Issued March 23, 2010, Vol. 6, Issue 2

Brad Udall – WWA Director
Jeff Lukas, Christina Alvord, Kristen Averyt – Editors/Writers
Lucia Harrop – Graphic Designer
Klaus Wolter, Gary Bates – Asst. Editors


March 2010 Summary

Temperature & Precipitation — February was another cold month across the region, with widespread temperature departures of 4–10ºF below average. Southerly storm tracks led to much-above-average precipitation in the southern tier of the Intermountain West, but left northern Utah, northwestern Colorado, and most of Wyoming drier than average.

Hydrological Conditions The overall low state of the regional March 1 snowpack reflects the persistent southward shift in storm tracks this winter, with only far southern Utah and southern Colorado reporting above-average snowpacks. Likewise, the March 1 streamflow forecasts are much below average across most of the region, except in southern Utah and Colorado.

ENSOThe current El Niño event has likely peaked and is expected to continue weakening, although El Niño conditions are forecasted to persist through spring. The southward shift in the storm tracks linked to El Niño is expected to relent in the next few months, but this is unlikely to help the driest areas in the northern part of the region.

Climate Forecasts For April and subsequent seasons, the CPC seasonal outlooks call for an enhanced risk of warmer-than-average temperatures for much of the western portion of the Intermountain region, and a slightly enhanced risk of above-average precipitation for southern and eastern portions of the region, centered on eastern Colorado.

RETURN TO TOP


Announcements & News

NOAA Climate Service proposed; would include RISAs such as Western Water Assessment

In an announcement on February 8, the Department of Commerce and NOAA proposed establishing a NOAA Climate Service. NOAA is increasingly asked for information about climate variability and climate change from across diverse sectors and interests. To meet this demand, the proposed NOAA Climate Service would provide a single, reliable and authoritative source for climate data, information, and decision-support services, akin to the role of the NOAA National Weather Service with respect to weather data and services. The central Web presence for the Climate Service will be http://www.climate.gov (see this month’s Focus Article). Many of the NOAA branches that conduct climate research and deliver climate products, including the National Climatic Data Center and the Climate Program Office (home of RISA programs such as WWA) would be incorporated into the NOAA Climate Service. While details of the implementation are still being worked out, NOAA expects to have a functional NOAA Climate Service up and running by late 2010 or early 2011.

At the Western Water Assessment, we don’t expect that the implementation of the NOAA Climate Service will cause major changes to our programs and activities. We do anticipate that the Climate Service will provide improved access to national- and global-level climate data, and foster new collaborations within NOAA, and partnerships with other agencies, that will expand the delivery of regional-level climate services to WWA’s partners and stakeholders. We will provide updates as the implementation of the NOAA Climate Service progresses.

RETURN TO TOP


Feature Article

What is the risk to Colorado River storage and deliveries under climate change scenarios?
A review of several recent studies

by Joe Barsugli, CIRES, and Jeff Lukas, WWA

(download pdf)

RETURN TO TOP


Focus Article

The New NOAA Climate Web Portal (www.climate.gov)

by Christina Alvord, WWA

(download pdf)

RETURN TO TOP


Recent Climate Conditions

Average temperatures for February ranged from below 15ºF in the high-elevation mountain regions up to 50ºF in the far southeast corner of Utah (Figure RC-1). Across western Utah, much of Colorado, and the southeastern corner of Wyoming, departures of 4–10ºF below average were observed (Figure RC-2). Temperatures were warmer than average only in northwestern Utah and parts of western Wyoming.

Figure RC-1. Average temperature for the month of February 2010 in °F. (Source: High Plains Regional Climate Center)

 

Figure RC-2. Departure from average temperature for the month of February 2010 in °F. (Source: High Plains Regional Climate Center)

 

Record

New  Record

Old Record

Year

February 6

Randolph, UT

High Min Temperature

20

11

2000

February 15

Casper, WY

Low Min Temperature

-14

-13

1978

February 19

Lander, WY

Daily Max Snowfall

8.2

8.1

1953

February 20

Cheyenne, WY

Daily Max Snowfall

4.6

4.3

1976

February 22

Lander, WY

Daily Max Snowfall

1.5

0.6

1967

Capitol Reef National Park, UT

Low Max Temperature

35

37

1975

February 23

Casper, WY

Low Min Temperature

-9

-8

1960

Table RC-1. Record temperature and precipitation events in the Intermountain West during February 2010. (Source: NOAA National Weather Service)

