589
FXUS65 KPSR 260533
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1033 PM MST Sat Jul 25 2026

.UPDATE...06Z Aviation Discussion.

&&

.KEY MESSAGES...

- Much above normal temperatures will continue through the
  weekend with readings approaching record levels and Extreme Heat
  Warnings in effect.

- Strong outflow boundary winds will move through South Central
  Arizona later this afternoon and this evening, with a slight
  chance to generate showers and storms over the lower deserts.

- Typical monsoon conditions are expected into next week with
  daily thunderstorm chances favoring Northern Arizona high
  terrain and Southeast Arizona and low chances in the South
  Central Arizona lower deserts.

- After a slight drop in temperatures during the first half of
  the coming work week, high pressure will strengthen over the
  region once again late in the week, resulting in another period
  of unseasonably hot temperatures and widespread Major Heat Risk.

&&

.SHORT TERM /TODAY THROUGH MONDAY/...
Current midlevel water vapor imagery and 500 mb analyzed heights
from the RAP place the center of an expansive subtropical
anticyclone approximately over the Four Corners/Colorado Rocky
Mountains early this afternoon. Meanwhile, an inverted trough
associated with the remnants of TC Bertha remains apparent in water
vapor imagery moving west northwestward over Baja California. To its
north, angling towards the center of the subtropical high, it
continues to slowly drag an axis of vorticity across portions of the
state. This had resulted in enough lift and a completely uncapped
environment over the prominent terrain stretching from Flagstaff
southward and along the Mogollon Rim such that thunderstorms began
firing as early as 11 AM MST. This activity will trend southward
through the afternoon, likely impacting the northern fringes of
Maricopa County and Southern Gila County and sending a strong
(potentially 30-50 mph gusts), somewhat organized outflow into the
lower elevations later this afternoon into the evening. It is highly
uncertain whether this boundary will produce enough lift to break
the cap and trigger lower desert showers/storms, thus chances remain
slight (10-20%). Inverted-V soundings and DCAPEs upwards of 1500-
1800 J/kg across South-Central AZ support strong, gusty winds with
any thunderstorms that do develop and will also help encourage a
long-lived outflow propagating through the Phoenix area and into
Southwest AZ this evening. Brief heavy downpours will be a secondary
hazard to contend with, especially with storms over the foothills
and higher terrain to the east. Limited instability (generally under
500 J/kg MLCAPE) over the South-Central AZ lower deserts will limit
the intensity of any storms that do develop, with better
probabilities for severe storms focused from Pinal County south and
east towards the international border, where SPC has indicated a
Marginal risk today. Marginally better shear and instability further
south will focus the threat for some of the most intense storms
mostly towards the international border.

Across the vast majority of the forecast area, the main hazard this
weekend remains dangerously hot temperatures. Despite the gradual
northward migration of the subtropical high, NAEFS mean 700-500 mb
temperatures and H5 heights are advertised in excess of the 90th
percentile of CFSR climatology through Monday, resulting in
continued above normal temperatures. After another morning with
Phoenix Sky Harbor tying the all-time record warm low (97F), highs
today should reach near 10F above daily normals but still likely
shy of the daily records by a 1F-3F. Phoenix Sky Harbor has
already reached 116F this afternoon as of writing this. With an
uptick in thunderstorm activity this weekend, there will also be
an increase in remnant mid and high level cloud decks, flowing
downstream over the forecast area and limiting overall insolation.
With outflow boundaries passing through the area, near-surface
moisture will also have increased by tomorrow, further limiting
the peak temperatures we may reach. Latest NBM seems to be picking
up on this and reducing forecast highs by several degrees Sunday,
but very warm overnight lows will maintain HeatRisk in a Major
category across much of the area. Major HeatRisk coverage drops
off further Monday, but is still evident across large portions of
the area. As such, Extreme Heat Warnings will remain in effect
across the area through Monday evening. Temperatures do not drop
off considerably heading into the middle of the work week, and so
extensions may be considered in future updates.

