Flash Flooding and Hail in Texas, May 26 to 27, 2025

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
650 PM CDT Mon May 26 2025

...New AVIATION...

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 206 PM CDT Mon May 26 2025

Key Messages:

- Level 3 of 5 risk for isolated to numerous severe storms tonight.
- Isolated pockets of heavy rainfall possible with more severe
  weather possible Tuesday.
- Tornado watch remains in effect until 10pm tonight.

As of this writing the current outflow boundary from this mornings
storms is just south of the I-10 corridor back into San Antonio on
west. The current thinking is strong to severe storms should be
ongoing by this evening along and just northwest of this boundary
with most models hinting at convection developing by 4pm or later
out west past the hill country and then moving eastward with time.
The latest run of the HRRR seems to have a pretty good grasp on this
scenario with supercells forming west and then growing into a big
complex that moves across our area by this evening. As such the SPC
has increased our severe risk to a level 3 of 5 for areas along and
east of the I-10 corridor and along and west of the I-35 corridor.
with a level 2 of 5 risk for almost everyone else except the Winter
Garden area which is in a level 1 of 5 risk. Bottom line expect
storms to form and be severe with very large hail, damaging winds
and some tornados especially for storms that can root themselves
along the surface boundary. In addition, pockets of heavy rainfall
rates could lead to isolated instances of flash flooding and WPC
also has most of the area in a level 2 of 5 risk for excessive
rainfall as well. In fact some models are hinting at more than 3
inches for the hill country. We are taking a more wait and see
approach due to how dry it has been and how models struggle with
small mesoscale convective systems.Current thinking is the storms
should be out of area by sunrise tomorrow if not earlier.

Tomorrow's forecast is highly conditional on what happens tonight. A
more mature complex of storms tonight would likely stabilize
conditions for much of the day on Tuesday, with convection delayed
until Tuesday night. However, a less robust system tonight would
open the door to earlier convective chances Tuesday afternoon,
especially across the Rio Grande, southern Edwards Plateau, western
Hill Country where SPC has a Level 2 of 5 risk for severe storms. A
level 1 of 5 risk exists for everyone else as well. Again very large
hail, damaging wind gusts and isolated tornados would all be
possible with any storms that do form tomorrow. It is possible we
could have a similar line of storms form out west and cross into the
Rio Grande Plains and continue pushing eastward. However tomorrows
convection forms, more clarity will come as we get closer and Hi-Res
models get into better focus. Lastly regarding temperatures, expect
more seasonable temps for Tuesday with highs around the upper 80s to
low 90s but cooler in spots where convection is ongoing, with lows
around/near 70.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 206 PM CDT Mon May 26 2025

Key Message:

- Strong to severe storms possible through the long term period.

Our active period of weather will continue into the start of the long
term forecast period. On Wednesday morning, a lead shortwave will be
moving through the southern CWA, likely sparking showers and storms,
with a few stronger storms possible. Weak westerly mid-level flow is
expected to transition to west-northwesterly flow by the late week
time frame, fostering shower and storm development through the
remainder of the period.

Forecast confidence remains low at this time, as most days' storm
chances will be highly dependent on previous mesoscale boundaries and
where those setup. One thing we do know is that the chance for strong
to severe storms with large hail, damaging winds, and locally heavy
rain are possible through the remainder of this week. Cooler
temperatures are going to be a welcome feeling through the week
though as increased cloud cover and convection will result in lower
temperatures than we've seen the past couple weeks. Hopefully we can
put a dent in this multi-year drought this week and add some much
needed water to reservoirs and streams.

&&

.AVIATION...
(00Z TAFS)
Issued at 637 PM CDT Mon May 26 2025

Slow moving, slow evolving storm complex is being guided by a strong
supercell moving into Llano and Gillespie Counties. This projects the
storm environment timing to push back a few hours to mainly 03Z to
07Z, but potentially earlier for AUS where feeder cell storms cold
form. The storms should, according to most model output, target the
San Antonio area and could linger around SAT/SSF vcntys almost until
daybreak. By around 10Z, there were likely be an MCV rotation showing
up with a weakening complex, and this will be the guiding light for
if and when the next rounds of convection are possible. For now will
go with prevailing stable conditions in the extended. Also there is a
prevailing MVFR cig possible in the early morning, that may be
dispersed in the downdraft air, but we'll only show that for SSF and
DRT where the storms either fail to make it or come in weaker.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              86  70  91  71 /  50  70  40  40
Austin Bergstrom Intl Airport  86  69  90  71 /  40  70  40  40
New Braunfels Muni Airport     89  70  92  71 /  40  60  30  40
Burnet Muni Airport            83  67  87  68 /  70  70  30  40
Del Rio Intl Airport          104  76  97  73 /  30  20  40  70
Georgetown Muni Airport        83  68  86  69 /  60  70  40  40
Hondo Muni Airport             98  70  94  70 /  40  50  30  50
San Marcos Muni Airport        88  69  92  70 /  40  60  30  40
La Grange - Fayette Regional   89  71  92  73 /  40  60  40  30
San Antonio Intl Airport       90  72  93  72 /  30  60  30  40
Stinson Muni Airport           94  73  94  74 /  30  40  30  40

&&

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

Short-Term...MMM
Long-Term...CJM
Aviation...18