Severe Thunderstorm Warning 174, NWS Austin/San Antonio, TX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1215 AM CDT Tue May 9 2023

...New AVIATION...

.UPDATE...
Issued at 1009 PM CDT Mon May 8 2023

Area radars show showers and thunderstorms developing along and west
of US 281 where some CAMs indicated they would develop. Have
maintained POPs in this area for the rest of this evening with a
continued slight chance for strong to severe storms due moderate to
strong instability and steep mid level lapse rates. Models show this
drifting east and have raised POPs for the remainder of our area for
the overnight hours. Remainder of the South Central Texas forecast
is on track.

&&

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 221 PM CDT Mon May 8 2023

|The latest GOES 16 satellite imagery, along with the latest regional
radar indicate storms have already started to light up along the
Sierra Madre Oriental Mountain range of northeastern Mexico. The
going thinking is that this convection will merge and grow upscale
into an MCS and move eastward late this afternoon into the evening
hours. After some coordination with SPC, a Slight Risk (Level 2 of
5) has been reintroduced for the Rio Grande Plains and southern
Edwards Plateau with large hail being the primary concern followed
by damaging winds. Storms will likely start out as hail threats
early evening before transitioning to a wind threat further to the
south over the southern Rio Grande Plains from Eagle Pass southward
into the CRP CWA. The main limiting factor today would be weak flow
aloft, however, with steep mid-level lapse rates and nasty levels of
instability, the thought is that storms will probably develop and
move off the higher terrain and over our western CWA. In fact, after
a cool start over the Rio Grande Plains and southern Edwards Plateau
in the lower to middle 60s, rapid warming has taken place as skies
remained clear. Some cumulus have started to bubble up over this
region, but activity is expected to start out west of the border
then move east.

Elsewhere, some of the 12Z CAMs indicated a threat for isolated to
scattered storms to develop over the middle Texas coast and slide
northward into the Coastal Plains early this afternoon. While cu
have started to bubble up over in this region, tops on the DCP RGB
do not indicate robust convection and things are likely still
somewhat capped from this morning's cloud cover. However, latest
ACARS soundings from AUS indicate that the cap may have already
eroded and convection could fire this afternoon by 20Z.
Additionally, latest SPC RAP mesoanalysis indicates significant
SBCAPE, on the order of 5000-6000 J/kg in place! Shear appears to be
the limiting factor here, but with such extreme instability, it
wouldn't take much to overcome weak shear.

On Tuesday, the shortwave disturbance over northern Mexico will
become closed off as a mid-level vorticity maximum over the Hill
Country. This should result in cooler temperatures along with
scattered to perhaps more numerous showers and thunderstorms
developing over the I-35 corridor, Hill Country, and Coastal Plains
Tuesday afternoon and evening. As of this writing, Tuesday is very
much so up in the air as far as convective development goes as
Monday's storms will place a big role in the placement and timing of
storms on Tuesday. Locally heavy rainfall could result in isolated
instances of flash flooding, especially where storms can train over
the same location. The forecast gets even MORE ACTIVE in the long
term. Please see below for more juicy details.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 221 PM CDT Mon May 8 2023

Scattered thunderstorms will remain possible Wednesday and Thursday
before the pattern becomes even more active and wetter from Friday
through this upcoming weekend.

While a closed off upper low is expected to exit our area toward the
east-northeast through Wednesday, enough lingering moisture along
with subtle shortwave energy and/or westerly flow aloft near the
southern flank of a stronger upper level system moving through the
Four Corners region should help aid in more diurnally driven
convection. This would be exacerbated by any lingering mesoscale
boundaries and/or features from convection from the day prior. With
temperatures peaking in the 80s for most and into the low 90s along
the Rio Grande, expect for instability to pool where SBCAPE could
exceed 3000 J/kg. Thursday looks to trend slightly higher with
instability as temperatures trend a couple of degrees warmer than
Wednesday and with a little less cloud cover. While the deep layer
shear remains quite modest, it could still remain sufficient enough
to where isolated strong to severe storms could be possible.

