015
FXUS65 KPSR 272127
AFDPSR

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

.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 1805Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:

Aviation concerns will remain low through the forecast period.
Somewhat elevated westerly winds are expected through the
majority, if not all of the upcoming TAF period. Gusts in the
upper teens to around 20 kt are expected this afternoon/early
evening and again tomorrow afternoon. There is low confidence in
an easterly shift tomorrow morning. Currently, only KIWA is
anticipated to go SE`rly during the overnight and early morning
hours tomorrow. FEW-SCT mid and high level clouds are expected
throughout the period.

Southeast California/Southwest Arizona including KIPL and KBLH:

Aviation concerns will remain low through the forecast period.
Current SE winds at KIPL will go SW`rly this evening, then back
SE`rly early tomorrow morning. Wind speeds are anticipated to
mainly be aob 10 kt. At KBLH, winds will stay southerly the whole
period with some gusts up around 20 kt expected this afternoon and
early evening. FEW-SCT mid and high clouds will persist.

&&

.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 (544-546-548-550-551.

     Extreme Heat Warning until 8 PM MST this evening for AZZ531-
     533>536-538-539-541-545-547-549-552>555-559.

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

     Extreme Heat Warning until 8 PM PDT this evening for CAZ560>566-
     568.

&&

$$

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

NWS Phoenix (PSR) Office