Drought Information for Arizona and Southeast California (Updated March 30, 2018)

DROUGHT CONTINUES TO WORSEN ACROSS THE REGION

Updated on Friday, March 30, 2018 - Mark O'Malley

Summary:

A persistent dry pattern has mostly remained locked in place over the Southwest since the autumn months with only an occasional beneficial storm system. Precipitation amounts for the Water Year 2017-18 (since Oct 1st) have been paltry with many locations in Arizona sitting in one of the top 5 driest winters ever recorded. This is typically a wet period for the region, especially across the mountains of northern and eastern Arizona where snow pack is accumulated and refills reservoirs in the spring.

Regional precipitation deficits have grown substantially, especially with respect to high elevation snow; and it will be impossible to recover to near normal levels before the dry spring season becomes fully established. As a result, drought conditions have continued to worsen over the past month with severe levels covering much of the area, and extreme drought expanding rapidly. 

Local Area Affected:

The National Drought Monitor has depicted worsening drought conditions over the region in the past several months. Extreme drought conditions have expanded over a large part of Arizona. Severe drought conditions exist much of the remainder Arizona, except the far northwest and southeast parts of the state where Moderate drought conditions exist. Extreme drought has expanded back into far southeast California with Severe and Moderate drought still holding firm through the rest of the southeast California deserts. 

Extreme Drought (D3) - across much of central, southern, and western Arizona, as well as Southeast California

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

In California: much of Imperial and far southeastern Riverside counties

Severe Drought (D2) - across parts of central, southern, and western Arizona; as well as far southeast California

In Arizona: southwest Maricopa, much of Pinal, and Yuma counties

In California: western Imperial and eastern Riverside counties

Moderate Drought (D1) -  southeast California.

In California: central Riverside County

           (Percent of normal precipitation since October 1st)

Local Climatology:

Below are water year precipitation totals since October 2017 and totals
since the beginning of 2018 from selected locations across Arizona and
southeast California:

Making the lack of rain worse has been the unseasonably warm temperatures this winter. Phoenix has barely experienced temperatures below 40 degrees, and reaching near record levels has been almost as common as being near normal. 

In fact, a large portion of the southwest United States is experiencing its warmest Water Year (Oct 1st-Feb 28th) in recorded history (since 1895). 

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 16, 2017. 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:

Most smaller, unregulated rivers through the state of Arizona are flowing at much below average rates with unusually low rain or snow amounts over the past 5 months or more. The exception has been parts of SE Arizona where one very beneficial storm system in February greatly aided in stream flow. Larger regulated rivers, including much of the Colorado River, remain in a near to normal flow rate due to management efforts.

Reservoir levels at this point of the year are quickly falling below levels at the same time last year. The amount of snow pack in the mountains above the reservoirs is far less than last year, and it will be impossible that additional precipitation the remainder of this winter season will reach anywhere near the seasonal normal. Several larger storm systems will be needed in the next month to have any sizable effect on reservoir levels later this year. 

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:

With prolonged drought conditions, impacts have included increased water hauling necessary for farmers and ranchers, distressed vegetation, and loss of forage acreage. Livestock on regional ranches have suffered the greatest impacts from drought conditions and many ranchers are considering selling off higher amounts of their herds this spring. Range land and pasture conditions have worsened substantially in the past couple months after monsoon rains stopped early and winter rain and snow have been lacking. 60% of the area pasture and range land has been rated poor or very poor versus just 19% at this time last year. 

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: Moderate to Very High category for the entire area

The current KDBI: Southwest Arizona and southeast California:

Ranging from Extreme in SE California and SW Arizona to Moderate to High towards central Arizona.

Palmer drought severity index (PDSI):
The current weekly PDSI shows long term deterioration across much of the region due to

lack of rain and snow. Only some improvement has been noted in SE Arizona resulting from a beneficial storm system in February.The Extreme Drought category covers much of northeastern Arizona with Severe (-3.0 to -3.9) Drought conditions encompassing SE California, as well as central Arizona. Moderate (-2.0 to -2.9) Drought exists over all of NW through SW and SE Arizona. 

Abnormally dry conditions have pushed 100-hour dead fuel moisture values further down into a 6-10% across the entire southern Arizona region with pockets of less than 5% observed. 

The smaller sized 10-hour dead fuel moisture values in a 3-5% range have expanded across all of the southern Arizona. Somewhat better conditions exist elsewhere in the region, especially at higher elevations. Further drying of these fine fuels will likely occur heading through the warmer spring months. The combination of these increasingly dry finer fuels and favorably dry 100-hour fuels may lead to enhanced behavior in the future should dry and windy weather conditions develop later in the spring. 

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 April 6-12 period calls for slightly better chances of above average temperatures and precipitation likely not too far from average. The 30 day outlook for April 2018 (not shown) indicates better chances for above average temperatures and below average precipitation. The 90 day outlook for the period April through June 2018 indicates much better chances for above average temperatures and modestly better chances of below average precipitation. 

La Nina conditions are continuing, but weakening fairly rapidly this spring. A shift to neutral conditions should occur later in the spring and summer. This La Nina likely has exhibited some influence on the drier winter so far, and will continue to tilt the odds towards drier weather in the near future. Once the shift to more neutral conditions occur, the predictable influence of this La Nina cycle will wane. There is little to no evidence suggesting whether the upcoming summer monsoon season would be wetter or drier than normal. 

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:

Mark O’Malley
Climate and Drought Services
National Weather Service-Phoenix
Co-Chair Arizona Drought Monitoring and Technical Committee
mark.omalley@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/