Phoenix Municipal Stadium Arizona Weather Forecast Discussion

755
FXUS65 KPSR 072325
AFDPSR
Area Forecast Discussion
National Weather Service Phoenix AZ
425 PM MST Tue Oct 7 2025
.UPDATE...Updated 00Z Aviation Discussion
&&
.KEY MESSAGES...
- Near to slightly above normal temperatures are expected through
  mid-week, peaking in the upper 90s to 100 degrees across the
  south-central Arizona lower deserts on Wednesday.
- Abundant moisture and rainfall will promote cooling temperatures
  this weekend with highs mainly the the upper 70s to mid 80s
  across the region starting Saturday.
- A period of active weather with multiple rounds of showers and
  embedded thunderstorms will begin by Thursday and persist into
  the weekend. Some locations could receive higher rainfall totals
  exceeding 2.00" which will promote excessive runoff into area
  watersheds, leading to flooding of low lying areas.
&&
.SHORT TERM /TODAY THROUGH WEDNESDAY/...
Latest GOES-18 wv and visible satellite imagery reveals an upper-lvl
pattern that is largely unchanged since yesterday with high pressure
aloft currently influencing weather across the Desert Southwest. The
subtropical high will keep the region dry with clear skies and above
normal temperatures through this afternoon and much of tomorrow.
High temperatures today will max out in the mid to upper 90s across
the lower deserts and upper 80s to lower 90s across the higher
terrain areas. High temperatures on Wednesday will increase by a few
degrees into the upper 90s to 100 degrees at Phoenix Sky Harbor.
This could very well be the last 100 degree day we see in Phoenix
this year. Dew points will still remain in the 30s and 40s tonight,
allowing temps to cool down into the upper 60s to lower 70s.
Hurricane Priscilla, which currently has a well defined circulation
and eye wall, is now located about 80 miles south of the tip of the
Baja Peninsula. This large category 2 storm is expected to continue
to track slowly N-NW and gradually weaken to a Tropical Storm and
eventually becoming a Depression later this week as it interacts
with cooler water off the coast of the Baja California. Low-lvl
moisture well out ahead this storm will begin to be drawn into
southern and southeastern AZ on Wednesday afternoon. Model
guidance shows PWATs nearing 1.25" across southeast Arizona or
around 200% of normal. As this moisture intrusion occurs, we will
see rain chances increase mainly across southeastern AZ. There
could be a few weak showers and isolated storms over the higher
terrain areas of S Gila County Wednesday afternoon. Given the
drier boundary layer in place across much of our forecast area, we
may even see gusty outflow winds from activity in the high terrain
reach the lower deserts early Wednesday evening. Moisture advection
will continue Wednesday night into which will promote increasing
cloud cover and shower activity heading into Thursday morning.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Forecast confidence is increasing in a long duration rain event
starting Thursday and lasting through at least Saturday. The main
drivers of this upcoming active period of weather will be the
record moisture from TC Priscilla advecting into our region for
Thursday through Saturday and the upper level dynamics from a
Pacific trough setting up to our northwest starting late Thursday.
Over the past 24 hours, models have trended even wetter while the
track of Priscilla has turned more to the east by Friday. Our
biggest concern is the amount of rainfall locations across south-
central and eastern Arizona will receive over the 2-3 day period.
The lack of expected instability during the event will likely
hinder thunderstorm development, but the amount of moisture and
the persistent forcing are expected to lead to intermittent
periods of at least moderate rainfall which may eventually lead
to flooding issues in some areas.
Strong moisture advection will continue Wednesday night into
Thursday with PWATs of 1.5-1.9" spreading over the entirety of the
lower deserts by Thursday afternoon. This amount of moisture for
the second week of October is basically unprecedented with
guidance showing a large area of record high PWATs stretching from
the Lower CO River Valley through the majority of Arizona.
Because moisture is expected to be throughout the entire
atmospheric column, lapse rates will be very marginal resulting in
MUCAPEs mostly below 500 J/kg. Since instability and DCAPEs will
be very limited, the chances of seeing strong storms should be
small. However, given 0-6km shear will be on the higher side for
much of the event we can`t completely rule out a few rotating
discrete storms that could produce some very localized strong
winds.
Rain chances should increase steadily Thursday into Friday with
the highest rain chances falling on Friday and Saturday. Showers
with some occasional embedded thunder should start off by Thursday
morning focused more to the north of the Phoenix area
southwestward into southeast California and southwest Arizona. Jet
forced dynamics along with weak to moderate southerly mid-level
upslope flow will help to drive the rain activity on Thursday. For
now, QPF amounts on Thursday are likely to stay on the lighter
side, but we can`t rule out some localized amounts upwards of
0.5".
