Dry soils are first in line for winter snowmelt.

Key Points

Extreme to exceptional drought continues across the Intermountain West.
Snow drought and early, accelerated snowmelt raise concerns about available water this summer.

U.S. Drought Monitor Conditions: Intermountain West | April 20, 2021

U.S. Drought Monitor

Current U.S. Drought Monitor map for the Intermountain West Drought Early Warning System region with data valid for April 20, 2021. The U.S. Drought Monitor is updated each Thursday to show the location and intensity of drought across the country.

Over half (56%) of the combined Intermountain West region is in Extreme (D3) to Exceptional (D4) drought.

Extreme (D3) drought conditions have been in place in this region since May 2020.
The extent of D4 drought in the Intermountain West reached a peak of 45% area in December 2020, a new record for the region.

Moderate (D1) or worse drought has been in the region since August 2009.

Source(s): NDMC, NOAA, USDA

U.S. Drought Monitor Categories

Last Updated: 04/20/21

87%

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

32%

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

80%

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

90%

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

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

Recent and Current Conditions

State Drought Plans, Declarations, or States of Emergency in Effect

Arizona	Colorado	New Mexico	Utah
Drought declaration from 2007 that has not been rescinded	State Drought Mitigation and Response Plan shifted from Phase 2 to Phase 3 (full activation) on November 30, 2020	Drought declaration and activation of the State Drought Task Force, December 9, 2020	Drought state of emergency issued on March 17, 2021

Current Snow Water Equivalent (SWE)

Snow drought and early, accelerated snowmelt raise concerns as we head into summer.
Colorado River Basin snowpack has reached its peak for the season and begun to melt.
At its peak, seasonal snowpack was near average east of the Continental Divide but below average west of the Divide.
Of note, the Colorado River basin (upper and lower) catchments are currently at 74% of Natural Resources Conservation Service 1981–2010 median.

Snow Water Equivalent in the Upper Colorado Region

Snow water equivalent (SWE) time series for winter 2020-2021 for the upper Colorado River Basin. Current SWE is 71% of the historical median. — Snow water equivalent for winter 2020–2021 for the Upper Colorado River basin through April 20, 2021. Source: USDA Natural Resources Conservation Service (NRCS).

Change in Snow Water Equivalent: March 24 vs. April 22

Snow Water Equivalent map of the Intermountain West for 21 April 2021. The Upper Colorado River Region is at 71% of normal, the Lower Colorado River Region is at 26% of normal. — Snow water equivalent (SWE) maps of the Intermountain West for March 24, 2021 (*left*) and April 22, 2021 (*right*). SWE is shown as a percent of the Natural Resources Conservation Service (NRCS) 1981–2010 median. Source: NRCS.

The impact of the early snowmelt is illustrated in the soil moisture graph below:

Extremely dry soil in autumn
Early snowmelt with rapid late March/early April warm period.

Soil Moisture in the Upper Colorado Region

8 inch depth average soil moisture averaged over the Upper Colorado River Basin. Soil was nearly half of the previous record low soil moisture. The influx of water from melting snow occurred nearly two weeks earlier than normal. — 8-inch soil moisture as a percent of saturation averaged over the upper Colorado River Basin for the Water Year. Note that the jump in soil moisture in late March/early April coincides with melting snowpack. Source: NRCS.

April Precipitation

Over the last 30 days, a series of small winter storms provided steady snow to the mountains of northern Utah and western Colorado. The accumulated precipitation was small compared to the average for this time of year.

Precipitation Conditions: March 21–April 20, 2021

30-day precipitation totals (in inches) for the Western U.S. through April 20, 2021.

30-day percent of normal precipitation for the Western U.S. through April 20, 2021. The accumulated precipitation was small compared to the average for this time of year. — Top: 30-day precipitation totals from March 22 to April 20, 2021. Bottom: 30-day percent of normal precipitation to from March 22 to April 20, 2021. Source: High Plains Regional Climate Center.