 


During February, storms persistently tracked along the southern edge of the Intermountain West, leading to a precipitation pattern consistent with El Niño expectations for late winter and early spring: dry in the north, and wet in the south. Above-average precipitation fell across southern Utah and southern and eastern Colorado, extending up into the southeastern corner of Wyoming (Figures RC-3 and RC-4). Much of this area experienced more than 200% of average February precipitation.


 

Figure RC-3. Precipitation for the month of February 2010 (inches). (Source: NOAA ESRL Physical Science Division)

Figure RC-4. Precipitation for the month of February 2010 as percent of average precipitation for February. (Source: NOAA ESRL Physical Science Division)


The north-south precipitation pattern is also observed in the 3-month SPI (Figure RC-5), reflecting the general southward shift in storm tracks throughout this winter (December–February). The 36-month SPI (Figure RC-6) shows the persistence of dry conditions in the western areas of Wyoming and very dry conditions in eastern Utah. 


Figure RC-5. 3-month Intermountain West regional Standardized Precipitation Index as of the end of February 2010 (data from 12/01/09–2/28/10). (Source: Western Regional Climate Center)

Figure RC-6. 36-month Intermountain West regional Standardized Precipitation Index as of the end of February 2010 (data from 3/01/07–2/28/10). (Source: Western Regional Climate Center)

 


The U.S. Drought Monitor for early March indicates that above-average precipitation has relieved abnormally dry conditions in southwestern Colorado, while conditions have worsened to severe drought (D2) in a portion of western Wyoming, and to moderate drought (D1) in a small area of northwest Colorado (Figure RC-7).


 

Figure RC-7. U.S. Drought Monitor from March 16, 2010 (full size) and February 16, 2010 (inset, lower left) for comparison. (Source: National Drought Mitigation Center)


Notes & Weblinks
(provides explanations of graphics and additional information sources)

RETURN TO TOP


Intermountain West Snowpack

The pattern of precipitation across the Intermountain West during February only reinforced the winter-long north-south gradient in snowpack status. As of March 1, snowpacks were well below average across Wyoming and the northern half of Utah and Colorado, and above average in areas to the south (Figure SP-1).


Figure SP-1. Snow water equivalent (SWE) as a percent of average for available SNOTEL and snow course sites, averaged across each basin, in the Intermountain West as of March 1, 2010. (Source: Natural Resources Conservation Service)

 

Figure SP-2. Current snow water equivalent (SWE) as a percent of average for individual SNOTEL sites as of March 5, 2010. (Source: Natural Resources Conservation Service)


In Colorado, the first half of February was dry throughout much of the state, but storms towards the end of the month increased snowpack percentages to near- or above-average in all but the northwestern basins.  Precipitation was below average for the fourth consecutive month in the Colorado, Yampa, White and North Platte Basins. March 1 basinwide snowpack percentages ranged from a low of 76% in the combined Yampa, White, North Platte and Laramie basins—the second lowest percentage since 1987 in these basins—to a high of 109% in the Rio Grande basin.

In Utah, the northern basins report below-average snowpacks (<90% of average) and the southwestern basins report average or above-average snowpacks.  Below-average February precipitation in northern Utah now leaves little chance for snowpacks and consequently streamflows to reach near-average levels. March 1 snowpack in the Bear River basin is the lowest since 1992, at 59% of average. Meanwhile, February precipitation in southern Utah was near or above average (83–105%), helping maintain snowpacks there.

February was a very dry month across most of Wyoming, with the driest conditions in the central and western basins. As a result, snowpacks across the state are still below average, with the majority of basins reporting 58–74% of average March 1 SWE (Figure SP-2). The only basins to receive near-average February precipitation (91% of average) were the Belle Fourche and Cheyenne basins. March snowpacks in these basins are highest in the state, ranging from 87–93% of average.

