072
FXUS65 KPSR 280501
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1000 PM MST Mon Jul 27 2026

.UPDATE...

Updated Aviation

&&

.KEY MESSAGES...

- Above normal temperatures will continue through the forecast
period with Extreme Heat Warnings in effect for portions of the area
through mid week.

- Typical monsoon conditions will continue for the next few days
with thunderstorm chances favoring Northern Arizona high terrain and
portions of Southeast Arizona and low chances in the South Central
Arizona lower deserts.

- High pressure will center itself over the region and strengthen
late this week, resulting in hotter temperatures and another period
of widespread Major to Extreme Heat Risk.

&&

.SHORT TERM /TODAY THROUGH THURSDAY/...
The most prominent feature across the Southwest and Central US is a
broad anticyclone centered approximately over NW/Western TX. In
midlevel water vapor imagery, dry air aloft is evident punching into
Eastern AZ as well as a vort max lifting northward through Central
AZ. The combination of these factors with subsidence on the backside
of the departing vort max has led to notable inhibition of
thunderstorms so far this afternoon, especially compared to this
same time over the last few days, with later timing of convective
initiation over terrain features across the state and lower coverage
of radar echoes. Despite this evolution so far, thermodynamics and
low level moisture remain suitable for deep moist convection, with
the 12Z PSR sounding (and PHX ACARS soundings in agreement) showing
upwards of 1000 J/kg MUCAPE and near-surface mixing ratios near 10-
12 g/kg. Upslope convergence over the most prominent terrain
features has been sufficient to trigger convection thus far today,
and as capping/subsidence decreases through the remainder of the
afternoon, an increase in thunderstorm coverage may be expected over
Southeast and far Eastern AZ. Latest HREF remains pessimistic on
development of thunderstorms over our CWA today, though better wind
shear towards Southeast AZ could help storms move off terrain
features, organize, and become more long-lived, pushing west
northwestward towards South-Central AZ. A highly uncertain and
conditional threat for an organized, long-lived outflow to push into
South-Central AZ and trigger additional showers and storms exists.
However, it is far more likely that the strongest storms will
congeal closer to the international border or over Sonora,
potentially forming an MCV this evening which will pass over Central
AZ tonight/Tuesday morning. This would help to trigger isolated to
scattered elevated convective showers over either South-Central or
Southwest AZ Tuesday morning.

Tuesday, conditions will be fairly similar to that of today but with
perhaps less inhibition late morning and early afternoon. HREF has
begun to indicate a similar thunderstorm evolution, with the best
coverage of strong thunderstorms over Southeast AZ near the
international border, potentially forming yet another MCV that could
spark showers over South-Central AZ late Tuesday night into
Wednesday morning as it lifts north. By Wednesday, a downtrend in
thunderstorm activity is anticipated, with drying conditions and
winds aloft shifting southerly and even slightly southwesterly for a
period. Latest GFS deterministic shows near-surface mixing ratios
dropping below 10 g/kg across the forecast area, essentially ending
lower desert storm chances. Ensemble mean PWATs will drop from
current values between 1.2-1.7" across the forecast area (110-150%
of normal) closer to 0.9-1.4" (80-100% of normal) by late Wednesday,
with good agreement between that these lower moisture levels will
persist through the remainder of the week and into the weekend.

Aside from the continued monsoon conditions the next few days, the
primary concern through the entire forecast period and especially by
late this week will be dangerously hot temperatures with little
overnight relief. Temperatures will be fairly stable through
midweek, especially across the western deserts, with afternoon highs
in a 108F-114F range, between 2F-8F above daily normals for the
typically hotter spots and Tuesday likely being the "coolest" of the
next 7 days. While most of the region will fall out of the Extreme
Heat Warning this evening, the Phoenix metro, Imperial Valley and
the Lower Colorado River Valley will remain under the effect of the
Warning through at least Wednesday evening. This is driven largely
due to overnight lows remaining well above normal leading to very
little relief in these areas. More expansive headlines will very
likely be needed again by late week as the subtropical high moves
closer and restrengthens. This is expected to drive temperatures
back in the upper teens, with the lower deserts between 112F-118F,
flirting with record highs yet again. H5 heights near the end of the
work week will climb to between 595-597 dam, or in the 99th
percentile to near max for climatology for this time of year.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
By the end of the of the week and heading into the weekend, most
global ensembles continue to support the strengthening of the high
pressure, with H5 heights up to 600dam and the center of the
anticyclone shifting to over northern AZ/southern UT. These heights
are near or at the max of NAEFS percentile for climatology for this
time of year, which are quite frankly impressive. The peak of the
extreme heat is expected to be Friday and Saturday, where the
chances of Phoenix Sky Harbor at least tying the record high (116F)
will be 65% on Friday and 50% Saturday. As mentioned previously, an
additional widespread Extreme Heat Warning will be likely near the
end of the workweek. Additionally, this setup will likely add more
subsidence over the area and subdue afternoon convection. Global
ensembles also show a slow downtrend in PWATs, falling under 1.5" by
Thursday- Friday. So, this is not great for the prospects of seeing
storms push into the lower deserts. However, the NBM keeps slight
PoPs focused in the AZ high terrain.

&&

.AVIATION...Updated at 0500Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Uncertainty in wind directions and chances of SHRA Tuesday morning
will be the main weather issues as thicker mid/high cloud decks pass
through the area. Confidence is good that west winds will prevail
well into the overnight as thick mid/high cigs spill north from a
convective complex over southern Arizona. While probabilities are
too low to include in this TAF package, a few SHRA and highly
erratic wind directions may impact terminals Tuesday morning before
clearing and reverting back to a westerly component. Enough evidence
exists to include a VCSH with VRB winds, though impacts could be
greater. Also, afternoon gusts may be delayed and/or muted due to
cloud cover earlier in the day. Otherwise, forecast confidence is
good that afternoon TS will once again remain relegated to mountain
locations well removed from the Phoenix metro.


Southeast California/Southwest Arizona including KIPL and KBLH:
Occasionally gusty winds will be the main weather issue through
Tuesday night under periods of passing mid/high clouds. Confidence
is good that wind directions will oscillate between SE and SW at
KIPL while a southerly component will be preferred at KBLH.
Occasional gusts 15-20 kt may affect either terminal at times during
the mid afternoon through mid evening.

&&

.FIRE WEATHER...
Typical monsoon conditions are expected through much of the
forecast, with thunderstorm activity mainly favoring the high
terrain of northern AZ and southeastern AZ and low chances (<10%) in
the lower deserts of south-central AZ. Above normal, temperatures
will contribute to seasonally dry afternoon conditions each day
through the first half of the week, before temperatures once again
heat up during the second half of the week. Minimum RH values of 15-
30% will be common through the first half of the week before
dropping into the 10-20% range late in the week as temperatures heat
up again. 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. 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 Wednesday for AZZ530-532-
     537-540-542>544-546-548-550-551.

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

&&

$$

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