Evaporative Drought Demand Index (EDDI)

4-Week EDDI for April 14, 2021

EDDI values have been favorable for Utah, Colorado, and Wyoming over the past month.
There is high evaporation demand for this time of year across southern Arizona.

The 4-week averaged Evaporative Demand Drought Index (EDDI) as of April 14, 2021, showing atmospheric evaporative demand for the contiguous U.S. Areas of average to low EDDI cover most the Northwest, including northern California. This area extends to northern Nevada, northern Utah, Wyoming, and northern Colorado. Areas of high EDDI cover southern California, Arizona, and New Mexico and also the Great Lakes region. — 4-week Evaporative Demand Drought Index (EDDI) for April 14, 2021. Source: NOAA/Earth System Research Laboratories/Physical Sciences Laboratory.

Seasonal Outlooks: May–July 2021

Temperature Outlook

For May–July, there is a greater chance for above-normal temperatures across the Intermountain West.

Precipitation Outlook

The precipitation outlook shows that below-average rainfall is the most likely outcome for May–July across the Intermountain West, including New Mexico, Colorado, Utah and Wyoming.

Drought Outlook

Long-term drought conditions are forecast to continue at least through June across the Intermountain West.

Climate Patterns

NOAA’s El Niño–Southern Oscillation (ENSO) alert system status is currently a La Niña advisory with ENSO-neutral conditions expected to return within the coming weeks.
Historically, the Southwest has experienced mixed rainfall conditions in the spring and summer during a La Niña. Southern Arizona is wetter while southern Texas is drier. As La Niña wanes, these connections will also break down.
For more information, please check out the NOAA ENSO blog and the Western Regional Climate Center information page about the La Niña impacts for the west.
ENSO forecasts from the International Research Institute (IRI) for Climate and Society show ENSO-neutral conditions returning within the coming months. An ENSO-neutral state is the most likely scenario for autumn and winter 2021, but a second La Niña cannot be ruled out, yet.

Probability of El Niño, La Niña, or Neutral Conditions: April 2021–February 2022

A bar graph showing the probability of El Niño, La Niña, or neutral conditions from April 2021 to February 2022. ENSO-neutral conditions are the most preferred outcome throughout the forecast period, followed by La Niña and then El Niño. — ENSO forecasts from the International Research Institute, showing the probability of El Niño, La Niña, or neutral conditions from April 2021 to February 2022. Source: International Research Institute.

State-Based Conditions and Impacts

Arizona

86.56% of Arizona is in Extreme (D3) or Exceptional (D4) drought.
Lake Mead is projected to be below 1,075 ft elevation on January 1, 2022, triggering a Tier 1 shortage.
Even with above-normal precipitation through the rest of spring, grass production will more than 30% below average as there is virtually no grass to start with (see map below).

Expected Grass Growth: Forecast Above-Ground Net Primary Production (ANPP) for April–May 2021

A map of expected grass growth, as measured using above-ground net primary production, for the months April and May for an above normal precipitation scenario. Even if precipitation was above average grass growth in southern Arizona and New Mexico would still be below average due to antecedent drought conditions. — Seasonal forecast of above-ground net primary production (ANPP) for the Southwest U.S., assuming above-normal precipitation from April 14 to May 31. Source: Grassland Productivity Forecast (Grass-Cast).

Colorado

Warm early April conditions have given way to anomalously cool weather through the middle of the month. Western Colorado snowmelt was on a rapid pace early, but has slowed.
One-third of SNOTEL-measured snowpack melted in southwest Colorado between late March and mid-April. In spite of this, key stream gages indicate rivers are still running at base flow, and reservoirs have yet to realize increases in storage. McPhee Reservoir storage is record low for this time of year. Conversely, seasonal snowpack in the South Platte Basin (northeast Colorado) is still increasing.
Remotely-sensed vegetative health indicators are coming back into season. The Vegetation Drought Response Index (VegDRI) indicates severe drought on the west slopes, and moderate drought conditions for the eastern plains.

