626
FXUS65 KPSR 231720
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1020 AM MST Thu Jul 23 2026

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- Temperatures much above normal will persist through the weekend
  with readings approaching near record levels resulting in
  Extreme Heat Warnings.

- The high pressure system responsible for the extreme heat will
  also restrict thunderstorm development with chances retreating
  into the mountains through the end of the week.

- Above normal temperatures should cool slightly early next week
  as increased thunderstorm coverage returns to the region.

&&

.SHORT TERM /Today through Saturday/...
Early morning WV imagery and objective analysis depicts a
retrogressive anti-cyclone over west Texas while the easterly
cyclonic wave that passed through the region earlier in the week
has lifted into northern Colorado. This places the region under a
more subsident regime with some modest drying aloft as total
column PWATs slowly deteriorate. While current boundary layer
mixing ratios sit around 10-12 g/kg, even these levels will be
pushed closer to 8-10 g/kg the next few days. As warmer
temperatures aloft advect into the area with subtropical ridging
building into Arizona, instability will be reduced while adding
substantial convective inhibition. HREF members suggest a few pop-
up pulse showers/storms over the most favored locations today and
Friday, though chances are essentially under 10%. As the center of
the anti-cyclone migrates north into the four corners over the
weekend, this will allow easterly waves and better convective
potential to return to east/southeast Arizona. While distinct
differences in thunderstorm coverage among models exists, there is
sufficient evidence that more aggressive outflows and isolated
storms descend into lower elevations.

Models remain in good agreement showing a 598dm H5 anti-cyclone
center becoming situated over western New Mexico on Friday with
596- 598dm readings across the forecast area. This will easily
result in widespread major HeatRisk with afternoon highs 5F-10F
above the daily normals Friday and Saturday. Numerical guidance
spread still exhibits a wider than expected range likely due to
uncertainty in surface dewpoints. With the expectation of boundary
layer moisture lingering through the weekend, official NBM 50th
percentile forecasts are likely sufficient, though some areas that
may scour away moisture could achieve levels closer to the 75th
percentile of the full ensemble envelop (i.e. some lower deserts
locations 115F to 120F). Regardless, the hottest temperatures will
settle over the region Friday and Saturday with excellent
forecast confidence of most lower desert communities reaching or
exceeding 115F. Even some higher elevation valley population
centers in Gila County will attain major HeatRisk Saturday, and
the Extreme Heat Warning has been expanded in these locations
prior to better thunderstorm potential Saturday evening.

&&

.LONG TERM /Sunday through Wednesday/...
During the first half of next week, the anti-cyclone center will
propagate across the four corners into central Colorado allowing
enhanced easterly flow and better chances of inverted shortwaves
entering the SW Conus. However, there is considerable uncertainty
regarding the timing and location of any particular feature which
would enhance thunderstorm chances, not to mention mesoscale
details from decayed convective complexes which further
complicates the forecast. However, as early as Saturday night,
long tracking, strong outflows may be sufficient to incur isolated
storm development over lower elevations, while deepening moisture
profiles, increasing total column PWATs, and setting the stage
for enhanced convective coverage on following days. Various
modeling suites highlight different days with a more preferred
chance of storms sweeping into lower elevations early next week,
but all models indicate at least one easterly wave influencing
enhanced activity.

This easterly flow will also help erode higher midlevel heights
and temperatures; and combined with the convective influences, may
significantly reduce and complicate heat related impacts. A
growing trend in models shows outflows and convection rapidly
cooling temperatures across Arizona early in the week such that by
Monday, readings return to normal levels. GFS BUFR soundings are
even more aggressive towards outflows affecting temperatures
suggesting extensive cloud cover much of the day Sunday, and
readings falling well short of 110F. Not putting too much stock in
these types of details 3-4 days in advance, but certainly the
pattern supports this evolution where somewhat lower temperatures
and a return to only moderate HeatRisk arrives quicker than
previously forecast.

&&

.AVIATION...Updated at 1720Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation weather concerns are expected throughout the TAF
period under occasional thin cirrus decks, distant high terrain
cumulus late this morning through the afternoon, and otherwise SKC
skies. The overall wind pattern will continue to favor diurnal
tendencies with speeds generally AOB 10 kts along with extended
periods of variable conditions.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns under FEW mid to high level
cloud decks are expected throughout the TAF period. Winds will
continue to vary between SE and SW at both terminals with speeds
generally AOB 10 kts sustained and occasional gusts into the teens
possible, especially this afternoon and evening.

&&

.FIRE WEATHER...
Thunderstorm chances will remain quite low the rest of the week with
only slight chances remaining over high terrain areas of far eastern
districts. Better chances for more expansive storm coverage and
wetting rainfall will arrive next week. Temperatures will warm
significantly with much above normal readings resulting in Extreme
Heat Warnings for lower elevations and foothill locations. Despite
the warmer and drier conditions, humidity levels will not fall
substantially with minimum afternoon readings in a 10-25% range
improving closer to 15-30% next week. Correspondingly, overnight
recovery will mostly be in a fair to good range of 30-60% with
somewhat higher values next week. Winds 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.

     Extreme Heat Warning from 10 AM Friday to 8 PM MST Saturday for
     AZZ556-560>562.

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

&&

$$

SHORT TERM...18
LONG TERM...18
AVIATION...Whittock
FIRE WEATHER...18

NWS Phoenix (PSR) Office