Areal Flood Advisory 19, NWS Austin/San Antonio, TX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1257 PM CDT Sat May 1 2021

.AVIATION...
A band of TSRA moving across the KSAT/KSSF areas at TAF issuance time
will move east of the sites in the next hour. This band will move
across the KAUS area in the next few hours while an area of -RA over
the Hill Country drifts over KAUS. An upper level low will move over
Central Texas overnight and have included mention of -SHRA at KAUS
while KSAT/KSSF should be south of the low and have left mention out.
Will monitor radar trends for possible later mention there. A mix of
IFR/MVFR conditions is expected at the I-35 sites through early this
evening, then VFR develops late evening and continues through Sunday.
Easterly winds 5 to 12 KTs become southerly tonight, then increase
to 10 to 15 KTs on Sunday.

At KDRT, kept mention of SHRA/VCSH at KDRT until passage of the
upper low late this evening. A TEMPO IFR will linger at KDRT for a
few hours, then VFR develops by late afternoon. Northwesterly winds 5
to 10 KTs become easterly tonight.

&&

.PREV DISCUSSION... /ISSUED 605 AM CDT Sat May 1 2021/

AVIATION...
The next round of showers and thunderstorms is developing over DRT
eastwards into the San Antonio sites. This activity will affect the
terminals for much of the day before some dry weather returns this
evening for all but AUS. AUS should see some continued chances for
lingering showers a bit longer than the other sites as wrap around
moisture moves overhead as the upper low moves east over the area.
MVFR/IFR ceilings will continue for much of the period as well before
VFR returns late tonight as drier air filters into the area.

PREV DISCUSSION... /ISSUED 145 AM CDT Sat May 1 2021/

SHORT TERM (Today through Sunday)...
After some heavy rainfall yesterday evening along and east of the
I35 corridor with pockets of flash flooding, only light to moderate
rainfall continues at the present time across the eastern counties.
To the west there are some isolated to scattered showers that
develop and then dwindles. The upper low remains near West Texas but
is expected to move east then northeast today and into the evening
hours. As it remains to our west today, rain chances will remain
quite high. There is fairly good agreement in the high-res models
that the area of precip in the east will slowly decrease in coverage,
but at the same time, additional activity will develop southwest of
Bexar Country and then overspread the area by daybreak. This
activity is not expected to be too heavy, but with already saturated
grounds, some additional flooding will be possible.

The last and final round of widespread rainfall will then develop
out in the far western counties by the mid-morning hours as the
upper low finally ejects to the east. High-res models show a line of
showers and storms moving east across the CWA in the late morning
and afternoon hours. Some of this activity could produce additional
locally heavy rainfall and possibly a strong storm. Instability
levels are lacking given the cool temperatures and lack of any
breaks in the clouds expected. This should tamper severe chances but
a strong storm with small hail is not totally out of the realm of
possibilities. While the bulk of the rainfall and the biggest threat
of heavy rain moves east with this last round, some residual light
rain will be possible on the backside of the low across the CWA
tomorrow evening through the early morning hours as the upper low
moves across the area. No heavy rainfall is really expected from
this activity and will not make any changes to the expiration time
of the Flash Flood Watch which is currently set to expire at 7 pm
this evening. While much of the eastern half of the area saw
beneficial rainfall in the past 12 hours, the western counties will
get their round this morning and in the early afternoon. Additional
rainfall totals from now through the end of the event should average
1-3 inches for most of the area with isolated higher amounts.

Things finally dry out for Sunday with the sun hopefully making an
appearance once again. Highs Sunday should top out in the middle 80s
to middle 90s. Went slightly cooler than the blends to account for
the slightly cooler temperatures expected with how moist the ground
is expected to be.

