194
FXUS65 KPSR 300539
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1039 PM MST Sun Jun 29 2025

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- Record highs are expected on Monday with temperatures topping
  out between 110-117 degrees across the lower deserts. Near
  record highs will be possible again on Tuesday. Temperatures
  will decrease to near normal later this week.

- Extreme Heat Warnings are in effect for the Phoenix metro today
  through Tuesday with the warning expanding across the rest of
  the lower deserts Monday and Tuesday as areas of Major HeatRisk
  develop.

- An influx of monsoonal moisture will lead to increasing chances
  of showers and thunderstorms from the Tuesday-Thursday time
  period across portions of AZ, with the best chances for activity
  confined across the higher terrain areas.

&&

.DISCUSSION...
Mid-lvl wv imagery and 500 mb streamline analysis reveals a highly
amplified pattern over the western CONUS with a strong ridge of
high pressure centered over the AZ/NM border while a deep cutoff
low sits off the CA coast. Our forecast area is under the presence
of the ridge as 590-592 dam heights expand across southcentral
AZ. These positive height anomalies have lead to very hot
temperatures across the lower deserts this afternoon with highs
now exceeding 110F in many locations. Thus, extreme heat will be
the main concern today and heading into the beginning of the
workweek as lower desert highs reach near record to record levels.
The ridge aloft is expected to strengthen further on Monday,
peaking at 592-593 dam. 850mb temps will also approach 32-33C
across southcentral AZ which will result in sfc highs between
110-117 degrees. For the Phoenix area, there is a high potential
(>70%) that a new record high will be set at Phoenix Sky Harbor.
The current record for Monday is 115 degrees set in 1979 and 1913.
Temperatures on Tuesday are expected to cool by a few degrees,
but will still be near record levels for Phoenix around 110-114
degrees. No changes have been made to the Extreme Heat Warning
which will continue through Tuesday.

The combination of the subtropical high migrating over the the Four
Corners Region and the aforementioned cutoff low settling off the
southern CA coast will help advect modest amounts of moisture
northward early this week. Therefore, an increase in shower and
thunderstorm activity is likely beginning as early as Monday
afternoon across the eastern Arizona higher terrain areas with
coverage increasing each consecutive day through Wednesday. Any
storms that do develop over the higher terrain could direct some
outflows into the lower deserts beginning Monday evening. The HREF
is currently showing a 30-50% probability of winds exceeding 30 kts
Monday evening across far E Maricopa and N Pinal Counties.

The forecast window for rain chances across southcentral AZ has
shifted earlier in the week (Tuesday-Wednesday time period) due to
the faster progression of the trough to our west which is forecast
to reach AZ on Thursday. NBM PoPs across southcentral AZ have not
changed much, ranging from 40-60% across the AZ high terrain to
around 20-30% for the lower deserts both days. Moisture levels
(PWATs) in the Phoenix area will increase above 1.00" beginning on
Tuesday, peaking at around 1.2-1.3" Wednesday before decreasing to
around 1.00" by Thursday. Thunderstorms will likely initiate over
the high terrain each afternoon, and send outflows into the lower
deserts, potentially kicking off additional thunderstorms by the
early evening. Forecast soundings show DCAPE values as high as
1500 J/Kg which will result in an environment conducive for
strong, gusty outflow winds and blowing dust.

As the trough continues to move further inland through much of the
Desert Southwest on Thursday, the westerly flow aloft will begin to
scour our moisture from W to E, leading to a downward trend in
monsoonal thunderstorm activity starting Thursday afternoon into
Friday and lasting into next weekend. With the decreasing heights
aloft from the incoming trough, temperatures during the middle to
latter half of the week are expected to take a noticeable downward
trend. Forecast highs by Wednesday are expected to be near normal,
before dropping a couple of degrees below normal Thursday and
Friday. Thereafter, as the trough lifts away and upper-level height
fields start to increase once again by next weekend, temperatures
will be on slight upward trend. The good news is that temperatures
should remain near normal with no extreme heat conditions expected
through the 4th of July Holiday Weekend.

&&

.AVIATION...Updated at 0539Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
Westerly winds will prevail through the middle of the night and
then a late and relatively brief period of easterlies are expected
tomorrow morning, mainly between 12-18Z at KPHX. Westerly winds
redevelop by tomorrow afternoon with gust reaching around 20 kts.
FEW mid level clouds, above 13K ft AGL can be expected at times
through the TAF period. There is potential for an outflow boundary
to move toward the Valley from the east tomorrow evening, but odds
and confidence are too low to include a reflection of one in the
TAFs. A strong easterly gradient wind will develop around 7Z
tomorrow night and push easterly winds up to 10-15 kts.

Southeast California/Southwest Arizona including KIPL and KBLH:
Westerly winds are favored at KIPL through most of the TAF period,
with occasional periods of light variability. Speeds will mostly
remain at or below 10 kts, with slightly highers speeds and some
20 kt gusts anticipated for tomorrow evening. Diurnal wind trends
are expected at KBLH, with periods of light variability, but wind
directions will mostly favor a S-SW component through the period
with speeds mostly at or below 10 kts. Skies will remain mostly
clear with few mid level cumulus at times in the afternoon and
evening.

&&

.FIRE WEATHER...
Very hot and dry conditions will persist through Monday as lower
desert high temperatures are expected to exceed 110 degrees. MinRH
values are expected to range between 5-15% with poor overnight
recoveries between 20-35% across most of the area. Low level
moisture will improve Tuesday and Wednesday with MinRH values
climbing to 20-25% across the eastern districts. The overall wind
pattern will follow typical diurnal tendencies with afternoon gusts
reaching 20-25 mph at times. There is a 30-50% chance of gusty
outflow winds reaching far eastern districts Monday evening.
Starting on Tuesday, increasing moisture will lead to higher
relative humidities as well as increasing chances for shower and
thunderstorm activity across the higher terrain areas. There will
be some initial concerns for dry lightning activity before a
further increase in moisture levels leads to a better potential
for wetting rains later in the week.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning from 10 AM Monday to 8 PM MST Tuesday for
     AZZ530>536-538-539-553-554-559.

     Extreme Heat Warning until 8 PM MST Tuesday for AZZ537-540-
     542>544-546-548-550-551.

     Extreme Heat Warning from 10 AM to 8 PM MST Monday for AZZ541-
     545-547-549-552-555-556-560>562.

CA...Extreme Heat Warning from 10 AM Monday to 8 PM PDT Tuesday for
     CAZ562-565>567-569-570.

&&

$$

DISCUSSION...Salerno/Lojero
AVIATION...Benedict
FIRE WEATHER...Salerno/Lojero