147
FXUS64 KEWX 180525
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1225 AM CDT Tue Jun 18 2024

...New AVIATION...

.SHORT TERM...
(Tonight through Tuesday night)
Issued at 145 PM CDT Mon Jun 17 2024

Moisture is on the increase across South-Central Texas with some
showers noted across areas east of the I35 corridor. Expect this to
continue through the afternoon with activity dwindling around sunset
with the loss of day time heating. Temperatures are currently in the
lower 90s for most locations and highs later today will be in lower
90s to 103 degrees out west. Most of the area will remain dry
overnight, but can`t rule out some streamer showers once again
across the eastern two-thirds of the area by daybreak. Will show
some 20 PoPs to cover that. Otherwise, lows tonight will be in the
middle to upper 70s with a return of nocturnal low-level stratus.

Rain chances tomorrow will mainly be back to areas east of I35 where
the best moisture will remain for one more day. Will show PoPs
generally in the 20-40 percent range. Highs will be in the lower 90s
to near 100 degrees out west. Moisture will begin to increase and
move west by late Tuesday night as moisture associated with a
tropical disturbance in the western Gulf of Mexico nears the area.
PoPs Tuesday night will be in the 20-50 percent range. The bigger
impacts will be in the long-term portion of the forecast below.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 145 PM CDT Mon Jun 17 2024

To say the long term period looks active would be a bit of an
understatement at this point. The latest info from the National
Hurricane center gives the disturbance associated with the Central
America Gyre over the southwestern Gulf of Mexico a 70% chance of
becoming a tropical depression/storm over the next 48 hours. Within
the 7 day window, the disturbance (91L) also has a 70% chance of
development. Ultimately, whether or not 91L develops is not
particularly important, as the bulk of the impacts from the system
will be heavy rain/flooding impacts.

With regard to the overall setup, the Subtropical High is situated
over North Carolina and will strengthen and expand in size over the
Ohio Valley by midweek. This will act to block 91L from moving into
the central Gulf, and allowing it to move into northern Mexico or
south Texas under southeasterly flow aloft. It looks as if PWATs
will be near or close to top 10 all time values within the
climatology based off of Corpus Christi`s sounding history. The max
is 3.00" from July 2010, and based off of the ensembles from the GFS
and ECM, that value could be challenged Tuesday evening through
Thursday morning, with values in the 2.7-3.0" range, some 3-4 sigma
above the mean. Those are some remarkable values given the
climatology, so we are working with a DEEP tropical airmass moving
into South Central Texas midweek. Showers and storms that develop
within this airmass will be incredibly efficient rain makers, with
rates likely approaching several inches per hour.

The latest 12Z guidance from the GFS still indicates that the
northern portion of the disturbance will send a bit slug of moisture
inland as early as Tuesday night, with this area of showers and
storms spreading inland over the Austin/San Antonio CWA from east to
west on Wednesday afternoon. The primary window for heavy rainfall
looks to be Wednesday morning through Thursday morning. WPC paints
most of the Coastal Plains and portions of the I-35 corridor south
of Austin through Bexar County in a Moderate Risk (level 3 of 4) for
excessive rainfall Wednesday morning through Thursday morning.
Flooding and flash flooding are looking increasingly likely, so
flood watches may need to be issued overnight as we get closer to
the event.

Continued shower and storm chances are expected beyond Thursday as
tropical moisture remains in place and the upper level pattern
remains conducive to an active stretch. Temperatures will moderate,
getting back into the 90s by the weekend.

&&

.AVIATION...
(06Z TAFS)
Issued at 1225 AM CDT Tue Jun 18 2024

MVFR CIGs prevail overnight into Tuesday morning, then become SCT-BKN
VFR around midday. Some streamer SHRA are expected early to mid
morning, however PROBs are low and will keep mention out for now.
Will monitor for possible updates to mention. MVFR CIGs return
Tuesday evening into night. Higher PROBs for SHRA/TSRA develop in the
hours after the current forecast period on Wednesday. Gusty E-SE
winds to around 25 KTs can be expected, at times, with sustained E-SE
winds around 10 KTs.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              75  80  75  88 /  20  60  60  40
Austin Bergstrom Intl Airport  74  80  74  87 /  20  70  60  40
New Braunfels Muni Airport     75  80  75  87 /  20  70  70  60
Burnet Muni Airport            73  78  73  86 /  10  50  70  40
Del Rio Intl Airport           78  92  77  87 /   0  40  80  80
Georgetown Muni Airport        73  78  72  86 /  20  60  60  40
Hondo Muni Airport             76  81  73  84 /  10  60  80  60
San Marcos Muni Airport        74  80  72  86 /  20  70  70  50
La Grange - Fayette Regional   76  80  75  86 /  30  70  40  40
San Antonio Intl Airport       76  80  75  85 /  20  70  70  60
Stinson Muni Airport           77  81  76  87 /  20  70  70  60

&&

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

$$

Short-Term...04
Long-Term...27
Aviation...04