785
FXUS64 KEWX 182330
AFDEWX

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

...New AVIATION...

.SHORT TERM...
(Tonight through Wednesday night)
Issued at 225 PM CDT Tue Jun 18 2024

Key Messages:

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

*Confidence increasing for greatest rainfall amounts to focus across
southern half of the region; Flood Watch has been expanded to
include Maverick, Zavala, and Dimmitt Counties.

*Isolated tornado possible across our southeastern-most counties on
Wednesday into Wednesday night.

Discussion:

Isolated to widely scattered showers have developed this afternoon
across the region, especially along and east of the I-35 corridor,
in combination with a weak upper level disturbance earlier this
morning located to our west-northwest and with activity coming off
the middle to upper Texas coast as higher moisture levels start to
inch westward. These should remain brief with a few locations
picking up a quick quarter inch or so. While lightning is not
expected to be common, a few strikes could be possible later this
afternoon with peak daytime heating. Partly cloudy skies otherwise
trend into this evening with highs into the low to mid 90s for most
except for the Rio Grande communities which may approach or reach
the 100 degree mark.

Deeper tropical moisture that is in association with Potential
Tropical Cyclone One over the southwestern Gulf with PWATs as high
as 2.7 inches and warm cloud layer depths that exceed 14,500 feet
should arrive into the Coastal Plains by early Wednesday morning
then gradually expand westward into the I-35 corridor and portions
of the Hill Country by mid to late morning and towards the Rio
Grande through Wednesday afternoon. Bands of moderate to locally
heavy rainfall will pivot across the region with this deeper
tropical moisture. Some embedded thunderstorms may be possible as
well but widespread thunderstorm activity will not be expected.
As stated within the previous forecast discussion, model solutions
have continued the trend of shifting the highest rainfall totals
farther to the south. This leads to the greatest confidence for
heaviest rainfall to commence across our southern counties with a
fairly tight gradient centered in our CWA. Not going to make any
major configuration changes to the issued Flood Watch except for
expansion across the remainder of the Rio Grande Plains. Amounts
will also be lowered within the product into the 1 to 4 inch range
with isolated totals up to or in excess of 6 inches across our
southern most counties. This is in step with most recent QPF
forecast from WPC. The newest released Day 2 Excessive Rainfall
Outlook from WPC has been adjusted as well to where the Moderate
(level 3 of 4) risk of excessive rainfall and flooding has been
shifted southward to include mainly our southern tier of counties
and points southward. Majority of the rest of the CWA will stay
within the slight (level 2 of 4) risk. Those locations where the
heaviest rainfall does occur could see some rises in the river
levels as well.

Gusty winds will be expected within some of the bands of rain as
well where gusts into the 25 to 35 mph range will be possible.
However, direct wind impacts associated with Potential Tropical
Cyclone One are to remain well south of our area. There will be
enough ingredients and vorticity for the potential of a brief
isolated tornado or two. Greatest focus would be across our
southeastern most regions, where SPC has highlighted a marginal
(level 1 of 5) risk for severe thunderstorms. Otherwise, high
temperatures on Wednesday will be well below normal due to the thick
clouds and fairly widespread rains, mainly ranging from upper 70s
into the 80s across most locations.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 225 PM CDT Tue Jun 18 2024

Rain and storms will be ongoing over the Rio Grande Plains Thursday
morning. Locally heavy rainfall remains a possibility through late
morning before the heaviest stuff moves off to the west. Continued
showers and storms appear likely Thursday afternoon as tropical
moisture remains in place with PWATs in excess of 2-2.5". WPC still
has a Slight risk ERO (level 2 of 4) for the western and
southwestern zones on Thursday, with the threat for flooding rains
remaining in play through the day Thursday. On the back side of the
inverted troughing over the region, continued showers and storms are
expected over the southern and western half of the region on Friday.

As we move into the weekend, we`ll be watching yet another area of
disturbed weather over the southwestern Gulf of Mexico for
development. As of right now, NHC gives it a low chance of
developing into a tropical storm over the next 7 days (1 in 5 odds).
Easterly flow aloft will continue through the weekend as well,
allowing showers and storms to be a possibility most days in the
long term forecast period. Temperatures should remain acceptable by
late June standards, but the humidity will continue due to recent
rains. While the Subtropical Ridge may attempt to build over
northeast Texas early next week, continued easterly flow on its
southern periphery will result in a slightly cooler than normal and
more active pattern than is typical for late June.

&&

.AVIATION...
(00Z TAFS)
Issued at 630 PM CDT Tue Jun 18 2024

VFR conditions will continue this evening. MVFR ceilings are forecast
to develop overnight, and lower into IFR Wednesday morning across
portions of the Coastal Plains, I-35 corridor, and Hill Country. RA
and SHRA activity, associated with Potential Tropical Cyclone One,
is forecast to move into the Coastal Plains and east of the I-35
corridor early Wednesday morning, spreading into the I-35 TAF sites
by around 14Z-16Z. This activity will expand west into portions of
the Hill Country in the afternoon and Rio Grande Wednesday evening.
E-NE winds are forecast to develop overnight, then strengthen from
the NE across the Coastal PLains and I-35 corridor during the day on
Wednesday, with gusts between 20-30KT forecast.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              93  75  83  75 /  20  10  70  60
Austin Bergstrom Intl Airport  93  74  82  75 /  20  20  70  60
New Braunfels Muni Airport     94  75  82  75 /  30  20  80  70
Burnet Muni Airport            91  73  82  72 /  20  10  60  60
Del Rio Intl Airport          101  79  91  75 /  20   0  40  80
Georgetown Muni Airport        92  73  82  73 /  20  10  60  50
Hondo Muni Airport             95  76  83  74 /  20  10  80  80
San Marcos Muni Airport        92  74  81  74 /  30  20  80  70
La Grange - Fayette Regional   91  75  82  76 /  30  40  80  50
San Antonio Intl Airport       94  76  82  74 /  30  10  90  80
Stinson Muni Airport           96  77  83  76 /  30  10  90  80

&&

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

&&

$$

Short-Term...Brady
Long-Term...MMM
Aviation...76