NIDIS Upper Colorado River
Regional Drought Early Warning System
May 26, 2015


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:

  • The UCRB and the rest of Colorado saw another round of widespread precipitation.
  • The Upper Green River basin saw between 1.00 and 2.00 inches through Sublette, Lincoln and Uinta county, with the eastern portion of Sweetwater County receiving between 2.00 to 4.00 inches.
  • The Wasatch and Uintah ranges in Utah saw between 1.00 to 2.00 inches with portions of Summit, Daggett and Duchesne counties in the 2.00 to 4.00 inch range.
  • Farther south in Utah, between 0.50 and 1.00 inches fell, with Grand, Emery, Wayne and San Juan counties seeing less than 0.50".
  • Western Colorado saw widespread precipitation of 1.00 to 2.00 inches of precipitation fell.  Along the Colorado-Utah border from Garfield County to the Four Corners, 0.50 to 1.00 inches fell, along with some spotty areas in the basin.
  • The San Juan Mountains saw up to 4.00 inches during the last week.
  • East of the Divide saw widespread precipitation amounts of at least 1.00 inches, with most of eastern Colorado seeing 2.00 to 4.00 inches.  Lower amounts, 1.00 to 2.00", fell in parts of Weld County and into the Denver Metro area.
  • Yuma and Kit Carson Counties received up to 6.00 inches over the last week.
  • The Rio Grande Basin saw precipitation in the range of 1.00 to 2.00 inches, with the southwest part of the basin seeing up to 4.00 inches.

April Precipitation:

  • April was a better month in terms of percent of normal than March, however there were still dry areas in the UCRB.
  • The Upper Green River Basin in Wyoming most received above normal April Precipitation, with some of the higher elevations in Sublette County seeing some below normal precipitation.  Uinta County in Wyoming saw an area of 300+ percent of normal precipitation.
  • Eastern Utah was a mix, with much of the Uintah Range seeing below normal, with the exception of Daggett and eastern Uintah County seeing above normal precipitation.  The Wasatch Range saw near normal precipitation, with areas of below normal.  Southeastern UT saw near or above normal precipitation, with Grand, Carbon, Emery, Wayne and Garfield counties seeing areas of 200+ percent of normal.
  • Western Colorado also saw a mix.  Much of the western counties, along the CO-UT boarder from Moffat south to Montrose, were near or above normal for April.  Mesa and Delta Counties saw areas of 200+ percent of normal.  Much of the rest of western CO was less than 70% of normal.
  • The San Juan Mountains saw less than 70% of normal precipitation for April, with a wide area less than 50% of April normal.
  • The Rio Grande Basin was also below normal, seeing less than 50% of normal.  The exception being eastern Saguache County, seeing better than 200% or normal.
  • East of the Divide, much of eastern Colorado saw an above normal Month, with Weld, Logan and Morgan Counties receiving more than 300% of normal April precipitation.  Park, Fremont and Teller Counties saw more than 200% of April normal.
  • El Paso, Lincoln, Crowley, Otero and Baca Counties were drier, seeing between 50-90% of normal April precipitation.

 

Water Year 2015 Precipitation (Oct-April):

  • The Water Year percent of normal continues to be below normal for much of the UCRB following a warm, dry winter.
  • The Upper Green river basin has seen above normal moisture for the water year through with the exception of south central Sweetwater County which is 30-90% of normal precipitation.
  • Much of northeastern Utah has seen below normal precipitation for the water year through April.  A few areas in the northern Wasatch Range and in western Uintah County, are slightly above normal.
  • Southeastern Utah has seen mostly near normal for the water year through April.
  • Much of Western Colorado has seen below normal precipitation, with much of the area in the 50%-70% of normal range, and some spots through the basin seeing less than 50% of normal.  Portions of Moffat, Routt and Rio Blanco counties are near or slightly above normal.
  • The eastern side of the Rio Grande Basin has seen above normal precipitation, while the western portion is slightly drier than normal.
  • Eastern Colorado is now above normal precipitation for the Water Year through April.  There are a few small drier areas, with less than 90% of normal in Prowers, Yuma and Phillips counties.

