NIDIS Upper Colorado River
Regional Drought Early Warning System
November 18, 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:

  • As is to become expected this time of year precipitation over the past week in the drought monitor region was focused over high terrain.
  • The Wasatch and Uintahs picked up 0.50-1.00" in most locations. Parts of Sevier and Summit Counties in UT and Uinta County in WY  received between 1 and 2". The valleys to the east were drier picking up 0.00-0.25" in most areas.
  • The northern/central mountains of Colorado picked up 0.50-2.00" with isolated areas receiving up to 3". 
  • The San Juan mountains were wet this week and received up to 2.00-3.00" of moisture over the week. The San Luis Valley to the east stayed mostly dry, and had less than 0.25" of precipitation. 
  • East of the divide conditions were drier. In northeast Colorado the Front Range averaged between 0.25" and 0.50". Less than 0.10" feel on the northeast plains.
  • Over southeast Colorado there was an east-west gradient in precipitation with parts of Costilla, Huerfano, and Custer Counties receiving between 1.00 and 2.00". Further out east totals were generally between 0.10 and 0.50".  

October Precipitation:

  • The majority of the UCRB had a well below average October for precipitation. The headwaters of the Green River in WY saw less than 50% of normal precipitation, with the exception of eastern Lincoln and northern Sweetwater counties seeing normal to slightly above normal precipitation.
  • Eastern UT saw less than 50% of normal precipitation for October with areas seeing less than 30% of normal.
  • Western CO was a bit better, however much of the area is 50-70% below average.  The exceptions are parts of Moffat, Rio Blanco and Routt counties, which saw slightly above average precipitation.
  • The San Luis Valley, in Alamosa, Rio Grande and Costilla counties saw above average precipitation for October.
  • East of the divide, southeastern CO saw above average precipitation for the month.  Much of the area south of the Palmer Divide saw at or above normal precipitation.  Prowers and Kiowa counties were slightly below average.
  • Northeastern CO saw below average precipitation, mainly less than 50% of normal.  The Front Range, especially Jackson, Larimer and Boulder counties were at or slightly above average for the month.

Water Year 2014 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 in Lincoln and Sublette Counties in Wyoming percentiles range from the single digits and teens (very dry), up to the lower 40s (lower end of normal).
  • The Uintah and Wasatch Mountains have also seen lower precipitation to kick off the water year, and are between the 3rd and 33rd percentile. This is at least an improvement since last week when percentiles in the area were between 0 and 22.
  • The northern and central mountains of Colorado are doing better with percentiles ranging from single digits up to the 59th percentile for precipitation to date.
  • The headwaters of the Colorado in Summit county are doing better than other areas. Some percentiles here are as high as 70, but farther northwest up in Routt County, CO and Carbon County, WY percentiles dip back down in to the single digits.
  • There is a west-east gradient in snowpack percentiles in the Gunnison River Basin. In Mesa County snowpack is as low as the 8th percentile, but up in the headwaters some percentiles are in the 70s. 
  • Percentiles in the San Juans range from the 15th percentile on the north side of the range to the 56th percentile in Hinsdale County.
  • In the Rio Grande Basin, percentiles range from 15th-52nd percentile.  The East side of the Rio Grande basin is looking slightly better off than the western portion. 

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

  • Most basins that feed the Upper Colorado River saw large improvements in snowpack this week, but are still below median values.
  • The Green River in southwest WY snowpack numbers are generally between 60 and 90% of normal with a few outliers. 
  • The Western slope of Colorado is still behind for snowpack, ranging from 74% to 91% of normal. 
  • East of the divide snowpack is normal at 117% of normal for the South Platte and 83% for the Arkansas basin.

SWE Timeseries Graphs:

  • All river basins had an encouraging recovery this week, but are still below normal for the season.
  • The Upper Green Group is at 85% of median snowpack to date. 
  • The Duchesne is at 73% of median snowpack to date. 
  • The Yampa-White is at 71% of median snowpack to date.
  • The Upper Colorado Mainstem Group is at 84% of median snowpack to date. 
  • The Gunnison Group is at 70% of median snowpack to date. 
  • The San Juan Group is at 99% of median snowpack to date, a huge increase from 50% of median last week. 