2020–2021 McPhee Reservoir Storage Compared to Historical Conditions

Time series graph showing 2020-2021 McPhee Reservoir storage in southwest Colorado versus the historical distribution. McPhee Reservoir storage is record low for this time of year. — McPhee Reservoir storage in southwest Colorado. Storage in 2020–2021 (black line) vs. historical distribution.

New Mexico

Snowpack across the state is still low to very low.
Precipitation for April-to-date has been below average, overall, for New Mexico.
- Precipitation is historically low in April.
Long-term drought shows up clearly in surface water levels in the Rio Grande and Pecos basins. For example, Elephant Butte storage is 11% of capacity.

Rio Grande and Pecos River Basin Reservoir Storage

Map of storages on the Rio Grande and Pecos River Basins. Elephant Butte is 11% full, Caballo is at 13%, Sumner is at 45%, Brantly is at 35% and Avalon is at 25%. — Rio Grande and Pecos River Basin storage as of April 22, 2021. Source: U.S. Bureau of Reclamation.

Utah

Water Year to date precipitation has been below the historical average for all of Utah. Some places, such as the Wasatch Mountains and southwest corner, have a precipitation deficit of more than 6 inches.
Snowpack across northern Utah is currently between 50%–77% of the median for this time of the season, while snowpack across southern Utah is below 50% for all basins.

Utah Water Year Departure from Normal Precipitation

Precipitation anomalies for the water-year-to-date (October 1, 2020 – April 21, 2021) showing very much below average precipitation for northern and southwestern Utah. — Precipitation anomalies for the Water Year to date (October 1, 2020–April 21, 2021). Source: High Plains Regional Climate Center.

Over Utah, “shallow groundwater” derived from GRACE satellites indicates a continual decline through April 26, despite multiple precipitation events in March. The ultra-dry subsurface diminishes the effect of recent precipitation, absorbing new moisture like a sponge.

Utah Shallow Groundwater and Surface Soil Moisture

Time series graph showing GRACE weekly percentiles of shallow groundwater and surface soil moisture for Utah from May 2020 to the present. Groundwater is at its historical low over the data’s 18 years of record. — GRACE weekly percentiles of shallow groundwater (*black*) and surface soil moisture (*blue*) over the state of Utah. Groundwater is at its historical low over the data’s 18 years of record.

Wyoming

A series of snow storms in April provided moisture to north-central Wyoming, which led to improvements in drought conditions in those areas.
Snowpack in all Wyoming basins is above 70% of median for this point in the season.
Precipitation from about the beginning of the Water Year has ranged from about 2.5 inches above normal in the eastern plains to more than 2.5 inches below normal in the south-central and most of the western mountains.

U.S. Drought Monitor Change Map: April 13 to April 20, 2021

Change in the U.S. Drought Monitor categories for Wyoming from April 13 to 20 April, 2021. Drought improved over central Wyoming while western Wyoming saw a degradation in drought conditions. — Change in the U.S. Drought Monitor categories for Wyoming from April 13 to 20 April, 2021. Source: National Drought Mitigation Center.

For More Information

More local information is available from the following resources:

Upcoming Events

April 27, 6–8 p.m. (MDT): Utah Agriculture Drought Impact Reporting: Building a Network for Drought Response.
April 29, 6–8 p.m. (MDT): USDA Southwest Climate Hub and Sustainable Beef Project Webinar on Tools for Managing Drought
April 30, 11 a.m.–12 p.m. (MDT): The Impacts of Climate Change on Snowpack and Streamflow in the Western U.S.

Prepared By

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

Nancy J. Selover
Arizona State Climatologist/Arizona State University

Simon Wang and Jon Meyer
Utah Climate Center/Utah State University

Dave DuBois
New Mexico Climate Center/New Mexico State University

Peter Goble
Colorado Climate Center/Colorado State University

Tony Bergantino
Water Resources Data System, Wyoming State Climate Office

Special Thanks

This drought early warning 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 updates as conditions evolve.

Drought Update for the Intermountain West