Drought Update for the Intermountain West

Another La Niña lowers the chance for a wet winter ahead.

Key Points

Extreme drought conditions continue in the Intermountain West, and abnormally dry conditions have developed in Colorado.
One of the wettest monsoon seasons on record for the Southwest ended with a lackluster September.
There is a 70%–80% chance that another La Niña will develop this winter.
- This usually means less snow for the Southwest.

U.S. Drought Monitor Conditions: Intermountain West | September 28, 2021

U.S. Drought Monitor

Current U.S. Drought Monitor map for the Intermountain West Drought Early Warning System region with data valid for September 28, 2021. The U.S. Drought Monitor is updated each Thursday to show the location and intensity of drought across the country.

Extreme (D3) to Exceptional (D4) drought persists across much of the Intermountain West.

Source(s): NDMC, NOAA, USDA

U.S. Drought Monitor Categories

Last Updated: 09/28/21

14%

of Arizona is in Extreme to Exceptional (D3–D4) Drought

15%

of Colorado is in Extreme to Exceptional (D3–D4) Drought

19%

of New Mexico is in Extreme to Exceptional (D3–D4) Drought

88%

of Utah is in Extreme to Exceptional (D3–D4) Drought

29%

of Wyoming is in Extreme to Exceptional (D3–D4) Drought

Recent and Current Conditions

U.S. Drought Monitor Conditions

Extreme (D3) to Exceptional (D4) drought persists, but has dropped to 34% of the Intermountain West.
Over the past four weeks, drought conditions have improved but remain in Arizona, New Mexico, and western Utah.
- Despite the small improvement, Severe (D2) to Extreme (D3) drought remains in Arizona and New Mexico.
Exceptional (D4) drought remains in Utah and Colorado.
Drought conditions have remained or deteriorated in eastern Colorado and southeast Wyoming.

U.S. Drought Monitor 1-Month Change Map

U.S. Drought Monitor 4-week change map for Arizona, Colorado, New Mexico, Utah, and Wyoming, from August 31 to September 28, 2021. Arizona, southwest Colorado and New Mexico have seen a 1-category improvement. Colorado and Wyoming have seen a 1-2 category degradation. — 4-week U.S. Drought Monitor change map, showing where drought has improved, remained the same, or worsened from August 30 to September 28, 2021. Source: National Drought Mitigation Center.

Southwest Monsoon 2021

Arizona measured its second wettest July on record—the wettest since 1919—followed by an average August.
Tucson, Nogales, and other locations exceed one foot of rainfall for the season.
September precipitation has been average to below average for most of the Intermountain West region.
Track the Southwest U.S. Monsoon:
- Tucson National Weather Service
- CLIMAS Monsoon Tracker

2021 Southwest Monsoon Rainfall vs. Normal

Bar graph showing rainfall totals for monsoon season 2021 at select Arizona locations. The locations and rainfall totals (in inches) are: Tucson Airport, 12.78; Noagles Airport, 12.33; Safford Airport, 6.82; Sierra Vista, 9.84; Oracle, 10.07; Wilcox, 7.4; Picacho Peak, 10.9; and Ajo, 6.99. — Accumulated rainfall totals from June 15 to September 26, 2021 for Arizona locations, comparing 2021 Monsoon rainfall to normal conditions. Source: National Weather Service Tucson Weather Forecast Office.

Tucson Historical Monsoon Rainfall: 1895–2021

Accumulated rainfall since June 15, 2021 at Tucson, Arizona compared with all historical years, going back to 1895. This monsoon season is the third wettest on record so far. — Accumulated rainfall for monsoon seasons from 1895–2021 at the Tucson Airport. Valid September 27, 2021. Source: National Weather Service Tucson Weather Forecast Office.

30-Day Percent of Normal Precipitation

Map of the western United States showing percent of normal precipitation for the 30 days from August 29 to September 28, 2021. Western Utah and the central Colorado Rockies have had less than 25% of normal precipitation for this period. Southern Arizona had 100 to 150% of normal precipitation for the period. — Percent of normal precipitation for the past 30 days through September 28, 2021. Source: University of California Merced, Climate Engine.

Forecasts and Seasonal Outlooks

Climate Patterns: La Niña Watch

NOAA’s El Niño–Southern Oscillation (ENSO) alert system status is currently at La Niña Watch—meaning a transition from ENSO-neutral to La Niña is favored in the next couple of months.
La Niña usually correlates with below-normal winter precipitation in the Southwest U.S.
Seasonal forecasts also show a drying pattern across the Southwest, consistent with a La Niña pattern.

3-Month Outlook (October–December 2021)

A warm and dry autumn is likely for the Intermountain West.

October–December Temperature Outlook

Climate Prediction Center 3-month temperature outlook, showing the probability of exceeding the median temperature for the months of October, November, December 2021. Odds favor above normal temperatures for all of the Intermountain West Region. — 3-month temperature outlook, showing the probability of above-normal, below-normal, or near-normal conditions during October–December 2021. Source: NOAA Climate Prediction Center.

October–December Precipitation Outlook

Climate Prediction Center 3-month precipitation outlook, howing the probability of exceeding the median precipitation for the months of October, November, December 2021. Odds favor below normal precipitation for the western US. — 3-month precipitation outlook, showing the probability of above-normal, below-normal, or near-normal conditions during October–December 2021. Source: NOAA Climate Prediction Center.

Seasonal Drought Outlook

Despite short-term drought improvement, the 3-month drought outlook shows drought continuing at least through the end of the year.

