NIDIS Upper Colorado River
Regional Drought Early Warning System
April 15, 2014


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.

 

Last Week Precipitation:

  • Last week, most of the higher elevations of the UCRB received over .25 inches of moisture
  • The Wasatch and Uintahs in northeast UT and the Wind River and Wyoming ranges in WY received between .10 and .50 inches
  • The northern and central Rockies in CO received between .50 and 2 inches of precipitation for the week
  • The San Juans in southwest CO received between .25 and 1 inch
  • The lower elevations in the UCRB were a bit drier, most areas receiving less than .25 inches
  • East of the basin, many parts of eastern WY received between .25 and 2 inches
  • Northeast CO and the Front Range received between .25 and 1 inches of precipitation, while areas of the Arkansas valley were drier, receiving less than .25 inches

March Precipitation:

  • The Upper Green River basin saw above normal moisture in March while lower elevations in Sweetwater received less than 70% of normal.
  • The Wasatch and Uintah ranges in Utah were at or above their March averages with the wettest areas in Rich county Utah and Uinta and Lincoln counties in Wyoming.
  • The low elevations of eastern Utah and western Colorado recieved below normal precipitation for the month of March.  Widespread areas saw less than 70% of normal.
  • The higher elevations in Colorado saw near to above normal conditions across the high country. 
  • East of the divide in Colorado was fairly dry for what would normally ramp up the wet season.  Widespread areas of less than 50% of normal predominated the Eastern plains of Colorado with the driest areas centered over the already drought devastated areas in Lincoln, Cheyenne and Kiowa counties. 
  • The southern basins of the Arkansas headwaters received much needed above normal moisture for the month of March. 
  • Areas near the Front Range faired slightly better than the Eastern plains with more near normal (70-110%) moisture falling in March.

Water Year Precipitation (Oct-Mar):

  • Much of the UCRB is showing normal to above conditions for the water year through March.  The driest areas are the lower elevations of eastern Utah and western Colorado (particularly the Four Corners) where WYTD precipitation is less than 70% of normal. 
  • The Yampa, White and Colorado basins are all showing above normal conditions for the water year through March.  Lower elevation areas (Routt, Rio Blanco, Garfield) did not fair quite as good with water year precipitation in the 50-90% of normal ranges.
  • East of the divide, the driest areas are mainly south of I70 and east of I25 with the entire area receiving less than 90% of normal for the water year through March.  Las Animas and Baca counties are reporting WYTD precipitation less than 50% of normal. 
  • The northern tier of the easter plains has gotten much better moisture (as did much of eastern Wyoming) with above normal conditons for the water year.  Conditions in Yuma county are slightly drier for the water year and fall in the 50-90% of normal range. 

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).

SNOTEL Precipitation Percentiles:

  • SNOTEL precipitation is at or above the median (50th percentile) for the northern and eastern part of the UCRB with drier percentiles along the western and southern portions
  • Percentiles in the Upper Green region are mainly above the 75th percentile.
  • In the northern and central CO mountains percentiles are at or above the median percentile, with most SNOTEL sites along the Continental Divide above the 70th percentile.
  • The Wasatch range in northern Utah is near the median. While in the Uintah range in northeast UT is drier with percentiles ranging from 9th to 56th with the lowest values on the southern flank of the range.
  • Percentiles in the San Juans range from single digits in the lower elevations of the SW side of the range to near and above median on the NE side of the range. 
  • In the Rio Grande Basin, percentiles are mainly below the 25th percentile.

Basin-wide Snow Water Equivalent (SWE) Percent of Normal:

  • The eastern and northern sub-basins in the UCRB currently have above normal snowpack, with the highest values in the Upper Green river basin in western WY
  • Snowpack in southwest CO is reporting below normal at 72%
  • East of the basin, snowpack is above normal

SWE Timeseries Graphs:

  • All sub-basins have peaked in the last week and have seen rapid snowmelt since
  • The Upper Green, Yampa-White, and Upper Colorado sub-basins peaked well above average and remain above average
  • The Gunnison sub-basin peaked near the median seasonal peak and is currently at 93% of median
  • The Duchesne and San Juan sub-basins peaked below their normal seasonal peaks and are currently at 84% and 81% of median, respectively

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.

Short Term (30-day):

  • Most of the UCRB is showing dry short-term indicators, with most SPIs between 0 and -2
  • Some areas of the central and northern Rockies along the Continental Divide are between 0 and +1
  • The driest area is around the Four Corners and extended northward from there
  • East of the basin, most of northern WY shows near normal SPIs with dryness increasing to the south
  • The Front Range urban cooridor mainly shows SPIs between 0 and -1.5
  • Most of the SPIs in eastern CO are between 0 and -1

Long Term (6-month):

  • The UCRB is mixed between wetter and drier regions, long-term
  • Eastern and northern UT are mostly drier, with SPIs ranging between 0 and -1.5
  • Western WY is slightly wetter, with SPIs between 0 and +1
  • Most of the higher elevations of CO are showing wetter SPIs
  • East of the basin, eastern WY is mostly wet, with SPIs between 0 and +1
  • Eastern CO is mostly drier, with most SPIs between 0 and -1.5 

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.

