NIDIS Upper Colorado River
Regional Drought Early Warning System
March 24, 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:

  • Another fairly quiet week across the UCRB. 
  • The Upper Green river basin saw very little precipitation over the week, as did the Wasatch and Uintah ranges in Utah.
  • Western Colorado was also fairly dry.  Highest precipitatio amounts fell over Eagle and Pitkin county where 0.50"-1.00" fell.  West and south of that area saw 0.01-0.50" for the week.
  • The San Juan Mountains saw less than 1.00" for the week with the highest amounts over northern La Plata coutny.  Mineral and Archuleta counties  also received upwards of 1.00".
  • East of the divide, the southern Front Range/urban corridor and Palmer divide picked up 0.25-1.00" for the week from Adams county south to the NM border and east to Kit Carson/Cheyenne counties. .  Lesser amounts fell farther to the north of this area.
  • Very little precipitation fell over NE Colorado, however the SE plains saw 0.01-0.50".

February Precipitation:

  • February was variable over the UCRB with above normal precipitation over the Green river basin and Four corners and dryer than normal conditions in the Duchesne, Yampa, White, Colorado and Gunnison basins. 
  • The headwaters of the Upper Green river basin saw normal to above normal moisture for February.
  • The driest areas were NE Utah and NW Colorado where less than 70% of normal precipitation fell, particularly over lower elevations.  The high country also struggled in the northern basins.
  • The Four corners saw above normal moisture for the month, particularly in San Juan county Utah.
  • Normal to above normal moisture fell over much of SW Colorado, however higher elevations in Hinsdale/San Juan/ La Plata counties saw below normal moisture for the month.
  • The Rio Grande saw above normal precipiation for the month.
  • East of the divide, precipitation was mainly above normal.  The driest areas were extreme NE Colorado where 50-90% of normal precipitation fell over Logan, Sedgwick and Northern Washington as well as SE Yuma counties.
  • There was also a dry pocket on the border of Prowers and Baca counties where 50-90% of normal precipitation fell. 

 

Water Year 2015 Precipitation:

  • The Water Year percents of normal in the UCRB are starting dry out a bit after a drier than normal January and much of February. 
  • The Upper Green river basin has seen above normal moisture for the water year through with the exception of Sweetwater county which saw 30-90% of normal precipitation.
  • The lower elevations of the UCRB have struggled for the water year through February where less than 90% of normal moisture has fallen over a large portion of Eastern Utah/Western Colorado.
  • The headwaters of the Yampa/White have below normal moisture for the water year, but conditions improve near the continental divide where amounts are more near normal for the water year.
  • The Upper Colorado has near normal precipitation through Grand/Summit/western Eagle couties, but dries out considerably west of the headwaters.  From Central Eagle down to Mesa county, 30-110% of normal precipitation has fell for the water year through February. 
  • The San Juan mountains have seen below normal precipitation for much of the water year.  Some areas are near to above normal in Montrose/San Miguel/Dolores/Ouray counties, but the rest of the area is below normal for the water year, mainly 30-90% of normal.
  • San Juan county, Utah saw near to above normal moisture with the exception of the northern portion of the county where 50-90% of normal fell.
  • The San Luis valley saw mainly above normal precipitation with the exception of the western side of the basin. 
  • Much of the Eastern plains are at or above normal for the water year.  The driest area is in portions of NE Colorado in Washington/Yuma/Sedgwick and Phillips county which saw 70-90% of normal for the water year.
  • The SE plains have seen above normal moisture for the water year, which is much needed and welcomed considering that region has been in drought since September 2010.  

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:

  • With another dry week across the basin, most percentiles have dropped since last week.
  • In the Upper Green River Basin, precipitation percentiles are starting to drop off with recent dryness.  They range from the 13th to the 56th percentile. 
  • Percentiles in the Wasatch and Uintah Ranges in northern Utah are very low, currently in the 0 to 21st percentile range with many SNOTEL stations indicating an all-time low.  
  • There is a large gradient in SNOTEL percentiles between the higher and lower elevation stations in the northern and central mountains. There is also an east to west gradient with the farther east stations showing higher percentiles. 
  • The Yampa and White River Basin are showing percentiles in the 4th to 47th percentile range.
  • Along the Continental Divide, and slightly east of the divide are mostly above the median, and in the 35th to 72nd percentile range.
  • SNOTEL stations in the Gunnison Basin are in the 0 to 47th percentile range.  The higher percentiles are near the headwarters of the Gunnison River, decreasing in the lower basin and Grand Mesa area.
  • The San Juan Mountains are still well below the median in most areas for the water year to date. Precipitation Percentiles are in the 3rd to the 59th percentile range. 
  • The Sangre de Cristo Mountains are showing precipitation percentiles near the median, between 35th and 76th.

