PRECIPITATION

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.

 

 


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).



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.


STREAMFLOW


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.



EVAPOTRANSPIRATION



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..


TEMPERATURE

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.


FORECAST AND OUTLOOK

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: (5/10)

  • Today and tomorrow afternoon showers are possible for southeast Colorado and the urban corridor, but the UCRB should stay mostly dry. 
  • A drying trend will set in later this week with Thursday through Saturday afternoon looking mostly clear for the basin and eastern Colorado. 
  • Saturday into Sunday a change is expected in the weather with an upper level trough moving into the region bringing cooler temperatures and raising the probability of precipitation. 
  • Precipitation totals for the upcoming week are expected to be highest east of the Continental Divide, and in the Upper Green River Basin with upslope flow developing Sunday into early next week. The southern portion of the UCRB will be mostly dry. Totals in western Colorado are forecast to range from 0.10-0.50" for the week to come, a fairly typical week. 
  • Longer Term:
  • The 8-14 day precipitation outlook shows increased chances for above average precipitation in the northern half of the Upper Colorado River Basin and northern Colorado. The southern half of the UCRB and southern Colorado will have equal chances of above and below average precipitation.
  • The 8-14 day temperature outlook shows increased chances for below average temperatures for the Upper Colorado river Basin. These chances are most strongly enhanced in the western and central portions of the basin. Eastern Colorado has equal chances of above and below average temperatures.
  • The Climate Prediction Center May through July outlook shows increased chances of above 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, and removal likely in the southeast corner of the state. 

U.S. DROUGHT MONITOR

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: May 24, 2016

The previous week across the UCRB was characterized by below average temperatures, and wet conditions over the high country. The northern and central Rockies, Uintahs, and western San Juans all finished the week with 0.50-1.00" of precipitation, some areas showing 1.00-2.00".  In Colorado, east of the Continental Divide, more spring moisture was received by most with 7-day totals over 0.50".  Southeastern Colorado was drier in comparison with areas such as Pueblo County getting only 0.01 to 0.10".  Month to date temperatures are 0-2 degrees below normal in western Colorado and 2-4 degrees below normal in eastern Colorado.  

Despite the cooler than average temperatures, snowmelt rates have been average over the past week in most parts of the UCRB.  As streamflows continue their rise towards seasonal peak levels most flows in the UCRB are staying in the normal range. The San Juan River near Bluff, Utah has come up over the last week and is now at 63% of normal in the 38th percentile. From a water supply perspective the biggest concern in the basin continues to be Lake Powell at 71% of average.  The Duchesne Basin also is still showing some seasonal dryness.  However, soils have improved from areas in the 2nd-5th percentile last week to a small area of 5th-10th precentile this week which is reflected in VIC modeled soil moisture.  Evaporative stress is still below average to start the growing season. 

Recommendations: 

UCRB: Some improvement of D0 in La Plata and San Juan counties in southwest Colorado are recommended.  This area has seen some beneficial precipitation over the last month and streamflows have increase through the San Juan River to the normal range.  The rest of the area that is in D0 has seen similar precipitation recently, however seen some longer term dryness, so we will hold off of recommending improvement.

Eastern Colorado: Status quo.