154
FXUS65 KPSR 291808
AFDPSR

Area Forecast Discussion
National Weather Service Phoenix AZ
1108 AM MST Tue Sep 29 2026

.UPDATE...18Z Aviation Discussion.

&&

.KEY MESSAGES...

- Bands of light to moderate rain with isolated thunderstorms will
  continue through the rest of this morning for much of Arizona
  before gradually shifting more over eastern Arizona this
  afternoon.

- Flood Watches are in effect through early evening for most of
  Arizona with the peak of the heaviest rainfall occurring this
  morning.

- Below normal temperatures are expected to persist across much of
  Arizona through the rest of the work week, while near normal
  readings return to the western lower deserts starting
  Wednesday.

- Dry conditions will prevail from Thursday through early next
  week as high pressure and gradual warming takes hold across the
  region.

&&

.SHORT TERM /TODAY AND TONIGHT/...
Active weather will continue for at least the first half of today
as an unseasonably strong Pacific low pressure system moves
eastward through the Desert Southwest. The low center is now
located across southern California prompting strong forced ascent
through much of Arizona. Lower level moisture advection yesterday
pushed mixing ratios upwards of 10-12 g/kg with the best moisture
across far eastern Arizona. However, drier air aloft has also
begun to work its way in from the southwest as it wraps in around
the low center. This drier air may limit rainfall rates some, but
all in all will not prevent much of the area from receiving decent
rainfall through the rest of this morning.

Current objective analysis shows the best moisture pooling out
ahead of the low with PWATs of around 1.5" across far south-
central Arizona. Modestly strong mid-level southwesterly flow will
continue to provide upslope ascent ahead of the low, while forced
ascent aloft, which is currently maximized over southwest
Arizona, gradually shifts eastward through this afternoon.
Scattered showers and thunderstorms have developed across southern
and central Arizona since midnight with rainfall rates close to
two inches per hour for the stronger convective cells. However,
due to a 30-35 kt steering flow, the storm residence time over one
location will not be very long and training of cells will be
needed for heavy rainfall amounts. A few of the thunderstorms are
also becoming more discrete and potentially strong enough to bring
strong winds to the surface. Although we can`t rule out strong to
near severe winds with the strongest storms, it is quite unlikely
due to the very limited (250-500 J/kg) CAPE. The biggest threat
for the rest of this morning will continue to be periods of
moderate to heavy rainfall with training of storms bringing
localized rainfall amounts of 1-2" of over a few hour period.
Flood Watches are now in effect for much of south-central and
eastern Arizona and last through early evening.

CAMs show these scattered showers and thunderstorms eventually
forming a somewhat broken line by sunrise as they slowly
transition from west to east. The peak of the rainfall for the
Phoenix metro is likely to fall between 4 AM and 8 AM this morning
before shifting mostly east of the Phoenix area later this
morning. The highest rainfall amounts are expected to be focused
across the higher terrain northeast and east of Phoenix from
around sunrise through noon. The band of showers and thunderstorms
is likely to fill in more by around sunrise as it begins to move
into eastern Arizona before winding down late morning into the
early afternoon. The threat for flash flooding will also peak
later this morning with the bulk of shower and thunderstorm
activity shifting out of our area this afternoon.

As the low center moves into central Arizona this afternoon and
evening, we are likely to have additional wrap-around showers and
thunderstorms but mostly focused over the higher terrain between
Flagstaff and Phoenix. We should have a few of these storms move
into northern La Paz, northern Maricopa, and eventually into Gila
County this evening but CAMs mostly show isolated to at most
scattered coverage. It seems likely the CAMs are underplaying this
potential, so it would not be surprising to have another round of
rainfall this evening across south-central Arizona. Lingering
chances for some showers and maybe some embedded storms will
remain possible over the eastern Arizona high terrain into the
overnight hours tonight before the low eventually ejects into New
Mexico by sunrise Wednesday morning.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Wednesday will be a transition day as the Pacific low gradually
exits the region. Some morning scattered showers are likely to
still be across the far eastern Arizona high terrain, but any
activity should quickly wind down in the afternoon. Elsewhere on
Wednesday, sunny skies and warmer temperatures are forecast for
southeast California and southwest Arizona while the south-
central Arizona lower deserts will see some lingering clouds and
well below normal temperatures.

Model guidance shows upper level ridging fully moving into our
region on Thursday and likely staying put through the upcoming
weekend. This will lead to gradual drying and mostly clear skies
while temperatures slowly rise closer to the normal range for the
south-central Arizona lower deserts. The western lower deserts
may reach 100 degrees again starting Friday, but for the eastern
half of Arizona some reinforcing cooler air from the east Friday
through Saturday should keep daytime highs at or just above 90
degrees through Saturday. This cooler easterly flow may even
continue into early next week with temperatures in the Phoenix
area staying right near seasonal normals for early October.

&&

.AVIATION...Updated at 1740Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
The main aviation weather concern throughout the TAF period will
be the lower CIGs through this evening. Most of the rainfall
activity that affected the area earlier this morning has pushed
well east of the terminals. There is a chance of a few spotty SHRA
later this afternoon/evening in the vicinity, however, chances of
occurrence is low at less than 20% and thus not mentioned in the
latest TAF package. The main issue through this evening will be
the CIGs with SCT-BKN coverage as low as 5-6 kft expected. Winds
this afternoon will be mainly out of the west with speeds aob 10
kts, with a return of the traditional nocturnal east component by
03-04z.

Southeast California/Southwest Arizona including KIPL and KBLH:
The main aviation weather concern throughout the TAF period will
be gusty north to northwest winds during the afternoon. Winds this
afternoon will be out of the north to northwest, shifting more out
of the west at KIPL early this evening. Afternoon gusts upwards of
20-25 kts are likely before subsiding by this evening.

&&

.FIRE WEATHER...
Widespread showers and isolated thunderstorms will affect much of
the area early today before mainly affecting the Arizona high
terrain this afternoon and evening. Moderate to heavy rainfall is
likely to impact the Arizona high terrain through at least early
afternoon. Humidities will begin to trend lower across the western
districts later today, but more so on Wednesday. Elevated
humidities will persist across the eastern districts through at
least Thursday. Winds will be breezy to locally windy at times
today before becoming light again on Wednesday. Drier conditions
and near to slightly above normal temperatures are forecast for
later this week and through the weekend.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Flood Watch until 9 PM MST this evening for AZZ534-537>563.

CA...None.
&&

$$

SHORT TERM...Kuhlman
LONG TERM...Kuhlman
AVIATION...Lojero
FIRE WEATHER...Kuhlman