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

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FXUS64 KEWX 211140 AAA
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
640 AM CDT Fri Jul 21 2017

.AVIATION.../12Z TAF CYCLE/

VFR conditions prevail at the TAF sites but MVFR ceilings lurk east
towards La Grange, TX. The MVFR ceiling coverage will be limited in
scope and erode quickly over through 8am CDT. VFR is expected through
much of the TAF period with 5 knot winds from south to southeast this
morning, increasing to near 10 knots with some low teen gusts. For
KDRT, wind gusts could be slightly higher, near 20 kt at times this
afternoon.

While VFR should prevail through Saturday morning as well, the
probability of patchy MVFR ceilings occurring at KSAT/KSSf/KAUS
appears to be slightly increasing based on latest model trends. NAM
sounds appear to be doing better this morning then the GFS soundings
per the observed MVFR deck across the coastal plains. Have left far
reaching temporal terminal TAFs VFR for now but did include a SCT015
group for Saturday morning that could at times become BKN in the
11-14Z time frame.

&&

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

&&

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

$$

Mesoscale/Aviation...Allen
Synoptic/Grids...Oaks



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