Drought Information Statement
Issued by NWS Phoenix, AZ

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6
000
AXUS75 KPSR 172211
DGTPSR

Drought Information Statement
National Weather Service Phoenix AZ
310 PM MST Thu May 17 2018

...Drought Slowly Worsens During the Driest and Hottest Part of
the Year...

Synopsis...

There has been little to no drought relief across the entire
Southwest region over the past month with only one weather system
bringing spotty rain and snow showers at the beginning of May.
Precipitation totals since last fall across the region have been
paltry, and many locations are recording one of their driest Water
Years on record (since Oct 1st). Now entering the drier spring
season, little additional precipitation will fall until the summer
monsoon and any improvement to drought conditions should not be
expected.

Extreme drought still covers a large majority of the area from
northeast Arizona through south-central and southwest Arizona, as
well as southeast California. The worst category of exceptional
drought continues to grow in northeast Arizona where the greatest
precipitation deficits and impacts have been experienced. Severe
drought encompasses much of the rest of the region, with the
exception of far southeast and northwest Arizona where slightly
better rainfall has been received this past 6 months. Over 60% of
Arizona is now in extreme drought compared to none of the state at
the beginning of the year. Severe drought now covers over 97% of
Arizona compared to just 4% at the start of the year.

La Nina conditions continue to weaken across the tropical Pacific
and a shift to neutral conditions is now occurring. Heading through
the spring and with more neutral conditions, there will be little to
no predictable influence from this cycle. There is little to no
evidence suggesting whether the upcoming summer monsoon will be
wetter or drier than normal.


Summary of Impacts...

The recent lack of precipitation has caused many stock ponds to dry
up and require water hauling for livestock. Distressed vegetation
and loss of high quality forage area have compounded the problem for
farmers and ranchers. In many areas, forage has been completely
absent and there are some reports around Arizona of evergreen and
native shrub mortality due to the lack of precipitation. Reports
around the state also indicate tank water storage for livestock is
now nearly non-existent. Rangeland and pasture conditions have
deteriorated substantially the past several months, and 100% of the
area is rated as poor or very poor. This compares to 86% one month
ago and just 15% at the same time last year.

Many native grasses remain dormant with the lack of rainfall while
shrubs and trees have become severely stressed with localized
mortality. Warmer than average conditions this winter have only made
the situation worse by heightening the topsoil moisture deficit in
non-irrigated locations. 10-hour and 100-hour dead fuel moisture
values have fallen below 5% and this type of fuel moisture is more
indicative of the height of the fire weather season in mid June
versus mid May. Several large wildfires have already been reported
around the state which is much earlier than usual. If weather
conditions become suitable later this spring, the annual spring fire
season could become even more active and destructive.


Climate Summary...

The Water Year (since Oct 1st) remains exceedingly dry with many
locations around the region experiencing one of the driest on
record. With the dry spring season now firmly entrenched, it will be
impossible for precipitation totals to reach anywhere close to
average. Totals and rankings are given below (please note some
stations have a limited historical record and rankings may not be as
significant).

                  Since     Since    Since      Percent     Rank
                  Oct 1     Jan 1    Oct 1      of Normal   Driest
                  2017      2018     Normal

Phoenix AZ        1.00      0.77     5.27        19         4th
Scottsdale AZ     1.30      0.98     6.99        19         Msg
Casa Grande AZ    1.69      1.39     5.88        29         2nd
Yuma AZ           0.25      0.18     2.22        11         4th
Blythe CA         0.17      0.17     2.60         7         4th
Tucson AZ         2.57      1.98     5.34        48        17th
Flagstaff AZ      5.70      5.69    13.07        44         5th


Precipitation/Temperature Outlook...

The approximate probability values for above, below, or near normal
temperatures and precipitation for June and the 3-month period June-
July-August are given below and valid for Southeast California and
Southwest and South-central Arizona. These probabilities are derived
from outlooks issued by the Climate Prediction Center and are
accessible through their website listed below. The temperature
outlook corresponds to the average temperature during the period,
while the precipitation outlook comprises the total precipitation
over the period.

Temperatures have a much better chance of being above normal during
the month of June, as well as the 3-month period of June through
August. Precipitation totals have equal chances of reaching above,
below, or near average amounts in June, as well as the June through
August period.

                               Temperature        Precipitation
                               Probability         Probability
                             Above/Near/Below    Above/Near/Below
                                  Normal              Normal
June 2018...................   62 / 30 /  8        33 / 33 / 33
June-July-August 2018.......   59 / 27 / 14        33 / 33 / 33


Hydrologic Summary and Outlook...

Reservoir levels have fallen well below levels recorded at the same
time last year. The mountain snow pack above these reservoirs is far
less than last year with the snow season just about over. Seasonal
spring runoff will certainly be below average this year (near record
low levels) and additional reservoir recharge will be minimal.

                    5/16/2018      5/16/2017       5/16/2016
                    ---------      ---------       ---------
Roosevelt             54              71              50
Horse Mesa            92              92              93
Mormon Flat           96              96              96
Stewart Mtn           92              92              93
Total Salt            61              75              58

Horseshoe              8              42              35
Bartlett              44              93              50
 Total Verde          30              74              44

 Total System         57              75              56


Next Issuance Date...

This Drought Information Statement will be updated on or around
June 22 2018.

&&

Related Websites:

Additional information is available at the following locations:

NWS Forecast Office Phoenix: weather.gov/Phoenix
National Integrated Drought Information System: drought.gov
US Drought Monitor: droughtmonitor.unl.edu
Climate Prediction Center: www.cpc.ncep.noaa.gov
Arizona State Climate Office: azclimate.asu.edu
Arizona Dept of Water Resources: new.azwater.gov/drought
Western Regional Climate Center: wrcc.dri.edu
US Geological Survey: water.usgs.gov

Acknowledgement:

Information included in this statement was compiled from various
federal, state, and local agencies.

Questions or Comments:

National Weather Service Phoenix
PO Box 52025
Phoenix, AZ 85072
E-mail: w-psr.webmaster@noaa.gov


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.