Special Weather Statement, NWS Austin/San Antonio, TX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
300 AM CDT Wed May 19 2021

.SHORT TERM (Today through Thursday)...

Showers and thunderstorms continued to develop ahead of an upper
level short-wave that is rotating through the base of an upper level
trough lifting northeast out into the Plains. These will gradually
form into one or more clusters and move across South Central Texas.
Although the models are not in agreement on the timing and movement
of the clusters, expect they will move across our southern and
eastern areas this morning into afternoon. Unseasonably high
moisture levels (PWs of 1.3 to 1.8 inches) along with training of
cells keep the threat of heavy rains and flooding going. Thus, have
maintained the Flash Flood Watch. An additional 2 to 4 inches of
rain are possible in the Flash Flood Watch area with isolated totals
of near 6 inches possible. WPC has our southeastern areas in a
Moderate Risk of excessive rainfall with the remainder of our area
in a Slight to Marginal Risk. A few strong to severe storms are also
possible due MUCAPES of 2,000 to 3,000 J/kg, mid level lapse rates
of 7.5 to 8.5 C/km, and SFC-6km shear of 40 to 45. Isolated showers
and thunderstorms will develop over the Serranias del Burro and
along the dryline in western Texas this afternoon. Steering flow may
take them into our Rio Grande areas late this afternoon into early
evening. SPC has our entire area in a Marginal risk of severe
storms. All clusters move off to the east later this afternoon into
evening with most models ending the showers and thunderstorms except
for isolated to widely scattered activity tonight into Thursday as
the unseasonably moist airmass lingers. It's possible that the Flash
Flood Watch may be able to be cancelled early. For now, will keep
chance POPs for our eastern areas with a threat of moderate rains
which may be enough to produce rapid runoff due to saturated soils.

&&

.LONG TERM (Thursday Night through Tuesday)...

A bit of a tricky forecast in the long term as models are latching
onto a bit of an omega block for late week into the weekend. A large
upper level low will remain situated to our west over the Great
Basin, with a weak cutoff low working southward over deep south Texas
late Thursday night. The GFS/ECMWF/Canadian are all in fairly decent
agreement that this small cutoff low will meander over the
Brownsville area and eventually weaken while getting absorbed into
the large scale upper trough as it moves slowly east this weekend.
The NAM on the other hand wants to bring this circulation inland,
with widespread showers and thunderstorms on Friday. I'm not quite
ready to bite on this solution, as it remains the outlier among
model solutions. Still believe that scattered showers and
thunderstorms will develop on Friday afternoon and evening, with
locally heavy rainfall possible that could lead to flash flooding in
areas that have received significant rainfall in recent days over the
Coastal Plains.

The weekend into early next week will feature a strengthening upper
level ridge to our east over the southeastern CONUS, and a deepening
upper level trough over the western United States. A bit of a
blocking pattern will develop, similar to an Omega block, however,
the upper level troughing to the west should eventually win out by
early next week, and start to slide east and northeastward, helping
to push the ridge to the east and southeast and into the eastern Gulf
of Mexico. This will allow moisture to continue streaming in over
South-Central Texas, resulting in a continued active pattern, with
daily rounds of showers and storms possible, especially towards the
afternoon and evening hours. Rain chances will start to wane by
midweek as the upper level flow flattens out, but will keep slight
chances in play through Wednesday.

&&

.PREV DISCUSSION... /ISSUED 1248 AM CDT Wed May 19 2021/

AVIATION...
Uncertain forecast with respect to SHRA/TSRA at the sites due to
differing locations where an eventual cluster moves across. Have only
minor adjustments to timing from earlier TAFs. SHRA/TSRA should move
over the I-35 sites in the morning and linger into the afternoon. A
few SHRA will be near KDRT overnight and although ISOLD TSRA are
possible over the mountains west of there in the afternoon, PROBs
are too to mention that they will impact the site. MVFR CIGs will
move over the sites in the next few hours, then there will be some
restrictions to VSBY in/near SHRA/TSRA on Thursday at the I-35 sites.
Skies will go VFR later in the afternoon, only to go back MVFR
Wednesday night. Easterly winds around 5 KTs will turn southeasterly
and increase to 8 to 15 KTs on Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              76  65  81  69  81 /  70  40  30  30  50
Austin Bergstrom Intl Airport  76  64  81  69  81 /  70  40  40  30  50
New Braunfels Muni Airport     78  64  83  70  82 /  70  20  30  20  40
Burnet Muni Airport            76  63  80  68  79 /  50  40  20  20  40
Del Rio Intl Airport           86  66  88  70  88 /  30  20  -   10  10
Georgetown Muni Airport        77  64  81  68  80 /  60  50  30  30  50
Hondo Muni Airport             79  63  83  68  83 /  70  20  20  20  30
San Marcos Muni Airport        77  63  82  68  82 /  70  30  30  30  50
La Grange - Fayette Regional   79  66  83  71  82 /  80  60  50  30  50
San Antonio Intl Airport       77  64  81  69  82 /  70  20  20  20  40
Stinson Muni Airport           78  65  83  70  83 /  80  20  20  20  40