Update: As of March 19, NRCS is reporting little change in SWE conditions since the March 1 reports. A few more SNOTEL sites in northwest Wyoming and northern Colorado along the Continental Divide are reporting well below-average SWE conditions (<75% of average). Drier conditions in the first half of March in northwest Wyoming are also reflected in the US Drought Monitor (Figure RC-7).

[Much of the text in this section comes from the NRCS State Basin Outlook Reports: http://www.wcc.nrcs.usda.gov/cgibin/bor.pl.]

Notes & Weblinks
(provides explanations of graphics and additional information sources)

RETURN TO TOP


Spring and Summer Streamflow Forecasts for the 2010 Runoff Season

Spring and summer streamflow forecasts issued March 1 call for near- or above-average runoff for southeastern Wyoming, southern Colorado, and southwestern Utah. For the rest of the region, significantly below-average flows are forecasted with the lowest flows (<50% of average) in western and central Wyoming, and northeastern Utah (Figure STRM-1). Since the initial WY 2010 streamflow forecasts were released in January, the streamflow outlook has worsened in Wyoming and northern half of Utah, remained the same across Colorado, and improved in southern Utah.


Figure STRM-1. NRCS outlook for natural streamflows for spring and summer in the Intermountain West region as a percent of average streamflows (data through March 1, 2010). (Source: Natural Resource Conservation Service)

 


In Colorado, streamflow forecasts in most basins call for below-average flows, with the low snowpack exacerbated by dry antecedent moisture conditions last fall.  March 1 forecasted streamflows are highest (90–109% of average) for the Rio Grande and San Juan, and Arkansas basins. The lowest streamflow forecasts (50–60% of average) are for the North Platte basins and headwaters of the Colorado and Yampa Rivers.

In Utah, the forecasted streamflows are below average across most of the state (50–69% of average). Streamflows are expected to range from a low of 15% of average in the Bear River basins to a high of 115% of average in the Sevier River basin.

In Wyoming, streamflow forecasts call for below-average flows with the exception of the Cheyenne and Belle Fourche River basins (104% of average). Forecasted streamflows across most of the state range from 45–70% of average. The lowest forecasted flows are for the Big Horn and Wind River Basins (31% of average). Expected April–July inflows to Flaming Gorge Reservoir are 43% of average.

Because of the unusually low snowpack in the Colorado headwaters, Yampa, White, and Green River basins, the March 1 expected inflows for Lake Powell for April–July have declined to 68% of average.

Notes & Weblinks
(provides explanations of graphics and additional information sources)

RETURN TO TOP


Reservoir Supply

March is typically the last full month for snowpacks to receive a boost in accumulation before warmer temperatures commence the spring runoff, and reservoirs begin to fill. As of the end of February, reservoir levels are generally near-average or above-average in Wyoming and Colorado, and below-average in Utah (Figure RES-1).

In Colorado, overall reservoir storage on March 1 is above average and will help offset projected below-average spring and summer streamflows across most of the state. Current statewide storage is 102% of last year’s, equivalent to an additional 84,000 acre-feet of storage above last year’s levels. Basin-wide reservoir storage is lowest in the combined San Juan, Animas, Dolores, and San Miguel basins at 88% of average, and highest in the Yampa River basin at 115% of average.

In Utah, combined storage in 41 major reservoirs throughout the state is 7% higher than last year’s, at 69% of average. Basin-wide reservoir storage ranges from a low of 36% of average in the Bear River basin to a high of 90% of average in Provo River basin. Bear Lake is at 48% of average capacity, which, combined with very low projected streamflows for that basin (15–58% of average), suggests severe water shortages unless conditions dramatically improve.

In Wyoming, reservoir storage is average or above average in many basins, and is at 109% of average for the entire state. This reflects above-average snowpack and streamflows in WY 2009, replenishing depleted water supplies from subpar water supplies in WY 2006–WY 2008. Water managers will likely rely on storage to meet demands this year due to well-below-average streamflows forecasted across most of the state.

