Glendale, Arizona Weather Forecast Discussion

840
FXUS65 KPSR 260508
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
1005 PM MST Thu Sep 25 2025
.UPDATE...
Updated Aviation
&&
.KEY MESSAGES...
- Showers and a few thunderstorms will continue through the
overnight across higher terrain east of Phoenix.
- Thunderstorms and rainfall will become more widespread across
south-central and eastern Arizona Friday. A few strong to severe
storms will be possible along with locally heavy rainfall that could
result in flash flooding.
- Temperatures will fall into a below normal range Friday, and
continue through the weekend with lingering chances for showers and
thunderstorms.
&&
.SHORT TERM /Today through Friday/...
The threat for strong to severe thunderstorms capable of producing
damaging winds, hail, and flash flooding will exist Friday. A Flood
Watch remains in effect for portions of south-central Arizona,
including the Phoenix metro.
Latest afternoon objective analysis shows an upper level closed low
now beginning to propagate inland and is currently centered over
central California. Given the position of the low and a ridge axis
near the AZ/NM state line, increased diffluence aloft has aided in
thunderstorm development for areas across southern Gila County where
a better axis of CAPE values upwards of 1500-2000 J/kg exists,
according to the latest RAP analysis. Chances for a few
showers/thunderstorms will exist through the overnight hours with
guidance keeping this primarily focused east of Phoenix.
The best chances for showers and thunderstorms will occur on Friday
as the aforementioned upper low shifts toward the southeast and
repositions over southern California. The better forcing along with
daytime heating maximizing MUCAPEs upwards of 1500 J/kg should align
from central Phoenix and points east resulting in increasing
thunderstorm coverage by late Friday morning and afternoon. Models
are showing the best instability and forcing to occur along with a
fairly robust 25-35 kts of 0-6km shear. This convective setup is
likely to result in a few hour period focused during the afternoon
hours Friday where several strong to severe thunderstorms are likely
to impact south-central Arizona. Model forecast soundings are
supportive of strong to severe winds, potentially some marginally
severe hail, and heavy rainfall. Guidance shows locations across
central Pinal County into eastern Maricopa County will have the best
chances for seeing strong to severe storms, but the threat may
extend through the entire Phoenix metro into the higher terrain east
of Phoenix.
The greatest threat for heavy rainfall Friday is expected to remain
across eastern portions of Maricopa and Pinal Counties and into
southern Gila County where training thunderstorms are most likely to
occur. However, some of the latest hi-res guidance show some of
these training thunderstorms extending into portions of the Phoenix
metro, particularly across the east Valley. The latest HRRR
indicates a westward propagating outflow pushing through the metro
tomorrow afternoon helping to spark new training convective
development. Not everyone is guaranteed to see heavy rainfall in the
Phoenix area, however, conditions are favorable enough that the
Flood Watch has been expanded to include the Phoenix metro with
instances of flash flooding possible. Rainfall amounts upwards of 1-
2" are likely to fall in some areas with very localized higher
amounts also possible.
&&
.LONG TERM /Saturday through Wednesday/...
By Saturday, the cut-off low will be quickly weakening with upper
level forcing waining while instability will be much more limited
than what is expected on Friday. Considerable cloudiness is also
likely to affect much of the area on Saturday limiting
destabilization. However, lingering moisture, residual weak upper
level forcing, and modest lapse rates should promote isolated to
scattered showers and thunderstorms more so during the afternoon
hours anywhere from southeast California into southern and central
Arizona. Additional rainfall amounts Saturday should be on the
lighter side, but we can`t rule out some very localized 0.50-0.75"
amounts due to the lingering convective potential.
Models are in good agreement the cut-off low will begin to open up
and quickly move northeast of the area during the day Sunday. Sunday
may allow for some isolated afternoon showers and a few
thunderstorms, but these are likely to be focused over the Arizona
high terrain. By Sunday night into Monday, our region will
transition more into zonal to weak ridging as a deep Pacific low
moves southward to off the Pacific Northwest coast. This will help
to usher in dry air across the region ending any rain chances by
Sunday night.
Temperatures will take a dive Friday into the weekend with the help
of the cut-off low and the rain cooled air. Forecast highs this
weekend are currently only in the upper 80s across the bulk of the
lower deserts, or 5-8 degrees below normal. Once we start to see
weak ridging back into our region early next week, highs should
creep up into the low to mid 90s by Monday or Tuesday.
&&
.AVIATION...Updated at 0505Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Several weather hazards will impact operations through Friday night
including abrupt wind shifts along outflow boundaries, periods of
cigs below 6K ft AGL, and potentially multiple rounds of TSRA with
MVFR or lower flight categories. An outflow boundary has essentially
stalled over KPHX late this evening, however confidence is good that
more pronounced E/SE winds will be reinforced after midnight, then
tend to veer more southerly Friday mid/late morning with gusts 15-
20kt common.
Confidence is moderate that SCT-BKN decks around 050-060 AGL will
move into part of the PHX airspace mid/late Friday morning as winds
become more southerly. Confidence is lower regarding wind forecast
during the afternoon, and whether a true westerly component will be
realized. Models remain consistent in developing scattered TSRA
across at least the eastern half of the PHX metro Friday afternoon.
TSRA could potentially erupt as early as 19-20Z, but would be more
prevalent closer to 21-22Z. While models suggest gusty easterly
outflows, winds may be highly erratic and gusty for several hours
with the possibly several rounds of storms. Any direct impacts from
TSRA would likely result in periods of MVFR (or lower) flight
categories before a trend in activity exiting the aerodromes around
02-03Z.
Southeast California/Southwest Arizona including KIPL and KBLH:
Gusty winds at KIPL this evening will be the primary weather issue
through Friday night under mostly clear skies. Gusts 20-30kt at KIPL
should weaken shortly after midnight with overnight decoupling.
Confidence is excellent that westerly winds will prevail though the
period at KIPL, and oscillate between SW and S at KBLH with a
tendency towards more variability Friday night.
&&
.FIRE WEATHER...
Isolated strong to severe thunderstorms will continue into this
evening across the southern Gila County higher terrain with strong
erratic outflow winds and heavy rainfall being the primary concerns.
Chances for thunderstorms will decrease going west into the lower
deserts, however, gusty easterly outflow winds will be possible.
Friday is expected to bring fairly widespread showers and
thunderstorms across the eastern districts with strong outflow winds
and heavy rainfall likely in some areas. Min RHs will increase
Friday and Saturday to upwards of 25-45% for most areas. Outside of
thunderstorm impacts, winds will become breezy at times with
occasional gusts around 20-25 mph with some stronger gusts possible
across Imperial County. The slow-moving low pressure system
impacting the region should continue to bring chances for wetting
rains on Saturday before drying conditions begin Sunday into early
next week. Below normal temperatures are forecast for Friday through
at least Monday.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch from Friday morning through Friday evening for
     AZZ537-540>553-555>558-560>563.
CA...None.
&&
$$
SHORT TERM...Smith/Kuhlman
LONG TERM...Kuhlman
AVIATION...18
FIRE WEATHER...Smith/Kuhlman

NWS PSR Office Area Forecast Discussion