-- Discussion containing changed information from previous version are highlighted. --
333
FXUS65 KPSR 052310
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
410 PM MST Wed Jun 5 2024

.UPDATE...
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Updated 00Z Aviation Discussion.
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&&

.SYNOPSIS...
High pressure building over the region will help promote the
hottest temperatures so far this year through the remainder of the
week, resulting in an Excessive Heat Warning that will be in
effect through Friday. Increasing cloud cover and a slight
relative cooldown in temperatures are anticipated by this
weekend.

&&

.DISCUSSION...
Atmospheric analysis reveals a ridge of high pressure firmly
entrenched across much of the western CONUS, which will allow for
the hottest temperatures so far this year, and even since last
September, over the next few days across the Desert Southwest.
Day-to-day temperatures will take a noticeable jump compared to
where we were yesterday, and for the better part of a week or
more, as lower desert highs this afternoon will generally reach
around 105-110 degrees. The full force of the heat dome will then
realized on Thursday and likely into Friday as NBM forecast highs
top out between 109-114 degrees. Phoenix is likely to experience
record setting heat on Thursday, with the current forecasted high
of 114 degrees besting the previous record of 111 degrees set in
2016. Widespread Major HeatRisk will develop across lower
elevation communities in conjunction with these unseasonably hot
temperatures, suggesting that this period will be dangerous for
most people, especially those who do not have access to effective
cooling/hydration. It is recommended to avoid being outside for
long periods during the peak heating hours of the day, but if you
must be outside, exercise caution by taking frequent breaks in a
cooler environment and hydrate accordingly. In response to this
forecasted heat episode, an Excessive Heat Warning has been posted
for the lower deserts through Friday evening.

As mentioned in previous discussions, a weak area of low pressure,
currently located west of the Baja Peninsula, will eventually
move over our forecast area during the weekend. This disturbance
should offer at least some relief from the excessive heat as it
helps to erode positive height anomalies, though temperatures will
remain above normal. This low, combined with the ridge becoming
more centered over New Mexico, will help provide increased
moisture flux over the Desert Southwest by as early as Thursday.
However, any chances for rain over lower elevations will be
limited due to much of this moisture being suspended aloft and a
very dry sub-cloud layer being in place. The best chances for
rainfall (30-50%) look to be over primarily southeastern Arizona
and the White Mountains, though the NBM is squeezing out 10-15%
PoPs for Thursday through Sunday for far eastern Gila County, so
it would not be surprising to see an isolated shower or
thunderstorm over this area during that time frame. At a minimum
this increase in moisture will provide us with a blanket of cloud
cover, which will also be a factor in providing our forecast area
with some relative cooling for this weekend.

Model clusters have come to more of an agreement regarding the
forecast for next week, but some spread remains. Models project
another closed-low developing over the eastern Pacific by Monday,
but where and how strong this low evolves and moves is the main
uncertainty at this point. If this feature were to stay further
west of our forecast area, another warming trend, with
temperatures approaching 110 degrees, would likely commence, while
a more easterly position would help to keep temperatures slightly
cooler. As of now, clusters favor the warmer outcome, but subtle
changes future trends may yield a relatively cooler forecast than
was is currently being indicated.

&&

.AVIATION...
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Updated at 2310Z.

South-Central Arizona including KPHX, KIWA, KSDL, KDVT; and
Southeast California/Southwest Arizona including KIPL and KBLH:

Winds will follow typical early Summer diurnal tendencies for all
terminals, with speeds generally aob 10 kt. Occasional gusts up
to 15-20 kts can be anticipated in the Phoenix area through the
early evening and again tomorrow afternoon. SKC will prevail until
FEW to SCT high cirrus spread over the Phoenix area Thursday
morning. SKC will prevail through the TAF period at the California
terminals.
-- End Changed Discussion --

&&

.FIRE WEATHER...
Hotter temperatures are expected over the next few days, while
seasonably dry conditions prevail. Lower desert highs are expected
to reach up to 110F today and in into the 110-115F range for
Thursday and Friday. Afternoon minimum RHs of around 10% will
continue through the end of the week, while overnight recoveries
will mainly range from 20-40%. Winds will remain fairly light
across all districts with typical diurnal tendencies and afternoon
gusts up to around 20 mph. A weak weather system is then expected
to move through the region Saturday into Sunday allowing
temperatures to start to lower, but will remain above normal.
Winds will also increase a bit which could push afternoon gusts up
to 25 mph in some locations.

&&

.CLIMATE...

Record high temperatures:

Date        Phoenix         Yuma         El Centro
----        -------         ----         ---------
June 5    113 in 2016    115 in 1957    114 in 2016
June 6    111 in 2016    114 in 1928    113 in 2002
June 7    115 in 1985    116 in 1985    113 in 1985

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Friday for AZZ530>556-
     559>562.

CA...Excessive Heat Warning until 8 PM PDT Friday for CAZ561-563-566-
     567-569-570.

&&

$$

DISCUSSION...Kuhlman/RW
AVIATION...Berislavich/Benedict
FIRE WEATHER...Kuhlman
CLIMATE...18