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 for the past 30 days in the UCRB have dried out significantly in transitioning from the end of a productive monsoon to an underwhelming beginning to the snow season.
  • The Upper Green river basin has been drier than average over the past month with 30-day SPIs between -2 and 0.
  • The Wasatch through the Uintah ranges are quite dry (particularly south of the Wasatch) with SPI ranging from 0 to -2
  • The Four Corners area has been near normal following a productive week of precipitation. SPIs here are between -1 and 0.
  • The San Luis Valley has near average SPIs that range from -1 to +1.
  • East of the divide in northern CO has been mostly dry, but shows a large variance in SPIs. The driest areas include Jefferson County with SPIs between -2 and -1.5, and Yuma County with SPIs between -2 and -1. Higher areas include Larimer, Adams, and Sedgwick Counties where SPIs are between 0 and 1.
  • Southeastern CO is showing mainly dry SPIs with a few stations reporting dry in Lincoln, El Paso, Pueblo and Las Animas counties.  SPI's range from +1 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.  These are between 0 and -1.  There is one SPI near Lake Powell of -2 to -1.5. The rest of the area is reporting SPIs between 0 and +2.5.
  • The San Luis Valley is showing a mixed bag with slightly dry to slightly wet (+1 to -1) SPI's.
  • East of the divide, a north/south gradient still remains, but has relaxed a bit in recent weeks.  The Arkansas basin ranges from +1 to -1.5 with the driest area on the border of Lincoln/Crowley counties. Huerfano, Las Animas, Baca, and Prowers counties all show slightly dry SPI's at the longer time scale.
  • SPIs on the Front Range and in northeast Colorado look healthy on the 6-month timescale with no values below -1. Most SPIs in this portion of the state range from 0 to +2. 

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:

  • Streamflows over much of the UCRB are mostly in the average range with a slight bias existing towards above average flows.
  • 89% of the gages are in the normalto high flow range for 7-day average streamflow.
  • 11% of gages in the UCRB are reporting 7 day average streamflow in the below to low to much below normal ranges (none are record low).  These gages are scattered between the San Juan Basin, Southern Utah, and the Gunnison Basin.
  • Streamflow on the Colorado River near the CO-UT state line is average range but has been dropping, reporting in the 50th percentile (95% of average).
  • The Green River at Green River, UT is showing decreasing flows and is in the 54th percentile (98% of average).
  • The San Juan River near Bluff, UT has fallen slighlty over the past week and reporting at the 30th percentile (67% 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 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 continues to depict soils between the 0th and 30th percentile in the area. 
  • Western CO is still showing a large area of above average soil moisture above the 70th percentile
  • Soil moisture in the Four Corners area is starting to show drying particularly in San Juan County, UT extending to the north and west up into Emery County, UT. Percentiles here range from 0 to 20.
  • The San Luis Valley has rebounded to the normal range showing percentiles between 30 and 70. 
  • East of the divide, the northern plains are showing normal to just above normal soil moisture conditions. 
  • Soil moisture conditions are in the normal range in southeast Colorado. The exception is southern Lincoln County where soil moisture is between the 10th and 30th percentile.

VegDRI:

  • Now midway into November the VegDRI product has gone out of season in eastern Colorado.
  • Much of the UCRB is showing average to moist vegetation conditions, with the exception of Sublette County, WY and the Uintah and Wasatch Ranges in UT.
  • The Four Corners area is still indicating dry vegetation conditions from San Juan county, UT east into the western San Luis Valley.  These areas are mainly in the pre-to-moderate drought category.
  • In western Colorado a north-south gradient exists where vegetative moisture is above average to the north in Moffat, Routt, and Jackson Counties, but below average in La Plata, Montezuma, and Archuletta Counties. 

