257
FXUS64 KEWX 282328
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
628 PM CDT Mon Sep 28 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 622 PM CDT Mon Sep 28 2026

- Above normal heat persists into mid-week, with some low rain chances
  along and east of I-35 Tuesday.

- An active pattern is expected mid to late week with widespread
  rain chances and a potential for flash flooding.

&&

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 138 PM CDT Mon Sep 28 2026

Currently our area remains under the influence of a subtropical
ridge with its center located over the Rio Grande Valley over
southwest TX. At the same time an upper level low is located over
the southwestern U.S. For now our area will continue to be
influenced by the subtropical ridge through Tuesday. Today expect
another hot and rather humid day for our area with highs well above
normal with most in the mid to upper 90s. We could see heat indices
within the 100-105 degree range with the increased humidity and
party sunny skies. Additionally, rain chances will remain low today
due to the aforementioned high near us with just some
spotty/isolated showers and storms over the far eastern areas of the
Coastal Plains. Tonight expect increasing clouds along with
temperatures remaining mild with many remaining in the low to mid
70s overnight.

By Tuesday the upper level low will continue to push eastward
towards the desert southwest thus shunting the subtropical ridge
currently over our area and pushing it off to the east. As this
happens lee side surface troughing east of the rockies will help to
bring in stronger southeasterly winds at the surface. This in turn
will help pull in more moisture up from the Gulf giving us a better
shot at rain and storm chances during the day along with our typical
seabreeze. For now have capped rain chances at 30 percent for areas
mainly along and east of the I-35 Corridor. By Tuesday night we
could start to see rain/storm chances increase as we begin to see
the beginning effects of the upper level low over the desert
southwest as it slowly deepens and progresses eastward towards the
Southern Plains. Additionally, significant amounts of moisture from
the remnants of Hurricane Polo and Odalys will be pulled into our
area in the upper levels along with lower level moisture being
brought in from the Gulf. We could see PWATS approaching and even
exceeding 2 inches. As such any storms that do form will be tropical
in nature and capable of very heavy rainfall. WPC currently has Val
Verde and parts of Edwards counties in a level 1 of 4 risk of
excessive rainfall for Tuesday with the risk shifting eastward and
increasing further as we get beyond Tuesday night. More about that
in the long term portion below. Regarding temperatures, Tuesday will
feel very hot and humid with most seeing low to upper 90s for highs.
When adding in the increasing humidity it`l feel more like 100-107
degrees. Parts of the Coastal Plains could briefly approach and
exceed heat advisory criteria before any afternoon rain/storms
occur. Lows Tuesday night once again will remain in the low to mid
70s as the area remains locked under increasing cloud cover
overnight.

&&

.LONG TERM...
(Wednesday through next Monday)
Issued at 138 PM CDT Mon Sep 28 2026

The advertised pattern change is on track for mid to late week with
increased showers and thunderstorm chances beginning Wednesday and
continuing through late week and beyond. An upper low will be
located over the Four Corners region Wednesday, eventually moving
east across the Central and Southern Plains late week bringing a
Pacific cold front across our area. Abundant moisture will be
available ahead of this system with some guidance showing PWATs
around 200 percent above normal. As to be expected with a strong
upper low, models still vary to a certain degree on its progression
and speed with the ECMWF continuing its slower trend compared to the
GFS. We`re starting to get a glimpse into hi-res guidance as this
event comes closer giving higher confidence to heavy rain in our
area beginning more late Wednesday night in the west and Thursday in
the east.

Ahead of an expected line of storms during this timeframe, isolated
to scattered thunderstorm activity will be possible across much of
the area as moderate onshore flow and hot and humid conditions
persist Wednesday. Heat index values exceed 100 degrees for a
majority of the area in the afternoon capped under mostly cloudy
skies with a breezy southeasterly wind. Any thunderstorm activity
will have a heavy rain threat given the environment and cannot rule
out some gusty wind or hail as well.

Returning to the Pacific front and the main focus of the extended
forecast, expect this feature to slowly move across our area late
Wednesday night through Friday. Thunderstorms are likely to develop
along the southwest to northeast orientation of the front and could
produce heavy rainfall leading to flash flooding. There remains
uncertainty in how quickly this front moves, how far it progresses,
and where the heaviest rain will fall over the area. An upper low
remains to the west Friday into Saturday with continued high
moisture residing over the area. This keeps medium to high rain
chances over the area Friday into the weekend with high uncertainty
on details this far out. Temperatures Friday into the weekend should
fall into the mid 70s and 80s given the rain chances and expected
cloud cover. While details remain blurred for our late week system,
continue to monitor the forecast and be prepared for potential heavy
rainfall.

&&

.AVIATION...
(00Z TAFS)
Issued at 622 PM CDT Mon Sep 28 2026

Breezy east-southeasterly winds are expected to continue at 10-15
kts with occasional gusts up over 20 kts through mid to late
evening before relaxing somewhat after 06Z. MVFR stratus looks to
rapidly form starting at SAT and SSF and then spreading outward,
reaching AUS around 08Z and DRT around 10Z. Expect this stratus to
take a bit more time to break to VFR than the last couple mornings
as low level moisture increases ahead of an approaching storm
system set to impact the region for mid to late week. Breezy
southeasterly flow returns by late morning Tuesday/early afternoon
around 10-15 kts with VFR.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              75  97  76  96 /   0  20  20  40
Austin Bergstrom Intl Airport  73  96  75  96 /   0  20  20  40
New Braunfels Muni Airport     73  95  74  96 /  10  30  20  40
Burnet Muni Airport            72  92  74  92 /   0  10  20  40
Del Rio Intl Airport           76  98  77  97 /   0   0  40  20
Georgetown Muni Airport        73  95  75  95 /   0  10  20  40
Hondo Muni Airport             74  95  75  96 /   0  10  20  30
San Marcos Muni Airport        73  96  74  96 /  10  30  20  40
La Grange - Fayette Regional   73  97  75  97 /   0  20  20  40
San Antonio Intl Airport       76  94  77  95 /  10  30  20  40
Stinson Muni Airport           76  95  77  96 /   0  20  20  30

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

SHORT TERM...CJM
LONG TERM....27
AVIATION...MMM