Extreme and Exceptional Drought Holds into the Dry Spring Season

Updated on Sunday, May 23, 2021

Summary:

The 2020-21 Water Year has been much drier than normal for the entire region with only a series of winter storms in late January providing some minor drought relief. Most of the area has received only occasional, spotty light precipitation the past several months with little to none of the typical spring green up. Overall benefits from the meager rain and snow this winter and spring have been muted and hardly sufficient to make a major dent in drought conditions.
The limited higher elevation snowfall has resulted in poor runoff challenging some of the worst years on record. Now in the midst of the dry spring months, the region will now have to wait until the summer monsoon for rainfall and potential drought relief.

Much of the drought impacts have been focused in short term influences such as forage for ranchers, water availability for land based wildlife, and small stream flow for aquatic wildlife. Recent wetness during the past couple winter seasons has resulted in adequate long term hydrologic stability. However with reduced snow melt this year, reservoirs will experience little recharge. 

Local Area Affected:

The National Drought Monitor depicts only minor deterioration of drought measures across Arizona and SE California.

Exceptional Drought (D4) - parts of south-central and southwest Arizona

In Arizona: far southeast Maricopa, southern Gila, eastern Pinal, and northern La Paz counties 

In SE California: far northeastern Riverside County

Extreme Drought (D3) - across much of central, southern, and eastern Arizona and SE California

In Arizona: much of Maricopa, western Pinal, and the majority of La Paz counties

In SE California: most of eastern Riverside County

Severe Drought (D2) -  parts of southwest Arizona and SE California

In Arizona: southern La Paz, northern Yuma and southwest Maricopa counties

In SE California: small part of Riverside County and northern Imperial County

Moderate Drought (D1) - southwest Arizona and SE California

In Arizona: southern Yuma County

In SE California: southern Imperial County

Abnormally Dry (D0) - southwest Arizona

In Arizona: far southern Yuma County

Local Climatology:

Below are precipitation totals since the beginning of the 2020-21 Water Year from selected locations across Arizona and southeast California (please note Normals have been adjusted to reflect the new 1991-2020 official climate period):

In addition to the precipitation deficit, drought conditions have worsened and expanded more rapidly as a result of extreme temperatures. Precipitation deficits over the past year are essentially at record low levels for the entire Southwest United States. Add in the near record to record heat over the past year, and it's fairly clear why Extreme and Exceptional Drought covers much of the Southwest. 

The U.S. Drought Monitor is a weekly collaborative effort between a number of federal agencies including NOAA/NWS, U.S. Department of Agriculture and the National Drought Mitigation Center. Details and explanations of the Drought Monitor can found at the web site:

http://droughtmonitor.unl.edu/ 

The categories of drought are defined as follows:

Abnormally Dry (D0) - Going into drought: short-term dryness slowing planting, growth of crops or pastures; fire risk above average. Coming out of drought: some lingering water deficits; pastures or crops not fully recovered.

Moderate Drought (D1) - Some damage to crops, pastures; fire risk high; streams, reservoirs, or wells low, some water shortages developing or imminent, voluntary water use restrictions requested.

Severe Drought (D2) - Crop or pasture losses likely; fire risk very high; water shortages common; water restrictions imposed.

Extreme Drought (D3) - Major crop/pasture losses; extreme fire danger; widespread water shortages or restrictions.

Exceptional Drought (D4) - Exceptional and widespread crop/pasture losses; exceptional fire risk; shortages of water in reservoirs, streams, and wells, creating water emergencies.

State and Local Actions:

A Drought Emergency Declaration remains in effect for the state of Arizona as signed by the governor in accordance with the Arizona Drought Preparedness Plan. The continuation of this Drought Emergency has been recommended by the Drought Interagency Coordinating Group in their bi-annual meeting on May 11, 2021. This recommendation is based on long term precipitation deficits, along with ongoing negative impacts across the state. . 

Additional information concerning the drought in Arizona can be obtained via the Arizona Department of Water Resources web site at:

https://new.azwater.gov/drought

Additional information concerning the drought in California can be obtained via the California Department of Water Resources web site at:

http://www.water.ca.gov/waterconditions

River, Stream Flow, and Reservoir Conditions:

Flow on smaller streams throughout Arizona continues to worsen resulting from the lack of precipitation the past 12 months. Snow melt has ended after only limited response and runoff. Forecast runoff the remainder of the spring continues to be adjusted downward, and will fall near the lowest recorded in many parts of the state. The more highly regulated larger rivers remain in a near normal flow rates due to continual management efforts.

Record low inflows were recorded on the Salt/Verde basin early in the Water Year reflecting a symptom of a poor 2020 monsoon and lingering dry soil moisture. A brief period of ample rain and snow in January helped the system, however limited snowfall since has allowed runoff to lag well behind average. With soil moisture remaining abnormally dry, total system forecast spring runoff continues to be adjusted down to the point where this year will be one of the lowest inflows ever recorded on the Salt/Verde basin. Fortunately, good precipitation the past 2 years along with excellent management keeps the system in good shape.