Westwide Snow Water Equivalent (SWE) Percent of Normal:

  • Snowpack in the Upper Green River basin ranges from 50 to 99 percent of median.
  • The Upper Green has the highest snowpack in the basin at 99% of median, which has also seen decreases over the past few weeks.
  • The Wasatch and Uintahs are much below normal ranging from 47-63% of median.
  • URCB sub-basins in western Colorado range from 70 to 84% of the median for the snow season to date. The lowest percent of median is along the San Juan, and the highest is in the headwaters of the Colorado River.   
  • The Rio Grande basin is at 77% of normal while both the Arkansas and South Platte are at 92% of normal.

 SWE Timeseries Graphs:

  • The Upper Green basin is at 87% of median snowpack to date, down 10% from last week.
  • The Duchesne basin is at 54% of median snowpack to date, down 8% from last week. 
  • The Yampa-White basin is at 68% of median snowpack to date, down 8% from last week.
  • The Upper Colorado basin is at 81% of median snowpack to date, down 8% from last week.
  • The Gunnison basin is at 73% of median snowpack to date, down 5% from last week.
  • The San Juan basin is only at 68% of median snowpack to date, down 6% from last week.
  • All basins have experienced some degree of melt over the past week, much earlier than normal peak date in Colorado of April 9th. 

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 variable SPI's.  Lincoln county, in Wyoming, stations are dry reporting SPI's between -1 and -2.5, while farther east SPI's are better between -1 and +1.
  • NE Utah is a mixed bag.  Stations in the Wasatch are dry with SPI's between 0 and -2.  Stations just south of the Uintahs are between 0 and +1.
  • Much of western Colorado is wet on the short term with most SPI's between -1.5 and +3.  The driest stations are in Routt, Rio Blanco, Mesa, Grand and Summit counties.  The driest station is Grand Lake 1NW.  While the Four Corners area is reporting the wettest short term numbers. 
  • The San Luis Valley is wet on the short term with SPI's ranging from 0 to +2.5.
  • There is a north to south gradient on the eastern plains.  The NE plains are dry with SPI's between 0 and -2 with the driest areas in Sedgwick county. 
  • The SE plains are showing wetter short term conditions with SPI's ranging from 0 to +2.5, the wettest area is over Lincoln and Crowley counties. 

Long Term (6-month):

  • The 6 month time scale shows much less variability than the short term with most areas slightly wet to slightly dry.
  • The Upper Green is wet at the longer time scale with SPI's between 0 and +1.5
  • The Duchesne basin is variable with SPI's between -1 and +1.
  • The Yampa/White/Colorado/Gunnison and San Juan basins are mainly wet at the 6 month time scale with just a few stations reporting down to -1 (Grand, Rio Blanco, Gunnison, Montezuma counties). 
  • East of the divide, the north to south gradient persists even at 6 months.  The NE plains are between 0 and -1, while areas farther south are mainly wet with SPI's between -1 and +2.5.  The Front Range urban corridor is mainly wet, especially around Colorado Springs. 

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:

  • After a warm week, quite a few gages broke out of ice.  111 of the 140 stream gages in the UCRB are reporting.  All others are still ice affected.
  • 78% of the gages are in the normal to much above normal range for the 7-day average streamflow, while 9% of the gages are at record high flow.  High flow gages are in the Upper Colorado and White river headwaters.
  • 8% of the gages are in the below normal range and 5% are in the much below normal range.  No gages are recording record low flows.
  • The lower flows are mainly along the Duchesne, lower White and Mancos drainages. 
  • The Colorado River near the CO-UT state line is reporting in the 60th percentile, 98% of normal and has seen an increase in flow over the past week.
  • The Green River at Green River, UT is at the 38th percentile, 77% of normal.
  • The San Juan River near Bluff, UT is now at the 27th percentile, 49% 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 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 in the 0-30th percentile range over much of the south and eastern part of the county.
  • Northeastern UT is showing normal to wet soils, with the exception of Uintah County, which is showing a small area of dry soils between the 10th and 30th percentile.
  • There are some very wet soils in the Upper Green River Basin. Near the Wyoming-Utah state line soil moisture is in the 70-100th percentile range.
  • Western CO is still showing a large area of above average soil moisture over the 70th percentile. The highest percentiles are in Routt County.
  • The Four Corners Region is mostly in the normal range with some isolated areas above the 90th percentile in Ouray county.
  • The San Luis Valley is in the normal range and slightly wet in the mountains surrounding the valley.
  • East of the divide, much of the eastern plains are showing normal soil moisture with a few exceptions. On the high side of average Boulder, southwester Larimer, and northern Jefferson Counties are now above the 70th percentile. On the low side, south Lincoln County and western Kit Carson County are now in the 5-30th percentile range. 
  • In southeast Colorado a small portion of Las Animas County is in the 20-30th percentile range, and Prowers, and eastern Kiowa Counties are above the 70th percentile. 