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 year to date percentiles are still very low if not record low across much of the UCRB, and are unlikely to rebound.  The numbers did show slight improvement with the moist conditions over the past few weeks.
  • In the Upper Green the percentiles range from the 7th to 65th with the highest along the Lincoln/Sublette county border.
  • The Wasatch and Uintahs are still very dry with percentiles ranging from the 0 to 37th.
  • The northern mountains in Colorado continue to struggle west of the continental divide where percentiles range from 7th to 50th.  
  • The lower elevations of the Colorado and Gunnison are still seeing percentiles below the 33rd percentile, however sites along the divide are more near normal.
  • The San Juans are reporting mostly below the 15th percentile, with the exception of one station in northern Hinsdale County in the 59th percentile. 
  • The Sangre de Cristo mountains in SE Colorado are slightly better with percentiles ranging from 17th to 47th. 
  • The South Platte stations are all mainly at or above the median.

 SWE Timeseries Graphs:

  • All sub-basins are well into the melt season.
  • The peak snowpack was 85% of normal.
  • The peak snowpack was 63% of normal.
  • The peak snowpack was 68% of normal.
  • The peak snowpack was 79% of normal.
  • The peak snowpack was 70% of normal.
  • The peak snowpack was 67% of normal.

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):

  • The Upper Green river basin is showing wet SPI's between +1.5 and +2.5
  • Northeast Utah is showing wet SPI's between +1 and +2.5
  • Southeast Utah is showing wet SPI's between 0 and +2.5
  • Northwest Colorado is showing wet SPI's between 0 and +2
  • Southwest Colorado is showing wet SPI's between 0 and +2.5
  • North central Colorado is showing wet SPI's between 0 and +2.5.
  • South central Colorado is showing wet SPI's between 0 and +3.
  • East of the divide, all SPI's are wet, between +1 and +2.5 on the 30-day timescale.

Long Term (6-month):

  • On the 6-month timescale SPI's are more of a mixed bag for the UCRB, but generally wet, with some of the higher elevations sites slightly dry.
  • The Upper Green has SPI's ranging from 0 to +2.5.
  • NE Utah shows some longer term dryness with SPI's ranging from -1 to +1.5
  • Southeast Utah has been in the normal range, and is reporting SPI's between 0 and +1.5
  • Western Colorado saw some improvement with the majority if SPI's between -1 and +2.  The driest are in Rio Blanco, Routt, Gunnison, Grand and Summit counties.
  • East of the divide, all SPI's are wet, even on the 6-month timescale. They range from 0 to +2.5. 
  • The Rio Grande basin is wet for long term SPI's, +1 to +2.5

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:

  • 138 of the 140 gages in the UCRB are currently reporting. There was a drop over much of the basin in streamflow, thanks to the cooler temperatures.
  • 57% of the gages in the UCRB are reporting in the normal to much above normal range for 7-day average streamflow. 
  • 33% of the gages are recording below normal for 7-day average streamflow, 8% in the much below normal, and 1% reporting lowest on record for the 7-day average streamflow.
  • Streamflow on the Colorado River near the CO-UT state line has made a bit of a recovery after a week of over the past week after a decrease. It is now at the 34th percentile, 69% of average. 
  • The Green River at Green River, UT is showing increases in flow. Currently the Green is flowing at the 44th percentile, or 84% of average. 
  • Flows along the San Juan are increasing, but it is still low. Right now the San Juan near Bluff is reporting at the 13th percentile, or 34% 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 plus SWE total soil moisture storage. The bottom 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:

  • Sweetwater County, WY has been shown as dry by the VIC for a considerable amount of time, and is finally improving, still showing soil moisture in the 5th to 30th percentile, however a much smaller area than last week.
  • Wet soils show up in the Upper Green River Basin, in Sublette and Lincoln counties, in the 70 to 90 percentile range.
  • Soils in northeastern UT are mostly in the average range.  The Wasatch range is showing wetter soils, in the 70th to 90th percentile.
  • Southeast Utah is also showing soil moisture mostly in the normal range. There is one dry spot in eastern Emery and Wayne Counties in the 10-30th percentile range. 
  • Western CO soils are mainly in the normal to above normal range. There is a channel of wet soils between the 70th and 90th percentile along the Upper Colorado Mainstem. 
  • The San Juan Mountain region is now completely in the normal range. 
  • The San Luis Valley is mostly in showing some wet soils, in the 80th to 90th percentile
  • Eastern Colorado is showing mainly normal to wet soil conditions.  Much of NE Colorado has soil moisture percentiles above the 80th percentile, with a large area in NE Colorado above the 98th percentile. Soils over SE Colorado are now above the 70th percentile, with a small area of normal soil moisture.

