Severe Thunderstorm Warning 157, NWS Austin/San Antonio, TX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
600 PM CDT Fri May 16 2025

...New AVIATION...

.UPDATE...
Issued at 507 PM CDT Fri May 16 2025

A Severe Thunderstorm Watch has been issued across Burnet, Llano,
Williamson counties until midnight tonight. Isolated thunderstorms
has developed and remain possible across these areas. Large to very
large hail is the main hazard followed by strong damaging winds. The
heat advisory remains in effect until 7 pm CDT as well for regions
generally along and east of the I-35 corridor where heat indices
currently are running in the 104 to 111 degree range.

&&

.SHORT TERM...
(Tonight through Saturday night)
Issued at 236 PM CDT Fri May 16 2025

Key Messages:

- Heat Advisory remains in effect through early evening for portions
  of South Central Texas.
- The heat continues on Saturday with elevated heat index values over
  portions of South Central Texas.
- Low chances for isolated strong to severe thunderstorms this
  afternoon/early evening and Saturday afternoon/evening.

The hot weather conditions continue across South Central Texas with
highs in the upper 80s across the Hill Country and lower to mid 90s
elsewhere as of 2 PM CDT. Heat indexes are ranging from mid to upper
90s with a few locations at 100-103 across the Hill Country and from
100 to 107 range over the coastal plains and the southern part of the
Rio Grande. Expect these values to increase as we hit the heating
peak time frame sometime between 4 and 6 PM CDT. With that said, heat
index values are likely to reach the 106 to 111 range over areas
included in the Heat Advisory. Other than the heat, we have a slight
chance for an isolated or two strong to severe storms to develop
across the Llano, Burnet, and Williamson Counties late this afternoon
ahead of the dryline (warm and moist sector). If they do develop,
they could produce large hail and damaging wind gusts.

As the evening progresses, increased moisture in the form of clouds
spreads across the local area with overnight lows in the lower to
upper 70s. Patchy fog is expected to develop across the coastal
plains as early as midnight and then pushes to the northwest toward
the I-35 corridor.

Saturday starts warm with mostly cloudy to cloudy skies, however, by
noon time, partly cloudy skies should dominate most locations of
South Central Texas. By noon time, temperatures should be in the mid
to upper 80s to lower 90s. Another hot day is in store with maximum
highs expected to reach the mid to upper 90s across most areas and
from 100 to 105 along the Rio Grande. With dewpoint temperatures in
the mid to upper 60s to lower 70s along and east of the I-35
corridor and the southern part of the Rio Grande, can't rule out
heat index values ranging from 106 to 108 across the coastal plains
and up to 111 across portions of the southern portion of the Rio
Grande. We are holding off on issuing a Heat Advisory for Saturday
at this time. Future weather forecast packages may include a Heat
Advisory using latest model guidance. Just continue to exercise heat
safety measures.

Saturday could look different across the Rio Grande, southern
Edwards Plateau, and the Hill Country as strong to severe
thunderstorms develop ahead of the dryline and couple of upper level
pulses of energy arriving in the afternoon and early evening. These
storms could produce large hail and damaging wind gusts. The
activity likely lingers through the middle evening period. Between
the rain and cool pool of these storms, overnight lows across the
southern Edwards Plateau and Hill Country are forecasted to drop
to the upper 60s with the rest of the local area in the 70s.

&&

.LONG TERM...
(Sunday through Friday)
Issued at 236 PM CDT Fri May 16 2025

Key Messages:

- Well above normal temperatures continue Sunday through Tuesday with
  risk of heat-related impacts
- Low chances (10-20%) for showers and storms late Monday afternoon
  and evening and on Tuesday
- Temperatures closer to normal Wednesday and Thursday

Dry conditions are forecast Sunday and Sunday night for most areas,
with the exception of a low (10-20%) chance of isolated late
afternoon and evening storms along the dry line across the northwest
Hill Country and southern Edwards Plateau. The dry line advances
farther east on Monday afternoon, tapping into better moisture,
producing low chances (10-20%) of isolated showers and thunderstorms
across the Hill Country and northern I-35 corridor. The dry line
retreats back west late Monday night, then a shortwave moving
through the southern Plains sends the dry line back east into the
Hill Country and I-35 corridor Tuesday, with a cold front overtaking
it Tuesday night. Low confidence in timing and chances of convection
with these features, and we are currently sticking close to the NBM
20% chances of showers and storms along and east of I-35/I-37
Tuesday.

Above average temperatures continue Sunday and through Tuesday, with
elevated heat indices east of the dry line. There is lower
confidence in the strength of the front and temperatures behind it
Wednesday and Thursday, but we have trended high temperatures cooler
than the NBM. This puts high temperatures close to, or slightly
above, normals for this time of year.

&&

.AVIATION...
(00Z TAFS)
Issued at 551 PM CDT Fri May 16 2025

This evening's convection over the Hill Country stretching from near
Mason to the Killeen area should remain to the north of our area
terminal sites. As a result, expect for continued VFR flight
conditions through the first half of the night before low clouds with
MVFR then IFR ceilings develop at the I-35 terminals (KAUS, KSAT,
and KSSF) after midnight into Saturday morning. A slight reduction in
visibility is possible at KAUS as well. KDRT should remain VFR
through the night but a few low clouds could arrive at or just after
sunrise Saturday. Ceilings should improve to VFR levels into Friday
afternoon. Isolated to widely scattered storm will again try to
develop late Saturday afternoon and evening. However, confidence at
this time remains too low to insert into this TAF package. Winds will
remain of light to moderate breezes out of the south-southeast over
the I-35 terminals and east-southeast to variable at KDRT.

&&

.CLIMATE...
Issued at 236 PM CDT Fri May 16 2025

RECORD MAX TEMPERATURES TUESDAY THROUGH MONDAY
(* TIED RECORD WITH MOST RECENT OCCURRENCE SHOWN)

         FRI        SAT       SUN       MON
        05/16      05/17     05/18     05/19
----------------------------------------------
AUS    97/2018*   97/2018   97/2022   97/2006
ATT    99/2022*   99/2022   98/2022   98/2022*
SAT    97/2022*  100/2022  101/2022  101/1989
DRT   107/2013   105/2013  107/2024  108/2020

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              76  95  74  98 /  10  20  20  10
Austin Bergstrom Intl Airport  76  96  74  97 /  10  20  10   0
New Braunfels Muni Airport     75  97  74  98 /  10  10  10   0
Burnet Muni Airport            74  94  72  95 /  30  30  30  10
Del Rio Intl Airport           80 100  79 103 /  10  30  20  10
Georgetown Muni Airport        75  95  72  96 /  20  30  30  10
Hondo Muni Airport             74  98  73  99 /  10  10  20   0
San Marcos Muni Airport        75  97  73  98 /  10  10  10   0
La Grange - Fayette Regional   77  93  75  95 /   0  10   0   0
San Antonio Intl Airport       77  98  76  98 /  10  10  10   0
Stinson Muni Airport           77  99  76 100 /  10  10  20   0

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 7 PM CDT this evening for Atascosa-Bastrop-
Bexar-Caldwell-Comal-De Witt-Dimmit-Fayette-Frio-Gonzales-Guadalupe-
Hays-Karnes-Lavaca-Medina-Travis-Uvalde-Wilson-Zavala.

&&

Short-Term...Brady
Long-Term...76
Aviation...Brady

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