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.

 

Last Week Precipitation:

  • Last week, most of the UCRB received less than 0.25 inches of moisture, with only higher elevations along the divide receiving more than 0.25".
  • Much of UT, southwestern WY and western CO received less than 0.10 inches
  • The San Juans in southwest CO received between 0.10 and 0.50", with the San Juan County, CO seeing the bulk of the precipitation.
  • East of the basin, many parts of eastern WY remained drier with precipitation between 0.10 and 0.50 inches
  • Northeast CO was dry last week, receiving no precipitation.
  • The northern Front Range received between 0.25 and 0.50 inches of precipitation from a few rain showers.
  • The southern Front Range in CO saw the best precipitation, with amounts between 0.25 up to 2.80 inches of beneficial precipitation.

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. 

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).


SNOTEL Precipitation Percentiles:

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

SWE Timeseries Graphs:


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.

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 with SPIs between -1 and -2
  • East of the basin, most of northern WY shows near normal SPIs with dryness increasing to the south
  • The northern Front Range urban corridor mainly shows SPIs between 0 and -1
  • The southern Front Range is now showing wet SPI for the short term between 0 and 1.
  • 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 -2
  • Western WY is slightly wetter, with SPIs between 0 and +1
  • Most of the higher elevations of CO are showing wetter SPIs
  • The Four Corners area is showing dry SPIs between -1 and -2.
  • East of the basin, the Foothills are showing near normal SPI between 0 and 1.
  • Eastern CO is mostly drier, with most SPIs between 0 and -2

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.

Streamflow Statistics:

  • The number of reporting gages has increased to 135 as gages come back online after being affected by ice. 
  • 82% of the gages in the UCRB are reporting above the 25th percentile (normal and above) for 7-day average streamflow, an increase from 77% last week
  • 18% of the gages are recording below the 25th percentile (below normal) for 7-day average streamflows
  • Overall, streamflows continue to increase across the basin as temperatures warm and snowmelt continues
  • The lowest streamflows 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 70th percentile
  • The Green River at Green River, UT has finally increased with near normal flows at the 40th percentile
  • The San Juan River near Bluff, UT remains low at the 16th percentile.

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 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:

  • The UCRB is showing a mix of wetter and 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:

  • Most of the major northern reservoirs in the UCRB are near to above their April averages, ranging between 81% (Lake Granby) and 101% (Dillon Reservoir) of average
  • The southern reservoirs are below average, ranging between 56% (Powell) and 75% (Navajo) of average
  • Blue Mesa is now at 110% 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

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.

Last Week Temperatures:

  • The UCRB saw  a mix of cooler and warmer than average temperatures
  • Eastern UT and southwest WY saw between 3 and 6 degrees above average, with Sublette County in WY seeing 3 to 9 degrees below average.
  • Northwest CO and the northern mountains in CO saw temperatures mostly 0 to 3 degrees below average
  • Southwest CO saw up to 3 degrees above average.
  • East of the basin, WY and CO also experienced a mix of cooler and warmer than average temperatures
  • The cooler than average temperatures were mainly in southeast CO, with departures of 3 degrees below average
  • The warmer than average temperatures were mainly between 0 and 3 degrees above average with a few spots up to 6 degrees above average.

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.

FORECAST AND OUTLOOK

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, Tuesday into Wednesday, bringing high winds and isolated rain and snow showers over the mountains and eastern CO.
  • The winds will bring blowing dust to the western slope and higher fire danger to eastern CO
  • Dry and above average temperatures is expected to the region late in the week
  • A stronger system may impact the area over the weekend with a chance of precipitation and cooler temperatures.
  • Precipitation amounts for the next week are expected to be less than 1 inch.

Longer Term:

  • The 8-14 day precipitation outlook shows increased chances of drier than normal conditions across the UCRB, with equal chances of above, below or normal precipitation in eastern WY and CO.
  • The 8-14 day temperature outlook (not pictured) is showing higher probability for warmer than average temperatures across the UCRB, 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

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: April 22, 2014

A quiet week in the Upper Colorado River Basin with less than 0.25" of precipitation falling throughout much of the basin.  Temperatures continue to warm up, melting the snowpack in the mountains, causing the streamflow to increase in most basins in the region.  Flows in the Colorado River and Green River have seen a nice increase, however with the low snowpack in the San Juan mountains, the  San Juan River has not seen that increase.

East of the Basin saw beneficial precipitation fall through the Upper Arkansas Basin, however didn't make it to the drought stricken area of southeastern CO.  The rest of Colorado remained dry, except for some rain storms that fell along the Foothills.

Recommendations**

UCRB: With changes last week in the basin, status quo is recommended.

Eastern Colorado:  After a week of beneficial precipitation and a good month to date, improvements in Pueblo and Huerfano are being recommended.  It is recommended the D0 in these counties be improved to D nothing and the D1 line be pushed east to improve the D1 in western Pueblo County to D0.

With continuing dry and windy weather in Kiowa County, range conditions continue to get worse in this area.  The small precipitation that has fallen recently had little to no impact on green up and wheat in the area.  It is recommended the D2 in Kiowa County be degraded to D3.  Also, it is recommended the D4 be pulled further east in Kiowa County.