VegDri:

  • The VegDri shows moist conditions over central Sweetwater County. Drier conditions are shown in Uinta, Sublette, Lincoln and northern Sweetwater Counties where the VegDri depicts primarily pre-drought to moderate drought conditions. 
  • The Wasatch are depicted in pre- to severe drought, the Uintah Mountains are doing better now, and have rebounded mostly into the normal range, with some pre-drought in the northern part of the range. 
  • VegDRI is shown in the pre-drought range in eastern Utah and western Colorado. 
  • In northwest Colorado, vegetative health is primarily depicted in the normal range, but starting to show some pre drought conditions, especially in Moffat and Rio Blanco Counties. 
  • The high mountain valleys in central Colorado are depicted as especially moist. This includes Chaffee, Park, Teller, Fremont, and Custer Counties. This area of very moist vegetation extends onto the Front Range mainly along the Palmer Divide into El Paso, Elbert, Douglas, Jefferson, Adams, and Arapahoe Counties. 
  • East of the Divide, northeastern Colorado is primarily showing moist vegetation, with the exception of Sedgwick and Phillips counties, where conditions are shown as pre drought. 
  • In southeast Colorado conditions are now mostly in the normal category.  Some pre-drought vegetative health conditions are showing up in southern Lincoln and portions of Baca counties.

Reservoirs:

  • Flaming Gorge is 103% of the May average.
  • Green Mtn is 128% of the May average.
  • Lake Granby is 142% of the May average.
  • Blue Mesa is 121% of the May average.
  • Navajo is 86% of the May average.
  • McPhee is 76% of the May average. 
  • Lake Powell is 62% of the April average and is 46% full, up from 45% full from last week.

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 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.

Reference Evapotranspiration:

  • Olathe: ET started above normal and has dropped below normal.
  • Cortez: ET began around normal but has started to trend below the normal.
  • Center: ET started at a record high and has slowed considerably, to near average.
  • Avondale: ET began just above average, but has slowed to below normal.
  • Idalia: ET started near average, and has fallen below average and approaching the record low year of 2009.
  • Holyoke: ET started around normal and has dropped below normal.
  • Lucerne: ET started normal and is now tracking at the lowest year on record (below 2009).


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 majority of the UCRB had below normal temperature over the past week.
  • The Upper Green Basin saw temperatures 0 to 4 degrees below normal in Sublette, Lincoln, and Uinta counties.  Northern Sublette County saw slightly warmer temperatures over the week in the 0 to 4 degrees above normal.  Sweetwater County was 4 to 8 degrees below normal.
  • The rest of the basin saw temperatures 4 to 8 degrees below average, with the exception of a 0 to 4 degree below normal swath along the divide.
  • East of the divide temperatures were 4 to 8 degrees cooler than normal in the Front Range.  Farther east, temperatures were 8 to 12 degrees below normal in eastern Colorado.  An few areas in Weld, Adams, Washington and Yuma counties saw temperatures to 16 degrees below normal.

April Temperatures:

  • The month of April saw mostly 0 to 2 degrees above normal temperatures in the UCRB.  Much of northeastern Utah saw 0 to 2 degrees below average, spilling into western Garfield and Mesa counties in Colorado.
  • A bulls eye of 2 to 10 degrees warmer than average shows up in Gunnison and Saguache counties.
  • East of the Divide, most of eastern Colorado saw temperatures 0 to 2 degrees above average for April.  The counties along the Colorado-Kansas boarder were slightly warmer for the month, 2 to 4 degrees warmer than average.


