NIDIS Upper Colorado River
Regional Drought Early Warning System
October 28, 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:

  • The majority of the UCRB had a quiet week in terms of precipitation.  The highest amounts fell in the Yampa and Colorado River headwaters. Parts of Rio Blanco and Routt Counties experienced over 1.00" of precipitation, and most of northwest Colorado was over a 0.25". 
  • The Uintah Mountain Range experienced some decent moisture with this week's totals mainly between a quarter and half an inch, and some areas of between 0.50" and 1.00".
  • The San Luis Valley was dry receiving 0-0.10" for the week. 
  • East of the divide was also dry only receiving 0-0.10" for the week.

September Precipitation :

  • The majority of the UCRB had a well above average September for precipitation. The headwaters of the Green River saw widespread areas of above 300% of average precip for the month. Some of these areas include parts of Uintah, and Grand Counties in Utah as well as Uintah, Sublette, and Lincoln Counties in Wyoming. 
  • East of the CO-UT state line precipitation totals were closer to normal for the month on average. 
  • The Four Corners area was generally between 100% and 200% of normal for the month. A small portion of Dolores County was below normal.
  • Precipitation was in the normal range for the northwest portion of the state with spotty areas receiving as much as 200% of normal. 
  • The San Luis Valley was mostly below normal for the month (between 50 and 90% of average). Some portions of Conejos and Saguache Counties reported as little as 30% of average precipitation for the month. 
  • East of the divide there is a large gradient in the percentage of average precipitation for the month of September right along the Palmer Divide. Areas just north of the Palmer Divide experienced well above average precipitation for the month. Douglas, Elbert, Arapahoe, Washington, and Yuma Counties show widespread areas above 200% of average. 
  • South of the Palmer Divide in El Paso, Fremont, and Lincoln Counties precipitation totals were between 30 and 50% of average. 
  • The northeastern CO counties saw much above average precipitation, mainly 150% to 100% of average precipitation for August.
  • The northern Front Range had an average month with precipitation totals between 70 and 130% of average. 
  • In the extreme southeast portion of the state there is a large gradient where precipitation totals were as much as 200% of average right at the corner of the state, but as little as 50% of average in large areas of Bent, Prowers, Otero and Las Animas Counties. 

Water Year Precipitation:

  • Much of the UCRB is now near or above average for the Water Year through August, with spotty areas below average.
  • Most of the northern portion of the basin in Wyoming is above average, with portions of Lincoln, Uinta, and southern Sublette counties 200% to 250% of average.  
  • Much of eastern UT is now near average, with no widespread areas clearly above or below normal. The distinction between above areas with above and below a normal water year here is very spotty. 
  • Western Colorado is a bit spottier than Utah with precipitation as a percent of average, however much of the area is near average for the Water Year.  Most of the western slopes are between 70 and 110% of average for the water year. Some spotty areas including parts of San Miguel, Mineral, and Mesa Counties were over 200% of average for the water year. 
  • The northern portion of the Colorado River headwaters area is still much above average, mainly greater than 130% of average.
  • East of the Divide a north-sound gradient exists in water year precipitation as a % of average. The north-south gradients in soil moisture and vegetative health echo this gradient quite clearly. 
  • Almost all of the northeastern plains were above average for the 2014 water year. Percents of average were between 90 and 150. 
  • Most of the Front Range was between 90 and 130% of average for the water year. 
  • Southeastern CO has improved, but still came in below normal for the 2014 water year across the majority of the region. Totals were mainly between 70 and 110% of average. 
  • A strip in the southern Colorado Rockies extending through Costilla, Huerfano, and Custer Counties had an above average water year. Totals were between 150 and 250% 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).

SNOTEL Precipitation Percentiles:

  • In the headwaters of the Green River up in Lincoln and Sublette Counties in Wyoming percentiles are above average for the water year thus far, and range between the 50th and 85th percentile.
  • The Uintah Mountains have seen less precipitation to kick off the water year, and are between the 0th and 40th percentile. 
  • Percentiles in the Wasatch range in UT precipitation percentiles are also low. Right now they range anywhere from the 3rd percentile in south Duchesne County to the 36th percentile in Sanpete County. 
  • Percentiles in the San Juans range from the 6th percentile on the south side of the range to the 56th percentile in Hinsdale County on the northeast side of the range. 
  • In the Rio Grande Basin, percentiles are mainly below the 25th percentile.
  • While the headwaters of the Arkansas basin are reporting above the median, the southern basins (Custer, Huerfano, Costilla counties) are reporting at or below the median. In Custer and Huerfano precipitation has started around normal for the water year, but it is below normal further south.
  • The headwaters of the Colorado and the South Platte Rivers up in northern Colorado have kicked off this water year above normal. Percentiles are generally in the 75-85 range east of the divide (South Platte) and 65 to 85 with some low outliers west of the divide (Colorado). 

