887
FXUS64 KEWX 181926
AFDEWX

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

...New SHORT TERM, LONG TERM...

.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...
(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-Dimmit-Fayette-Frio-Gonzales-
Guadalupe-Karnes-Lavaca-Maverick-Medina-Wilson-Zavala.

&&

$$

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