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Thursday afternoon for Atascosa-Bandera-
Bastrop-Bexar-Blanco-Burnet-Caldwell-Comal-De Witt-Fayette-Frio-
Gillespie-Gonzales-Guadalupe-Hays-Karnes-Kendall-Kerr-Lavaca-Lee-
Llano-Medina-Travis-Williamson-Wilson.

&&

Short-Term/Aviation...04
Long-Term...Morris
Decision Support...Brady

Hazardous Weather Outlook
National Weather Service Austin/San Antonio TX
902 PM CDT Tue May 18 2021

TXZ171>173-183>194-202>209-217>225-228-200215-
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-
902 PM CDT Tue May 18 2021

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

.DAY ONE...Tonight.

Lingering flash flooding is possible into the overnight hours
across areas east of Interstate 35 that saw anywhere from 3 to 6
inches of rainfall Tuesday evening. A strong storm or two is
possible late tonight into early Wednesday morning.

A flash flood watch is also in effect for the eastern half of
South-Central Texas...or along and east of a line from Mountain
Home to Dilley. The heavy rain threat will greatly increase this
evening as storms organize out west and move through the region
late tonight.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Several rounds of showers and thunderstorms are possible through
the week, especially Wednesday through Thursday. Thunderstorms
could be strong to severe at times, and there is a Marginal Risk
(Level 1 of 5) for severe storms Wednesday for most of South-
Central Texas.

A flash flood watch is in effect east of a Mountain Home to
Dilley line through 1 PM CDT Thursday. Daily rainfall amounts of
1 to 4 inches are possible, and portions of Central Texas could
end up with multiple day rainfall totals up to 10 inches. These
heavy rainfall totals will likely send some area rivers and
streams into minor or moderate flood stages.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report severe weather and/or flash flooding
to the National Weather Service.

Special Weather Statement
National Weather Service Austin/San Antonio TX
200 AM CDT Wed May 19 2021

TXZ220>224-190745-
Karnes TX-Atascosa TX-De Witt TX-Gonzales TX-Wilson TX-
200 AM CDT Wed May 19 2021

...SIGNIFICANT WEATHER ADVISORY FOR DEWITT...KARNES...SOUTHWESTERN
GONZALES...NORTHEASTERN ATASCOSA AND WILSON COUNTIES UNTIL 245 AM
CDT...

At 200 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 10 miles east of Pleasanton to 6 miles south of
Runge. Movement was northeast at 45 mph.

Half inch hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Pleasanton, Cuero, Floresville, Jourdanton, Kenedy, Karnes City,
Poth, Yorktown, Stockdale, Kosciusko, Nixon, St. Hedwig, Elmendorf,
La Vernia, Runge, Falls City, Smiley, Nordheim, Pandora and Gillett.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 2889 9733 2892 9743 2867 9778 2872 9792
      2870 9799 2879 9810 2875 9814 2891 9856
      2942 9816 2936 9811 2938 9800 2914 9701
      2911 9698
TIME...MOT...LOC 0700Z 223DEG 39KT 2893 9833 2880 9774

BRADY

Special Weather Statement
National Weather Service Austin/San Antonio TX
248 AM CDT Wed May 19 2021

TXZ193-208-209-223>225-190830-
Caldwell TX-Lavaca TX-Bastrop TX-De Witt TX-Fayette TX-Gonzales TX-
248 AM CDT Wed May 19 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN CALDWELL...
NORTHEASTERN DEWITT...SOUTH CENTRAL BASTROP...GONZALES...SOUTHWESTERN
FAYETTE AND LAVACA COUNTIES UNTIL 330 AM CDT...

At 248 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Smiley to near Thomaston. Movement was
northeast at 55 mph.

Half inch hail and wind gusts of 50 to 55 mph will be possible with
these storms.