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

  • Most of the UCRB has started the water year well below normal in terms of snowpack. The Lower Green River Basin is the notable exception with areas between 93 and 100% of normal. 
  • Closer to the headwaters of the Green River snowpack values are not as high. In Southwest WY snowpack numbers are between 14 and 47% of average. 
  • The Western slopes of Colorado have started the water year way below average in terms of snowpack. Percents of average here range between 4 and 51. 
  • East of the divide snowpack is at 25% of noramal for the South Platte and 21% for the Arkansas. 

SWE Timeseries Graphs:

  • All river basins appear to be off to a slow start to the snow season. 
  • The Upper Green Group is at 2.7% of median snowpack to date. 
  • The Duchesne is at 30% of median snowpack to date. 
  • The Yampa is at 43% of median snowpack to date. 
  • The Upper Colorado Mainstem Group is at 31% of median snowpack to date. 
  • The Gunnison Group is at 9% of median snowpack to date. 
  • The San Juan Group is at 10% of median snowpack to date. 

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):

  • SPIs are in the normal range across the entire UCRB for the last month. There is a bit of a bias towards above average SPIs with most SPIs between 0 and +1. Some SPIs, mostly along the Colorado River Mainstem near Lake Powell, are between -1 and 0. 
  • East of the divide SPIs are mostly, but not completely in the normal range. One station in central El Paso County is showing a SPI of +2 to +2.5. Along the border of Lincoln and Elbert Counties SPIs are between +1.5 and +2, but in south Lincoln County there is a SPI between -1 and 0. A station in Sedgwick County whose data has regularly been called into question this growing season indicates a SPI of -2 to -1.5. 

Long Term (6-month):

  • For the longer term, much of the UCRB continues to report wet SPIs.  There are a few dry areas reported around the Four Corners and in Gunnison County.  These are between 0 and -1.  The rest of the area is reporting SPIs between 0 and +2.  The wettest areas are in Routt County, CO and along the mainstem of the Colorado River. One SPI in Grand County, UT is between +2 and +2.5.
  • The San Luis Valley in Colorado is fairly dry with the majority of valley stations reporting SPIs between 0 and -1. There are a couple SPIs here above the 0 mark in Saguache, Alamosa, and Conejos Counties. 
  • East of the divide, a north/south gradient still remains.  The Arkansas basin is reporting drier SPIs along with a few wetter SPIs between -1 and +1.  The NE plains are wetter with the majority of stations reporting between 0 and +2.  The dry SPI in Sedgwick still exists and is again thought to be erroneous due to missing data.

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:

  • 9% of gages in the UCRB are reporting 7 day average streamflow in the below to much below average category.  These gages are mainly located along the San Juan drainage.
  • 45% of the gages are in the normal category (25th-75th percentiles).
  • 51% of gages are above to much above normal and 1% are reporting record high flows for the 7 day period.
  • Streamflow on the Colorado River near the CO-UT state line is on the high end of the average range, reporting in the 73rd percentile (116% of average).
  • The Green River at Green River, UT is also reporting above average, in the 53rd percentile (99% of average).
  • The San Juan River near Bluff, UT has fallen once again into the below normal range. Flows are at the 18th percentile (42% 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:

  • The overarching pattern shown across the UCRB this week by the VIC is normal, or above normal soil moisture.
  • Sweetwater County, WY still shows dry soils between the 10th and 30th percentile, with a few pockets showing up that are down to the 5th percentile. This area is typically quick to dry out in the VIC product.
  • Soil moisture is in the normal range in the Four Corners area.
  • The San Luis valley is showing normal soil moisture conditions.
  • East of the divide, the northern plains are showing average to just above average soil moisture conditions in the 30th-80th percentile. 
  • Along the Front Range soil moisture is the highest near the Denver Metro Area and just to the west of there.
  • Soil moisture conditions are in the normal range in the southeast quadrant of Colorado. The exception here is south Lincoln County where soil moisture is between the 10th and 30th percentile. 

VegDRI:

  • Nearing the end of October the VegDRI product is quickly going out of season, and there are some significant pockets of missing data. 
  • In the headwaters of the UCRB the VegDRI is indicating predominantly slightly moist to moist vegetative conditions. 
  • The Four Corners area is still indicating dry vegetation conditions from San Juan county, UT east into the San Luis valley.  These areas are mainly in the pre- to moderate drought category.
  • The San Luis Valley is indicating drier conditions than areas farther west.  This index gets down into the severe drought classification in the valley. 
  • The Front Range is showing vegetative health conditions in the normal range, however an east-west gradient has developed where dry conditions exist in the urban corridor, and moist conditions in the foothills and Rockies to the west. 
  • East of the divide there is a north-south gradient.  The northern plains are doing well in terms of vegetation health and the dry area in Sedgwick County is likely not valid based on ground reports (likely SPI driven). 
  • Farther south on the eastern plains is showing a mixed bag of conditions.  Irrigated areas along the Arkansas river are showing wet conditions while the surrounding areas are mainly reporting in the pre- to moderate drought classification.  Some areas in Pueblo, Lincoln, Las Animas and Baca have spotty areas of severe drought classified by VegDRI.

