462
FXUS65 KPSR 182316
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
416 PM MST Fri Jul 18 2025

.UPDATE...Updated Aviation Discussion.

&&

.KEY MESSAGES...

- A few isolated showers or weak storms may form over prominent
  terrain features this afternoon, such as in Western Joshua Tree
  National Park, La Paz County, and Tabletop Mesa south of Phoenix.

- Chances for showers and thunderstorms mostly confined to the
  eastern Arizona high terrain and southeastern portion of the
  state this weekend through the middle of the upcoming work week.

- Temperatures hover near to slightly below daily normals through
  the middle of next week, with lower desert highs generally
  between 100 and 108 degrees, resulting in Minor to Moderate
  HeatRisk.

&&

.SHORT TERM /TODAY THROUGH SATURDAY/...
Convective cumulus developed rapidly across the region today, but
so far the cumulus have mostly struggled to see much vertical
growth. Even the showers that have developed so far over the AZ
high terrain north of Phoenix have been fairly weak and short-
lived. There are a few factors contributing to this today,
including an active drying trend. Despite mesoanalysis showing
very limited inhibition, CAPE values are relatively low, sub-
optimal for strong updrafts, and forcing is very limited. Surface
to 6 km shear of 25-35 kts is also shearing off some of the early
afternoon updrafts. Still spotty convection is expected this
afternoon, mainly favoring terrain areas like Joshua Tree NP, the
Kofas and Harcuvar Mtns in La Paz County, Tabletop Mesa south of
Phoenix, and southern Gila County. Strong storms are not expected
in this environment. HREF neighborhood probabilities for 40 dBZ
radar echoes is quite low for most of the area at 5-10%. So,
expect very minimal impacts from any convective showers today.
Similar conditions are expected tomorrow, but with continued
drying, most notably out in western AZ and SoCal, afternoon
convection will mostly be limited to the high terrain east of
Phoenix. There is potential as well for some overnight and early
morning high-based convection in South-Central AZ through Sunday
morning, with any mid-level gravity waves emanating from stronger
monsoon activity well to the east and southeast, as supported by
a few hi-res models, including the HRRR. If any of this activity
materializes it could provide some rumbles of thunder, a brief
light rain, and localized gusty winds, but that is about it.

Aside from the meager storm chances the next couple of days,
temperatures will continue to hover right around seasonal norms,
with high pressure centered over the Southern Plains and a
weakening low pressure centered over Northern Baja, keeping H5
heights around seasonal levels (589-592 dam). Lower desert highs
the next couple of days will be around 104-109 degrees, with
tomorrow being the warmer of the two days. Morning lows will
mostly be in the 80s. Despite being seasonal, these temperatures
will result in Moderate HeatRisk for all lower desert communities.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Overall quiet and not so hot weather conditions are expected to
continue through the middle of the upcoming workweek. As a result
of the upper level flow pattern (dry S-SW flow over much of the
CWA with S-SE flow encroaching on eastern AZ), which should be
maintained through Monday, ensemble mean PWATS should continue to
remain around 100-120% of normal over the eastern half of the
state, allowing daily chances (20-35%) for isolated showers and
thunderstorms over the high terrain (Rim, White Mountains) and
southeastern portion of the state. Chances for showers/storms over
the South-Central AZ lower deserts remain generally below 15%,
though chances may improve slightly Monday PM with some models
indicating additional moisture drifting northwestward from Mexico.
Early next week, the very weak upper low over SoCal is likely to
join with a trough over the Pacific Northwest that is then
advertised to split off of the northern stream and retrograde
offshore, settling off the CA Coast midweek. During this time, the
proximity of this trough will act to suppress heights aloft and
strengthen deep SW flow over the region, resulting in ensemble
mean PWATS dropping to around 50% of normal by the latter half of
the upcoming workweek and further suppressing rain chances. The
latest NBM continues to show afternoon highs near or even a few
degrees below normal through midweek. This should keep the
HeatRisk over our area anywhere from high-end Minor to low-end
Moderate.

&&

.AVIATION...Updated at 2315Z.

South Central Arizona including KPHX, KIWA, KSDL, KDVT:
No major aviation concerns are expected during the TAF period.
There is a hint of a push of moisture, mid/high clouds and a light
shower or two into the vally late tonight after 08z, pushing
northeast from storms now moving into far southeast AZ. Have
introduced more mid/high clouds for this timeframe, but VCSH not
confident enough to include in any TAFs and not expected to be
impactful. Otherwise, winds will be generally light with a slight
diurnal shift out of the east or southeast late tonight if not
just variable.

Southeast California/Southwest Arizona including KIPL and KBLH:
No aviation concerns are expected over the next 24 hours. Winds
will continue to favor diurnal trends, with some periods of
variability, especially during the overnight and early morning
hours. Besides a FEW afternoon mid clouds, skies should be
generally clear.

&&

.FIRE WEATHER...
A few isolated showers or weak thunderstorms may form over
prominent terrain features across the area this afternoon, but
most places will stay completely dry and areas that do see a
shower or storm will see very little rainfall. Shower and storm
chances will remain limited to the South-Central Arizona high
terrain east of Phoenix this weekend, with perhaps a slight
increase in chances (15-20%) for the lower deserts Monday evening.
Afternoon MinRHs will be around 12-20% for most areas and nearly
every day. Winds should mostly follow diurnal patterns with only
light periodic breezes in the afternoons and early evenings, with
peak gusts mostly between 15-25 mph.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&

$$

SHORT TERM...Benedict
LONG TERM...Whittock
AVIATION...Frieders
FIRE WEATHER...Benedict/Whittock