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

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FXUS64 KEWX 210945
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
445 AM CDT Mon Aug 21 2017

.SHORT TERM (Today through Tuesday)...
A TUTT low currently located over the central Gulf of Mexico will
make steady westward progress through tonight. To the west of this
low, an axis of higher moisture (precipitable water values around
2") is currently located over the western Gulf of Mexico. This axis
of higher moisture will gradually work into south Texas today. The
increased moisture and daytime heating will result in mainly isolated
afternoon convection for areas east of the I-35 corridor. Any
activity that manages to develop will be on the decrease by mid-
evening as daytime heating decreases. Otherwise, another day of above
normal temperatures is expected today. Peak heat index values of
102-107 degrees are anticipated along and east of I-35 and across
portions of the Rio Grande plains today. On Tuesday, the above
mentioned TUTT low will begin to weaken and slow it`s westward
progress as it encounters the subtropical ridge axis. We should
still see enough moisture for some afternoon showers and storms to
develop across the coastal plains and Highway 77 corridor and we will
keep a low chance for rain in the latest forecast. Little change in
high temperatures is expected on Tuesday with highs ranging from the
mid 90s in the Hill Country to near 100 along the Rio Grande.

&&

.LONG TERM (Tuesday Night through Sunday)...
On Wednesday, the TUTT low over the western Gulf/Texas coast will
continue to weaken. Meanwhile, a cold front is expected to gradually
move southward across OK into north Texas. We continue to see some
differences in how the models handle this front, with the ECMWF
continuing to show a more aggressive southward movement of the front
compared to the GFS. Suspect the southward progress of the front will
largely be dominated by the amount of convection that develops along
and behind the boundary. With the ECMWF showing a little more
consistency and the GFS beginning to trend upward with precipitation
chances, will lean slightly toward the ECMWF solution at this time.
The approaching front along with a west to east oriented mid-level
Theta-E ridge axis should result in isolated to scattered convection
for most of south central Texas beginning Wednesday. The forecast for
late in the work week into the upcoming weekend becomes increasingly
complex as we will likely see redevelopment of the remnants of
Harvey over the Bay of Campeche. The latest round of medium range
guidance is showing a more northward track with Harvey as we head
into Thursday and Friday. While the track and intensity of Harvey
will likely change in subsequent forecasts, we do expect enough
moisture to result in isolated to scattered showers and thunderstorms
through late this week. As mentioned above, the GFS is beginning to
trend toward the wetter ECMWF solution and we have gone ahead and
boosted rain chances slightly, with the main emphasis likely to
remain across the coastal plains and Rio Grande plains. We also
expect a gradual lowering of temperatures Thursday through Sunday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              98  76  98  76  99 /  10  -    0  -   20
Austin Bergstrom Intl Airport  97  74  98  75  99 /  10  -   -   -   20
New Braunfels Muni Airport     97  74  98  74  99 /  10  -   -   -   20
Burnet Muni Airport            96  73  95  74  95 /  10  -    0  -   30
Del Rio Intl Airport          100  77 100  78 101 /   0   0   0  -   10
Georgetown Muni Airport        96  74  97  75  97 /  10  -    0  -   30
Hondo Muni Airport             98  74  99  74 101 /  -    0   0  -   10
San Marcos Muni Airport        98  75  99  74 100 /  10  -   -   -   20
La Grange - Fayette Regional   98  75  99  75  99 /  30  10  20  -   20
San Antonio Intl Airport       97  76  97  76  99 /  10  -    0  -   20
Stinson Muni Airport           97  75  97  75  98 /  10  -   -   -   20

&&

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

$$

Mesoscale/Aviation...Oaks
Synoptic/Grids...24



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