Drought Information Statement
Issued by NWS Phoenix, AZ

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Drought Information Statement
National Weather Service Phoenix AZ
755 AM MST Thu Apr 19 2018

...Drought Conditions Show No Improvement Across the Region...

Synopsis...

There has been little relief to drought conditions across the entire
Southwest region over the past month with only spotty rain and snow.
Precipitation totals across the region have been paltry and many
locations are recording one of their driest winters on record. The
winter season is typically a wetter period of the year where
mountain snow in northern and eastern Arizona is accumulated and
eventually helps recharge area reservoirs. Entering the drier spring
season, little additional precipitation will fall until the summer
monsoon.

Extreme drought still covers a rather large area from northeast
Arizona through south-central and southwest Arizona, as well as
southeast California. 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
winter. Even some pockets of exceptional drought have materialized
where greater precipitation deficits have been most evident. Nearly
50% of Arizona is now in extreme drought compared to none of the
state at the beginning of the year. Severe drought now covers over
90% of Arizona compared to just 4% at the start of the year.

La Nina conditions continue to slowly weaken across the tropical
Pacific and a shift to neutral conditions will occur later this
spring. Heading through the spring and with more neutral conditions,
there will be little 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 non-existent
and there are some reports around Arizona of evergreen mortality due
to the lack of precipitation. Rangeland and pasture conditions have
deteriorated substantially the past several months, and 86% of the
area is rated as poor or very poor. This compares to 57% one month
ago and just 19% at the same time last year.

Many native grasses remain dormant with the lack of rainfall while
shrubs and trees have become stressed. 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 early June
versus mid April. Several wildfires have already been reported
around the state which is earlier than usual. If weather conditions
become suitable later this spring, the annual spring fire season
could become very active.


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 settling in, 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     5.15        19         4th
Scottsdale AZ     1.24      0.92     6.80        18         Msg
Casa Grande AZ    1.69      1.39     5.68        30         3rd
Yuma AZ           0.25      0.18     2.14        12         5th
Blythe CA         0.17      0.17     2.56         7         4th
Tucson AZ         2.57      1.98     5.15        50        17th
Flagstaff AZ      5.02      5.01    12.38        41         6th


Precipitation/Temperature Outlook...

The approximate probability values for above, below, or near normal
temperatures and precipitation for May and the 3-month period May-
June-July 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 better chance of being above normal during the
month of May, as well as the 3-month period of May through July.
Precipitation totals have equal chances of reaching above, below, or
near average amounts in May, as well as the May through July period.

                               Temperature        Precipitation
                               Probability         Probability
                             Above/Near/Below    Above/Near/Below
                                 Normal              Normal
May 2018...................    55 / 33 / 12        33 / 33 / 33
May-June-July 2018.........    59 / 28 / 13        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 and
additional reservoir recharge will be minimal.

                    4/17/2018      4/17/2017       4/17/2016
                    ---------      ---------       ---------
Roosevelt             57              70              52
Horse Mesa            92              96              93
Mormon Flat           96              97              95
Stewart Mtn           93              92              92
 Total Salt           63              74              60

Horseshoe              8              68              41
Bartlett              45              97              45
 Total Verde          31              87              44

 Total System         59              76              58


Next Issuance Date...

This Drought Information Statement will be updated on or around
May 18 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



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