Severe Thunderstorm Warning 230, NWS Austin/San Antonio, TX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
629 PM CDT Thu Oct 24 2019

.AVIATION...
A strong cold front is currently progressing across the area and has
already passed over KDRT. Scattered to widespread thunderstorms are
ongoing ahead and along the front with both the AUS and SAT under an
Airport Weather Warning for lighting within 5 miles. Winds will be
gusty behind the front gusting up to 35 kts from the north. The front
will approach the I-35 terminals within the next couple of hours.
Showers and thunderstorms will continue along and slightly behind the
front, before clearing all terminals early tomorrow morning.

&&

.PREV DISCUSSION... /ISSUED 310 PM CDT Thu Oct 24 2019/

SHORT TERM (Tonight through Friday Night)...
At 3PM the cold front was just south of a Brady to Sonora line with
the dry line pushing into far northwest Val Verde County. As
mentioned in the morning update, the 12Z HREF guidance has converged
nicely on the timing of the front and convective evolution across the
area.

Capping has almost completely eroded and SPC mesoanalysis reveals
MLCAPE of around 1500-2000 J/kg developing through portions of the
southern Edwards Plataea and northwest Hill Country. We expect
additional shower and storm development through the late afternoon
across this region as forcing from the front arrives and overtakes
the dryline. Initially some storms could produce small to marginally
severe hail in addition to stronger downdrafts producing gusty winds.
Guidance is in agreement with a line of storms evolving this evening
into the remainder of the Hill Country and I-35 corridor trailing
all the way back to the Rio Grande. There still could be a window for
strong to marginally severe storms up through the I-35 corridor,
before updrafts begin to get undercut by the cold pool.

However, the main threat as the storms develop into portions of the
southeast Hill Country and urban areas of the I-35 corridor will be
heavy rainfall. Rainfall rates could lead to localized areas of flash
flooding concerns. A widespread 1-2 inches of rainfall is indicated
across this region. However, convective allowing and global models
have been consistent with indicating pockets of 3-4 inches. Where
these pockets occur is difficult to pinpoint, but will likely be the
locations for the potential for flooding.

Hi resolution and global models have trended more progressive with
the rain ending west to east early Friday morning, and so has our
forecast, as dry slotting around the base of the mid and upper level
low occurs across South Central Texas.

A Wind Advisory has been issued for post frontal winds. Initially a
strong surge of wind is forecast to develop down the Rio Grande and
portions of the I-35 corridor behind the front this evening, then a
little more widespread mid morning through early afternoon on Friday.
Sustained winds of 20-30 mph are expected, with some locations
seeing gusts around 35-40 mph.

Much cooler on Friday with high temperatures tricky. The NAM12
is colder and slower clearing out the cloud cover versus the global
models. Generally mid an upper 50s are forecast through the Hill
Country and Central Texas with low to mid 60s elsewhere, however the
gusty north winds will make it feel cooler.

Winds gradually subside late in the day on Friday, with lows by
Saturday morning into the 40s for most locations, and even upper 30s
across portions of the Hill Country.

LONG TERM (Saturday through Thursday)...
Another upper level trough is forecast to develop across the western
CONUS on Sunday and move east through the southern Rockies and into
the Plains on Monday. A warming trend is expected across the area
over the weekend. This some disagreement still in the models on
whether a weak, dry frontal boundary will make it into the area on
Monday, with the GFS indicating a passage but the 12Z ECMWF not
indicating the weak front until Tuesday. Global models do agree on a
stronger front for Wednesday, however the GFS is dry while the ECMWF
and Canadian develop precip along and behind.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              48  59  46  70  48 / 100  20  -    0   0
Austin Bergstrom Intl Airport  49  60  45  70  46 / 100  20  -    0   0
New Braunfels Muni Airport     48  64  44  71  46 / 100  10  -    0   0
Burnet Muni Airport            44  56  41  68  45 / 100  10  -    0   0
Del Rio Intl Airport           46  65  41  76  47 /  50  -   -    0   0
Georgetown Muni Airport        46  58  43  69  46 / 100  20  10   0   0
Hondo Muni Airport             47  65  43  74  46 / 100  -   -    0   0
San Marcos Muni Airport        47  60  44  71  45 / 100  10  -    0   0
La Grange - Fayette Regional   52  61  46  70  46 / 100  20  -   -    0
San Antonio Intl Airport       49  63  46  71  49 / 100  10  -    0   0
Stinson Muni Airport           50  65  46  71  48 / 100  10  -    0   0

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 4 PM CDT Friday for Atascosa-Bandera-Bastrop-
Bexar-Blanco-Burnet-Caldwell-Comal-De Witt-Dimmit-Edwards-Fayette-
Frio-Gillespie-Gonzales-Guadalupe-Hays-Karnes-Kendall-Kerr-Kinney-
Lavaca-Lee-Llano-Maverick-Medina-Real-Travis-Uvalde-Val Verde-
Williamson-Wilson-Zavala.

&&

Aviation...YB
Short-Term/Long-Term...05

Hazardous Weather Outlook...UPDATED
National Weather Service Austin/San Antonio TX
318 PM CDT Thu Oct 24 2019

TXZ171>173-183>194-202>209-217>225-228-252030-
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-
318 PM CDT Thu Oct 24 2019

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

.DAY ONE...This Afternoon And Tonight.

Scattered showers and thunderstorms will develop through the
northern Hill Country and northern Rio Grande this afternoon,
developing into a line of showers and thunderstorms through the
remainder of the Hill Country and I-35 corridor late afternoon
and evening . The line of storms is forecast to push into the
Coastal Plains late evening and overnight.

Some storms could become strong to severe through the late
afternoon and evening, producing hail up to the sized of quarters
and wind gusts to 60 mph. In addition, locally heavy rainfall is
forecast over the Hill Country, I-35 corridor, and eastward.
Rainfall rates could lead to pockets of flash flooding, especially
over portions of the Hill Country and urban areas of the I-35
corridor.

In the wake of the cold front, strong northerly winds are
expected tonight through mid afternoon on Friday. Sustained winds
of 20 to 30 mph sustained winds and gusts in some areas between
35 to 40 mph are forecast. A Wind Advisory has been issued.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Sustained winds of 20 to 30 mph sustained winds and gusts in some
areas between 35 to 40 mph are forecast on Friday. A Wind
Advisory has been issued.

Elevated to near critical fire weather conditions are possible
Friday afternoon across western Val Verde County, where little
rain is expected tonight and gusty winds and low relative humidity
develop.

No additional hazardous weather is expected.

.SPOTTER INFORMATION STATEMENT...

Spotter are encouraged to reports any hail, wind damage, or heavy
rainfall and flooding reports.

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