 
RESERVOIR
current storage
(af)
capacity
(af)
% full
% of average for 2/28
COLORADO
Dillon Reservoir
244,117
257,304
95%
112%
 
Turquiose Lake
65,729
129,390
51%
83% 
 
Lake Granby
379,277
539,758
70%
127% 
 
Blue Mesa
544,867
829,500
100%
122% 
 
Pueblo
257,500
354,000
73%
153% 
 
UTAH
Strawberry
974,400
1,106,500
88%
153%
 
Utah Lake
862,900
870,900
99%
105%
 
Bear Lake
 434,500
1,302,000
33%
48% 
 
Lake Powell
13,786,000
24,322,000
57%
79% 
 
WYOMING
Fontenelle
123,105
344,800
36%
79% 
 
Flaming Gorge
3,181,000
3,749,000
85%
109% 
 
Seminoe
676,796
1,017,273
67%
150%
 
Boysen
590,072
741,594
80%
103% 
 
Buffalo Bill
431,907
644,126
67%
107% 

Figure RES-1. Table of several large reservoirs in the Intermountain West Region. All reservoir content data are from February 28, 2010. Reservoir data are shaded according to the "% of Average" value as follows: green: >80% of average; light green: 60–79%; yellow: 40–59%; orange: 20–39%; red: 0–19%

RETURN TO TOP


ENSO Status and Forecast

While sea-surface temperature warm anomalies across the tropical Pacific decreased from late December to mid-February, as of mid-March they remained at values which indicate a moderate El Niño event (Figure EN-1).


Figure EN-1. Observed SST (upper) and the observed SST anomalies (lower) in the Pacific Ocean.  The Niño 3.4 region encompasses the area between 120°W–170°W and 5°N–5°S.  The graphics represent the 7-day average centered on March 1, 2010. (Source: NOAA Climate Prediction Center)


Across a broad set of dynamical and statistical ENSO forecast models, nearly all indicate that the current El Niño will continue to weaken, although weak to moderate El Niño conditions will be maintained during the March–May season currently in progress (Figure EN-2). By the summer season (June–August) and beyond, most of the models forecast a return to neutral ENSO conditions, although a few models either maintain or re-develop weak or moderate El Niño conditions by late summer, while an equal number develop a La Niña event.

The NOAA ENSO Diagnostic Discussion will be updated on the first Thursday of April 2009.


Figure EN-2. Forecasts made by dynamical and statistical models for sea surface temperatures (SST) in the Niño 3.4 region for nine overlapping 3-month periods from March–May 2010 to November 2010–January 2011 (released March 16, 2010). (Source: International Research Institute (IRI) for Climate and Society)

Notes & Weblinks
(provides explanations of graphics and additional information sources)

RETURN TO TOP


Temperature Outlook
April–August 2010 (Released March 18, 2010)

The latest temperature outlooks from the NOAA Climate Prediction Center indicate an enhanced risk of above-average temperatures for the northwest and far western US, in April 2010 and subsequent seasons (Figures TEMP-1 to TEMP-4). This region of likely warmer-than-average temperatures extends into the western portions of the Intermountain West, with the most enhanced risk of warming seen for southeastern Utah for the May–June and June–August seasons. A slightly enhanced risk of cooler-than-average temperatures is shown for eastern Colorado for April.

Note: These climate outlooks are intended for use prior to the start of their valid period (in this case, prior to the beginning of April).  Within any given valid period, observations and NWS short- and medium-range forecasts should be consulted. The April 2010 temperature forecast will be updated on March 31st on the CPC web page.  This “zero-lead” monthly update will incorporate information from the short range numerical weather prediction models and the latest monthly predictions from the Climate Forecast System models. The Seasonal Outlooks are updated on the third Thursday of the month, and the next one will be issued on April 15th.

 


Figure TEMP-1. Long-lead national temperature forecast for April 2010. (Source: NOAA Climate Prediction Center)

Figure TEMP-2. Long-lead national temperature forecast for April–June 2010. (Source: NOAA Climate Prediction Center)

Figure TEMP-3. Long-lead national temperature forecast for May–July 2010. (Source: NOAA Climate Prediction Center)

Figure TEMP-4. Long-lead national temperature forecast for June–August 2010. (Source: NOAA Climate Prediction Center)

Notes & Weblinks
(provides explanations of graphics and additional information sources)

RETURN TO TOP


Precipitation Outlook
April–August 2010 (Released on March 18, 2010)

The CPC precipitation outlook for April 2010 (Figure PPT-1) shows a slightly enhanced risk of above-average precipitation for much of the Intermountain West, with the most enhanced risk in southeastern Colorado. For the April–June season, the area of enhanced risk of wetter-than-average conditions shifts to the north and west, covering all of Colorado and Utah, and southern Wyoming (Figure PPT-2). For the summer seasons, this area contracts so that only eastern Colorado is included (Figures PPT-3 and PPT-4).