Hourly and forecast river stages out to 90 days can be found at the National Weather Service's (NWS) Advanced Hydrologic Prediction Service (AHPS) web page:

http://water.weather.gov/ahps2/index.php?wfo=psr

Additional Current stream and river stages may be viewed at the following USGS Web Site:

http://waterwatch.usgs.gov/

Agriculture Impacts:

Rangeland and pasture conditions remain mostly in a poor to very poor condition. 90% of the state pasture land rated as poor to very poor compared to just 13% at this time last May, and the 5-year average of 35%. While a couple winter precipitation events aided topsoil moisture, recent dry, breezy weather has started depleting available moisture. Rainfall needed in the spring for healthy forage area was mostly absent, and supplemental feed has become necessary. Reports continue to indicate many stock ponds low or empty requiring water hauling. Ranchers continue to experience the worst impacts from this extreme and exceptional drought.

For additional information on agriculture impacts may be viewed at the United States Department of Agriculture (USDA) National Agricultural Statistics Service NASS Web Site:

        https://www.nass.usda.gov/Statistics_by_State/
index.php

Fire Danger Hazards:

The National Fire Danger Rating: High to Very High category across the region

The current KDBI: Southwest Arizona and southeast California: Ranging from Extreme lower elevations of SE California and southern Arizona and High in some of the higher elevations of northern and eastern Arizona

Palmer drought severity index (PDSI):
The current weekly PDSI shows a marked deterioration over the past month. The worst PDSI measure have spreads from NE Arizona where drier than normal conditions have been most prevalent over the past several years through the majority of Arizona and SE California. Even in SW Arizona and SE California where long term drought severity has been more muted, PDSI measures are falling rapidly.  

Ample precipitation during the beginning of 2020 spurred growth of fine 1 and 10-hour fuels along with some 100-hour fuels in lower elevations. Wildfires were a tremendous problem in Arizona last year with over 959,000 acres burned in the state - almost double the previous 2 years combined.

With hot, dry spring weather returned, dry fuels have also returned as long term drought persists. Acreage burned by wildfires already this spring is outpacing last year with fuels ripe for burning. Stage 1 fire restrictions have been put in place across much of Arizona for state owned lands attempting to limit further
wildfire starts given the very high fire danger.

100-hour dead fuel moisture has deteriorated below 5% at lower elevations and into a 6-10% range across higher terrain. 10-hour dead fine fuels are now ripe to burn falling into a 3-4% range. 

The Keetch-Byram Drought Index (KBDI) is a drought index that is specifically related to fire potential. The KDBI is broken into four categories which indicate the susceptibility of ground fuels to fire danger. Below are the four categories and a brief description of each.

KBDI and Dead Fuel Moisture data can be found on the Wildland Fire Assessment System (WFAS) web site at:

http://www.wfas.net

Precipitation/Temperature Outlooks:

The 8-14 day temperature outlook for May 30-June 5 period calls for somewhat better chances of above average temperatures and best odds in a near normal rainfall range. The 90 day outlook for the period June through August 2021 indicates much better chances for above average temperatures and equal chances for above, near, or below normal precipitation. 

 La Nina peaked in the tropical Pacific during the winter with sea surface temperatures now moderating around average. Overall, winter 2020-21 was fairly typical for La Nina in the Southwest with widespread below average precipitation. The equatorial Pacific and
atmospheric flow has transitioned into a neutral state, and will remain as such through the summer. There is about a 50% chance of La Nina returning again in the fall/winter 2021-22 with little chance of a transition to El Nino.

For updated temperature and precipitation probabilities consult the following Climate Prediction Center (CPC) Web Sites:

8 to 14 Day Outlook:

http://www.cpc.ncep.noaa.gov/
products/predictions/814day/

30 Day Outlook:

http://www.cpc.ncep.noaa.gov
/products/predictions/30day/

90 Day Outlook:

http://www.cpc.ncep.noaa.gov/products
/predictions/long_range/seasonal.php?lead=01

Questions or Comments:

If you have any questions or comments about this information
please contact:

w-psr.webmaster@noaa.gov

Acknowledgements:

The Drought Monitor is a multi-agency effort involving NOAA’s National
Weather Service and National Centers for Environmental Information, 
the USDA, state and regional center climatologists and the national
drought mitigation center. Information for this statement has been gathered
from NWS and FAA observation sites, cooperative and volunteer observations,
USDAFS, the USDA and USGS.

Related Websites :

NWS - http://www.weather.gov/phoenix

CPC - http://www.cpc.ncep.noaa.gov

Drought Monitor - http://droughtmonitor.unl.edu/

USGS - http://waterwatch.usgs.gov/

COE - http://www.spk.usace.army.mil/