917
FXUS65 KPSR 211802
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1102 AM MST Fri Aug 21 2026

.UPDATE...18Z Aviation Discussion.

&&

.KEY MESSAGES...

- Highs will return to around 110 degrees today across the lower
  deserts and continue into early next week before heating up to
  around 114 degrees during the latter half of next week.

- Extreme Heat Warnings have been extended through next Friday
  evening due to continued areas of major HeatRisk through early
  next week and increasing to widespread Extreme HeatRisk during
  the latter half of next week.

- Isolated thunderstorms are expected to remain confined to the high
  terrain through at least Saturday.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...
The subtropical high is currently centered over the Four Corners
region early this morning and models are in good agreement that it
will slowly progress eastward through tomorrow and eventually settle
over eastern CO/NM. This will cause winds over our region to become
more southerly, which will usher in much drier air. PWATs early this
morning currently range from 1.0-1.5" over our area and models show
PWATs decreasing to 0.9-1.3". Models also show mixing ratios as low
as 7-8 g/kg. This will result in dry conditions across the lower
deserts and only slight chances for some isolated showers and storms
over the higher terrain areas. Models do show slight chances of a
weak outflow boundary trying to move into the lower deserts.
However, any outflows are expected to wash out as they move off the
terrain, similar to last night.

Despite the high shifting eastward over the next couple of days,
models show 500mb heights of 593-596dm over our area. Skies will
return to mostly clear by this afternoon, which will allow
temperatures to heat back up today and are forecasted to be around
110-114 (98-108) degrees across the lower deserts (higher terrain)
this afternoon. Similar temperatures are forecasted for Saturday and
may be a degree or two warmer than today in some locations. These
hot temperatures will result in widespread Major HeatRisk across the
lower deserts and in some areas of the higher terrain (specifically
the San Carlos area). As a result, the Extreme Heat Warning for the
lower deserts and San Carlos area remains in effect. Make sure to
practice smart heat safety by drinking plenty of water and
electrolytes and limiting your time outdoors, especially during the
afternoons.

&&

.LONG TERM /SUNDAY THROUGH NEXT FRIDAY/...
Model uncertainty remains quite high for the first half of next week
as the position of the high is likely to set up somewhere over
eastern New Mexico and western Texas by Monday. This position can
cause higher uncertainty in moisture levels for our area with the
latest guidance trying to advect some moisture into our area by
Sunday or Monday, but NBM forecast PoPs are at most 10-15% for the
lower deserts. At this point, we could continue to see mostly slight
chances favoring the high terrain into early next week, but if
moisture does eventually improve enough storm chances are likely to
be higher than what the NBM is depicting. Another wildcard will be
the potential influence of an upper level trough that may attempt to
move into western portions of our region Sunday into Monday. If this
occurs, it may be enough to improve convective potential across
southeast California and western Arizona for Sunday and/or Monday.
By Tuesday, drier air will filter back into the region as the
subtropical high begins to retrograde back over our region. This
will end limit low end rain chances to the higher terrain areas with
the lower deserts remaining dry. By the latter half of next week,
the NBM shows PoPs being confined to the Mogollon Rim with no
chances for our CWA.

Temperatures are expected to continue to be more influenced by the
strong subtropical high as H5 heights hover between 593-596dm across
the Desert Southwest through early next week. Daytime highs are not
expected to change much from Sunday to Monday, barring any
significant change with the convective chances. As mentioned above,
by Tuesday the subtropical high will start to retrograde back to the
west and center will eventually settle over AZ/NM during the latter
half of the workweek. The high will also strengthen to around 595-
597dm during this time. The combination of the center settling over
our region and strengthening will result in temperatures heating up
to around 10 degrees above normal for this time of year. Afternoon
highs (morning lows) will be in the 110-116 (85-95) degree range
across the lower deserts and in the 100-110 (75-85) degree range
across the higher terrain areas. The increase in temperatures will
also result in an increase in HeatRisk, with widespread Extreme
HeatRisk forecasted for the majority of the CWA for the latter half
of the workweek. Due to these hot temperatures and widespread
Extreme HeatRisk expected next week, the Extreme Heat Warning has
been extended through next Friday.

&&

.AVIATION...Updated at 1750Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No major weather concerns will exist through the forecast period
under occasional mid/high cloud decks. Winds will fully shift out
of the W-SW by 20Z-21Z this afternoon with speeds remaining aob 8
kts. There is still a low chance (<20%) that a distant outflow
could reach the metro area late this evening, causing winds to
briefly shift out of the south. Otherwise, winds will follow
normal diurnal patterns.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major weather issues will exist at the SE California terminals
through the TAF period. Winds will fluctuate between SE and W at
KIPL and remain S to SW at KBLH with limited gustiness. There is a
low chance of a an outflow reaching KIPL late this afternoon
which could cause an early westerly wind shift.

&&

.FIRE WEATHER...
Drier air will filter into the region today and Saturday with even
lower chances for rain while temperatures heat back up to 5 to 8
degrees above normal. Only slight chances for isolated storms exist
over the higher terrain through Saturday. MinRHs of 15-25% today
decrease to 12-20% tomorrow. MinRh then increases again to 15-25%
Sunday and Monday before decreasing back to 10-20% beginning
Tuesday. Overnight recovery will generally be in the 30-60% range,
with the best night being Sunday night. Winds should overall follow
the typical diurnal tendencies with some modest afternoon upslope
gustiness.

&&

.CLIMATE...
Record highs:

Date       Phoenix         Yuma         El Centro
----       -------         ----         ---------
Aug 21   114 in 2019    115 in 1969    117 in 1969
Aug 22   113 in 2011    115 in 1969    117 in 1969
Aug 23   114 in 2011    115 in 2011    116 in 1969
Aug 24   115 in 2020    119 in 1985    117 in 1985
Aug 25   113 in 2011    116 in 1962    117 in 1962
Aug 26   117 in 2011    115 in 2020    115 in 1981
Aug 27   114 in 2023    120 in 1981    117 in 1981
Aug 28   117 in 2023    118 in 2023    117 in 2009

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Friday for AZZ530>544-546-
     548>551-553>555-559-560.

CA...Extreme Heat Warning until 8 PM PDT Friday for CAZ562-565>567-
     569-570.

&&

$$

SHORT TERM...Berislavich
LONG TERM...Berislavich/Kuhlman
AVIATION...Salerno
FIRE WEATHER...Berislavich
CLIMATE...18