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

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FXUS64 KEWX 211718
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1218 PM CDT Fri Jul 21 2017

.AVIATION DISCUSSION...FOR 18Z TAF PERIOD...
VFR conditions expected to prevail through the period. There are
some indications of sporadic MVFR in the early morning hours but
similar to previous mornings, confidence is low of impacts to any
terminals. Removed any non-category changing lines but some scattered
1.5 kft clouds may be in the vicinity of the I-35 terminals in the
morning.

&&


PREV DISCUSSION... /ISSUED 401 AM CDT Fri Jul 21 2017/

SHORT TERM (Today through Saturday)...
South Central Texas continues to dry out beneath strong mid-level
ridging and broader upper level ridging that spans much of the
Southern US. Will continue to show highs a degree or two over the
blended guidances that have been running cool as rainfall has become
scarce. Onshore flow in the daytime hours will keep enough moisture
pooled over our sern counties to generate a few showers and perhaps
a brief thunderstorm. Heat indices will continue to climb into the
104-108 degree range over these areas through Saturday. Subsidence
will remain enhanced through Saturday as the west side of an
approaching TUTT low adds to the subsidence. Some moisture is
expected to wrap wwd into Central TX late in the day leading to some
isolated convection possibly getting a litter further inland Saturday
versus today.

LONG TERM (Saturday Night through Thursday)...
The TUTT low that is currently over the FL panhandle looks stronger
than what the models depict as it moves into TX late in the weekend.
Hopefully this would lead to model underestimation of rain chances.
Given the general moist bias seen by deterministic models and
numerical guidances for much of the summer, the mostly dry model
depiction of mainly isolated activity in the medium range is
followed. A general wsw direction of the upper low track should lead
to another glancing blow of mid/upper level shear and another pattern
that fails to generate a robust onshore flow through a deep layer as
is sometimes expected from TUTT lows.

On Sunday, the NAM/GFS solutions show a pocket of mid-level dry air
to curb expectations for moisture as the surface to 500 mb flow turns
uniformly SE over the Coastal Bend. By the time the moisture
recovers from persistent onshore flow Wednesday, the TUTT low is
mostly in Mexico with only a weak inverted trough in the mid levels
over South TX. Late in the week, the upper low remains broad enough
over Mexico to keep a persistent onshore low to mid level flow which
would possibly extend isolated rain chances a day or two. The deeper
onshore flow can also help take the edge of the heat indices by
keeping steady and gusty afternoon/evening breezes.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              77 101  77 100  77 /  -   10  20  20  20
Austin Bergstrom Intl Airport  76  99  76  99  76 /  -   10  20  20  -
New Braunfels Muni Airport     76  99  76  98  75 /  10  10  20  20  -
Burnet Muni Airport            74  98  75  98  74 /  -   -   10  20  10
Del Rio Intl Airport           77 102  78 101  77 /   0  -    0  10   0
Georgetown Muni Airport        76  98  77  98  76 /   0  10  10  20  10
Hondo Muni Airport             75 102  76 100  75 /   0   0  -   10  -
San Marcos Muni Airport        76 100  76  98  76 /  10  10  20  20  -
La Grange - Fayette Regional   77  97  77  99  77 /  10  30  20  30  10
San Antonio Intl Airport       77 101  78 100  77 /  10  -   10  20  -
Stinson Muni Airport           77 100  77 100  77 /  10  -   10  10  -

&&

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

$$

Mesoscale/Aviation...TB3
Synoptic/Grids...Runyen
Public Service/Data Collection...YB



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