043
FXUS65 KPSR 291051
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
351 AM MST Wed Jul 29 2026

.UPDATE...12Z Aviation Discussion

&&

.KEY MESSAGES...

- High pressure will center itself over Arizona and strengthen
  late this week resulting in record to near record temperatures
  and widespread major to extreme Heat Risk.

- Extreme Heat Warnings have been expanded to cover the entire
  forecast area starting Thursday, and continuing through the
  weekend.

- Drier air filtering into the region will limit any chances for
  showers and thunderstorms with only isolated coverage over the
  far eastern Arizona high terrain.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
A worked over atmosphere from yesterday`s early morning rainfall
along with a strengthening of the upper level ridge centered over
New Mexico resulted in very little convection during the
afternoon/evening hours yesterday. Temperatures were held down a
few degrees due to the morning cloud cover and rain-cooled air,
but the extra humidity still made it feel quite uncomfortable.

Drier air already working into southeast California and southwest
Arizona will spread eastward through Thursday, lowering PWATs to
slightly below normal for late July while surface dew points drop
into the upper 40s to the mid 50s. The ridge center is also
forecast to strengthen as it shifts directly over Arizona by
Friday, increasing the subsidence across the region. The
combination of the drier air and the stronger subsidence will
essentially end monsoon activity across all but the far eastern
Arizona high terrain. For today through Friday, any monsoon
activity is likely to be confined to the White Mtns and maybe
over portions of the Mogollon Rim.

The main forecast concern for the rest of the week will be the
building heat and the expected widespread Major HeatRisk setting
up over much of the area by Friday. Guidance has been consistent
in showing the ridge strengthening from around 595dm currently to
600dm by Friday as the center shifts directly over Arizona. The
expected strength of this ridge will reach record levels for this
time of year over a good portion of the Southwestern U.S. by
Friday. As the heat worsens over the next few days, humidities
will lower somewhat but it should still feel a bit humid with
daytime heat indices essentially mirroring air temperatures. High
temperatures today should top 110 degrees across the western lower
deserts to right around 110 degrees in the Phoenix area, but we
are expecting to add 2 degrees each day through Friday or
Saturday. Fairly widespread Major HeatRisk is expected beginning
Thursday followed by widespread Major to localized Extreme
HeatRisk starting Friday. Daytime highs should top 115 degrees
over the hottest lower deserts by Friday with overnight lows
increasing into the upper 80s to the mid 90s.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Dangerous heat will impact the region over the weekend and
potentially extending into early next week. The peak strength of
the upper level ridge is forecast to occur on Friday and Saturday
before weakening Sunday into Monday. Even though guidance is
forecasting record H5 heights on Friday and Saturday, forecast
highs are barely reaching daily records. This is either due to the
modest low level moisture remaining in place holding down daytime
temperatures a bit, or the NBM is under forecasting temperatures.
We are leaning toward the NBM deterministic forecast temperatures
not being hot enough, but not enough to warrant nudging the
forecast upward. It would not be surprising to have actual highs
closer to the 75-90th percentile of guidance, or a couple degrees
higher than the current forecast. We are likely to have some areas
reaching 120 degrees across the lower deserts of southeast
California on Saturday and Sunday, while the Phoenix area could
conceivably reach 118 or even 119 degrees. Overnight lows will
also provide little relief from the extreme heat with readings
mostly in the upper 80s to the lower 90s to as high as the mid 90s
in the urban core of the Phoenix metro.

Monsoon activity is expected to remain very limited on Saturday
with little to no shot at any outflows nearing the lower deserts,
but that may change by Sunday or Monday. As the ridge begins to
weaken Sunday into Monday, guidance shows evidence of increasing
low level moisture and more monsoon activity across eastern
Arizona and northern Mexico. However, chances still remain fairly
low on Sunday and Monday with high terrain PoPs of 20-30% and
10-15% into the Phoenix area during the evening hours. As long as
the ridge continues to weaken early next week, monsoon convection
should also increase, especially by the middle of next week as
there are hints of a potential easterly wave moving into or near
Arizona. As the ridge weakens and moisture increases, temperatures
are likely to drift lower, but another day or two of Major to
Extreme HeatRisk looks possible for Monday and/or Tuesday,
especially across southeast California and southwest Arizona.

&&

.AVIATION...Updated at 1051Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major aviation concerns are expected throughout the TAF period.
Westerly winds are expected to prevail through the morning at
KPHX, as confidence is low that an easterly shift will occur.
Elsewhere a short period of easterly, to mostly VRB this morning
before returning to westerly flow by 16-18Z. Wind speeds will
generally aob 10 kts. FEW-SCT mid to high level clouds will be
common throughout the period.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation concerns are expected throughout the TAF period.
KBLH will continue with southerly flow with gusts up to 20kts
possible this afternoon. KIPL is expected to be southeasterly
shifting southwesterly by the evening hours. Otherwise mostly
clear skies with just FEW high level passing clouds.

&&

.FIRE WEATHER...
Strong high pressure will gradually build over the region through
the rest of the week, while drier air also moves in from the
southwest. These two factors will severely limit monsoon activity
as very little activity is expected through at least Friday.
Expect humidities to gradually lower over the next couple of days
with MinRHs settling at 10-15% by Friday. Record to near record
temperatures are also forecast for Friday and through the upcoming
weekend. Winds will mostly follow diurnal patterns, but west
southwesterly winds will be dominant much of the time with
afternoon gusts of 15-20 mph at times.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Sunday for AZZ530-532-537-
     540-542>544-546-548-550-551.

     Extreme Heat Warning from 10 AM Thursday to 8 PM MST Sunday for
     AZZ531-533>536-538-539-541-545-547-549-552>563.

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

     Extreme Heat Warning from 10 AM Thursday to 8 PM PDT Sunday for
     CAZ560>566-568.

&&

$$

SHORT TERM...Kuhlman
LONG TERM...Kuhlman
AVIATION...Ryan
FIRE WEATHER...Kuhlman

NWS Phoenix (PSR) Office