Special Weather Statement, NWS Austin/San Antonio, TX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
644 PM CDT Tue May 7 2019

.AVIATION...
Clusters of thunderstorms have developed over the last hour that is
only impacting AUS. This activity is expected to wane heading into
the late evening hours. I-35 sites look to drop ceilings to IFR
conditions around 7-9Z period and DRT staying low-end MVFR. A front
that looks to develop convection moves over the region in the early
morning hours. Timing of this line is still in question with the
CAMs having it moving into the I-35 corridor anywhere from 15-21Z.
DRT is not expected to see any convection but should see a wind
shift. Another lowering of ceilings for AUS and SAT is expected just
beyond the TAF period.

&&

.PREV DISCUSSION... /ISSUED 248 PM CDT Tue May 7 2019/

SHORT TERM (Tonight through Wednesday Night)...
Isolated showers and thunderstorms continue across mainly the eastern
two-thirds of the area at the present time. The best lift and
subsequent coverage of rainfall is east of our CWA. Latest high-res
model guidance does show an uptick in coverage east of I35 later this
afternoon as the surface heats a bit more. Overall this activity is
not expected to be severe, but some stronger storms can produce brief
gusty winds, small hail, and brief heavy rainfall. The focus then
shifts out west for later this afternoon and evening. A dry line sits
west of Val Verde County and there could be some isolated
thunderstorm development on this boundary. Any storms would move east
and could impact Val Verde County. The environment across this area
is more conducive for stronger to severe storms, and there is a
slight risk of severe storms for Val Verde County.

A much higher coverage of showers and thunderstorms is expected
across Northwest Texas this afternoon and evening where there are
significant chances for severe weather. Latest high-res models show
this activity eventually congealing into a line of storms overnight
as it moves to the east/southeast. Some of the high-res guidance is
much quicker with its progression of the line with it entering our
northern counties by 7 AM. The activity should then continue
progressing east through the morning and early afternoon hours. Some
activity could linger into the late afternoon and evening hours. The
quicker timing is supported by the ECMWF, but the TTU WRF, NAM, GFS
are all a bit later. The timing of the line will have a big
determination on the severity and types of severe weather. If the
line moves through early, straight line winds and perhaps isolated
tornadoes will be possible. If the line is a bit later then large
hail becomes a big risk as CAPE values in the afternoon could be over
4000 J/kg.

In addition to the risk of severe weather, locally heavy
rain is possible, especially if we get a solid line of convection
into the area. The latest Day 2 Outlook has most of the area in a
slight risk and areas north of a Blanco to San Marcos to Giddings
line in an enhanced risk. Rainfall amounts will average 1-2 inches
with higher amounts in the northern CWA where the activity is
expected to be highest. With grounds remaining moist after previous
rainfall, it won't take much to cause some problems in low-lying
locations. Will see how things set up this evening and tonight, and
future shifts will monitor for any possible headlines. The activity
should push mostly east of the area by the late evening hours and
will show decreasing PoPs Wednesday night.

LONG TERM (Thursday through Tuesday)...
A cold front is expected to push into the area by Thursday morning on
the backside of the upper trough currently moving through the plains.
At the same time, another shortwave trough embedded in southwest flow
aloft will approach the area. These two features will provide a
scenario for some widespread rainfall across the area. If storms
remain rooted in the boundary layer ahead of the front, some severe
storms would be possible. However, latest guidance shows most
activity behind the boundary which would be elevated. There could be
a chance of some hail out of this scenario. SPC has most of the area
outside of the Hill Country in a marginal risk and this seems
reasonable.

Rainfall intensity behind the front is expected to be highest late
Thursday afternoon or Thursday night depending on the exact timing of
the trough. Rainfall totals could reach another 1-3 inches with
isolated higher amounts. The higher amounts look to be across the
eastern CWA, where there is a slight and moderate risk of excessive
rainfall from WPC. The front is expected to push well south of us on
Friday limiting the threat of continued heavy rainfall Friday.
Temperatures Friday will be quite cool, in the 60s.

