Severe Thunderstorm Warning 119, NWS Austin/San Antonio, TX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
414 AM CDT Sun May 19 2019

.SHORT TERM (Today through Monday)...
Early morning surface analysis revealed the dryline had retreated to
a Mineral Wells to Rocksprings to Langtry line. With the KDFX VAD
wind profiler showing south to southeast winds around 20 knots
through 3kft AGL and nocturnal cooling of air north of this boundary,
current expectations are for the dryline to nudge a bit farther to
the north through the remainder of the pre-dawn hours. South of the
dry line, dewpoints surging into the mid to upper 70s have resulted
in patchy fog development across most of South Central Texas. Deep
moist convergence within the vicinity of the dryline is allowing for
thunderstorm development occur across Kinney and Val Verde Counties
early this morning. SPC Mesoanalysis for this area shows some very
high SBCAPE values in the 4000-5000 J/kg range as well as some modest
mid-level cold air advection associated with the passage of the
large trough over the Central Plains. Both of these factors, combined
with effective bulk shear in excess of 40 knots, will result in a
risk for an isolated severe thunderstorm or two for areas along the
Rio Grande early this morning. One such thunderstorm was currently
ongoing as of this writing just southeast of Del Rio. Large hail
appears to be the main threat, but a damaging wind threat also cannot
be ruled out. Farther east, patchy fog is expected to lift mid to
late morning with onset of daytime heating.

After a warm start this morning with several locations again possibly
tying or setting record high minimum temperatures today (more
information in the climate section below), convergence along the
dryline may allow for a secondary round of thunderstorms to develop
across Val Verde County this afternoon. The rest of the region is
expected to remain dry today with highs in the upper 80s to mid 90s
under partly cloudy skies. Southeast flow persisting across the
region tonight and associated warm air advection may allow for a few
streamer showers to develop for areas roughly east of Highway 281 by
sunrise Monday with another round of patchy fog possible. Best
chances for this fog appear to be across the Coastal Plains and into
the Interstate 25 corridor where winds are forecast to be lighter.
Very warm overnight lows in the low to mid 70s are expected again
tonight.

On Monday, a closed low off the California coast early this morning
swings into the Four Corners region and amplifies the southwest flow
aloft over the Southern Plains. Height falls associated with this
system are four standard deviations below normal for this time of
year and this will only help to induce rapid lee cyclogenesis along
the Front Range of the Rockies. While the overall trajectory of this
system places the best dynamics over portions of the Texas Panhandle,
Oklahoma, and Kansas, the strength of this system will result in
increasing winds across South Central Texas during the day on Monday
with winds increasing into the 15-25 MPH range across central and
eastern portions of the region and 20-30 MPH along the Rio Grande.
This will also allow for a few streamer showers to linger during the
day across much of the region with an isolated thunderstorm or two
possible along the dryline in Val Verde County during the afternoon.
Highs on Monday are forecast to range from the mid 80s across the
Hill Country to upper 90s in the Rio Grande Plains.

&&

.LONG TERM (Monday Night through Saturday)...
By Monday night, the closed low becomes an open wave as it swings
into Colorado and pushes the dryline eastward. This may allow for
another broken line of showers and thunderstorms to develop and push
into the region late Monday night and Tuesday morning, with streamer
showers developing ahead of the line Monday night. As we saw this
weekend, the strength of the cap will play a big role in how far
south these storms will be able to extend and presently expect best
rain chances to materialize for areas of north Interstate 10. Given
the wind energy associated with this system, a strong wind gust or
two may be possible with these storms. Expect this system to push
east of the region by Tuesday evening. Generally dry conditions are
expected through the remainder of the forecast as upper ridging
spreads into the region with temperatures near to above normal as a
result.

&&

.CLIMATE...
Above normal overnight temperatures are forecast to continue for the
next few days across South Central Texas and many locations may tie
or set new record high minimum temperatures. The record high minimum
temperatures for May 19 and May 20 for the four South Central Texas
climate sites are listed below.

MAY 19 RECORD HIGH MINIMUM TEMPERATURES
LOCATION            RECORD HI MIN     YEAR
Austin Bergstrom         76           1960
Austin Camp Mabry        77           1902
San Antonio              76           2017
Del Rio                  76           2013

MAY 20 RECORD HIGH MINIMUM TEMPERATURES
LOCATION            RECORD HI MIN     YEAR
Austin Bergstrom         75           2010
Austin Camp Mabry        76           1902
San Antonio              77           1989
Del Rio                  76           1939

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              92  74  89  74  86 /  10  10  10  30  60
Austin Bergstrom Intl Airport  92  74  89  74  87 /  10  10  10  30  60
New Braunfels Muni Airport     93  74  91  74  89 /  10  10  10  30  60
Burnet Muni Airport            91  72  87  69  86 /  -   10  10  40  60
Del Rio Intl Airport           95  75  96  72  93 /  20  10  20  20   0
Georgetown Muni Airport        92  73  88  73  85 /  10  10  10  30  60
Hondo Muni Airport             94  76  94  73  92 /  10  10  10  30  30
San Marcos Muni Airport        92  74  89  73  88 /  10  10  10  40  60
La Grange - Fayette Regional   92  77  91  76  88 /  10  10  10  20  50
San Antonio Intl Airport       93  75  90  75  90 /  10  10  10  30  50
Stinson Muni Airport           94  76  92  76  92 /  10  10  10  30  40

&&

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

Aviation...Treadway
Short-Term/Long-Term/Climate...Huffman

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