812
FXUS65 KPSR 101947
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1247 PM MST Sun Aug 10 2025

.KEY MESSAGES...

- Above normal highs and warm overnight lows will continue to
  yield widespread Moderate to localized Major HeatRisk through
  early this week.

- Major HeatRisk will be concentrated particularly over the
  central AZ lower deserts, the Lower Colorado River Valley, and
  Imperial Valley where Extreme Heat Warnings remain in effect
  through Tuesday evening.

- Chances for showers and thunderstorms will continue to remain quite
  limited through the first half of this week, generally favoring
  the eastern Arizona high terrain.

- Increasing moisture by late week will result in better coverage
  of thunderstorm activity across much of the region including
  the lower deserts

&&

.SHORT TERM /Today through Tuesday/...
The latest objective analysis shows the 850-300mb mean flow out
of the north to northwest in response to a large trough situated
over the central CONUS and a ridge repositioning over northern CA.
Another round of thunderstorm activity is expected to develop
over the Mogollon Rim this afternoon and steered southward towards
portions of southern Gila County and possibly into northern
Maricopa County. As the activity attempts to descend into the
lower elevations, it will be on a weakening trend due to strong
convective inhibition present across the lower deserts. However,
even though the activity will be on a weakening trend, some gusty
outflow winds may still affect the area. Based on the latest HREF,
with chances of gusts of 35+ mph is at 10-30% across the lower
deserts of south-central AZ and near 50% across the higher
elevations to the east of Phoenix. Another area that may see an
isolated thunderstorm this afternoon is across Joshua Tree
National Park as enough moisture combined with orographic lift
will result in conditions favorable for isolated development.

Heading into Monday and Tuesday, the northerly flow aloft will
result in a decrease in the overall moisture content and thus
thunderstorm coverage will become more isolated, with the best
chances confined across the eastern and southeastern third of
AZ. As the upper-level ridge strengthens slightly, resulting in a
slight increase in heights aloft, temperatures will be on the
slight increase as well with afternoon highs ranging between
108-112F across the south-central AZ lower deserts and 110-115F
across the western deserts. These high temperatures in combination
with warm overnight lows will result in areas of Major HeatRisk to
continue, particularly over the lower-deserts of south-central AZ
as well as across the Lower Colorado River Valley and Imperial
Valley with Extreme Heat Warnings remaining in effect through
Tuesday evening.

&&

.LONG TERM /Wednesday through Saturday/...
Starting Wednesday, ensemble guidance continues to indicate a
trough entering the Pacific Northwest while the ridge over the
Great Basin begins to weaken and shift eastward toward the Four
Corners area. This will allow a more favorable E-SE flow to set up
over the forecast region. Despite some model uncertainty between
the EPS and GEFS regarding timing of the better moisture return,
the overall trends during the latter half of next week favor
increasing moisture (PWATs reaching 1.4"-1.6") followed by a
return of monsoon rain chances by the Thursday through Saturday
timeframe. NBM PoPs continue to trend upward by the latter part of
this week, peaking around 20-40% across the lower deserts on
Thursday and Friday. Due to the increasing moisture, a cooling
trend is expected to transpire from Wednesday-Saturday, with highs
falling back into the normal range by next weekend.

&&

.AVIATION...Updated at 1730Z.

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

Main challenges and uncertainty for this forecast will be with
any potential for wind shifts from outflows later today. Most
storms forecast well removed from TAF sites, so outflows right now
appear to wash out before being an impact to TAFs. There is a low
chance (20%) that a north/northeast outflow could push into the
valley in the 01z to 04z timeframe. Confidence is low so have not
included yet until we monitor trends with late day storms.
otherwise any diurnal windshift overnight could be subtle and
more light and variable.

Southeast California/Southwest Arizona including KIPL and KBLH:

No aviation weather concerns are expected over the next 24 hours
under generally clear skies. Winds at KIPL will generally remain
out of the SE through Sunday afternoon, while KBLH will continue
to see more S`rly winds with some occasional afternoon gusts
around 20 kts.

&&

.FIRE WEATHER...
Above normal temperatures will continue through the middle of this
week. There will continue to daily thunderstorm activity over the
high terrain through the first half of the week followed by a better
potential for scattered showers and thunderstorms across much of
the region late in the week. Chances of wetting rainfall will
remain below 10% over the next few days, resulting in potential
for dry lightning and new fire starts. Minimum afternoon humidity
levels will mostly range between 15-20% with fair to good
overnight recoveries. Winds will retain an afternoon upslope
component with gusts to 15-20 mph common.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Extreme Heat Warning until 8 PM MST Tuesday for AZZ530-532-534-
     537>544-546-548>551-553>555-559.

CA...Extreme Heat Warning until 8 PM PDT Tuesday for CAZ562-563-566-
     567-569-570.

&&

$$

SHORT TERM...Lojero
LONG TERM...Salerno
AVIATION...Frieders
FIRE WEATHER...Salerno