049
FXUS65 KPSR 290954
AFDPSR

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

.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 0505Z.

South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Weather issues through Tuesday evening will include periods of
SHRA/TSRA, lower CIGs, and erratic wind directions. A break
impactful weather will likely persist for several hours beyond
midnight, though cigs could locally flirt with 6K ft AGL. Confidence
remains good that periods of SHRA/TSRA, lowering cigs, and periods
of MVFR vsby will impact terminals in a 09-15Z time frame. MVFR vsby
appears almost certain in moderate SHRA with cigs falling below 6K
ft AGL. Brief instances of IFR vsby/MVFR cigs are possible around
sunrise, however temporal and areal extent should be limited.

Winds may become highly erratic in SHRA/TSRA overnight, potentially
obtaining a prolonged period of a northerly direction, however
directions should become E/NE as SHRA move east of terminals during
the mid morning. Guidance suggests directions quickly shifting to
westerly early Tuesday afternoon as 040-050 BKN decks develop with
afternoon heating. After sunset, lower cigs will dissipate while
winds weaken, then obtain the traditional nocturnal east component
by midnight.

Southeast California/Southwest Arizona including KIPL and KBLH:
The main weather issues will be SHRA/TSRA exiting the KBLH tonight,
then gusty NW winds Tuesday. Confidence is good that winds will
gradually veer to a W/NW component overnight, as scattered SHRA/TSRA
move eastward into Arizona. Probability of direct impacts at KBLH
are too low to include in this TAF, but brief heavy rain and lowered
vsby are possible overnight. Confidence is excellent that winds will
settle on a N/NW direction Tuesday with gusts 20-30kt developing in
the afternoon.

&&

.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 through this evening for AZZ534-537>563.

CA...None.

&&

$$

SHORT TERM...Kuhlman
LONG TERM...Kuhlman
AVIATION...18
FIRE WEATHER...Kuhlman

NWS Phoenix (PSR) Office