U.S. Drought Outlook: September 16–December 31, 2021

A map of the continental United States showing the probability drought conditions persisting, improving, or developing from September 16 through December 31, 2021. Current drought conditions over the western U.S. are forecast to persist. — U.S. seasonal drought outlook for September 16 to December 31, 2021, showing the likelihood that drought will remain, improve, worsen, or develop. Source: NOAA Climate Prediction Center.

State-Based Conditions and Impacts

Arizona

After an impressive early monsoon, September precipitation largely returned to normal or below-normal amounts across the state. Still, the monsoon precipitation will end the season at above-average levels in Arizona.
Range and pastureland vegetation continued to improve; however, increased growth has potentially contributed to increased wildland fire fuel.
The wind regime started transitioning to westerly patterns near September 10. Precipitation events later in September largely occurred from cyclonic activity.

Arizona 90-Day Departure from Average Precipitation

Arizona departure from average precipitation for June 30–September 27. The 2021 monsoon recorded above average precipitation, particularly in central and southern Arizona, ultimately improving meteorological, agricultural, and ecological drought across most of the state. — Arizona departure from average precipitation, from June 30–September 27, 2021. Source: Western Regional Climate Center.

Colorado

September has been a much warmer than normal month for Colorado. The eastern plains have been 3–5 degrees above normal over the last 30 days. Warm conditions in September can be advantageous for finishing late season crops, but summer moisture was low.
Conditions have degraded on the eastern plains. Akron, CO had its driest summer on record. Due to a wet spring, however, Akron still had a wetter-than-normal water year.
Monsoonal rains improved conditions in western Colorado, but hydrological drought remains. Cumulative streamflows on major rivers exiting the state will still be in the bottom quartile for the water year, and baseflows have not recovered to normal levels. Reservoir storage statewide will also be below normal this winter, meaning above-normal snowpack will be necessary this winter to break out of drought.

Cumulative Streamflow Conditions

Utah

A warm and generally dry month of September has led to a loss of much of the soil moisture gained during late July and August monsoon rainfall. Following record high soil moisture to start the month, the state looks to end September with near-normal soil moisture for this time of year.
Reservoir levels remain exceptionally depleted across the state with approximately 3 out of 4 reservoirs below 50% capacity. Lake Powell has continued to drop in September and now sits at 30% capacity, while the Great Salt Lake continues to drop deeper into record low levels.
Drought metrics show little change in drought stress to vegetation or evaporative demand over the month of September. Status quo for drought classification is the expected path forward for the Fall months.

Utah Soil Moisture Conditions

Time series of depth averaged 8 inch soil moisture for the state of Utah over the past year, through September 29, 2021. — State-averaged 8-inch soil moisture for 2021 (black line) compared to historical conditions. Valid September 29, 2021. Recent July and August heavy monsoon rainfall returned the state’s near-surface soil moisture to healthy levels. September’s warm and dry weather has removed much of the high soil moisture, leaving the state at roughly normal soil moisture for this time of year. Source: USDA Natural Resources Conservation Service.

Utah Reservoir Conditions

Utah’s reservoir fill percentage as of 9/27/2021 showing the extent of the ongoing hydrologic drought. Approximately 3 out of every 4 reservoirs are below 50% capacity. — Utah’s reservoir fill percentage as of September 27, 2021, showing the extent of the ongoing hydrologic drought. Source: Utah Department of Natural Resources.

Wyoming

Wyoming has had two snow events in the higher elevations around the state since September 20.
Temperatures:
- Average temperatures across the state have been generally 3 to 6 degrees Fahrenheit above average east of the Divide and up to 3 degrees Fahrenheit above average west of the Divide over the last 30 days.
- Minimum temperatures were average to 3 degrees Fahrenheit above average statewide, with some areas 3 to 6 degrees Fahrenheit above normal in the east and eastern flanks of the Wind River and Bighorn Ranges. Some scattered areas in the west and south-central parts of the state were as much as 3 degrees Fahrenheit below average.
Precipitation has been above average in south-central Wyoming as well as parts of the northeast, but the remainder of the state has been below to well below average, especially in the north.
A flash drought appears to be emerging in the north and north-central part of the state affecting the Bighorn Basin, with precipitation in the area at 50% of average over the last 30 days and some areas under 10% of average over that period. This, coupled with temperatures up to 6 degrees Fahrenheit above average, has led to a rapid deterioration of conditions there, with Severe (D2) and Extreme (D3) drought conditions expanding in the last week.

Wyoming 30-Day Percent of Normal Precipitation

Wyoming 30-day precipitation as a percent of the 1991-2020 average, showing conditions from August 31 to September 29, 2021. Precipitation has been above average in south central Wyoming and parts of the northeast, but the remainder of the state has been below average. — 30-day precipitation as a percent of the 1991–2020 average, for August 31–September 29, 2021. Source: Wyoming State Climate Office.

For More Information

More local information is available from the following resources:

Upcoming Events

October 26, 2021: Southwest Drought Briefing

Prepared By

Joel Lisonbee
NOAA/National Integrated Drought Information System (NIDIS)

Erin Saffell
Arizona State Climatologist/Arizona State University

Erin Boyle
Service Hydrologist, National Weather Service, Tucson, Arizona

Peter Goble
Colorado Climate Center/Colorado State University

Jon Meyer
Utah Climate Center/Utah State University

Tony Bergantino
Water Resources Data System – Wyoming State Climate Office

Special Thanks

This drought status update is issued in partnership between the National Oceanic and Atmospheric Administration (NOAA), and the offices of the state climatologist for Arizona, Colorado, New Mexico, Utah and Wyoming. The purpose of the update is to communicate a potential area of concern for drought expansion and/or development within the Intermountain West based on recent conditions and the upcoming forecast. NIDIS and its partners will issue future drought status updates as conditions evolve.