Locations impacted include...
Cuero, Gonzales, Yoakum, Luling, Schulenburg, Hallettsville, Shiner,
Flatonia, Moulton, Waelder, Smiley, Sublime, Cheapside, Hochheim,
Palmeto State Park, Rosanky, Thomaston, Cistern, Ezzell and Speaks.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 2906 9694 2910 9698 2897 9717 2938 9783
      2999 9738 2967 9684 2963 9687 2961 9684
      2958 9684 2958 9679 2934 9656
TIME...MOT...LOC 0748Z 217DEG 48KT 2935 9765 2904 9715

BRADY

Special Weather Statement
National Weather Service Austin/San Antonio TX
334 AM CDT Wed May 19 2021

TXZ209-225-190915-
Lavaca TX-Fayette TX-
334 AM CDT Wed May 19 2021

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN FAYETTE AND NORTHERN
LAVACA COUNTIES UNTIL 415 AM CDT...

At 333 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 7 miles east of Moulton to 6 miles northeast of
Speaks. Movement was northeast at 40 mph.

Wind gusts up to 50 mph will be possible with these storms.

Locations impacted include...
La Grange, Schulenburg, Hallettsville, Fayetteville, Sublime,
Komensky, Swiss Alp, Freyburg, Dubina, Moravia, Rutersville, High
Hill, Engle, Breslau, Ellinger, Witting, Ammannsville, Vsetin,
Vienna, and Rek Hill.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 2926 9667 2953 9715 3003 9678 2993 9660
      2963 9687 2961 9684 2958 9683 2958 9679
      2934 9656
TIME...MOT...LOC 0833Z 231DEG 36KT 2954 9702 2931 9661

BF

Special Weather Statement
National Weather Service Austin/San Antonio TX
429 AM CDT Wed May 19 2021

TXZ193-194-209-190945-
Bastrop TX-Fayette TX-Lee TX-
429 AM CDT Wed May 19 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN BASTROP...LEE AND
NORTHEASTERN FAYETTE COUNTIES UNTIL 445 AM CDT...

At 429 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 7 miles southeast of Elgin to near Round Top.
Movement was northeast at 75 mph.

Half inch hail and wind gusts up to 50 mph will be possible with
these storms.

Locations impacted include...
Giddings, Lexington, Dime Box, Round Top, Fedor, Paige, Lake
Somerville State Park & Trailway, Tanglewood, Carmine, Knobb Springs,
Blue, Old Dime Box, McDade, Ledbetter, Cedar Hills, Loebau, Hills,
Leo, Winedale, and Lincoln.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3029 9739 3042 9727 3046 9715 3056 9696
      3054 9692 3046 9690 3046 9688 3039 9679
      3032 9674 3032 9669 3029 9664 3025 9669
      3024 9674 3020 9674 3016 9679 3014 9677
      3017 9669 3015 9668 3015 9665 3003 9661
TIME...MOT...LOC 0929Z 225DEG 63KT 3031 9727 3009 9662

BF

Special Weather Statement
National Weather Service Austin/San Antonio TX
549 AM CDT Wed May 19 2021

TXZ220-191130-
Atascosa TX-
549 AM CDT Wed May 19 2021

...SIGNIFICANT WEATHER ADVISORY FOR WESTERN ATASCOSA COUNTY UNTIL 630
AM CDT...

At 549 AM CDT, a strong thunderstorm was reported over Charlotte,
moving northeast at 35 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Pleasanton, Jourdanton, Poteet, Charlotte, Leming, Dobrowolski,
Amphion, Espey, Graytown, and Davis.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 2879 9880 2890 9880 2916 9854 2912 9843
      2909 9838 2902 9832 2871 9871
TIME...MOT...LOC 1049Z 224DEG 30KT 2884 9873

BF

Special Weather Statement
National Weather Service Austin/San Antonio TX
608 AM CDT Wed May 19 2021

TXZ221-222-191200-
Karnes TX-Wilson TX-
608 AM CDT Wed May 19 2021

...SIGNIFICANT WEATHER ADVISORY FOR NORTHERN KARNES AND SOUTHEASTERN
WILSON COUNTIES UNTIL 700 AM CDT...

At 608 AM CDT, Doppler radar was tracking a strong thunderstorm over
Cestohowa, or near Kosciusko, moving northeast at 25 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Karnes City, Kosciusko, Nixon, Falls City, Pandora, Cestohowa,
Gillett, Hobson, Ecleto, Paweleville, Pana Maria, and Helena.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 2900 9809 2933 9785 2928 9779 2911 9762
      2907 9767 2888 9793
TIME...MOT...LOC 1108Z 220DEG 24KT 2900 9796

BF