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

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FXUS64 KEWX 180052
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
752 PM CDT Thu Aug 17 2017

.UPDATE...
Heat index values have fallen below advisory levels and we let the
advisory expire at 7 PM. One outflow boundary moving across the
Sonora to Ozona areas encountering a moisture convergence zone over
the Edwards Plateau may generate isolated showers and thunderstorms
north of a Rocksprings to Langtry line for the next couple of hours.
Another outflow boundary moving across the Temple to Burnet to Llano
to Mason line is not generating any convection as it`s running into
a capped airmass. However, will keep slight chance POPs there for the
next hour. Temperatures have cooled behind this second boundary
faster than earlier forecast. Have reestablished trends to the
temperatures, dewpoints, and winds for the remainder of this evening.
No other changes. Subtropical Ridge will be the dominant feature this
weekend, then a TUTT low will move west across Texas bringing chances
of showers and thunderstorms next week.

&&

.PREV DISCUSSION... /ISSUED 624 PM CDT Thu Aug 17 2017/

AVIATION...
VFR conditions will prevail at all area airports through the evening
and much of the overnight period. Winds will be breezy out of the
south at 10 to 15 kts through the evening. MVFR CIGs will develop in
Austin and San Antonio early Friday morning and rebound to VFR by
late morning. DRT will be VFR through the entire period.

PREV DISCUSSION... /ISSUED 239 PM CDT Thu Aug 17 2017/

SHORT TERM (Tonight through Friday Night)...
Hot and dry weather continues across South-Central Texas this
afternoon. Clouds and thunderstorm activity should remain to our
north where old convective outflows remain in place from previous
convection. There is a low probability that some of this could slowly
move into Burnet or Llano County this evening but chances were too
low to mention in the forecast at the present time. Otherwise,
temperatures are currently in the middle to upper 90s. Across the
eastern Zones, dewpoints have lowered into the lower 70s with the
help of the southwest winds. This will actually help keep heat index
values from being too high. However, heat indices are already near
107 within the advisory and will make no changes to the heat advisory
as 108 degree values are still likely.

Low temperatures tonight should not be quite as warm as last night.
With the slightly lower dewpoints this afternoon, temperatures should
drop off a bit better. Temperatures will still be warm, but widespread
lows over 80 degrees are not likely. Lows should be in the upper 70s
to near 80 for much of the area. Model guidance is showing even
better mixing tomorrow afternoon and therefore, highs should be a bit
warmer, near 100 degrees for most locations. With the slightly drier
air, heat index values should remain below advisory criteria across
the CWA.

LONG TERM (Saturday through Thursday)...
The beginning of the long-term forecast will remain dry with highs in
the upper 90s to near 100 degrees across the CWA. Models continue to
show a TUTT low moving from east to west across the Gulf of Mexico
and into South Texas on Tuesday. Overall the atmosphere looks to be
too dry for a lot of convection, but will have 20 PoPs across the
Coastal Plains Monday through Wednesday afternoon as this feature
remains near the region for a few days. Behind the departing system,
rain chances could encompass most of the CWA as deep onshore flow
brings better moisture conducive for isolated storm development
across the area. Will show 20 PoPs across the CWA on Thursday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              78 100  77 101  76 /  10   0   0  -   -
Austin Bergstrom Intl Airport  77 100  76 100  75 /  10  -    0  -   -
New Braunfels Muni Airport     76 100  75 100  75 /  -    0   0  -   -
Burnet Muni Airport            75  97  74  97  74 /  20   0   0  -   -
Del Rio Intl Airport           79 101  78 103  78 /  -   -   -   -   -
Georgetown Muni Airport        77  98  75  99  75 /  20   0   0  -   -
Hondo Muni Airport             76 101  74 102  74 /   0   0   0  -   -
San Marcos Muni Airport        77 100  75 101  75 /  10  -   -   -   -
La Grange - Fayette Regional   78 100  76 100  76 /  10  -   -   10  10
San Antonio Intl Airport       77 100  76 101  76 /   0   0   0  -   -
Stinson Muni Airport           77  99  76  99  76 /   0   0   0  -    0

&&

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

$$

Mesoscale/Aviation...05
Synoptic/Grids...04
Public Service/Data Collection...Williams


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