828
FXUS65 KPSR 050545
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1045 PM MST Fri Oct 4 2024

.UPDATE...Updated 06z Aviation Discussion.

&&

.SYNOPSIS...
Record-breaking heat will continue through at least Monday, with
very little day-to-day changes in the weather pattern. An
Excessive Heat Warning remains in effect through Monday as
afternoon high temperatures reach upwards of 15 degrees above
normal. A slight downtrend in temperatures is expected by the
middle to end of next week as a weak disturbance moves in from
the west, but temperatures will continue to remain above normal.

&&

.DISCUSSION...
Excessive heat continues across the region as record-breaking
temperatures persist in the forecast. Phoenix is now at 11
consecutive days where temperatures have tied or broken daily
record highs and 7 consecutive days with record warm lows. This
streak is set to continue through the weekend and into at least
the beginning of the new week.

A strong, persistent ridge of high pressure remains situated over
the southwest CONUS with current 500 mb heights over the forecast
area around 590 dm. Ensemble guidance are in good agreement that
this ridge will strengthen over the region through the weekend
pushing 500 mb heights to around 592-593 dm. NBM shows temperatures
warming up slightly this weekend as a result with highs forecast to
reach 110 degrees or ~15 degrees above normal across many lower
desert locales through Monday. Temperatures in Phoenix are forecast
to shatter daily record highs through early next week with records
during the mid to latter part of next week expected to remain in
jeopardy. This heat will continue to promote widespread Major to
areas of Extreme HeatRisk through Monday, so anyone with weekend
plans should continue to exercise heat safety to protect against the
heat. The Excessive Heat Warning remains in effect for much of the
lower deserts through Monday evening.

Going into the middle part of next week, a weak trough is expected
to setup near the southern California coast and possibly even move
inland. This will help drop heights over the region some and thus
lead to a slight downtrend in temperatures for the mid to latter
part of next week. Despite this downtrend, temperatures will
continue to remain above normal as the NBM shows good agreement and
very little spread that highs will continue to remain in the triple
digits. Ensemble guidance also show an increase in moisture going
into the middle part of next week. This could be enough to promote
some shower activity across the Arizona high terrain while the lower
deserts are favored to remain dry. There are indications that by the
end of next week into next weekend deeper troughing may develop
across the eastern Pacific that could help further push temperatures
down, potentially even under 100F, but will have to wait and see how
this trends given that it`s more than a week out at this point.

&&

.AVIATION...Updated at 0545Z.

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

Winds will follow their typical diurnal tendencies over the next
24 hr. period. Extended periods of light and variable winds
and/or calm conditions will also be common. Skies will remain
mostly clear.

&&

.FIRE WEATHER...
Dry and abnormally hot conditions will persist through early next
week, with lower desert highs ranging between 103-111 each
afternoon. There will be little to no day-to-day change in the
weather through Monday with the continued heat, mostly clear
skies, and light winds. MinRH values will range between 5-15%
each afternoon, while MaxRH readings are expected to be between
20-35%, with locally higher values in Yuma and Imperial Counties.
There will be a very slight increase in moisture beginning around
Tuesday that may keep MinRH values from falling into the single
digits, but most areas will still see 10-15% readings in the
afternoon through the end of next week. There will also be
potential for some regional rain showers with the moisture
increase, but at this time the chances are very low (5% or less)
and CWR is near zero. Winds will follow familiar diurnal trends,
with occasional afternoon gusts near 15-25 mph.

&&

.CLIMATE...

Record highs through next Wednesday:

Date        Phoenix         Yuma         El Centro
----        -------         ----         ---------
Oct 4     105 in 2020    109 in 1952    106 in 1952
Oct 5     105 in 2020    108 in 1917    106 in 2020
Oct 6     105 in 1917    108 in 1980    106 in 1964
Oct 7     104 in 1991    108 in 1987    105 in 1991
Oct 8     104 in 1987    107 in 1996    106 in 1996
Oct 9     103 in 1996    106 in 1996    104 in 1996

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Monday for AZZ530>544-546-
     548>551-553>555-559.

CA...Excessive Heat Warning until 8 PM PDT Monday for CAZ562-566-567-
     569-570.

&&

$$

DISCUSSION...Smith/Benedict
AVIATION...Young
FIRE WEATHER...Benedict/RW
CLIMATE...18