Reservoirs:

  • A few 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.  Lake Granby, Blue Mesa, Dillon and Navajo all had increases last month. Flaming Gorge, Green Mountain, McPhee and Lake Powell decreased in volume last month. 
  • Flaming Gorge is 105% of the November average.
  • Green Mtn is 79% of November average.
  • Lake Granby is 133% of November average.
  • Lake Dillon is at 111% of the November average.
  • Blue Mesa is 100% of the November average.
  • Navajo is 82% of the November average.
  • McPhee is 68% of the November average. 
  • Lake Powell is 62% of November average and 49% 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 a large north-south temperature anomaly gradient. In the Rio Grande Basin temperatures were in the 5-10 degree above average range. 
  • Tracing from Lake Powell up the Green River to its headwaters in Lincoln and Sublette County, WY the week's temperature anomalies go from +5 to -15 F.
  • The headwaters of the Colorado River in Colorado were slightly to moderately below normal for the week. Temperatures ranged from 0 to 10 degrees F below normal.
  • East fo the divide experienced a large cold snap that was record-setting in some areas. Temperature anomalies in parts of Weld, Arapahoe, and Adams Counties were more than 25 F below normal. 
  • Nearly the entirety of the area east of the divide was at least 15 F below normal for the week. The cold weather was less extreme in southern Las Animas and Baca Counties where temperatures were 5-15 F below normal for the week.

Last Month Temperatures:

  • October temperatures in the UCRB, Wyoming and Colorado were above average. 
  • Most of the basin saw temperatures 2 to 4 degrees warmer than average, with southwestern WY up to 8 degrees above average.  There was an area of 0 to 2 degrees above average that caught Duchesne, Uintah and Grand counties in UT and Mesa and Garfield counties in CO.
  • Eastern CO also saw 2 to 4 degrees above average for October.  Southeastern WY and northern CO were warmer up to 6 degrees above 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:

  • The UCRB is expected to undergo a moderate warming trend and stay dry through the remainder of the week. During the day Saturday a wave is forecast to enter the region from the west-north-west which should carry some promising moisture for the Wasatch and Uintah Ranges as well as the Northern Rockies. This air will cool the area, but is not arctic, so temperatures won't go far below normal.
  • East of the divide warming should be significant through the week as the arctic airmass exits to the north and east and more seasonal temperatures return As the low pressure system progged to track over the drought monitor region passes this weekend the Front Range will see warmer, breezier conditions at first, but once the low exits to the east this will allow more cold air to spill into northern and eastern Colorado. This doesn't look like a large precipitation-producing event east of the divide. 

Longer Term:

  • The 8-14 day precipitation outlook shows increased chances for below average moisture over Colorado and eastern Utah with equal chances of above and below average precipitation in southwest Wyoming near the headwaters of the Green River.
  • The 8-14 day temperature outlook shows increased chances for below normal temperatures across the drought monitor region, most notably in western Colorado. 
  • 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 November 18, 2014: 

The high terrain of the Upper Colorado River Basin (UCRB) experienced some beneficial snowfall over the past week which took a chunk out of the deficits in seasonal snowpack to date, but snowpack is still below average. Snowpack in the Upper Colorado is generally between 60 and 90% of normal now. Arctic air lead to a below-average week for the UCRB temperature-wise with some area of exception in the southwest part of the region. 

East of the divide precipitation was moderate in the mountains and foothills (0.50-1.00") and minimal out on the plains (0.01-0.10"). Temperatures were well below normal after being hit with several rounds of arctic air over the course of the week. 

Streamflows have been dropping across the UCRB this week, but remain near normal. Reservoirs continue to be in great shape in northern Colorado and Wyoming, but are far from full further south. 

Recommendations:

UCRB:

Status Quo: If snowpack stays low over the next few weeks as streamflows continue to diminish this area will be subject to degradations, but if conditions continue to improve as they have over the past week there would be no need for such degradations. It is still very early in the cold season. 

 

Eastern CO:

Status Quo: Southeastern Colorado is being watched closely. The last week was cold with precipitation, so degradations wouldn't be prudent this week. Precipitation is expected to be below normal for the region the next two weeks, but the 8-14 day temperature outlook also shows increased probability of cold air anomalies, so water losses should be lessened. We will be very interested in ground reports of winter wheat productivity and dust storms (if they occur). 

 

**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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