While the main upper level low that moved over the Four Corners
region is expected to pivot into the north-central plains into and
through Friday, a sub-tropical jet with the split flow aloft will
approach from the west and this helps to carve out a deeper upper
level trough over the Desert Southwest and across the Baja
California peninsula. These synoptic setups are notorious for
bringing in high amounts of moisture and precipitable water values
across our region are expected to approach 2 inches and into the
97.5 to 99 percentile anomalies for this time of year. The models
are remaining consistent on indicating a heavy rainfall event from
Friday night through the weekend. The midday update of the Day 5
excessive rainfall outlook (12Z Friday through 12Z Saturday) from
the WPC has expanded the slight risk to cover our western and
central portions of our CWA within a slight risk while a marginal
risk exists across the remainder of the area. The latest medium
range and ensemble guidance remains in good agreement with the
potential for several inches of rain with localized amounts that
could exceed 5 inches. As mentioned in the previous long term
forecast discussion, the NBM probabilities continue to indicate
greater than 50% chance of at least 3 inches of rain from Friday
through the weekend. While this is a good sign that a lot of the
area will receive beneficial rainfall, there is the concern for
Flash Flooding, if too much rain comes down in a too short of a
period of time. Otherwise, expect for cooler daytime temperatures
with all the cloud cover and moisture while the overnights will
remain warm and humid. Stay tuned to the forecast during the days
ahead as confidence increases leading up to this potential heavy
rainfall event.

&&

.AVIATION...
(06Z TAFS)
Issued at 1211 AM CDT Tue May 9 2023

Reductions to MVFR and IFR are possible through the overnight hours
at the I-35 sites. Showers and thunderstorms will be possible through
the duration of the period at the I-35 terminals with an upper
disturbance in the vicinity. Confidence in precise timing and
placement remains low, so have handled this potential with a
combination of VCSH and VCTS groups, with the intention of amending
to prevailing RA/TSRA groups as confidence increases. Additional
reductions are likely at AUS/SAT/SSF Tuesday night into Wednesday
morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              68  81  70  86 /  30  50  10  40
Austin Bergstrom Intl Airport  66  80  69  85 /  30  50  10  40
New Braunfels Muni Airport     68  81  70  86 /  30  50  10  30
Burnet Muni Airport            66  81  68  84 /  20  40  10  30
Del Rio Intl Airport           72  90  73  92 /  40  20  20  10
Georgetown Muni Airport        66  79  69  84 /  30  50  10  40
Hondo Muni Airport             69  84  70  87 /  30  40  10  40
San Marcos Muni Airport        67  80  69  85 /  30  50  10  40
La Grange - Fayette Regional   69  81  70  84 /  40  50  10  40
San Antonio Intl Airport       69  81  71  86 /  30  40  10  40
Stinson Muni Airport           70  83  72  87 /  30  40  10  40

&&

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

Short-Term...MMM
Long-Term...Brady
Aviation...Quigley

Hazardous Weather Outlook
National Weather Service Austin/San Antonio TX
1114 PM CDT Mon May 8 2023

TXZ171>173-183>194-202>209-217>225-228-100415-
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-
1114 PM CDT Mon May 8 2023

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

.DAY ONE...Today And Tonight.

Isolated to scattered thunderstorms are possible this afternoon
and into tonight across South Central Texas. The concern for
severe storms is generally west of Highway 281, mainly across the
southern Edwards Plateau and Rio Grande Plains. Large hail and
damaging winds are the most likely hazards.

In addition, locally heavy rainfall is also possible which could
lead to isolated Flash Flooding concerns.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

There is a Slight Risk of excessive rainfall across portions of
the Coastal Plains Tuesday and Wednesday. The region has seen
wetter than normal conditions recently and additional heavy
rainfall could lead to minor flooding impacts.

We will be entering an even wetter pattern Friday through Sunday.
While it's too far away for any specific details, there will
likely be a threat for areas of heavy rain in the region next
weekend. Confidence is increasing in the risk for flooding impacts
during this period.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

Special Weather Statement
National Weather Service Austin/San Antonio TX
1056 PM CDT Mon May 8 2023

TXZ184-185-090445-
Edwards TX-Real TX-
1056 PM CDT Mon May 8 2023

...A strong thunderstorm will impact portions of northeastern Edwards
and northern Real Counties through 1145 PM CDT...

At 1055 PM CDT, Doppler radar was tracking a strong thunderstorm 12
miles south of Telegraph, or 17 miles northeast of Rocksprings,
moving south at 15 mph.

