-3 degrees. The Upper Green River Basin was even cooler with respect to normal. Sublette County and northern Lincoln County were 6-9 degrees cooler than normal. Northeast Colorado was 0-3 degrees cooler than normal for the most part. Southeast Colorado fell on the warm side of the gradient and experienced temperatures 0-3 degrees above normal. 

Streamflow has come way down over the past month as the spring supply of snowmelt and soil moisture diminishes. In the UCRB flows are in the normal range for this time of year in most places. Flows are in the normal range in eastern Colorado too. The Duchesne River Basin and the headwaters of the San Juan are seeing below normal flows. The mainstem of the Green River is beginning to drop into the below normal range as well. 

Vegetation across the UCRB is gradually trending towards more stressed than average conditions. Soils are also drying, but still mostly in the normal range. The eastern half of Utah and much of southwest Colorado is showing pre-to-moderate drought. The Upper Green River Basin and the Yampa and White Basins are still in the normal-to-moist range. East of the divide, vegetation is mostly in the normal-to-moist range with respect to average. Larimer, Grand, and southeast Jackson Counties are in moderate drought as this area has not received normal precipitation from thunderstorms. 

Continued monsoonal flow is expected to benefit western Colorado through Thursday. The San Juans and Central Rockies may see over an inch of rainfall. On Friday and beyond more dry airflow is expected out of the west. We will continue to track this drying trend, but due in part to the cooler temperatures seen over the basin this past week, and rainfall across much of eastern Colorado, no degradations appear to be warranted at this time. 

Recommendations

UCRB: Status Quo

Eastern Colorado: Status Quo

 

**Disclaimer: The above recommendations are recommendations only, based on data, impacts, and input from local experts. These recommendations are sent to the U.S. Drought Monitor author on Tuesdays. The USDM author has sole discretion on final changes made in the region and can accept, reject, or modify the above recommendations and may have additional modifications. Additionally, any recommendations discussed during the NIDIS webinars that are agreed upon by the local experts and USDM author are still subject to change. Changes are final and official as of Thursday morning, and can be viewed on the official U.S. Drought Monitor website.

Additional Drought Index Links: (will take you to an outside website)
Palmer Drought Severity Index for Climate Divisions Updated Weekly
WestWide Drought Tracker's PDSI Updated Monthly
Surface Water Supply Index

When available, maps and text are updated Tuesday afternoons.

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