634
FXUS65 KPSR 102059
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
159 PM MST Mon Aug 10 2026

.KEY MESSAGES...

- Extreme Heat Warnings are in effect through this evening for Western
  Imperial County as well as along the Lower Colorado River
  Valley as heat indices are forecast to peak between 110 and 120
  degrees.

- Deeper moisture will provide favorable conditions for daily
  shower and thunderstorm activity to materialize across the area
  through the middle of the week, along with noticeably cooler
  temperatures.

- Thunderstorm chances will decrease noticeably by the end of the week
  into next weekend as drier air filters in.

&&

.SHORT TERM /Today through Tuesday/...
High pressure remains positioned over the Four Corners region
continuing to bring easterly to southeasterly flow aloft over
Arizona. With easterly flow in place moisture will continue to be
advected into the region with model projecting PWATs this
afternoon/evening climbing upwards of 1.5" with the 18Z sounding
already measuring a PWAT of 1.45". Models are in good agreement in
another round of thunderstorms will development in the northeastern
AZ high terrain, and especially in southern AZ, late this
evening/tonight. With any thunderstorm development in these areas
outflows are very likely with the HREF showing up to a 70% chance of
winds above 35 mph in the higher terrain and southern AZ, with a 30-
50% chance of winds above 35 mph surviving into NW Pinal County and
Maricopa County. Similar to last night, these outflows will have the
potential of triggering storms in the lower deserts, however the
location of where exactly storms are likely to develop in the lower
deserts is where model agreement begins to fall apart. As mentioned
previously, development is still favored for tonight as the
atmosphere continues to see similar conditions to last night. Hi-res
models continue to show CIN eroding to below 100 J/kg and MLCAPE
climbing near to slightly above 1000 J/kg this evening. With these
conditions, strong downburst wind gusts and locally heavy rainfall
will continue be the main hazards across the lower deserts of south-
central AZ, to include portions of the Phoenix area. There will also
be a potential for areas of blowing dust to materialize as well in
the dust prone areas. Atmospheric conditions will not vary much on
Tuesday, especially in the eastern higher terrain, however,
depending on this evening`s activity Tuesday could turn out to be
more of a down day for the lower deserts.

Otherwise, afternoon high temperatures today will continue to be
above normal, ranging between 105-110 degrees, resulting in
widespread Moderate HeatRisk. Out west the dew points will remain
quite high, in the mid 60s to mid 70s, resulting in heat indices
peaking between 110-120 degrees this afternoon. Due to this the
Extreme Heat Warning remains in effect through this evening along
the Lower Colorado River Valley and the Imperial Valley. By Tuesday
temperatures "cool" slightly back near normal, and the HeatRisk
becoming widespread minor to localized Moderate, with Moderate
mostly across the western lower deserts.

&&

.LONG TERM /Wednesday through Sunday/...
Model guidance continues to be consistent in indicating another more
active period materializing Wednesday into the first half of
Thursday. The flow by Wednesday is forecast to shift out of the
south as the subtropical high shifts into Texas and a upper-level
low meanders off the California coast. This southerly flow is likely
to bring additional moisture northward from Mexico, with projected
PWATs increasing to 1.7-2.0" and low-level mixing ratios increasing
to 12-13 g/kg. In addition, there will likely more favorable upper-
level forcing from the aforementioned upper-level low in the form of
divergence aloft as well as the potential of an easterly wave moving
into the region from Mexico as indicated by both the GFS and ECMWF.
The more favorable upper-level forcing is likely to enhance the
convective activity, with flash flooding becoming more of a threat
given the deeper moisture profiles that will be in place. The latest
NBM PoPs for Wednesday through the first half of Thursday remain
elevated, ranging between 40-60% across much of south-central and
southeast AZ.

Heading towards the end of the week and next weekend, the guidance
is in good agreement in showing the subtropical high relocating
towards the Gulf Coast Region while the aforementioned upper-
level low remains situated off the west coast. This pattern
configuration will cause the flow to shift more out of the
southwest, bringing in a drier airmass as PWATs drop under
1.2-1.3". As a result, an overall downtrend in thunderstorm
activity is expected, with afternoon activity limited to the
eastern third of AZ.

Temperatures during the middle to latter half of the week will run
slightly below normal as afternoon highs will top out in the low
100s across the south-central AZ lower deserts to the mid 100s
across the western deserts. In fact, with the potential for abundant
cloud cover as well as lingering rainfall activity, afternoon highs
on Thursday may struggle to reach the triple digits across the south-
central AZ lower deserts. Temperatures will gradually rebound Friday
and into next weekend but remain near seasonal levels with no
extreme heat in sight for at least the next seven days.

&&

.AVIATION...Updated at 1800Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The primary aviation concerns this evening will once again be the
potential for gusty outflow winds, blowing dust, and reduced vsby
due to TS at the metro terminals. Over the next several hours,
westerly winds around 10-11 kts are expected with gusts into the
teens to around 20 kts developing during the afternoon. Confidence
in the wind forecast decreases considerably this evening with many
discrepancies still existing from the arrival of potential outflow
boundaries. Thunderstorms are expected to again form over the high
terrain to the north and east of Phoenix and in southeast AZ. Both
complexes of storms will be capable of producing long-lived
outflows which will push towards the terminals by this evening.
The northeasterly outflow may briefly cause an easterly shift, but
the southerly outflow is likely to be the stronger of the two.
These outflows could carry some blowing dust, especially the
southerly outflow and then may be followed by TS development in
the Phoenix area mainly between 04Z-06Z tonight. Amendments will
likely be needed to the current TAF as conditions evolve.

Southeast California/Southwest Arizona including KIPL and KBLH:
No major aviation weather concerns are expected through the next
24 hours under periods of FEW-SCT mid to high cloud decks and
otherwise mostly clear skies. At KIPL, winds will primarily stay
southeasterly with a switch to westerly by this evening. There is
a low chance (10%) for an isolated strong TS within the vicinity
of KIPL this afternoon, which could cause an abrupt wind shift
(likely out of the southwest) and strong gusts. At KBLH, winds
will generally fluctuate between SSE and SSW. Overall, wind speeds
should generally remain AOB 12 kts.

&&

.FIRE WEATHER...
Gradual cooling temperatures to near to slightly below normal
levels can be expected throughout the week. Elevated moisture
will maintain afternoon MinRHs between 20-30% each afternoon
along with good to excellent overnight recoveries. The chances for
shower and thunderstorm activity as well as wetting rainfall will
remain elevated through the middle of the week, especially across
the eastern districts. The chances for showers and thunderstorms
will decrease noticeably by the end of the week through next
weekend as drier air filters in. Outside of gusty and erratic
winds due to thunderstorms, winds will follow the familiar diurnal
trends, with typical afternoon upslope breeziness around 20 mph.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST this evening for AZZ530-532.

CA...Extreme Heat Warning until 8 PM PDT this evening for CAZ563-566-
     567-569-570.

&&

$$

SHORT TERM...Ryan
LONG TERM...Lojero
AVIATION...Salerno
FIRE WEATHER...Ryan/Lojero