157
FXUS65 KPSR 271050
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
350 AM MST Fri Sep 27 2024

.Update...Updated 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
degree range, with the hottest days of this stretch expected to
be today and tomorrow. 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...
Unseasonably hot, record-breaking temperatures will continue to
be the primary weather headline through the remainder of this week
and into next week. Daily record highs have now been either tied
or broken in Phoenix the past three days with yesterday`s high of
110 degrees breaking the previous record of 108 degrees. New
record highs are likely to be set each day through the first part
of next week as the intense heat persists.

The strong ridge of high pressure responsible for the anomalous heat
has shifted westward and is now centered over the international
border with 500 mb heights across the area around 590 dm. Over the
next couple of days, the repositioning and strengthening of the
ridge will cause 500 mb heights to rise upwards of 591-593 dm and
thus will further boost temperatures today and tomorrow with these
days being the hottest in the forecast. By Saturday, temperatures
will peak upwards of 15-20 degrees above normal for this time of
year as forecast highs push upwards of 110-115 degrees. If Phoenix
reaches 115 degrees Saturday as currently forecast, this would
shatter the daily record of 108 degrees set in 1992 by 7 degrees.
Additionally, this would of course be the latest 115+ degree
temperature on record for Phoenix, with the current record for
latest 115+ degree temperature set on September 5th earlier this
month and in 2020. Going forward as temperatures remain well above
normal into next week, widespread Major HeatRisk as well as some
areas of Extreme HeatRisk will be in place for most lower desert
locales. Thus, Excessive Heat Warnings are in effect for much of the
forecast area through Tuesday.

Temperatures will trend down closer to around 105-110 degrees Sunday
and Monday as heights lower somewhat along with an uptick in
moisture over the area. Nevertheless, temperatures will remain above
normal with Widespread Major to areas of Extreme HeatRisk persisting.
By Wednesday, NBM shows highs around 105-108 degrees, which will
promote continued areas of Major HeatRisk and thus could lead to
an extension of the Excessive Heat Warning if trends hold. Going
through the mid to latter part of next week, global ensembles
indicate heights gradually lowering over the Desert Southwest as
the ridge weakens, allowing for temperatures to cool some. Despite
the ridge weakening some as indicated by global ensembles,
temperatures will continue to remain above normal as highs remain
in the triple digits. Dry weather will continue to accompany the
unseasonably warm temperatures with no chances for rain in the
forecast.

&&

.AVIATION...Updated at 1050Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation weather concerns under mostly clear skies are expected
through the TAF period. Winds will follow typical diurnal trends
with speeds aob 10 kts. Moments of variability may also occur
during directional shifts.

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 west to northwest component at
KIPL and west to north component at KBLH through the period with
speeds aob 8 kts. There will likely be extended periods of
variable and nearly calm winds as well.

&&

.FIRE WEATHER...
Hot, dry weather conditions will continue, with temperatures
remaining well above normal into next week as a blocking pattern
keeps strong high pressure over the region. Many places across the
lower deserts will see high temperatures approach or exceed 110
degrees each day with Saturday expected to be the hottest day as
temperatures top out upwards of 110-115 degrees. Min RHs will
range around 7-15% each day, while Max RHs range around 20-30% for
most places through the weekend. 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 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 this morning 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 this morning to 8 PM PDT
     Tuesday for CAZ562-566-567-570.

&&

$$

DISCUSSION...Smith
AVIATION...Lojero/RW
FIRE WEATHER...Smith
CLIMATE...18