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

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FXUS64 KEWX 160543
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1243 AM CDT Tue Oct 16 2018

.UPDATE...
See below for the 06z aviation discussion...

&&

.AVIATION...
Scattered showers are ongoing across the region. Intermittent
showers should continue to impact all terminals throughout the
overnight and morning hours. Showers should become more isolated at
DRT by around 14z Tuesday, SAT/SSF by around 19z Tuesday, and AUS by
around 20z Tuesday, thus, have downgraded from SHRA to VCSH at those
times. CIGs are expected to hover near the IFR/MVFR border
throughout the overnight and morning hours before a slight
improvement to low end MVFR by early Tuesday afternoon. Visibilities
may briefly drop if a particularly heavier shower impacts the
terminals. Winds have begun to relax a bit this morning, but 10 to 15
knot sustained north/northwesterly winds are expected to persist
through the TAF period.

&&

.PREV DISCUSSION... /ISSUED 921 PM CDT Mon Oct 15 2018/

UPDATE...
While the ongoing forecast is in good shape minor tweaks were made
to the QPF, PoP, and weather grids to reflect ongoing radar trends
and to align the forecast with what the high resolution models show
for the rest of the night.

A flash flood situation has developed across the Hill Country
through the evening as 1 to 3 inches of rain have fallen over the
last 6 hours, bringing the daily total across much of Llano,
Gillespie, and parts of Burnet county up to 5 to 6 inches. While this
rain has fallen over several hours the ground is so saturated from
recent rains that anything that falls is turning into runoff
resulting in Flash Flooding across these areas. Reports from county
EMs and sheriffs offices in Llano and Gillespie county show that
multiple roads are closed across both counties due to water over the
roadways. This include roads that typically do not flood or are not
considered low water crossings. The message tonight across the Hill
Country is that if you don`t have to get out and travel, stay home.
Flooded roadways at night are difficult to detect, and with such
widespread flooding and multiple roads closed being out and about
across these areas  tonight is dangerous.

Over the next several hours the HRRR, Texas Tech WRF, and other high
resolution models show rainfall moderate rain continuing to move
northeast over the Edwards Plateau and Hill Country before lifting
northward out of the area Tuesday morning. Because of the saturated
soils this has become less about intense rainfall rates, and more
about longer duration rains resulting in runoff and flooding. Flash
and River Flooding will continue to be a possibility through the
night from Edwards through Kerr, Gillespie, up to Llano and Burnet
Counties. Area rivers have also responded to the rainfall with parts
of the Nueces, Guadalupe, and Llano Rivers all above flood stage
tonight.

To those along and east of I-35 isolated to scattered light rain will
be possible through the overnight hours with lows dropping into the
mid to upper 40s.

PREV DISCUSSION... /ISSUED 714 PM CDT Mon Oct 15 2018/

AVIATION...
Periods of SHRA are expected at the terminals through at least 14-18Z
Tuesday as an upper level speed maxima overrides a frontal boundary
located around 850 MB draped north of the terminals. This will result
in visibilities dropping as low as LIFR in heavier SHRA, with
IFR/MVFR conditions prevailing as ceilings remain trapped beneath a
low level frontal inversion. With the surface pressure gradient
relaxing, expect northerly winds to begin decreasing but remain
generally elevated in the 10-15 knot range. Amendments are expected
to handle more intense SHRA that approach the terminals.

PREV DISCUSSION... /ISSUED 410 PM CDT Mon Oct 15 2018/

SHORT TERM (Tonight through Tuesday Night)...
Much cooler temperatures along with widespread rain and a few
thunderstorms can be found across south central Texas this afternoon.
Temperatures are currently in the upper 30s to upper 40s across the
region, compared to 24 hours ago when temperatures were mainly in the
80s to lower 90s.

Widespread rain along with a few embedded thunderstorms are expected
to continue through tonight as southerly warm air advection above
the cold low-level northerly flow continues. For the early part of
this evening, the main concern is expected to remain out west along
the Rio Grande, where the HRRR suggests some stronger convection from
Mexico will move northward into the Rio Grande plains. For the
overnight hours, the models suggest additional showers and embedded
thunderstorms will continue, with the heavier totals expected to
remain across the Rio Grande plains, southern Edwards Plateau and
Hill Country. Locally heavy rainfall may also spill over into Tuesday
and with this in mind, we have opted to extend the Flash Flood Watch
into early Tuesday evening. Storm total amounts through Tuesday of 1
to 3 inches with a few totals of 4 to 6 inches are expected.

LONG TERM (Wednesday through Monday)...
We could see a brief break in the rainfall on Wednesday for areas
along and east of I-35. However, west of I-35, rain chances continue
to remain high as additional shortwave energy moves out of Mexico
into the Rio Grande plains. Rain chances look to increase again on
Thursday as the medium range models show a series of disturbances
moving up from deep south Texas into the region. The forecast for the
upcoming weekend into early next week remains uncertain as the
operational GFS and ECMWF diverge on the mid-level flow pattern. The
GFS suggests a drier forecast with a surge of cool and dry air on
Saturday. The ECMWF also shows this surge of cooler air, but
maintains a warm air advection pattern and keeps much higher rain
chances intact. For now, we will keep rain chances in the forecast,
but have gone a little lower than the ECMWF.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              47  45  54  49  59 /  80  50  40  30  70
Austin Bergstrom Intl Airport  47  43  55  49  60 /  80  50  40  40  70
New Braunfels Muni Airport     49  45  56  51  59 /  70  40  30  40  70
Burnet Muni Airport            44  43  53  48  57 /  80  60  50  30  70
Del Rio Intl Airport           48  46  54  50  60 /  70  70  70  50  60
Georgetown Muni Airport        46  45  53  49  59 /  80  50  40  30  70
Hondo Muni Airport             50  48  57  49  62 /  70  50  40  60  80
San Marcos Muni Airport        48  46  55  52  59 /  70  40  30  40  70
La Grange - Fayette Regional   50  49  58  53  62 /  60  30  30  40  50
San Antonio Intl Airport       49  46  57  51  61 /  70  40  40  50  80
Stinson Muni Airport           52  48  58  51  61 /  70  40  30  50  80

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through this evening for Bandera-Blanco-Burnet-
Edwards-Gillespie-Kendall-Kerr-Kinney-Llano-Maverick-Medina-Real-
Uvalde-Val Verde-Zavala.

&&

$$

Aviation...BMW
Short-Term/Long-Term...04


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