Drought Information Statement for Arizona and SE California - January 28, 2021

Winter Storms Provide Minor Improvement to Regional Drought

Updated on Thursday, January 28, 2021

Summary:

After an extremely warm, dry autumn and early winter where precipitation totals 
were the driest in recorded history for much of the area, a series of winter storms
 finally brought some minor drought relief to the region. Snowfall amounts 
through higher terrain locations of Arizona fared quite well allowing snow cover 
to rebound up to 70% of the median value. Even in some lower elevations, 
generous rainfall totals were quite beneficial; parts of SW Arizona actually 
received around one quarter of their average annual rainfall in just a couple days.

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 reduction in Exceptional Drought over much of Arizona recently, and additional small improvements in SE California.  Severe and Moderate drought conditions only exist in portions of SE California and far SW Arizona where winter and spring 2020 precipitation was abundant and recent rainfall very beneficial 

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, much of La Paz, and northeast Yuma counties

In SE California: far northeast Riverside County

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

In Arizona: northern Yuma and far southwest Maricopa counties

In SE California: central Riverside counties

Moderate Drought (D1) -  small part of SE California

In Arizona: southern Yuma Cpunty

In SE California: most of 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 6-7 months have been record breaking in all possible respects with the majority of the area at all-time 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 6-9 months. Recent rainfall has allowed some flow on lower elevation streams, however 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.

Recent 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 along with limited runoff input early in the water year 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 continue to deteriorate with the lack of rain and lingering effects of heat last year. The latest rainfall may aid in rangeland recovery once warmer temperatures emerge in the spring. Forage area remains depleted and reports indicate many stock ponds are dry requiring extensive water hauling. Thus far, ranchers have experienced the worst impacts from this extreme and exceptional drought. The percentage of pasture and range land rated as poor to very poor stands around 89%.

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 to Moderate category for most of the entire area

The current KDBI: Southwest Arizona and southeast California: Ranging from High 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 only minor changes over the past month with some worsening areas. 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 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 bringing welcome rain and snow along with much colder temperatures have helped the fire threat potential significantly. 100-hour dead fuel moisture has rebounded above 16% across the entire region while 1-hour dead fine fuels have become increasingly moist above 20%.

While these measures will preclude much fire danger in the near future, the underlying long term drought, available fuels, and inevitable hot, dry late spring months will bring the 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 4-10 period calls for better chances of below average temperatures and slightly elevated odds for below normal rainfall. The 90 day outlook for the period February through April 2021 indicates better chances for above average temperatures and enhanced odds for below normal precipitation. 

La Nina seems to be reaching 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 for the remainder of the winter and early spring. The current forecast still suggests around a 60% chance the
late winter/early spring will end up in the drier than normal, while the chance of wetter than normal conditions continuing for an extended period outside of late January is less than 10%.

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/