Area Forecast Discussion
Issued by NWS Austin/San Antonio, TX

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FXUS64 KEWX 181122

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

...New AVIATION...

(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.


(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.


(12Z TAFS)
Issued at 622 AM CDT Tue Jun 18 2024

SHRA will be in the VCNTY of KDRT through mid morning. SHRA/TSRA may
approach the I-35 sites this afternoon, however PROBs are low and
have left mention out of forecasts. There are higher PROBs for the
I-35 sites on Wednesday and have introduced mention of SHRA for the
morning hours with TSRA likely by midday. Otherwise, MVFR CIGs lift
to SCT-BKN VFR late this morning to midday, then MVFR/IFR CIGs
return late this evening into overnight. Some restrictions to VSBYs
are expected on Wednesday. Gusty E-SE winds to 25KT+ are expected
today, then NE-E tonight into Wednesday.


Austin Camp Mabry              93  75  82  75 /  20  10  70  60
Austin Bergstrom Intl Airport  92  75  81  74 /  20  20  80  60
New Braunfels Muni Airport     94  75  81  75 /  20  20  80  70
Burnet Muni Airport            91  73  81  73 /  20  10  60  70
Del Rio Intl Airport          101  79  93  77 /  20   0  40  80
Georgetown Muni Airport        91  73  81  72 /  10  10  70  60
Hondo Muni Airport             95  75  82  73 /  20  10  70  80
San Marcos Muni Airport        92  73  79  72 /  20  20  80  70
La Grange - Fayette Regional   90  75  79  75 /  30  40  80  40
San Antonio Intl Airport       94  76  81  75 /  20  10  80  70
Stinson Muni Airport           95  77  82  76 /  20  20  80  70


Flood Watch from Wednesday morning through Thursday afternoon for
Atascosa-Bexar-Caldwell-Comal-De Witt-Fayette-Frio-Gonzales-