Areal Flood Advisory 29, NWS Austin/San Antonio, TX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
813 PM CDT Mon May 3 2021

.UPDATE...
Severe storms are moving east through San Antonio and northeast near
Blanco. Have extended Severe Thunderstorm Watch 135 for Hays,
Guadalupe, and Wilson counties.

&&

.PREV DISCUSSION... /ISSUED 708 PM CDT Mon May 3 2021/

UPDATE...
A couple of thunderstorms have developed southwest of San Antonio.
Convective parameters show they could go severe. Have issued Severe
Thunderstorm Watch 135 for one county either side of a line from
Lake Buchanan to Castroville to Dilley. The storms should dissipate
by late evening with loss of heating after sunset.

PREV DISCUSSION... /ISSUED 654 PM CDT Mon May 3 2021/

AVIATION...
Area radars show SHRA/TSRA southwest of KSAT/KSSF between KCVB and
KCOT. Flow would take them near KSAT/KSSF and have mentioned VCTS for
early this evening. SHRA/TSRA are developing too far to the northwest
of KAUS and have removed any mention for this evening there. A cold
front will move across our area overnight into Tuesday morning. Have
mention of VCSH at the I-35 sites with PROB30s for KAUS where
conditions are more favorable for development. VFR skies prevail this
evening. MVFR CIGs will move over the I-35 sites late this evening
into the overnight while KDRT remains VFR. VFR skies will return to
all sites by midday on Tuesday. At the I-35 sites, southeasterly
winds of 7 to 14 KTs will shift to northerly with the frontal
passage, then increase to 10 to 20 KTs with gusts to 28 KTs on
Tuesday. At KDRT, Variable winds will become northerly later this
evening, then increase to 10 to 20 KTs with gusts to 28 KTs
overnight, then slowly decrease Tuesday afternoon.

PREV DISCUSSION... /ISSUED 241 PM CDT Mon May 3 2021/

SHORT TERM (Tonight through Tuesday Night)...

A highly conditional environment is setting up today as an
approaching dryline to our west could initiate strong to severe
storms this evening. A capping inversion is in place and if it holds
tight, there will be no storms with this dryline. However, given the
great amount of instability in the area, if enough destabilization
takes place to break the cap, severe storms are likely to develop.
With the dryline approaching near max heating, the convective
temperature, which is the temperature that would allow convection, is
near equal to the actual forecasted temperatures for the area. CAPE
values as high as 5800 J/kg and very steep mid level lapse rates
indicate that where storms do develop, they will likely intensify
rapidly, producing large hail, damaging winds and possible tornado.
The high resolution models have been inconsistent with initial
development, again due to the conditional environment. SPC has the
area along the I-35 corridor down to San Antonio highlighted in a
marginal risk. A smaller area of slight risk is highlighted in our
northern counties including Williamson and Burnet. This area is also
noted for the potential of very large hail greater than 2 inches,
given that storms come to fruition. Timing for these severe storms
chances is from 5 PM - 9 PM.

A second chance for storms comes with the arrival of a cold front
overnight. Showers and storms along the leading edge of the front
will move in from the northwest to southeast. Behind the front, north
to northeasterly winds bring in relatively cooler and drier air.
Tomorrow's high temperatures will be close to 10 degrees cooler than
today with skies clearing from west to east. Tomorrow night,
overnight lows will be in the 50s and low 60s to the south.

LONG TERM (Wednesday through Monday)...

A zonal flow is forecast for Wednesday with surface northerly winds
over most areas with the exception of the Rio Grande. A surface
southerly flow is forecast along the Rio Grande as a surface high
pressure over the Southern Plains pushes into the Middle Mississippi
Valley. Highs will range from the upper 70s across the Hill Country
to upper 80s over parts of the southwest counties under sunny skies.

The upper level flow changes on Wednesday night into Thursday as an
upper short wave moves across the area. With limited moisture in
place, expect another day on Thursday with plenty of sunshine and
temperatures warming into the mid 80s across the Hill Country and mid
to upper 80s along the Interstate 35 corridor.

An upper northwest flow aloft will keep the area dry and warm on
Friday. Surface southerly winds will dominate the area this upcoming
weekend with increasing clouds Friday night into Saturday morning.
Clouds are expected to stay around for most of the day on Saturday
and finally breaking by the middle afternoon period. Saturday's high
are expected to range from the middle 80s across the Hill Country to
upper 90s across portions of the southwest counties. Dry conditions
are expected to continue through early next week.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              68  79  56  80  57 /  30  10   0   0   0
Austin Bergstrom Intl Airport  68  80  55  80  56 /  30  20   0   0   0
New Braunfels Muni Airport     69  83  57  83  57 /  30  10   0   0   0
Burnet Muni Airport            63  77  52  79  56 /  20  -    0   0   0
Del Rio Intl Airport           66  88  61  88  63 /  -    0   0   0   0
Georgetown Muni Airport        66  79  54  79  56 /  30  10   0   0   0
Hondo Muni Airport             66  85  57  85  58 /  20  -    0   0   0
San Marcos Muni Airport        68  81  55  81  56 /  30  20   0   0   0
La Grange - Fayette Regional   72  81  57  81  59 /  30  30   0   0   0
San Antonio Intl Airport       68  82  59  83  59 /  60  10   0   0   0
Stinson Muni Airport           71  84  59  84  59 /  90  10   0   0   0

&&

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

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

Hazardous Weather Outlook
National Weather Service Austin/San Antonio TX
1159 AM CDT Mon May 3 2021

TXZ171>173-183>194-202>209-217>225-228-041700-
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-
1159 AM CDT Mon May 3 2021

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

.DAY ONE...This Afternoon And Tonight.

There are low chances for a strong to severe storm to develop this
afternoon with possible large hail and damaging winds across the
eastern half of the CWA. Higher chances are in the northern
counties, including Williamson and Burnet. These chances are
highly conditional, but if a storm does develop in this area,
severe chances are higher.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.

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