Severe Thunderstorm Warning 319, NWS Austin/San Antonio, TX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
705 PM CDT Sun Sep 24 2023

...New AVIATION...

.SHORT TERM...
(Tonight through Monday night)
Issued at 129 PM CDT Sun Sep 24 2023

Synopsis/Mesoanalysis: At 500mb south-central Texas remains in the
northeastern periphery of a ridge with zonal/westerly flow across
the northern portion of the state. A shortwave, currently across the
Panhandle, will quickly move into north and northeast Texas this
afternoon, which will interact with a slow moving cold front at the
surface. This cold front currently extends along a SW to NE line
from just south of KFST to near KLUD. To the south of this boundary,
rapid destabilization has been ongoing late this morning/early this
afternoon with further destabilization forecast to occur through
peak heating. High temperatures of around 100F and dewpoints
generally from 65-70F should lead to 2000-3000 J/kg of MLCAPE across
the forecast area according to SPC Mesoanalysis. Given the proximity
of the ridge to the southwest, shear will be modest, yet sufficient
in the 25-35 kt range later this afternoon with the help of the
aforementioned shortwave. One of the main factors leading to some
forecast uncertainty this afternoon is the presence of weak
CINH/capping. ACARS Soundings out of KAUS have shown this cap around
850mb slowly weakening over the last couple of hours, though it
still remains as of 1815Z. Given the lack of cloud cover across the
region, intense heating is likely to erode the cap by mid-afternoon
across most areas, but as the sun begins to set CINH is expected to
quickly increase again.

This afternoon-overnight: Eyes will be on the northern Hill Country
for initial storm development late this afternoon/early evening,
though a few storms will be possible across the Edwards Plateau and
northern Mexico as well. Storm movement will likely be slow to the
SE through the remainder of the evening before activity begins to
wane by 06z. However, isolated activity continuing overnight cannot
be ruled out across portions of the Hill County/I-35 corridor as the
front and lingering outflow boundaries continue to slowly push
south. There remains a Level 2/5 risk for severe thunderstorms with
this activity, with large hail and damaging wind gusts being the
main threats due to the unstable atmosphere. Tornadoes are not
expected due to small hodographs and weak flow near the front. Heavy
rain will be possible as well with the strongest cells as PWATs will
be near 1.8". While the ongoing drought will greatly limit the
threat for flooding, there is a Level 1/4 risk for excessive
rainfall/flash flooding. Both of these risks are generally across
the northern half of the forecast area.

Tomorrow-tomorrow night: The front will continue into central and
southern portions of the forecast area by tomorrow afternoon. As
destabilization occurs with diurnal heating, widely scattered
thunderstorm activity is expected to develop along and south of the
surface boundary. Increased cloud cover both from the front itself
and today and tonight's convection will limit instability tomorrow
compared to today, but the atmosphere will still be unstable enough
to pose a more isolated risk for severe weather (wind and hail). The
level 1/4 risk for excessive rainfall/flash flooding will continue
as well. Activity should once again wane through the late
evening/overnight hours with potential for continued isolated
activity, mainly across the western portion of the area.

&&

.LONG TERM...
(Tuesday through Sunday)
Issued at 129 PM CDT Sun Sep 24 2023

A broad, weak upper trough axis will be centered to our east to
start the long term period on Tuesday morning, and it's likely that
any remaining sfc cold front will have been pushed to our south by
rounds of convection today and tomorrow. No well-defined upper level
or surface features are forecast the rest of the week in our region.
Although isolated lingering showers and perhaps a thunderstorm will
be possible Tuesday into Wednesday, most locations will remain dry.
Low-end rain chances will return to the Coastal Plains late this
week into the weekend, but rainfall amounts in the long term will be
paltry at best. The expectation is for cooler, but still above
normal temperatures to prevail Tuesday through the rest of the week.
Highs will be mainly in the 90s, with lows in the 60s to lower 70s,
ticking back upwards towards next weekend. Above normal temperatures
will continue into the first week of October.

&&

.AVIATION...
(00Z TAFS)
Issued at 633 PM CDT Sun Sep 24 2023

Convection continues to develop over the Hill Country with some slow
movement toward the I-35 noted. We have pushed back the timing for
the TEMPO group for TSRA at AUS and have opted for only VCTS at SAT
and SSF this evening. Other changes at AUS include a brief mention of
MVFR cigs between 11-15Z. For tomorrow afternoon, convection chances
appear favored from the southern Edwards Plateau, western Hill
Country and Rio Grande plains. We will mention PROB30 groups at SAT
and SSF with VCTS at DRT.

&&

.CLIMATE...
Issued at 257 AM CDT Sun Sep 24 2023

Record High Temperatures and year last reached:

9/23
AUS - 101 (2005)
ATT - 99 (2011)
SAT - 102 (2005)
DRT - 103 (2005)

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              75  95  72  93 /  40  30  20  20
Austin Bergstrom Intl Airport  75  95  72  93 /  30  30  20  20
New Braunfels Muni Airport     76  98  73  95 /  20  40  20  20
Burnet Muni Airport            74  93  70  91 /  50  20  10  10
Del Rio Intl Airport           79 100  75  96 /  20  30  50  20
Georgetown Muni Airport        74  93  71  92 /  50  30  10  10
Hondo Muni Airport             74  97  73  94 /  20  40  30  20
San Marcos Muni Airport        75  96  71  94 /  20  40  20  20
La Grange - Fayette Regional   76  93  73  91 /  30  40  30  20
San Antonio Intl Airport       76  96  74  94 /  20  40  30  20
Stinson Muni Airport           78  98  75  96 /  20  40  40  20

&&

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

&&

Short-Term...Platt
Long-Term...Brady
Aviation...Platt

Hazardous Weather Outlook
National Weather Service Austin/San Antonio TX
523 PM CDT Sun Sep 24 2023

TXZ171>173-183>194-202>209-217>225-228-252230-
Llano-Burnet-Williamson-Val Verde-Edwards-Real-Kerr-Bandera-
Gillespie-Kendall-Blanco-Hays-Travis-Bastrop-Lee-Kinney-Uvalde-
Medina-Bexar-Comal-Guadalupe-Caldwell-Fayette-Maverick-Zavala-
Frio-Atascosa-Wilson-Karnes-Gonzales-De Witt-Lavaca-Dimmit-
523 PM CDT Sun Sep 24 2023

This Hazardous Weather Outlook is for South-Central Texas..

.DAY ONE...Tonight.

A slight (level 2/5) risk continues this evening over portions of
Hill Country and the I-35 Corridor, where scattered storms have
begun to develop. A Severe Thunderstorm Watch has been issued by
the Storm Prediction Center through 11 PM for Blanco, Burnet,
Gillespie, Llano, and Williamson Counties. Large hail and
damaging wind gusts will be the main hazards in any severe storms.
Have multiple ways of receiving warning information over this
portion of South-Central Texas this evening.

Dangerous heat & humidity will continue through early evening
along/east of I-35 and over portions of the southern Edwards
Plateau. A Heat Advisory remains in effect through 7 PM.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Additional showers and thunderstorms are expected across the area
on Monday afternoon. Locally heavy rainfall, gusty winds, and hail
will be possible in this activity. A marginal (level 1/5) risk for
severe thunderstorms continues over most of the area given this
potential, in addition to a marginal (level 1/4) risk for
excessive rainfall.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

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