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: (5/26)

  • The upper-level weather pattern that has aided in bringing anomalously moist conditions to the UCRB and eastern Colorado over the past month has finally broken. The trough over the southwest United States has flattened, and now upper-level flow is more straight east to west. 
  • Over the next three days a small low pressure disturbance is forecast to track west to east across the UCRB. Temperatures will continue to rise as the low pressure works its way into the region and then dip slightly in its wake, but there is not an intense shot of cold air in behind this system. Precipitation totals over the next three days are forecast to eclipse half an inch for much of the Upper Green River Basin and the Uintah Mountain Range. The northern half of the UCRB is likely to see at least a quarter of an inch while the southern half stays dry or nearly dry. 
  • East of the divide, the shortwave will have a similar effect as it travels nearly due west to east with the center of the low moving over southern Wyoming. Precipitation totals over the next three days will likely be highest towards the northeast corner of the state where at least half an inch is likely. Areas in the northeast quadrant of the state are likely to receive at least a quarter of an inch of precipitation while areas in the southeast quadrant are more likely to experience just a tenth to a quarter of an inch.  
  • Over the Friday to Sunday time period a similar pattern to what has been seen the majority of last month emerges. A cool high pressure airmass sits over the north central US while low pressure rebuilds over the southwest. This pattern will not be as strong as it has at times over the last month, but it will be favorable for cool, moist conditions east of the divide. The UCRB is forecast to stay mostly dry over the weekend with some spill over precipitation possible for the western slopes of Colorado, the Upper Green River Basin, and portions of east and central Utah. Accumulations here are likely to be less than a quarter of an inch. 
  • East of the divide temperatures are expected to drop into the low 50s and low 60s over the weekend with over 0.50" of precipitation likely down the i25 corridor. The eastern plains should expect 0.25-0.50" of accumulation over the 4-5 day time frame with more likely close to the northern border of the state. 
  • Sunday evening through Tuesday of next week looks much quieter as a high pressure ridge finally builds back in from the southwest. There may be some light precipitation impacts from a low pressure spinning up near the Montana-Canada border, but most of the region will be dry with temperatures rebounding up to or above average. 

Longer Term:

  • The 8-14 day precipitation outlook shows increased chances for below average precipitation for the Wasatch Range on the western edge of the Upper Colorado River Basin. The rest of the UCRB, and Colorado east of the divide, are forecast equal chances of above and below average precipitation.
  • The 8-14 day temperature outlook shows increased chances of above average temperatures for the UCRB. These chances are strongest in eastern Utah and southwest Wyoming where there is at least a 40% chance that temperatures will be above average. Temperatures east of the divide over the 8-14 day time frame are more likely to be above average in the northeast quadrant of the state. Southeast Colorado has equal chances of above and below average temperatures.
  • The Climate Prediction Center 3-month precipitation outlook shows increased chances for above normal precipitation for the entirety of the UCRB, and the area in Colorado east of the divide for the June to August period. These chances are forecast above 40% for all of Colorado except the four corners, extreme northeast Utah, and the eastern portion of the Upper Green River Basin.
  • The seasonal drought outlook indicates that drought removal is likely for the areas of the UCRB in a current drought category of D1 or D0. Areas currently in D2 are forecast to see improvement. Drought removal is also forecast as likely over southeastern Colorado.


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 for May 26, 2015:  

It was yet another week of above average moisture and below average temperatures across the Upper Colorado River Basin and the eastern plains of Colorado.  The cool temperatures for another week slowed snowmelt over much of the basin, which also brought a decrease in streamflow this week.  The 3-month SPI is on the positive side for the entire UCRB, eastern Colorado and Wyoming, however there are still some -1 SPI on the 6-month, reflecting the low snow season.  Many SNOTEL sites are still showing very dry years, suggesting lower elevation precipitation is better than higher elevations.  The low snowpack also leads to a possible low water supply year on the western slope.  With cooler temperatures, increased humidity and above average precipitation water usage from the water supply has been lower than normal, easing the possible supply issues.  Improvements in the UCRB will be recommended.

East of the Divide also saw much above average precipitation and much below average temperatures for the week.  The plains are seeing a green up of vegetation, however severe weather and excess rain has lead to some crop damage.  With all the precipitation that has fallen over the last 6 weeks, soils are saturated to the point were even light rain can cause runoff.  Due to this, more improvements will be recommended.

Recommendations:

UCRB: A widespread 1-category improvement over much of the UCRB is recommended.  We are recommending the D0 that currently is in the basin stay, only improving the D1 and D2.  Even with the low snowpack and snotel precipitation percentile numbers throughout the basin, the recent above average precipitation seems to justify this improvement.

In the Rio Grande Valley, from Saguache County to the CO-NM border, we are recommending the existing D0 be removed along with the improvement from D1 to D0.

Eastern CO: A one-category improvement is recommended across southeast Colorado.  After another week of above average precipitation and below average temperatures, the recommendations are justified.

**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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