824
FXUS64 KEWX 181745
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1245 PM CDT Tue Jun 18 2024

...New UPDATE, AVIATION...

.UPDATE...
Issued at 1226 PM CDT Tue Jun 18 2024

Have expanded the areal coverage for isolated to widely scattered
showers this afternoon across the region in response to the ongoing
activity across the area. A few locations may be able to pick up a
quick quarter of an inch or so of rain from this activity. The rest
of the forecast remains on track.

&&

.SHORT TERM...
(Today through Wednesday)
Issued at 204 AM CDT Tue Jun 18 2024

Key Points...

*Bands of moderate to heavy rains expected to begin early Wednesday
and continue into Thursday.

*A Flood Watch has been issued beginning Wednesday morning and
continuing through Thursday midday.

Deep tropical moisture with PWs above 2 inches is lurking offshore
over the Gulf of Mexico early this morning. As potential Tropical
Cyclone One develops, this moisture will surge across the Coastal
Plains today and over South Central Texas tonight into Wednesday as
the potential cyclone approaches the northeastern Mexican coast.
This is due to a relative weakness in the Subtropical Ridge over
Texas. With the initial increase in moisture, streamer showers can
be expected this morning. Then, as the moisture deepens further,
showers and thunderstorms will spread from the Coastal Plains late
this morning to near the I-35 corridor this afternoon into early
evening. The increase in moisture and associated cloudiness should
keep high temperatures closer to normal today. The showers and
thunderstorms will taper off this evening.

As the slug of deep tropical moisture with PWs as high as 2.7 inches
surges over our area on Wednesday, showers and thunderstorms spread
from the Coastal Plains early in the morning to the I-35 corridor by
midday, then over the Hill Country and the Rio Grande in the
afternoon. Recent model trends show the heaviest rains shifting to
the south as the Subtropical Ridge begins to build back to the
southwest over Texas. However, still expect heavy rains over parts
of our area, especially along and south/east of I-10/I-35 where WPC
has maintained a Moderate (level 3 out of 4) risk of excessive
rainfall and flooding. We have issued a Flood Watch for this area.
Have included Bexar county/San Antonio Metro area due to the flashy
nature of urban runoff. Expect Watch to be reconfigured going into
the long term as this heavy rainfall event evolves. There is a
Slight (level 2 out of 4) risk of excessive rainfall and flooding
across the remainder of our area. Gusty winds can be expected within
the bands of rain. However, any direct wind impacts from the
potential tropical cyclone will be well south of our area. Wednesday
high temperatures will be well below normal due to the thick clouds
and fairly widespread rains.

&&

.LONG TERM...
(Wednesday night through Monday)
Issued at 204 AM CDT Tue Jun 18 2024

South Central Texas will be in the midst of the expected heavy rain
event for the start of the long term period. Wednesday night,
showers and thunderstorms will be ongoing across much of the area in
an environment with impressive precipitable water values exceeding 2
inches. Breezy easterly to northeasterly wind is expected with gusts
to around 30 mph possible, but the main hazard will be the heavy
rain and potential for flooding and flash flooding. Highest
confidence for the heaviest rain totals remains over the southern
half of counties where model guidance, including the most recent
runs, have been most bullish. Overnight into Thursday morning, the
heaviest precipitation totals should be progressing westward across
the area. By Thursday morning, most activity should be located along
the Rio Grande. A Flood Watch is currently in effect through 1 PM
Thursday while the WPC slight risk for excessive rainfall (level 2
of 4) remains over the western half of the area for Thursday.

Rain should become more scattered and light as the
day progresses on Thursday, with much lower precipitation chances
across the eastern half of the area Thursday night. This will lead
to improving conditions to any flooding/flash flooding, although
rivers may still be responding and those near any banks that receive
decent rainfall upstream should pay attention to the forecast.

While generally drier conditions exist Friday through the weekend,
some low end precipitation chances remain with more than sufficient
moisture in place, mainly over the Coastal Plains. Granted, any rain
would be much more isolated/scattered than the round of rain
expected Wednesday into Thursday. The cooler temperatures in the
upper 70s and 80s on Thursday will increase day by day Friday
through early next week. By Sunday or Monday, most locations will be
back to near or slightly above normal highs for mid to late June.

&&

.AVIATION...
(18Z TAFS)
Issued at 1226 PM CDT Tue Jun 18 2024

Spotty isolated to widely scattered rain showers have popped up for
areas along and east of I-35 and activity may remain possible over
the next several hours. Added VCSH to KAUS, KSAT, and KSSF until
mid-afternoon for this activity. Otherwise, VFR flight conditions
should primarily prevail through this evening at all area TAF sites.
MVFR ceilings develop overnight as clouds increase and bases lower
as tropical moisture in association with Potential Tropical Cyclone
One approaches the region. The deeper tropical moisture then moves
into and through Wednesday morning across the I-35 corridor. This
results in rain bands, with some heavy rainfall, pivoting into and
across the region and for ceilings to lower into the IFR range with
this activity at KAUS, KSAT, and KSSF from mid-morning Wednesday
onward through the end of the forecast period. Some lightning will
also be possible with this activity and have added PROB30 groups at
those sites from 14/15 UTC onward. Winds will trend gusty at times
into the 25 knot range with the east-southeasterly winds today
shifting east-northeasterly on Wednesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              75  83  75  90 /  10  70  60  40
Austin Bergstrom Intl Airport  74  82  75  90 /  20  70  60  40
New Braunfels Muni Airport     75  82  75  87 /  20  80  70  50
Burnet Muni Airport            73  82  72  87 /  10  60  60  30
Del Rio Intl Airport           79  91  75  88 /   0  40  80  80
Georgetown Muni Airport        73  82  73  88 /  10  60  50  30
Hondo Muni Airport             76  83  74  85 /  10  80  80  60
San Marcos Muni Airport        74  81  74  87 /  20  80  70  50
La Grange - Fayette Regional   75  82  76  88 /  40  80  50  40
San Antonio Intl Airport       76  82  74  86 /  10  90  80  60
Stinson Muni Airport           77  83  76  87 /  10  90  80  60

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Wednesday morning through Thursday afternoon for
Atascosa-Bexar-Caldwell-Comal-De Witt-Fayette-Frio-Gonzales-
Guadalupe-Karnes-Lavaca-Medina-Wilson.

&&

$$

Short-Term...Brady
Long-Term...27
Aviation...Brady