Areas of above- or below-average precipitation are largely due to expected El Niño impacts on climate, including the typical El Niño-influenced tilt of the odds towards above-average precipitation for some areas of the southern tier, and towards dry conditions for the Pacific Northwest and Ohio Valley.

Note: these climate outlooks are intended for use prior to the start of their valid period (in this case, prior to the beginning of April).  Within any given valid period, observations and NWS short- and medium-range forecasts should be consulted. The April 2010 precipitation forecast will be updated on March 31st on the CPC web page.  This “zero-lead” monthly update will incorporate information from the short range numerical weather prediction models and the latest monthly predictions from the Climate Forecast System models. The Seasonal Outlooks are updated on the third Thursday of the month, and the next one will be issued on April 15th.


Figure PPT-1. Long-lead national precipitation forecast for April 2010. (Source: NOAA Climate Prediction Center)

Figure PPT-2. Long-lead national precipitation forecast for April–June 2010. (Source: NOAA Climate Prediction Center)

Figure PPT-3. Long-lead national precipitation forecast for May–July 2010. (Source: NOAA Climate Prediction Center)

Figure PPT-4. Long-lead national precipitation forecast for June–August 2010. (Source: NOAA Climate Prediction Center)


According to the experimental SWcast discussion, while the El Niño event of 2009-10 appears to have peaked recently, its effects should linger well into the spring season. The experimental forecast guidance for the late spring season (April–June) is favorable for a wet spring from northern Utah across northwestern Colorado into the high plains of eastern Colorado and New Mexico, much of this consistent with El Niño effects (Figure PPT-5). The dry forecast for southwestern Colorado contradicts typical El Niño outcomes.

As expected, the El Niño shifted the main storm track southwards this past winter, suppressing snowfall amounts over northern Colorado and northern Utah. Over the next couple of months, this storm track is expected to move northwards, bringing more moisture to some, but not all, of the drier areas from this winter.


 

Figure PPT-5. Experimental precipitation forecast guidance. Forecasted shifts in tercile probabilities for April–June 2010. (Source: NOAA ESRL Physical Science Division)

 

Notes & Weblinks
(provides explanations of graphics and additional information sources)

RETURN TO TOP


Seasonal Drought Outlook
through June 2010 (Released March 18, 2010)

The U.S. Seasonal Drought Outlook (DO) builds on the Drought Monitor categories to project how these drought areas might change or where new drought areas might develop. The area of moderate (D1) and severe drought (D2) in western Wyoming and extreme northeastern Utah is expected to persist and expand in coverage over the next few months, linking up to the area of moderate drought in northwest Colorado (Figure DO-1). Improvement is forecasted for the area of abnormally dry conditions (D0) in far southern Utah.

Readers interested in the next 5 and 6–10 days can consult the “Looking Ahead” section of each week’s Drought Monitor for near-term drought outlook conditions. The next Seasonal Drought Outlook will be issued April 1st.


 

Figure DO-1. Seasonal Drought Outlook for March 18–June 2010. (Source: NOAA Climate Prediction Center)

Notes & Weblinks
(provides explanations of graphics and additional information sources)

RETURN TO TOP


The Intermountain West Climate Summary is published periodically by Western Water Assessment (WWA), a joint project of the University of Colorado Cooperative Institute for Research in Environmental Sciences (CIRES) and the National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory (ESRL), researching water, climate, and societal interaction.

Disclaimer - This product is designed for the provision of experimental climate services. While we attempt to verify this information, we do not warrant the accuracy of any of these materials. The user assumes the entire risk related to the use of this data. WWA disclaims any and all warranties, whether expressed or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose. This publication was prepared by CIRES/WWA with support in part from the U.S. Department of Commerce/NOAA, under cooperative agreement NA17RJ1229 and other grants. The statements, findings, conclusions, and recommendations are those of the author(s) and do not necessarily reflect the views of NOAA.