For Friday, we are likely to see a bit stronger jet forced and
upslope ascent with periods of moderate to possibly heavy showers
and embedded thunder. The best potential for persistent training
of activity is likely to be over south-central Arizona with a
focus in the foothills and mountain areas north and northeast of
Phoenix. Friday`s rain activity should easily be enough to get
washes flowing in many areas with some low-land minor flooding
also possible. Expected rainfall amounts for Friday are likely to
range from 0.25-0.50" across southeast California and southwest
Arizona to 0.5-0.75" across much of south-central Arizona. This
also places the bulk of the area in a Marginal Risk (5-10%) for
localized flooding.
Guidance currently shows the peak of the rainfall event is likely
to occur Friday night and Saturday with the potential mid-level
remnants of TC Priscilla passing through portions of our region.
This timeframe should also match up with stronger mid-level
upslope flow as the Pacific trough to our northwest moves onshore
into northern California and Nevada. Models show a strong
35-50kts of mid-level southwesterly flow for Saturday centered
over central Arizona. The combination of this impressive upslope
forcing and the continuation of the upper level dynamics may allow
for a band of moderate to heavy rainfall to form across the area,
likely focused across central Arizona. Localized rainfall rates
upwards of 0.50-1.00" per hour may occur on Saturday leading to
localized additional accumulations of 1-2". WPC has placed much of
central and northern Arizona in a Slight Risk for excessive
rainfall on Saturday.
Predicting the amount of rainfall for Thursday through Saturday
is not easy, but models are definitely showing impressive amounts
for much of Arizona. The latest guidance shows average amounts of
up to 0.5" over southeast California and 0.5-1.0" over southwest
Arizona. The highest amounts are likely to be over central and
eastern Arizona where 1-1.5" is likely across the lower deserts to
1.5-2.5" over higher terrain areas. These are just the average
expected rainfall amounts through Saturday and it`s quite likely
some locations will see higher amounts. In fact for Phoenix, there
are roughly 30% of the GEFS members and 20% of the EPS members
showing greater than 2" of rainfall. Given much of this rainfall
is likely to be spread out over a couple of days, urban flooding
is not expected. However, it seems quite likely washes and small
streams/creeks will see some decent flow with some flooding
possible.
The rain for some areas is not likely to be over after Saturday
as the Pacific trough to our north northwest will stick around and
a second tropical system may attempt to move up Baja at some point
on Sunday into early next week. Forecast uncertainty is even
higher for this next potential weather system, but for now its
more likely to affect southeast Arizona to maybe as far north as
south-central and east-central Arizona. Our forecast does put a
20-40% chance for rain on Sunday and Monday, but it could be
underdone depending on what happens with the next tropical system.
Guidance does show potential for another 0.5-1.0" of rainfall for
portions of our area on Sunday and Monday, but as stated earlier
uncertainty is quite high.
Temperatures are mostly an afterthought given the potential for
impactful rainfall later this week. Guidance has definitely
trended cooler given the higher likelihood of widespread rainfall.
NBM forecast highs are now only in the lower 90s by Thursday with
at least the western deserts down into the 80s starting Friday.
By Saturday, the entire lower deserts should be well into the 80s
for highs, or at least 5 degrees below normals. Highs very well
could average in the mid 80s through early next week depending on
what happens with the second potential tropical system.
&&
.AVIATION...Updated at 2324Z.
South Central Arizona including KPHX, KIWA, KSDL, and KDVT:
No aviation concerns are expected during the TAF period. Typical
diurnal tendencies will continue through most of the TAF period
with periods of VRB this evening. However winds will develop a
S`rly flow tomorrow afternoon instead of the typical W`rly
direction. Clear skies will prevail through tonight before FEW
mid-level clouds start to filter in over the region.
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 extended periods of VRB
to even calm conditions. Clear will persist through Wednesday
morning, where then FEW mid-level clouds will develop Wednesday
afternoon.
&&
.FIRE WEATHER...
Dry conditions with clear skies and no rain chances are expected
through tonight with only minimal chances for an isolated shower
or thunderstorm across Gila County on Wednesday. Temperatures will
remain slightly above normal through Wednesday. Expect light and
diurnal winds to continue across the lower elevations with some
afternoon upslope gusts around 20-25 mph across the higher terrain
of southcentral AZ. Minimum humidity will bottom out around
10-15% today before improving quickly from east to west Wednesday
into Thursday. On Thursday, we are likely to see a shift to a more
active period of weather with abundant moisture helping to bring
shower and thunderstorm chances to the area. There will be chances
for wetting rainfall from Thursday through at least Saturday.
There is also some potential for heavy rainfall during this time,
but forecast uncertainty remains high. MinRHs will at least
increase into the 20-30% range by Thursday and likely higher by
the weekend with overnight recoveries of 45-65%. Due to the
increase in moisture and rain chances, temperatures will gradually
cool from near normal to below normal by this weekend.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...None.
CA...None.
&&
$$
SHORT TERM...Salerno
LONG TERM...Kuhlman
AVIATION...Ryan
FIRE WEATHER...Kuhlman/Salerno

NWS PSR Office Area Forecast Discussion