Drought Improvement Stalls as a Dry Weather Pattern Returns

Updated on Saturday, February 20, 2021

Summary:

After a series of winter storms finally brought some minor drought relief to the region in January, a dry weather pattern has settled back into the region this February. Despite the recent lull in precipitation, snow cover through higher terrain locations of Arizona remains modest ranging from 40-80% of normal. Lower elevation rainfall totals in January were quite beneficial with parts of SW Arizona actually receiving around one third of their average annual rainfall in just a couple days. However most of the region received far lower totals, and overall benefits were rather muted.

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. 

Local Area Affected:

The National Drought Monitor depicts some minor drought reduction over parts of Arizona recently, and additional small improvements in SE California.  Severe and Moderate drought conditions only exist in portions of SE California and SW Arizona where winter and spring 2020 precipitation was abundant.

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

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

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

In Arizona: most of Maricopa, western Pinal, and northern La Paz counties

In SE California: far northeast 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: central Riverside counties

Moderate Drought (D1) - southwest Arizona and SE California

In Arizona: southern Yuma County

In SE California: Imperial County

Abnormally Dry (D0) - southwest Arizona and SE California

In Arizona: far southern Yuma County

In SE California: far southwest Imperial County

Local Climatology:

Below are precipitation totals since the beginning of the 2020-21 Water Year from selected locations across Arizona and southeast California:

Aside from limited precipitation, drought conditions have worsened and expanded more rapidly as a result of extreme temperatures. The majority of entire Southwest experienced an abnormally warm year in 2020 - in many areas the warmest or 2nd warmest on record. The past 6 months have also been record breaking in most respects with the majority of the area at record levels. 

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 November 10, 2020. 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:

Smaller streams throughout Arizona have been suffering as a result of the lack of rainfall the past 9 months. January rainfall allowed some enhanced flow on lower elevation streams, however that affect has waned. For the most part, snow melt has yet to begin and higher terrain streams have yet to respond. The more highly regulated larger rivers remain in a near normal flow rates due to continual management efforts.

Dry weather during the fall and early winter has been a minor detriment on the Salt and Verde systems with record low inflows reported. However, excellent winter precipitation in the past 2 years leaves the system in very good shape. Recent snowfall will be beneficial later in the spring runoff season though the latest snowfall is just beginning to make up for the deficits already accumulated this water year. In addition, the lack of precipitation and record heat since last summer has lessened soil moisture and eventually could negatively affect spring runoff. 

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. 89% of the state pasture land rated as poor to very poor compared to just 26% last February. The recent January rainfall may aid in rangeland recovery once warmer temperatures emerge in the spring. Forage area remains depleted and reports indicate many stock ponds still low or empty requiring water hauling. Thus far, ranchers have experienced 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: Low in higher elevations to High category at lower elevations 

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

Palmer drought severity index (PDSI):
The current weekly PDSI shows very little change over the past month. The worst PDSI measure remains in NE Arizona where drier than normal conditions have been most prevalent over the past several years. More moist conditions are still recorded in southwest Arizona and southeast California combining index values from last winter along with recent January rainfall.

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 past 2 years combined.

A series of winter storm systems in January brought welcome rain and snow along with much colder temperatures to the region. This has helped the lessen the fire threat, however the recent return to a dry pattern has allowed dead fuel moisture to fall back. 100-hour dead fuel moisture has deteriorated back into a 6-10% range while 1-hour dead fine fuel values have plummeted back into a 3-4% range. 

The underlying long term drought, available fuels, and inevitable hot, dry late spring months will undoubtedly bring a substantial fire threat back to Arizona. 

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 Feb 27-Mar 5 period calls for somewhat better chances of below average temperatures and slightly elevated odds for below normal rainfall. The 90 day outlook for the period March through May 2021 indicates better chances for above average temperatures and enhanced odds for below normal precipitation. 

La Nina has reached its peak in the tropical Pacific with models suggesting a gradual transition towards a neutral state by early summer. A prolonged dry period, typical in the Southwest during La Nina winters, was broken during the middle of January, however the greatest forecast odds still point towards drier than normal weather returning through the bulk of the spring season. The current forecast still suggests around a 50% chance the spring will end up in the drier than normal, while the chance of wetter than normal conditions are only around 15%.

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/