However, the bad news is another shortwave trough is expected to move
into the southern plains on Saturday. The ECMWF develops a surface
low to the east of our area, which drags the front back north. These
features will bring another chance of heavy rainfall to the area.
Still plenty of time to watch this system, but with systems tomorrow,
Thursday night, and Saturday there is the potential for significant
rains in our CWA. The latest 7 day WPC rainfall forecast has 6"+ in
our eastern counties. We are stressing flood safety this week and
having a plan when potential Flash Flood Warnings are issued.

Should see a break in systems for Sunday, and will carry just 10-20
PoPs Saturday night and Sunday. Chances of rain will increase again
Monday and Tuesday as yet another system moves into the region.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              70  81  69  82  58 /  40  80  40  60  70
Austin Bergstrom Intl Airport  70  82  68  83  57 /  40  70  50  70  70
New Braunfels Muni Airport     69  81  67  82  58 /  40  80  30  70  70
Burnet Muni Airport            68  79  65  78  54 /  40  80  20  50  70
Del Rio Intl Airport           69  90  66  88  61 /  40  10  -   60  50
Georgetown Muni Airport        69  80  67  81  56 /  40  80  40  50  70
Hondo Muni Airport             70  85  67  84  60 /  40  80  10  70  70
San Marcos Muni Airport        69  81  67  82  57 /  40  70  40  70  70
La Grange - Fayette Regional   72  85  71  85  61 /  40  70  50  70  80
San Antonio Intl Airport       71  82  69  83  59 /  40  80  20  70  70
Stinson Muni Airport           71  83  69  82  61 /  40  70  20  70  70

&&

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

Aviation...EWilliams
Short-Term/Long-Term...17
Public Service/Data Collection...EWilliams

Hazardous Weather Outlook
National Weather Service Austin/San Antonio TX
509 AM CDT Tue May 7 2019

TXZ171>173-183>194-202>209-217>225-228-081015-
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-
509 AM CDT Tue May 7 2019

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

.DAY ONE...Today And Tonight.
Chances for severe storms in the western portion of the CWA,
including Val Verde County and the Edwards Plateau late this
afternoon. Large hail and damaging wind are possible with these
storms, as well as the potential for locally heavy rain.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
The greatest threat for severe storms will be on Wednesday. There
is a potential of very large hail, damaging wind gusts, and even
isolated tornadoes. Training of storms could lead to locally
heavy rains. Expect periods of showers and thunderstorms through
Monday.

.SPOTTER INFORMATION STATEMENT...

Please report any severe weather or flooding to the National
Weather Service.

Special Weather Statement
National Weather Service Austin/San Antonio TX
641 PM CDT Tue May 7 2019

TXZ173-192-080030-
Williamson TX-Travis TX-
641 PM CDT Tue May 7 2019

...SIGNIFICANT WEATHER ADVISORY FOR SOUTH CENTRAL WILLIAMSON AND
CENTRAL TRAVIS COUNTIES UNTIL 730 PM CDT...

At 641 PM CDT, Doppler radar was tracking a strong thunderstorm near
Windemere, moving north at 20 mph.

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

Locations impacted include...
Austin, Round Rock, Cedar Park, Georgetown, Pflugerville, Taylor,
Anderson Mill, Serenada, Windemere, Leander, Hutto, Weir, Georgetown
Dam, Sun City, Brushy Creek, Wells Branch, Jollyville and Jonah.

LAT...LON 3030 9764 3037 9784 3073 9774 3063 9745
TIME...MOT...LOC 2341Z 200DEG 16KT 3041 9772

Special Weather Statement
National Weather Service Austin/San Antonio TX
752 PM CDT Tue May 7 2019

TXZ192-080130-
Travis TX-
752 PM CDT Tue May 7 2019

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL TRAVIS COUNTY UNTIL 830
PM CDT...

At 751 PM CDT, Doppler radar was tracking a strong thunderstorm near
Onion Creek, or near Tanglewood Forest, moving northeast at 15 mph.

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

Locations impacted include...
Austin, Tanglewood Forest, Austin Bergstrom Int Airport, Manor,
Rollingwood, Onion Creek, Shady Hollow, Hornsby Bend, Manchaca,
Sunset Valley, San Leanna, Del Valle, Pilot Knob and McKinney Falls
State Park.

LAT...LON 3011 9780 3018 9787 3040 9765 3027 9746
TIME...MOT...LOC 0051Z 225DEG 12KT 3020 9777