577
FXUS64 KEWX 221722
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1222 PM CDT Sun Sep 22 2024

...New AVIATION...

.UPDATE...
Issued at 645 AM CDT Sun Sep 22 2024

The only minor update to the forecast this morning is to include a
low chance for some isolated showers across the coastal plains to
near the I-35 corridor.

&&

.SHORT TERM...
(Today through Monday)
Issued at 338 AM CDT Sun Sep 22 2024

Low clouds continue to expand in coverage early this morning as
noted on the latest GOES Nighttime Microphysics satellite imagery.
Upslope flow and low-level moisture will remain in place this
morning allowing for a continuation of low clouds. We may even see
an isolated shower or two develop across portions of the western
Hill Country and southern Edwards Plateau where models show stronger
winds around 925mb and 850mb. Otherwise, some light winds and less
cloud cover over the coastal plains may allow for some patchy fog
development closer to sunrise. For late this afternoon and evening,
a cold front will begin to move through west central Texas, with the
boundary eventually approaching portions of the western Hill Country
and southern Edwards Plateau around sunrise Monday. The hi-res
models differ with regards to the amount of convection that develops
ahead of and along this front. For now, we will show the higher rain
chances during the early morning hours on Monday, mainly for areas
north of a Del Rio to Rocksprings line. With the stronger large
scale forcing remaining farther to our north, we will keep rain
chances capped at 50% for now. For most of our forecast area,
suspect the front will not line up with the stronger forcing to our
north. The exception could be across the far northern portions of
Val Verde and Edwards counties and the SPC does maintain a Marginal
Risk for severe storms across these areas. Should any stronger
storms manage to develop, gusty outflow winds and hail will be the
main severe weather concerns. The leading edge of the front may slip
southward into portions of the Hill Country and perhaps even a small
portion of the I-35 corridor on Monday. We will maintain a low
chance for showers and storms into Monday afternoon for areas
generally along and north of an Eagle Pass to Llano line. A few
showers and storms may also develop over the coastal plains region
during the afternoon hours.

As for temperatures, highs remain above normal for all areas today
with near 90 in the Hill Country to the mid/upper 90s elsewhere.
With the above mentioned cold front expected to drop southward into
portions of the Hill Country and southern Edwards Plateau, highs
will trend downward into the 80s over these areas. Farther south,
not much change in the forecast highs are expected, with perhaps a
degree or two drop depending on the amount of cloud cover that
lingers into the afternoon hours. Lows tonight will be warm again,
with 70s in store for most of the region.

&&

.LONG TERM...
(Monday night through Saturday)
Issued at 338 AM CDT Sun Sep 22 2024

By Monday evening, the cold front is forecast to be along the Hill
Country and the southern Edwards Plateau. The GFS and ECMWF
solutions keep the boundary across the Hill Country and southern
Edwards Plateau on Monday night into Tuesday while the NAM guidance
has the boundary to the south of Interstate 35 stretching from near
Georgetown to the southwest into San Antonio and then into Carrizo
Springs. It is hard to tell if it dissipates or pushes back to the
north as a warm front with winds returning from the southeast. Let`s
go with the GFS/ECMWF guidance. Overnight lows are forecast to range
from the upper 60s across the Hill Country to mid 70s along the
Coastal Plains. The overnight period likely stays rain-free. As the
day progresses on Tuesday, temperatures are forecast to go up into
the upper 80s across the Hill Country to mid 90s along the Coastal
Plains. Mostly cloudy skies are expected to dominate South Central
Texas through the period.

From this point on (Tuesday afternoon into the evening), the
forecast becomes challenging as the NAM solution brings the
seabreeze from the Coastal Plains into the I-35 corridor and a surge
of northeast winds into the Hill Country. The GFS solution keeps a
stationary boundary across the Hill Country with an upper level
trough axis pushing across the local area which translates into
scattered showers and isolated thunderstorms across most areas of
South Central Texas. The unstable weather conditions continue on
Wednesday as a stronger cold front pushes through the local area
with scattered showers and thunderstorms in addition to cooler
temperatures. WPC Day 3 ERO shows the northern part of the Hill
Country under a marginal risk for exceeding rainfall amounts.
Therefore, a few locations could get a few inches of rainfall but
for the most part, half inch and less is expected for most areas
based on this forecast package. This is an evolving system.
Wednesday`s highs are forecast to range from the lower 80s across
the Hill Country to the mid and upper 80s elsewhere. The dry and
cooler air mass spreads across the local area Wednesday evening into
Thursday with limited to none chances of rain through the period.
Overnight lows are forecast to drop to the upper 50s across the Hill
Country and within the 60s for the rest of South Central Texas.

Dry weather conditions persist the latter part of the work week into
the weekend with temperatures running close to the normal climate
values (mid to upper 80s for highs/low to upper 60s for lows) for
late September.

&&

.AVIATION...
(18Z TAFS)
Issued at 1222 PM CDT Sun Sep 22 2024

CIGs will lift to VFR across all areas by 19Z, then lower back to
MVFR overnight into Monday morning. As a front moves into our area,
SHRA/TSRA will develop across portions of the Hill Country, Edwards
Plateau, and Rio Grande this evening through Monday. Have maintained
VCSH at KDRT, however later updates could go with prevailing or TSRA
based on model/radar trends. Southeasterly winds prevail at 7 to 15
KTs, become light this evening, then gradually turn to northerly on
Monday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              96  74  95  73 /   0   0  10  10
Austin Bergstrom Intl Airport  95  73  95  72 /   0   0  10  10
New Braunfels Muni Airport     96  73  96  73 /  10   0   0  10
Burnet Muni Airport            93  72  89  70 /   0  20  20  20
Del Rio Intl Airport           96  77  92  75 /   0  20  20  10
Georgetown Muni Airport        94  73  92  71 /   0  20  10  10
Hondo Muni Airport             94  73  94  73 /  10   0   0  10
San Marcos Muni Airport        95  72  94  71 /  10   0  10  10
La Grange - Fayette Regional   94  72  93  72 /   0   0  10  10
San Antonio Intl Airport       95  75  94  75 /   0   0   0  10
Stinson Muni Airport           96  75  95  75 /   0   0   0  10

&&

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

$$

Short-Term...04
Long-Term...36
Aviation...04