NIDIS Upper Colorado River
Regional Drought Early Warning System
April 26, 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

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

The top left image shows VIC modeled soil moisture as a percentile ranking. The top right image shows VIC+SWE.

The above image shows last month's and this month's current volumes of the major reservoirs in the UCRB, with percent of average and percent of capacity.
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
Bureau of Reclamation Upper Colorado River Basin Teacup Diagrams

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 3 months Precipitation outlook. The bottom left image shows the Hydrologic Prediction Center's Quantitative Precipitation Forecast accumulation for the five days between Tuesday 12Z and ending Sunday 12Z. The bottom right image shows the Climate Prediction Center's most recent release of the U.S. Seasonal Drought Outlook.

Short Term: (4/25)

  • A cooler, wetter than average week is forecast for the entirety of the UCRB and eastern Colorado. Every time a new wave is ejected onto the plains the upper-level low is forecast to reestablish itself over the Great Basin. No clear days with a high pressure airmass overhead are anticipated over the next seven days. This will come more gradually for the UCRB with much of the moisture expected between now and Friday. The heaviest precipitation totals in northeast Colorado are likely to occur Friday night. The southeast corner of the state may be drier Friday night, but see more favorable moisture Sunday into Monday. 
  • In the Upper Green River Basin 1-2" of precipitation is expected over the next seven days at elevation, and 0.5-1.0" in the valleys. 
  • Eastern Utah should likewise see 1.00-2.00" of precipitation over the next seven days in the Wasatch and Uintah Mountain Ranges. Totals in the valleys should range from 0.50-1.50", and diminish towards the southern end of the domain. 
  • Western Colorado should see 1.00-2.50" of precipitation over the coming week.
  • Eastern Colorado should see 1.00-4.00" of precipitation over the coming week. The southeast corner of the state is forecast to be on the low end of these totals. The Front Range from Fort Collins all the way down to Pueblo are likely to see 1.50-3.00" with some even higher totals at elevation. The northeast corner of the state may be in the perfect position for heavy rain as well according to current model runs. 
  • Longer Term:
  • The 8-14 day precipitation outlook shows increased chances for above average precipitation across the entirety of the UCRB and eastern Colorado. These chances are most highly enhanced in southern Utah and southwest Colorado. 
  • The 8-14 day temperature outlook shows increased chances for above average temperatures in the norther portion of the basin, equal chances for above and below average temperatures through northern Colorado to southeastern Utah, and above increased chances for below average temperatures in southern Colorado.
  • The Climate Prediction Center May through July outlook shows increased chances of above average precipitation for the entirety of the UCRB and eastern Colorado. This is a typical forecast from CPC for the exsiting El Nino.
  • The seasonal drought outlook for Colorado and the UCRB shows no likely drought development over the next three months, and removal likely in the southeast corner of the state. 

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: April 26, 2016

Last week most of the Upper Colorado River Basin saw lower precipitation amounts through much of the area.  Temperatures were closer to normal, with the northern portion of the basin seeing the most above normal temperatures.  All sub-basins within the UCRB appear to have peaked and are in full melt mode.  Most of the northern basins, with the exception of the Duchesne Basin, peaked near the normal peak snowpack.  The southern basins saw lower than normal peaks this year.  An area that has been drying out over the past few months is eastern Utah, which should see some expansion of D0 this week.  30-day SPIs aren't as bad, however this area is showing dryness going out to 120-days.

Most of eastern Colorado saw less than 0.50 inches through the week.  Thunderstorms developed on Monday afternoon and continued through the night over much of the northern Front Range, with portions of Larimer and Weld County seeing up to 0.75 inches. 

The mountains east of the Divide have passed the normal peak.  Both the Arkansas and South Platte River Basins are seeing later than normal peaks.  The Arkansas has peaked at 99% of the normal peak, while the South Platte is currently at 107% of the normal peak.

The next two weeks look to have some active weather impacting the area, so there could be some more improvements coming in the next weeks.



UCRB: We are recommending expansion of D0 in southeast Utah.  This area has been drying out quickly over the past few months.  While the 30-day SPI in the area is in the 0 to +1 range for most of the SPI points, the area turns dry when looking at the 60-day and 90-day SPIs.  While the temperatures and evaporative demand have not been high, the lack of precipitation and drying of soils is driving this degradation.

Eastern Colorado: Status quo.  With the changes last week and little change in conditions this week, no changes are needed this week.

**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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