Streamflow Statistics:

  • The number of reporting gages has increased to 130 as gages come back online after being affected by ice. 
  • 77% of the gages in the UCRB are reporting above the 25th percentile (normal and above) for 7-day average streamflow, an increase from 61% last week
  • 24% of the gages are recording below the 25th percentile (below normal) for 7-day average streamflows
  • Overall, streamflows have increased across the basin as temperatures have warmed and snowmelt has begun
  • The driest streams are the San Juan river in SW Colorado and the Duchesne River in NE Utah
  • Flows on the Colorado River near the CO-UT state line are in the near normal range, currently at the 58th percentile
  • The Green River at Green River, UT is currently reporting much below normal flows at the 4th percentile
  • Record low flows are currently being reported on the San Juan River near Bluff, UT (only 16% of average)

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 modeled soil moisture combined with SWE as a percentile ranking.


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.

VIC:

  • Much of the UCRB is showing drier soil moisture conditions
  • Soil moisture throughout northeast UT and southwest WY are between the 2nd and 30th percentiles
  • The Four Corners region is showing drying soil moisture, with much of the region below the 30th percentile
  • Western CO continues to show wetter soil moisture conditions, above the 70th percentile
  • East of the basin, most of northern WY shows very wet soil moisture conditions
  • Soil moisture is near normal across most of the Front Range, with drier soil moisture conditions across most of the eastern CO plains

Reservoirs:

  • All of the major northern reservoirs in the UCRB are near to above their March averages, ranging between 82% (Lake Granby) and 103% (Dillon Reservoir) of average
  • The southern reservoirs are below average, ranging between 55% (Powell) and 74% (Navajo) of average
  • Blue Mesa is now at 105% of average after seeing abnormal increases (or smaller releases) during most of the winter
  • Navajo, McPhee, Blue Mesa and Flaming Gorge have seen increases since the end of last month while the remaining reservoirs have seen decreases in preparation for Spring runoff season

Additional Surface Water Links: (will take you to an outside website)
NLDAS Drought Monitor
Bureau of Reclamation Upper Colorado River Basin Teacup Diagrams


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.

Last Week Temperatures:

  • All of the UCRB saw warmer than average temperatures
  • Temperatures ranged between 2 and 10 degrees above average, with the warmest anomalies across UT
  • East of the basin, all of WY and CO also experienced warmer than average temperatures

Last Month Temperatures:

  • The Upper Green river basin saw temperatures 0 to 6 degrees above normal for March.
  • Eastern Utah and western Colorado saw temperatures 0 to 2 degrees above normal for the month with the Yampa basin slightly warmer in the 2 to 4 degree above normal range. 
  • The San Luis Valley was warmer than normal in the range of 2 to 6 degrees above normal. 
  • East of the divide was more seasonal to cooler.  The NE plains were mainly 0 to 2 degrees above while the SE plains were 0 to 2 degrees below normal.  Farther to the south in Las Animas and Huerfano county was 0 to 2 degrees above normal.


The top two images show Climate Prediction Center's Precipitation outlooks for 8 - 14 days (top left) and 3 months (top right). 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:

  • A system will be moving into the region mid-week, bringing moisture throughout the region, with the highest accumulations of moisture confined to the southern CO mountains east of the Continental Divide and the southeast CO plains
  • Dry and mild weather returns to the region late in the week
  • A weak, disorganized disturbance is expected to pass over the region this weekend, bringing increased chances of scattered precipitation with it

Longer Term:

  • The 8-14 day precipitation outlook shows increased chances of wetter than normal conditions across the northern and western edges of the UCRB in WY and UT, with best chances for near normal conditions across CO
  • The 8-14 day temperature outlook (not pictured) is showing higher probability for warmer than average temperatures across the UCRB and CO, likely ramping up rapid snowmelt next week
  • The CPC 3-month outlook shows equal chances for wet, dry, or near normal conditions across the entire basin for April-May-June
  • The seasonal drought outlook shows a probability of drought persisting across the western portion of the basin and across southeast CO and northern UT


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 15, 2014

Many of the higher elevations reached peak snowpack for the season and began rapid snowmelt last week in response to the warmer than average conditions throughout the region.  Flows in the UCRB have subsequently increased, and should be expected to continue increasing (with volume increases in the reservoirs) as temperatures continue to warm and snowpack continues to melt.  Flooding is a concern in northeast CO where flows are already high (from September flooding) and snowpack peaked well above the average.  In southeast CO, dry conditions persist, although the Arkansas River should see improvements in flows in response to melting of decent snowpack.

Recommendations**

UCRB: The current U.S. Drought Monitor (USDM) author has already shown improvement from D0 to D-nothing in southwest WY as a response to above average snowpack in the region.

It is also recommended that the D1 and D2 in southwest CO be slightly expanded northward.  The D1 expansion (red shape) will cover the lower percentile SNOTEL sites, and the D2 expansion (maroon shape) are expanded to Durango and Cortez, where there have been reports of very dry conditions.

Eastern Colorado:  Status quo is recommended for northeast and southeast CO.  Possible improvements may be made in the next week following accumulations of beneficial moisture - mostly confined to the foothills and higher elevations of the Sangre de Cristos.  Any precipitation that has recently accumulated (or is forecast for the next week) has been of limited benefit to the driest areas of southeast CO, which is still suffering from severe impacts to soil moisture, crops, and grazing lands.  The area continues to experience high winds and dust storms as well.

 

**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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