435
FXUS65 KPSR 300501
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1000 PM MST Wed Jul 29 2026

.UPDATE...
Updated Aviation

&&

.KEY MESSAGES...

- High pressure will center itself over Arizona and strengthen late
this week resulting in record to near record temperatures and
widespread major to extreme Heat Risk.

- Extreme Heat Warnings have been expanded to cover the entire
forecast area starting Thursday, and continuing through the weekend.

- Drier air filtering into the region will limit any chances for
showers and thunderstorms with only isolated coverage over far
eastern Arizona high terrain.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
Weak troughing entering the Great Basin has displaced the monsoon
high off to our east with the center of the anti-cyclonic rotation
now over New Mexico. Deep southerly flow remains in place for much
of Arizona, keeping moisture levels relatively elevated as PWATs
continue to hover around 1.2-1.6", according to mesoanalysis, across
our lower desert areas. However, it does not appear that the
moisture profile will be conducive enough to spark much, if any,
shower and thunderstorm activity, even for the mountainous areas of
Gila County. The entire state will not be completely deprived of
rainfall today though as orographically induced convection is
expected for parts of the Flagstaff and Tucson CWAs.
Convective activity will diminish noticeably during the back half
of the week across most of Arizona, with the exception being the
White Mountains, as drier air spreads over the region and
subsidence increases as the sub-tropical high shifts to the west.

Due to the lack of monsoon activity, the main forecast concern
during the remainder of the workweek will be the building heat and
the introduction of widespread Major, to locally Extreme, HeatRisk.
Temperatures this afternoon will not be too out of the ordinary with
lower desert readings hovering around 108-113 degrees, but we add
about two degrees each day through Friday as the previously
mentioned high strengthens to around 598-600dm during this
timeframe, which will be near climatological records for this time
of year. With dryer air in place as well, heating will be more
efficient, allowing for temperatures, to near, and even exceed, 115
degrees for many locations. The highest values the NBM shows during
the short term is around 116 degrees by Friday, but given how
relatively dry it will be, and how strong the high will become, it
seems that those readings might be a bit underdone. It would not be
surprising that during the next few subsequent forecasts the NBM
values climb a few degrees, with some areas, mainly the deserts of
SE CA and far SW AZ, potentially even seeing MaxT projections
nearing 120 degrees.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Dangerous heat will impact the region over the weekend and
potentially extending into early next week. The peak strength of the
upper level ridge is forecast to occur on Friday and Saturday before
weakening Sunday into Monday. Even though guidance is forecasting
record H5 heights on Friday and Saturday, forecast highs are barely
reaching daily records. This is either due to the modest low level
moisture remaining in place holding down daytime temperatures a bit,
or the NBM is under forecasting temperatures. We are leaning toward
the NBM deterministic forecast temperatures not being hot enough,
but not enough to warrant nudging the forecast upward. It would not
be surprising to have actual highs closer to the 75-90th percentile
of guidance, or a couple degrees higher than the current forecast.
We are likely to have some areas reaching 120 degrees across the
lower deserts of southeast California on Saturday and Sunday, while
the Phoenix area could conceivably reach 118 or even 119 degrees.
Overnight lows will also provide little relief from the extreme heat
with readings mostly in the upper 80s to the lower 90s to as high as
the mid 90s in the urban core of the Phoenix metro.

Monsoon activity is expected to remain very limited on Saturday with
little to no shot at any outflows nearing the lower deserts, but
that may change by Sunday or Monday. As the ridge begins to weaken
Sunday into Monday, guidance shows evidence of increasing low level
moisture and more monsoon activity across eastern Arizona and
northern Mexico. However, chances still remain fairly low on Sunday
and Monday with high terrain PoPs of 20-30% and 10-15% into the
Phoenix area during the evening hours. As long as the ridge
continues to weaken early next week, monsoon convection should also
increase, especially by the middle of next week as there are hints
of a potential easterly wave moving into or near Arizona. As the
ridge weakens and moisture increases, temperatures are likely to
drift lower, but another day or two of Major to Extreme HeatRisk
looks possible for Monday and/or Tuesday, especially across
southeast California and southwest Arizona.

&&

.AVIATION...Updated at 0500Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No significant weather concerns will exist through Thursday night
under occasional mid/high cloud decks. Winds should follow similar
trends to the past 24 hours with uncertainty regrading whether
directions complete an easterly switch overnight. KPHX may never
fully complete the switch with a variable component briefly
materializing before quickly reverting to west by late morning. Any
afternoon gustiness will be limited in time and space while TS
remain well removed from the terminals.


Southeast California/Southwest Arizona including KIPL and KBLH:
No weather concerns will exist through Thursday night under clear
skies. Trends in winds should be very similar to the past 24 hours
featuring a preference towards a southerly direction and only modest
afternoon/early evening gusts around 15kt.

&&

.FIRE WEATHER...
Strong high pressure will gradually build over the region through
the rest of the week, while drier air also moves in from the
southwest. These two factors will severely limit monsoon activity as
very little activity is expected through at least Friday. Expect
humidities to gradually lower over the next couple of days with
MinRHs settling at 10-15% by Friday. Record to near record
temperatures are also forecast for Friday and through the upcoming
weekend. Winds will mostly follow diurnal patterns, but west
southwesterly winds will be dominant much of the time with afternoon
gusts of 15-20 mph at times.

&&

.CLIMATE...
Record high temperatures:

Date       Phoenix         Yuma         El Centro
----       -------         ----         ---------
Jul 31   116 in 2020    119 in 1957    119 in 2020
Aug 1    116 in 1972    117 in 1993    118 in 1993
Aug 2    114 in 2025    117 in 1918    117 in 1969
Aug 3    116 in 2024    116 in 1998    117 in 2021

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Sunday for AZZ530-532-537-
     540-542>544-546-548-550-551.

     Extreme Heat Warning from 10 AM Thursday to 8 PM MST Sunday for
     AZZ531-533>536-538-539-541-545-547-549-552>563.

CA...Extreme Heat Warning until 8 PM PDT Sunday for CAZ567-569-570.

     Extreme Heat Warning from 10 AM Thursday to 8 PM PDT Sunday for
     CAZ560>566-568.

&&

$$

SHORT TERM...RW
LONG TERM...Kuhlman
AVIATION...18
FIRE WEATHER...Kuhlman
CLIMATE...18