Reservoirs:

  • Some of the Reservoirs in the UCRB continue to increase in volume as a consequence of an above average monsoon season in August and early September. Flaming Gorge, Lake Powell, Navajo, and Dillon have all shown increases since last month. Lake Granby, Green Mountain, Blue Mesa, and McPhee are now decreasing in volume. 
  • Flaming Gorge is 103% of the October average.
  • Green Mtn is 80% of October average.
  • Lake Granby is 127% of October average.
  • Lake Dillon is at 109% of the October average.
  • Blue Mesa is 93% of the October average.
  • Navajo is 81% of the October average.
  • McPhee is 69% of the October average. 
  • Lake Powell is 63% of average and 51% full.

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:

  • The UCRB saw above average temperatures last week in the range of 3-12 deg above normal. Most of the area was between 6 and 9 degrees above normal.
  • The San Luis valley was 6-9 degrees above average for the week.
  • East of the divide temperatures were 9-12 degrees above normal most places with some areas as much as 12-15 degrees above normal. 

Last Month Temperatures:

  • September temperatures in the UCRB, Wyoming and much of Colorado were mostly above average. 
  • The Upper Green River basin in WY was mostly 1 to 3 degrees above average, with southern Lincoln County, WY was 3-5 degrees above average.
  • Eastern UT saw temperatures mainly 3 degrees above average with a few areas 4 degrees warmer than average.
  • Northwestern CO saw temperatures 1-3 degrees above average, while temperatures farther south were 3-4 degrees above average, with pockets near the Four Corners area up to 5 degrees above average.
  • East of the divide most of the Front Range was between 1 and 2 degrees below average for September with Larimer County being near average. 
  • The eastern plains saw 1 to 2 degrees above average for the month.
  • The San Luis Valley saw temperatures greater than 4 degrees above average.  These warm temperatures saw their way east in to Las Animas County.


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:

  • For the next three days the UCRB and Colorado east of the divide are not expected to see any moisture as high pressure and large-scale subsidence persists. 
  • Friday night into Saturday a cold frontal passage is expected to sweep across the UCRB from the northwest. This will bring the best chance for significant moisture to the Wasatch and Uintah Mountain Ranges in Utah. The western slopes of Colorado may see some limited precipitation as well. 
  • East of the divide winds are forecast to ramp up early in the weekend followed by cooler conditions and a chance for some modest wrap-around moisture totals on Sunday. 

Longer Term:

  • The 8-14 day precipitation outlook shows increased chances for below normal precipitation the UCRB and for Colorado east of the divide. The certainty for this is greatest east of the divide where there is at least a 50% chance of below normal precipitation. The Four Corners and the San Luis Valley are more likely to see below average precipitation over the 8-14 day timescale than areas further north and west. 
  • The 8-14 day temperature outlook shows increased chances for above normal temperatures in the UCRB and east of the divide. With the exception of the very western edge of Colorado the whole state is forecast at least a 50% chance of above average temperatures. Eastern Utah and the Green River headwaters in southwest Wyoming are forecast at least a 40% chance of above average temperatures. 
  • The CPC 3-month outlook shows equal chances for wetter or drier than normal conditions over the UCRB in Utah, Colorado, and Wyoming, with chances of above average precipitation over southern UT and CO.
  • The seasonal drought outlook indicates that drought is expected improve or be removed in southeast Colorado, the Four Corners Region, and the San Luis Valley. There is now hints that drought may persist or intensify in northeast Utah. 


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 October 28, 2014: 

Indian Summer has persisted over the past week across Colorado and the UCRB with high pressure conditions dominating across the region. A couple shortwave disturbances brought some moderate rainfall totals to northwest Colorado and northeast Utah. Outside of this area the precipitation that fell across the drought monitor region was nearly unanimously either 0.01-0.10" or nil. 

Temperatures were much above average this week, especially east of the divide where temperatures were at least 9 degrees above the normal. In the UCRB it was still a warm week, but temperature anomalies were a little more modest, and mostly in the 6-9 degree above average range. Following an August and mid-September that were wetter and cooler than normal and transitioning out of the cold season these temperatures aren't especially concerning yet. The level of concern will rise, however, if snowpack totals at high elevations continue to follow current trends for any extended period of time. 

Recommendations:

UCRB:

Status Quo: The areas of the UCRB that received substantial precipitation over the past week are not currently in drought. Northeast Utah did receive 0.25"-0.50" of precipitation in most areas, and up to 1.00" of precipitation in some select areas, but given the temperature anomalies over the past week this is not enough to justify improvements. 

As per NWS Grand Junction's recommendation we will keep a close eye on the Four Corners Region as it sits in a gradient zone between abnormally dry and severe drought conditions. Should the above average temperature and below average precipitation conditions we have seen the last two weeks persist some degradations may be mandated in short order.  

 

Eastern CO:

Status Quo: Warm, dry conditions across Eastern Colorado over the last two weeks certainly don't justify making any improvements in southeast Colorado at this time. Ground reports indicate that although drought persists in this region summer moisture was sufficient for a promising start to winter wheat season. 

 

**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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