724
FXUS64 KEWX 181752
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1252 PM CDT Mon Aug 18 2025

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

.KEY MESSAGES...

- Isolated storms this afternoon and evening mainly from the Coastal
  Plains to the I-35 corridor.

- Rain chances increase during the week with scattered to widespread
  rain possible midweek.

- Potential for isolated flash flooding from slow moving storms
  Wednesday through at least Friday.

&&

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 1247 PM CDT Mon Aug 18 2025

An upper-tropospheric trough axis is moving west across South-
Central Texas this afternoon. The feature is weakly influencing
winds at the mid- and low-levels, but has nudged ridging enough to
provide an opening for rising air supporting isolated showers and
storms today. The most favored region for ascent is over East Texas,
but activity should spread into our area given northeasterly to east-
northeasterly mid-level flow. Most of the high-resolution guidance
depicts storms developing by late afternoon along outflow boundaries
or the seabreeze front tracking east to west across the area, mainly
over the Coastal Plains and potentially reaching the I-35 corridor.
Some storm development might also occur off-boundary near the I-35
and US-281 corridors as afternoon temperatures in the upper 90s near
convective temperatures. Most of the sunshine-aided action should
weaken quickly after sunset, though storms over the Coastal Plains
might persist a little longer if they latch onto the seabreeze as
depicted by previous runs of the HRRR, HRW ARW and HRW FV3. Minimal
wind shear will put a damper on the strength of storms today, but
typical summer thermal profiles will support brief heavy downpours,
gusty thunderstorm winds, and lightning.

East-northeasterly flow aloft becomes even more pronounced Tuesday
as the trough pushes southwest and displaces ridging a little
farther back into the Four Corners region. This supports a similar
round of isolated to scattered showers and storms, though the
westward push of the trough means the areas of favored development
also spread farther west into the Hill Country and southern Edwards
Plateau. This should allow for more widespread pop-up shower
activity Tuesday afternoon, with similar potential for brief and
localized heavy downpours, gusty winds, and lightning. Additional
rains could also push in from the east with the seabreeze, adding to
rain chances over the Coastal Plains.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 1247 PM CDT Mon Aug 18 2025

An active weather pattern is in store beginning midweek. As the
upper-level ridge continues to be kept in check over the western US,
the door opens for troughing to amplify along its eastern periphery
and wedge into our area from the northeast. A weak front or shear
axis reaches our area Thursday and then slowly sags south into the
weekend. This will likely serve as a focus for daily rounds of
storms, with chances better favored during the daytime hours. Rain
chances pick up Wednesday and peak Thursday as the front arrives
with scattered to widespread activity possible, consisting of slow-
moving storms capable of producing heavy rain. Opportunities for
rounds of storms continue Friday and into the weekend, slowly
shifting south in tandem with the front. The WPC has indicated a
level 1 of 4 (Marginal) risk for heavy rainfall capable of producing
flash flooding Wednesday, Thursday, and Friday for most of South-
Central Texas.

Wednesday looks similar to Tuesday with a lack of strong synoptic-
scale features in our area, though more northerly mid-level winds
support more north-to-south storm motions as storms spark along
residual outflow boundaries and bands of moisture convergence across
the region. Thursday looks like the most likely day for rains in our
area as current modeling is in good consensus in moving the front
over South-Central Texas by then. Although the north-to-south
distribution of rain will hinge on the position of the front, the
zonal flow of moisture along the front and general lack of
subsidence indicates rain chances extend fully east to west across
the area from the Coastal Plains to the Rio Grande. The latest
combined GEFS/ENS/GEPS ensemble indicates PW values will likely
exceed 2 inches over the Coastal Plains with values closer to 1.7
inches over the Hill Country. While these values are only slightly
above average for this time of year, the presence of the front as a
focus for moisture convergence with slow-moving storms in this
environment leads to the potential for heavy rain and locally
elevated rainfall totals. Without much of a low-level jet (in fact,
850 mb flow is forecast to be generally from the north during the
period), the best chances for rain midweek onwards will be during
the daytime with storms diminishing overnight. While there is good
model agreement regarding the general weather setup in play midweek
to late week, there is less agreement on the evolution for the
front/shear axis which leads to uncertainties in rainfall amounts.
The GFS and CMC depict lobes of vorticity moving southwest through
our area along the front while the ECMWF has tended to keep
vorticity a little more concentrated towards a more persistent,
singular feature. The former scenario is slightly more conducive to
rain over our area, and the latest GEFS and ENS ensemble suites show
slight preference for more mid-level vorticity over South-Central
Texas.

The most favored areas for rain follows the front slowly southward
across the region Friday and Saturday, with slight intrusions of
drier continental mid-level air from the north causing a slight
decrease in rain coverage but likely with still enough convergent
flow along the front to support scattered storm activity. Most of
the vorticity drops south of our region Sunday, but residual
isolated rain could continue into Monday. Towards Monday, an eastern
lobe of the ridge extends into Texas and more distinctly lower rain
chances. However, this slightly drier period could be short lived as
stronger troughing over the Mississippi River distorts the ridge.

Increased cloud cover and rain Thursday into the weekend is forecast
to keep daytime highs in the low to mid 90s regionwide, with values
near to slightly below average for late August.

&&

.AVIATION...
(18Z TAFS)
Issued at 1247 PM CDT Mon Aug 18 2025

VFR flight conditions generally prevail. The period begins mainly
clear but do expect for few to sct cumulus development during the
afternoon and early evening. Eastern areas could see some isolated
showers or storm this afternoon. Of the local TAF sites, activity
could approach the closest to KAUS where we have added a VCSH into
that TAF. Rain and storm chances will trend better during Tuesday
afternoon compared to this afternoon and confidence is enough for
the inserting of PROB30 groups for -TSRA within the 30 hr TAFs of
KAUS and KSAT. Otherwise, expect for light breezes around or below
10 kts throughout the period with wind directions shifting from
south-southeaterly today to more east to east-northeasterly on
Tuesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry             100  78 100  77 /  20  10  40  10
Austin Bergstrom Intl Airport 100  76 100  76 /  20  10  50  20
New Braunfels Muni Airport    100  75  99  74 /  20  20  40  20
Burnet Muni Airport            97  76  97  75 /  20  10  30  10
Del Rio Intl Airport          102  79 101  78 /   0   0  20  20
Georgetown Muni Airport       100  77 100  76 /  20  10  30  10
Hondo Muni Airport            100  75 100  74 /   0  10  30  20
San Marcos Muni Airport       100  75 100  74 /  20  20  50  20
La Grange - Fayette Regional   98  75  97  75 /  30  20  60  20
San Antonio Intl Airport      100  78  99  77 /  10  20  40  20
Stinson Muni Airport          101  78 101  77 /  10  20  40  20

&&

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

$$

Short-Term...Tran
Long-Term...Tran
Aviation...62