Over the next few days, the position of the high, easterly to
southeasterly flow, and sufficient moisture in place will remain
supportive of daily thunderstorms forming over the northern AZ high
terrain and portions of Southeast AZ during the early-mid afternoon.
Later in the afternoon and into the evening, chances for storms over
the South-Central AZ lower deserts cannot be ruled out, with
moderate instability in place and 10-11 g/kg mixing ratios. However,
latest HREF has backed off considerably on storm coverage for
tomorrow, perhaps picking up on subsidence from the departing weak
inverted trough axis.

&&

.LONG TERM /Tuesday through Friday/...
Strong, expansive ridging will remain nearly in place through next
week across the southwest and central United States with the
anti-cyclone center rotating back from central Colorado into New
Mexico and Arizona. Early in the week, sufficient easterly flow
will prevail over the region juxtaposed with marginally supportive
mixing ratios of 9-11 g/kg for scattered storms. There remains
considerable uncertainty regarding a more preferred time frame for
higher POPS in any given location with mesoscale details likely
becoming more important towards convective evolution. Overall,
this appears to be a very typical monsoon pattern with alternating
convectively active and inactive days. However, by the latter
half of the week, there are a handful of NAEFS members indicating
notable strengthening of the high pressure with 600dm H5 heights
materializing and the center of the anticyclone shifting to over
northern AZ/southern UT. It appears the NBM/WPC forecasts are
latching onto this scenario as POPs dwindle to much lower than
expected values given the ensemble mean synoptic pattern. The
larger impact of this outcome would be a return to major HeatRisk
and extreme heat thresholds towards the end of the week, after the
very short-lived reprieve at the beginning of the week. As a
result, the current Extreme Heat Warning may actually be extended
as one prolonged warning event.

&&

.AVIATION...Updated at 0530Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Aviation concerns will remain minimal through the forecast period.
A secondary outflow boundary will progress through the Phoenix
Metro over the next few hours. This will promote a continuation of
easterly to southeasterly flow at all terminals through tonight.
Winds will then return out of the WSW early Sunday morning, mainly
around 15Z-16Z. Westerly flow will increase through the afternoon
with gusts reaching into the teens to around 20 kts. There is a
much lower chance of an outflow reaching the metro TAF sites on
Sunday. SCT to BKN mid to high clouds will prevail.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are anticipated through the forecast period.
Aside from a gusty easterly winds at KBLH over the next hour or
two, winds should follow typical diurnal trends at both terminals
through the period with a predominant southerly component at KBLH
and a southeasterly direction at KIPL. Speeds should remain at or
below 10 kts at both terminals. FEW to SCT mid to high clouds will
continue to progress over the region.

&&

.FIRE WEATHER...
There will be better chances for showers and storms this weekend
into early next week, than the previous few days, but with
activity still mostly favoring the high terrain of northern AZ and
southeastern AZ and slight chances (10-20%) in the lower deserts
of south-central AZ. There is high confidence that strong gusty
thunderstorm outflow winds will progress into the lower deserts
late this afternoon and this evening, which may offer slightly
better odds for rain over the lower deserts today than in the
following few days. Extreme, well above normal, temperatures will
contribute to seasonally dry afternoon conditions. Hottest
temperatures will be today, with minimum afternoon RH values in
the 10-20%. Temperatures then fall several degrees heading into
the beginning of next week and moisture increase slightly, leading
to minimum RH values improving slightly to 20-30%. Temperatures
will warm back up again during the latter half of next week and
minimum RHs will again fall to the 10-25% range. Overnight
recoveries will be fair most nights with RH values mostly in the
35-50% across lower deserts to 45-65% across southern Gila
County. Daily afternoon thunderstorms will continue through next
week, mostly across higher terrain and outside of thunderstorm
outflows, wind speeds should be fairly light through the period
with only local afternoon gusts 20-25 mph.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Monday for AZZ530>555-559.

CA...Extreme Heat Warning until 8 PM PDT Monday for CAZ560>570.

&&

$$

SHORT TERM...Whittock
LONG TERM...18/Benedict
AVIATION...Salerno
FIRE WEATHER...Benedict