LONG TERM (Sunday Night through Friday)...
A dryline will move toward the I-35 corridor Monday allowing
temperatures to soar into the upper 80s to middle 90s across the CWA.
Forecast soundings show a weak capping inversion at time of peak
heating that may be able to be broken by the dryline and strong
heating. This will lead to slight chances of showers and
thunderstorms for the area along and east of I-35 Monday evening.
Forecast soundings also show MUCAPEs of 2,000 to 3,000 J/kg along the
dryline indicating a potential for an isolated strong to severe
storm. A cold front and upper level trough will move across our area
Monday night into Tuesday. Upward forcing by these features will
generate isolated to widely scattered showers and thunderstorms over
the eastern half of the CWA where moisture will be deepest.
Convective parameters are forecast to decrease Monday night into
Tuesday, however there still may be sufficient instability and shear
for strong storms. Dry northwesterly flow aloft will bring fair
weather Wednesday through Friday. Temperatures will average within a
degree or two of normal for mid to late next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              74  63  87  68  91 / 100  70  -    0  -
Austin Bergstrom Intl Airport  73  63  87  68  91 / 100  70  -    0  -
New Braunfels Muni Airport     74  63  90  69  93 /  90  50   0   0   0
Burnet Muni Airport            71  61  86  67  91 / 100  70  -    0   0
Del Rio Intl Airport           76  60  95  66  96 /  90  20   0   0   0
Georgetown Muni Airport        72  63  86  68  91 / 100  80  -    0   0
Hondo Muni Airport             77  59  91  65  94 /  90  20   0   0   0
San Marcos Muni Airport        73  62  88  68  91 /  90  60  -    0   0
La Grange - Fayette Regional   74  66  87  70  90 /  90  80  -    0  -
San Antonio Intl Airport       74  63  88  68  92 /  90  30   0   0   0
Stinson Muni Airport           76  63  91  68  93 /  90  20   0   0   0

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 7 PM CDT this evening for Atascosa-Bandera-
Bastrop-Bexar-Blanco-Caldwell-Comal-De Witt-Fayette-Gillespie-
Gonzales-Guadalupe-Hays-Karnes-Kendall-Kerr-Lavaca-Lee-Medina-
Travis-Wilson.

&&

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

Hazardous Weather Outlook
National Weather Service Austin/San Antonio TX
1133 AM CDT Sat May 1 2021

TXZ171>173-183>194-202>209-217>225-228-021045-
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-
1133 AM CDT Sat May 1 2021

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

.DAY ONE...This Afternoon And Tonight.

Numerous showers and scattered thunderstorms are forecast to
continue this afternoon into evening. Up to 3 inches of additional
rainfall can be expected. This could lead to additional flash
flooding. In addition, a strong storm is possible with gusty winds
and hail the main threats.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to submit storm or flooding reports to
the National Weather Service.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
107 PM CDT SAT MAY 1 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0106 PM     FLASH FLOOD      2 SSW SAN ANTONIO       29.40N 98.51W
05/01/2021                   BEXAR              TX   BROADCAST MEDIA

            I-35 AT NOGALITAS ST. FLOODED AND VEHICLES
            ARE STRANDED.

&&

JR

Special Weather Statement
National Weather Service Austin/San Antonio TX
114 PM CDT Sat May 1 2021

TXZ205>207-220>222-011915-
Guadalupe TX-Karnes TX-Comal TX-Atascosa TX-Bexar TX-Wilson TX-
114 PM CDT Sat May 1 2021

...SIGNIFICANT WEATHER ADVISORY FOR GUADALUPE...NORTHWESTERN
KARNES...EAST CENTRAL ATASCOSA...WILSON...EASTERN BEXAR AND EASTERN
COMAL COUNTIES UNTIL 215 PM CDT...

At 113 PM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from near Hollywood Park to St. Hedwig to 7 miles
northeast of Campbellton. Movement was northeast at 25 mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
San Antonio, New Braunfels, Schertz, Seguin, Cibolo, Universal City,
Live Oak, Selma, Floresville, Kenedy, Karnes City, Poth, Stockdale,
Kosciusko, Randolph AFB, Canyon Lake Dam, San Antonio Int Airport,
Canyon Lake, Kirby and Windcrest.

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.

Occasional 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 2879 9834 2938 9836 2965 9853 2994 9815
      2985 9803 2976 9800 2980 9794 2968 9781
      2940 9782 2935 9786 2931 9782 2881 9783
TIME...MOT...LOC 1813Z 234DEG 20KT 2965 9841 2943 9820 2884 9823

RUNYEN

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
144 PM CDT SAT MAY 1 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0141 PM     FLASH FLOOD      4 ENE CHINA GROVE       29.42N 98.30W
05/01/2021                   BEXAR              TX   EMERGENCY MNGR

            SEVERAL LOW-WATER CROSSINGS FLOODED WITH 1
            TO 2 FEET OF WATER DEPTH ACROSS EASTERN
            PORTIONS OF BEXAR COUNTY.

&&

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