151
FXUS64 KEWX 300555
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1255 AM CDT Wed Sep 30 2026

...New SHORT TERM, LONG TERM, AVIATION...

.KEY MESSAGES...
Updated at 1200 AM CDT Wed Sep 30 2026

- A Flood Watch is in effect from Wednesday evening through Friday evening
  for much of South Central Texas. Heavy rainfall may lead to
  life-threatening flash flooding somewhere in the Watch area.

- Some storms Wednesday night through Friday morning may become strong
  to severe with strong wind and hail the main hazards. Flooding
  continues to be the main concern.

- Low to medium rain chances linger through the weekend then
  decrease heading into next week.

&&

.SHORT TERM...
(Today through Thursday)
Issued at 1200 AM CDT Wed Sep 30 2026

Regional satellite imagery shows an upper level low over
southern Arizona while the remnants of Hurricane Polo have quickly
raced northeast into northern Mexico, and broad southwesterly
flow is beginning to slide eastward over south central Texas. At
the surface, southeasterly low-level flow will begin to ramp up in
response the approaching upper-level low and associated surface
low and trailing cold front. PWATs per the latest HREF will
rapidly climb to near record territory, around 2.1-2.4" Wednesday
afternoon. Despite additional cloud cover, the added humidity will
make it feel even hotter Wednesday. Thankfully, it looks as if
this will be our last truly hot day in awhile as cooler
temperatures and daily rain chances are in the picture through the
remainder of the forecast.

Tonight, we expect to see an increase in coverage of precipitation
as mid to upper level forcing arrives from the west. For Wednesday-
Wednesday night, there is a level 2 of 4 (Slight) risk for flooding
from the I-35 Corridor and westward, and a level 3 of 4 (Moderate)
risk for the western Hill Country, Edwards Plateau, and northern Rio
Grande Plains. There may be some ongoing convection early this
morning, but the bulk of the rain and storm coverage will develop
later this evening and continue through the overnight hours into
early Thursday over the Rio Grande Plains and Edwards Plateau. HREF
members and REFS members show storms developing and training over
these areas mentioned above tonight into early Thursday. Some of
these members even show storms developing further east closer to San
Antonio, but development further west initially makes the most sense
given the setup.

On Thursday, WPC places a Level 2 to 3 of 4 risk over much of south
central Texas, with a Level 3 of 4 (Moderate) risk in place for the
Hill Country, I-35 Corridor, southern Rio Grande Plains, and eastern
parts of the Edwards Plateau. A line of convection oriented
northeast to southwest should develop on Thursday and slowly slide
eastward. At this time, it is still uncertain how quickly the
Pacific front will push east and south, so there remains concerns
for heavy rains to linger over the Hill Country or I-35 Corridor
Thursday afternoon and Thursday night. Convection may be ongoing
Thursday morning and how far south and east the front moves will
determine how long heavy rains linger over the I-35 Corridor. We
could see widespread rainfall amounts of 2-4" with local amounts up
to 8 inches Wednesday night through Friday morning, and a Flood
Watch is in effect for all areas except portions of the Coastal
Plains from 7pm today to 7pm Friday.

&&

.LONG TERM...
(Thursday night through Tuesday)
Issued at 1200 AM CDT Wed Sep 30 2026

Thursday night through Friday will be the most hardest part of
the forecast given the uncertainty in the timing and placement of
the cold front. The ECMWF and GFS guidance and their ensembles are
in agreement on sending the front into the Coastal Plains by
Friday afternoon, but despite the front pushing further south,
some lingering convection is expected and with likely saturated
soils from Wednesday`s and Thursday`s rains, additional flooding
is possible.

For the weekend, some mid-level energy will remain in place which
may spark additional showers and storms each day. The mid to upper
level trough will get stuck over southwest Texas, resulting in those
continued rain and storm chances. By Monday, medium range guidance
shows cooler and drier weather along with pleasant humidity,
something we`ve waited months for. Fall is here.

&&

.AVIATION...
(06Z TAFS)
Issued at 1232 AM CDT Wed Sep 30 2026

A near solid line of convection looms to the west of DRT at the
TAF issuance time. A lot of the models dissipate this activity
quickly in the next couple hours so we are going conservative with
VCSH. This will probably not hold up though, and an AMD to DRT
will likely be issued to upgrade to a -TSRA prevailing for a
couple hours. After 09z conditions for convection are low end or
uncertain, so we`ll stick to the MVFR CIGs and carry on like the
prior morning have behaved with a mid-morning burn-off. Afternoon
convection is possible over most areas, but we`ll defer to the
more likely category PoPs to mention in the TAFs and just start
with DRT at 00Z. In the next routine updates we might consider the
convection reaching I-35 closer to 12Z Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              97  77  91  73 /  40  60  90  90
Austin Bergstrom Intl Airport  97  76  91  71 /  40  50  90  90
New Braunfels Muni Airport     97  77  91  71 /  40  50  90 100
Burnet Muni Airport            94  73  85  71 /  30  60  90  80
Del Rio Intl Airport           98  74  89  70 /  30  90  70  40
Georgetown Muni Airport        96  75  89  72 /  30  50  90  90
Hondo Muni Airport             97  75  86  71 /  20  60  90  90
San Marcos Muni Airport        97  77  91  71 /  40  50  90  90
La Grange - Fayette Regional   96  77  93  73 /  30  30  80  90
San Antonio Intl Airport       96  78  88  73 /  30  50  90 100
Stinson Muni Airport           98  78  89  73 /  30  40  90 100

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Flood Watch from this evening through Friday evening for
TXZ171>173-183>193-202>208-217>221-223-228.

&&

$$

SHORT TERM...MMM
LONG TERM....MMM
AVIATION...18