Special Weather Statement, NWS Austin/San Antonio, TX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
652 PM CDT Tue Jun 23 2020

.AVIATION...
VFR skies prevail across South Central Texas this afternoon. Patchy
cumulus extend from the Rio Grande Plains into the Austin Metro area
thanks to a Mesoscale Convective Vortex across North Texas. This MCV
has produced shower and thunderstorm activity east of the terminals
this afternoon, and any convection that develops this evening should
be well south and east of the terminals. MVFR cigs should return to
the I-35 corridor between 09z and 12z tomorrow morning with decent
moisture still in place. Short range models have backed off on
precipitation chances tomorrow during the day so have converted the
PROB30 groups to mainly VCTS groups at AUS/SAT/SSF and VCSH at DRT.
If models continue to trend drier even these precip mentions may be
overkill, but in general models have been struggling with placement
of precipitation in this overall pattern.

&&

.UPDATE...
Have made some changes to the PoP configuration for the evening hours
through tomorrow based on current radar trends and the short term
models. For the rest of this evening thing any shower and
thunderstorms should be concentrated along the Coastal Plains as a
boundary extending south from the MCV across north Texas helps spark
off convection. In general reduced PoPs through the evening and
overnight by 10-30 percent. Based on the current, mostly clear radar
picture, and some of the high resolution models PoPs may need to be
drawn back even further later this evening. With global models
keeping the compact low pressure centered over Houston's area they
have also trended drier for tomorrow, keeping most of the
precipitation to the east of our CWA. Have also reduced PoPs 20-30
percent for Wednesday. High PoPs continue in the afternoon hours with
the GFS and ECMWF showing some convection back building to the west,
and impacting areas to the east of I-35. Again, will need to monitor
model trends overnight, and further adjustments of PoPs will be done
with the mid-shift package early Wednesday AM.

Radar returns (large area of 20 to 40 dBZ) over the Interstate 35
corridor this afternoon is most likely bugs that were stirred up by
the morning rains and the northerly wind. Reports of termites and/or
grasshoppers being observed have come in. Dual-Pol variables like
correlation coefficient and differential reflectivity support these
returns being purely biological. In addition they do not correspond
with any cloud cover via GOES-16.

&&

.PREV DISCUSSION... /ISSUED 224 PM CDT Tue Jun 23 2020/

SHORT TERM (Tonight through Wednesday Night)...
Rather unstable pattern will remain in place through the short term.
Decaying MCS from north TX last night moved over the region this
morning and dropped 1/2 inch to 2.5 inches over the Hill Country and
I-35 corridor along with gusts up to 40 mph. Today's rainfall will
be important to consider heading forward with additional
accumulations in the forecast. Residual convective boundary has been
left draped just south of the region with several convective
allowing models hinting of possible redevelopment along this
boundary most likely late this afternoon/evening. Bulk of this
activity is expected to remain southeast of the area. Clearing is
taking place across much of the region, had to bump up high
temperatures expected this afternoon as a result. Initial thinking
was that this convective boundary would set up over south central TX
today and bring prolonged chances for rain and possibly severe
storms later today. With it reaching much further south, chances for
rain have been tweaked down a bit and chances for strong to severe
storms is almost negligible.

A moist airmass still remains pooled over the region and remnant
boundaries with upper level support from weak low over southeastern
TX will result in quite a messy pattern for Wednesday and onwards.
Low confidence on placement and timing of storms until storms
initiate and high res guidance can initialize their placement. But
have left mention of slight chances of storms throughout the short
term. Looks like best chances for storms will come throughout the
day tomorrow with daytime destabilization. Temperatures will remain
below normal for Wednesday with the cloud cover and chances for rain
around.

LONG TERM (Thursday through Tuesday)...
Weak upper level troughing will remain in place over Texas for the
latter half of the week. The low level flow will continue to be from
the Gulf. Models have trended a bit drier today, but still have
likely POPs for the eastern half of the CWA for Thursday and Friday.
Higher PW air will be limited to the eastern half of the area and any
chance for locally heavy rain will be confined to this area. Showers
and thunderstorms may linger into Saturday and Sunday, but most
places will be dry for the weekend. The subtropical ridge will take
control for the beginning of next week. The temperature forecast is
trending up with less rain expected. Highs will still be below normal
for the end of the work week and then will climb back to near normal
during the early part of next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              71  89  72  89  74 /  20  40  20  50  40
Austin Bergstrom Intl Airport  71  89  71  88  73 /  20  40  20  50  40
New Braunfels Muni Airport     72  89  72  87  73 /  20  40  20  50  40
Burnet Muni Airport            68  87  70  87  71 /  20  30  20  30  30
Del Rio Intl Airport           73  98  74  95  75 /  20  20  20  10  20
Georgetown Muni Airport        70  89  71  89  72 /  20  40  20  40  30
Hondo Muni Airport             72  93  72  92  73 /  20  30  30  30  40
San Marcos Muni Airport        70  89  71  88  72 /  20  40  20  50  40
La Grange - Fayette Regional   73  89  72  89  74 /  50  60  30  60  40
San Antonio Intl Airport       73  91  74  90  74 /  20  40  20  50  40
Stinson Muni Airport           73  91  74  89  74 /  30  40  30  40  40

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&

Short-Term/Aviation...Treadway
Long-Term...BMW

Hazardous Weather Outlook
National Weather Service Austin/San Antonio TX
111 PM CDT Tue Jun 23 2020

TXZ171>173-183>194-202>209-217>225-228-241815-
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-
111 PM CDT Tue Jun 23 2020

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

.DAY ONE...This Afternoon And Tonight.
Thunderstorms could redevelop tonight, most likely for our
southeastern counties. These storms could pose an isolated flash
flooding threat with locally heavy downpours of 1 to 2 inches.

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

There will remain a good chance of showers and thunderstorms
across much of South Central Texas Wednesday through Friday.
Pockets of heavy rainfall will be possible each day. Prolonged
chances for rain have led to localized flooding concerns by the
end of the week.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

Special Weather Statement
National Weather Service Austin/San Antonio TX
759 PM CDT Tue Jun 23 2020

TXZ224-240200-
De Witt TX-
759 PM CDT Tue Jun 23 2020

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL DEWITT COUNTY UNTIL
900 PM CDT...

At 758 PM CDT, Doppler radar was tracking a strong thunderstorm near
Yorktown, moving southeast at 15 mph.

Penny size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Cuero, Yorktown, Arneckville and Meyersville.

LAT...LON 2887 9730 2888 9731 2887 9732 2890 9734
      2889 9735 2890 9738 2892 9738 2892 9742
      2887 9750 2913 9756 2918 9737 2896 9718
TIME...MOT...LOC 0058Z 336DEG 14KT 2903 9741

BMW

Special Weather Statement
National Weather Service Austin/San Antonio TX
802 PM CDT Tue Jun 23 2020

TXZ225-240145-
Lavaca TX-
802 PM CDT Tue Jun 23 2020

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN LAVACA COUNTY UNTIL
845 PM CDT...

At 802 PM CDT, Doppler radar was tracking a strong thunderstorm 8
miles southeast of Sublime, or 15 miles east of Hallettsville, moving
southeast at 15 mph.

Penny size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Sublime, Speaks and Vienna.

LAT...LON 2922 9672 2950 9685 2953 9674 2934 9656
TIME...MOT...LOC 0102Z 333DEG 14KT 2942 9668

BMW