HAZARD...Winds in excess of 40 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Prade Ranch and Devil's Sinkhole State Natural Area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3012 9976 3008 9976 3008 9973 2999 9969
      2995 9969 2984 10014 3019 10019 3029 9987
      3029 9985
TIME...MOT...LOC 0355Z 344DEG 15KT 3015 9997

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...40 MPH

BF

Special Weather Statement
National Weather Service Austin/San Antonio TX
1114 PM CDT Mon May 8 2023

TXZ203-218-090500-
Uvalde TX-Zavala TX-
1114 PM CDT Mon May 8 2023

...A strong thunderstorm will impact portions of southwestern Uvalde
and northwestern Zavala Counties through MIDNIGHT CDT...

At 1114 PM CDT, Doppler radar was tracking a strong thunderstorm 8
miles west of La Pryor, moving north at 25 mph.

HAZARD...Winds in excess of 40 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Uvalde, La Pryor, Uvalde Estates, Dabney, Blewett and Washer.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 2885 9987 2888 10010 2926 10011 2922 9973
TIME...MOT...LOC 0414Z 195DEG 20KT 2893 9999

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...40 MPH

BF

Special Weather Statement
National Weather Service Austin/San Antonio TX
1123 PM CDT Mon May 8 2023

TXZ185-186-090515-
Kerr TX-Real TX-
1123 PM CDT Mon May 8 2023

...A strong thunderstorm will impact portions of west central Kerr
and northeastern Real Counties through 1215 AM CDT...

At 1123 PM CDT, Doppler radar was tracking a strong thunderstorm near
Tuff, or 8 miles north of Leakey, moving north at 5 mph.

HAZARD...Winds in excess of 40 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Prade Ranch.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 2977 9962 2977 9983 3001 9993 3003 9962
TIME...MOT...LOC 0423Z 176DEG 6KT 2985 9976

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...40 MPH

BF

Special Weather Statement
National Weather Service Austin/San Antonio TX
1201 AM CDT Tue May 9 2023

TXZ218-090530-
Zavala TX-
1201 AM CDT Tue May 9 2023

...A strong thunderstorm will impact portions of southwestern Zavala
County through 1230 AM CDT...

At 1201 AM CDT, Doppler radar was tracking a strong thunderstorm 11
miles north of Cometa, or 11 miles southwest of La Pryor, moving
north at 20 mph.

HAZARD...Nickel size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

This storm will remain over mainly rural areas of southwestern Zavala
County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 2872 9992 2879 10011 2894 10009 2893 9979
TIME...MOT...LOC 0501Z 201DEG 16KT 2883 9999

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...<30 MPH

BF

Special Weather Statement
National Weather Service Austin/San Antonio TX
1207 AM CDT Tue May 9 2023

TXZ219-090530-
Frio TX-
1207 AM CDT Tue May 9 2023

...A strong thunderstorm will impact portions of southwestern Frio
County through 1230 AM CDT...

At 1207 AM CDT, Doppler radar was tracking a strong thunderstorm over
Derby, or near Dilley, moving northwest at 15 mph.

HAZARD...Nickel size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

Locations impacted include...
Dilley, Divot, Derby, Hilltop and Bluff.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 2893 9930 2881 9895 2864 9900 2864 9938
TIME...MOT...LOC 0507Z 131DEG 12KT 2874 9915

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...<30 MPH

BF

Special Weather Statement
National Weather Service Austin/San Antonio TX
103 AM CDT Tue May 9 2023

TXZ219-090645-
Frio TX-
103 AM CDT Tue May 9 2023

...A strong thunderstorm will impact portions of Frio County through
145 AM CDT...

At 103 AM CDT, Doppler radar was tracking a strong thunderstorm near
Dilley, moving northeast at 20 mph.

HAZARD...Penny size hail.

SOURCE...Radar indicated.

IMPACT...Minor damage to outdoor objects is possible.

Locations impacted include...
Pearsall, Dilley, North Pearsall, Divot, Derby and Hilltop.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 2866 9939 2902 9919 2888 9893 2864 9914
      2864 9935
TIME...MOT...LOC 0603Z 212DEG 18KT 2868 9926

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...<30 MPH

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