 

Reservoirs:

  • Flaming Gorge is 105% of the March average.
  • Green Mtn is 103% of the March average.
  • Lake Granby is 153% of the March average.
  • The data for Lake Dillon are missing, but the reservoir is near full.
  • Blue Mesa is 138% of the March average.
  • Navajo is 86% of the March average.
  • McPhee is 69% of the March average. 
  • Lake Powell is 65% of the March average and is only 45% 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 and all the rest of Colorado saw above normal temperatures over the past week for another week.
  • Most of the UCRB saw temperatures 4 to 12 degrees above normal. 
  • East of the divide saw temperatures in the 8-16 degrees above normal over the NE plains, and 0-8 degrees above normal over the SE plains.

February Temperatures:

  • The month of February was warm across the UCRB. 
  • The Upper Green basin was 3-15 degrees above normal for the month.
  • The Wasatch and Uintah ranges were the warmest part of the basin and experienced temperatures 9-15 degrees above normal.
  • The Yampa/White/Colorado/Gunnison basins were 3-9 degrees above normal while the San Juans were slightly more moderate with departures ranging from 0-9 degrees above normal with a small bullet of 9-12 degrees above normal over NE La Plata county.
  • The San Luis valley was also warm with temperatures 3-12 degrees above normal for the month.
  • East of the divide saw much more seasonal tempertures than the west slope.  Departures on the plains were 0-6 degrees above normal with a few pockets of cooler than normal temperatures. 


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 (3/24):

  • Currently a weak trough is diving down through the UCRB out of the north northwest. There is not substantial moisture with this system, and much of the region will be left mostly dry and windy. The main beneficiaries of this trough will be the high central Rockies in Colorado both in the northern and southern portions of the state. Most areas of central Colorado will only see 0.10-0.25" of precipitation with eastern Utah and southwest Wyoming staying mostly dry. 
  • After the passage of this system northeasterly winds will bring increased cloud cover and some light precipitation to eastern Colorado on Wednesday, but totals are forecast to be under a quarter of an inch. 
  • Friday and Saturday will be warm and dry again across the UCRB and Colorado east of the divide as the ridge rebuilds once more from the southwest. Some areas in southeast Colorado may see temperatures as high or higher than 80 degrees. 
  • On the 6-7 day timescale models are still showing above average temperatures and mostly dry with some potential for thunderstorms initiating over the high terrain on Monday. There is no large scale temperature or moisture change in sight for the region within range of reliable numerical weather prediction. 

Longer Term:

  • The 8-14 day precipitation outlook shows slightly increased chances for below average precipitation in the UCRB. East of the divide the 8-14 day outlook shows slightly increased chances for below average precipitation in most places as well, but the northeast corner of the state is still forecast equal chances. 
  • The 8-14 day temperature outlook shows increased chances for above average temperatures for the entirety of the UCRB and Colorado east of the Continental Divide. These chances are strongest near the four corners, and weakest in the northeast portion of Colorado. 
  • 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 April to June period with the exception of the northeast corner of Colorado. These chances are highest in southern and western Colorado. This forecast has been made more conservative following a dry March. 
  • The seasonal drought outlook indicates that drought is expected to persist or intensify in western Colorado and eastern Utah. Drought improvement and removal is forecast as likely for southeast 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 March 24, 2015:  

Another dry and warm week over the UCRB has dropped snowpack numbers, precipitation percentiles and increased streamflows around the region.  The 5 day QPF maximizes over the high country at around 0.8" of moisture, which barely keeps up with climatology for this time of year.  The mountains should be picking up around 1" of moisture per week, so recovery is not expected over the next week.  Past this week, forecasts for higher chances of drier than normal as well as increased chances for above normal temperatures are forecast out to 14 days. 

Due to the current state of snowpack and persistent warm temperatures across the region, degradations will be suggested around the area.  

Recommendations:

UCRB:  A  D1 to D2 degradation is suggested due to low snowpack, little to no mid-elevation snow and persistent warm temperatures over portions of the central and southern Colorado mountains.  Streamflows are starting to increase as snowpack graphics are showing signs of snowmelt ramping up 2-3 weeks earlier than normal.  A slight eastward expansion of D1 in Routt and Eagle counties in Colorado is suggested to incorporate the lower snotel precipitation percentiles there. The Wasatch range is looking nearly as dry as the Uinta range and degradations are also suggested in that area from D0 to D1 in order to better match the depiction with observations, we would prefer guidance in this area since we only have the percentiles and low SPI numbers to go on.  

 

Eastern CO: 
A small expansion of D0 of NE Colorado is recommended.  While impacts are not yet being reported there, SPI's are dry and temperatures have been persistently warm.

**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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