691
FXUS65 KPSR 262337
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
437 PM MST Thu Sep 26 2024

.UPDATE...Updated 00z Aviation Discussion...

&&

.SYNOPSIS...
Excessive heat will continue through the first half of next week as
an unseasonably strong high pressure system remains overhead. Lower
desert communities will see daily high temperatures in the 106-115
range, with the hottest days of this stretch expected to be on
Friday and Saturday. Temperatures look to cool off slightly by the
end of next week, but will remain above normal. Dry conditions and
mostly clear skies will also continue through next week.

&&

.DISCUSSION...
The overall synoptic pattern remains largely unchanged with high
pressure entrenched over western CONUS, a low pressure system over
the Lower Mississippi Valley, and Hurricane Helene expected to
make landfall in the panhandle of Florida this evening. This
blocking pattern will keep high pressure over western CONUS well
into next week. As of this afternoon the high pressure system is
centered over New Mexico, with H5 heights still in the 587-589dm
range. This high pressure will migrate westward over the next
couple of days and move overhead on Saturday. As the high pressure
system migrates westward H5 heights are expected to rise into
590-592dm range.

Unseasonably high temperatures will continue through the first
part of next week, with each day expected to break record high
temperatures or at least be near record levels. As the high
pressure strengthens and moves overhead over the next couple of
days afternoon high temperatures are expected to top out in the
106-115 range across the lower deserts, with the hottest day
expected to be on Saturday. Temperatures will cool a few degrees
for the first part of next week, but will still be well above
normal. With temperatures 10-15 degrees above normal continuing
through the first part of next week we will continue to see
widespread Major HeatRisk with localized areas of Extreme
HeatRisk. Due to this the Excessive Heat Warning for the Lower
Colorado River Valley and the lower deserts of southeastern
California and southwestern and south-central Arizona has been
extended through Tuesday evening.

Heading into the middle to latter half of next week ensembles start
to differ on the overall strength of the high pressure system. Some
start to weaken the high pressure system as early as Wednesday with
flow overhead becoming more zonal, whereas others don`t weaken the
high pressure overhead until Thursday or Friday. If the high
pressure remains strong on Wednesday the Excessive Heat Warning will
likely need to be extended another day. Either way temperatures
are expected to cool at some point during the latter half of next
week, however, temperatures are still expected to be around 10
degrees above normal. Dry weather with mostly clear skies will
continue to accompany these unseasonably high temperatures through
next week.

&&

.AVIATION...Updated at 2335Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation weather concerns under mostly clear skies are
expected through the TAF period. Winds will be exhibiting the
typical diurnal tendencies with speeds aob 7 kts. There will
likely be extended periods of light and variable winds as well.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation weather concerns under clear skies will exist through
the TAF period. Winds will favor a W/NW component through the
period with extended periods of variability and nearly calm
conditions.

&&

.FIRE WEATHER...
A blocking weather pattern will keep the unseasonably high
pressure system over the region through at least the first half of
next week. This will result in dry conditions with well above
normal temperatures (10-15 degrees) continuing through at least
Tuesday. MinRHs in the lower deserts will be around 10% and around
15% across the higher terrain areas. Winds will remain fairly
light generally following diurnal wind patterns with the exception
of some breezier conditions on Saturday.

&&

.CLIMATE...

Record highs this week:

Date        Phoenix         Yuma         El Centro
----        -------         ----         ---------
Sep 26    108 in 1989    111 in 2010    110 in 2010
Sep 27    107 in 2009    111 in 1963    111 in 2009
Sep 28    108 in 1992    108 in 1994    109 in 2009
Sep 29    107 in 2003    110 in 1980    110 in 1969
Sep 30    107 in 2010    109 in 2020    108 in 2020
Oct 1     107 in 2020    110 in 1980    110 in 1980

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Excessive Heat Warning until 8 PM MST Tuesday for AZZ530-533-534-
     537>544-546-548>551-553>555-559.

     Excessive Heat Warning from 10 AM Friday to 8 PM MST Tuesday for
     AZZ531-532-535-536.

CA...Excessive Heat Warning until 8 PM PDT Tuesday for CAZ569.

     Excessive Heat Warning from 10 AM Friday to 8 PM PDT Tuesday for
     CAZ566-567-570.

&&

$$

DISCUSSION...Berislavich
AVIATION...Lojero
FIRE WEATHER...Berislavich/Kuhlman
CLIMATE...18