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

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FXUS64 KEWX 232108
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
408 PM CDT Wed Aug 23 2017

...Harvey could bring heavy rains to South Central Texas
Friday into the weekend...

.SHORT TERM (Tonight through Thursday Night)...
Top story first...

Tropical depression Harvey is expected to approach the middle Texas
coast Friday and move inland late Friday into Saturday. This tropical
system could bring heavy rain late Friday into the weekend across
South Central Texas. Word of caution, there remains a lot of
uncertainty about the track and intensity of Harvey as it moves to
the northwest through Friday. Below are some of the key messaging
points that we are advertising for situational awareness purposes.

Messaging Key Points
1) Heavy rainfall possible east of I-35 Friday through the weekend, possibly
leading to flash flooding and river flooding.
2) Average rainfall
amounts of 6 to 10 inches possible east of I-35 with isolated higher
amounts in excess of 12 inches in the Tropical Storm Watch area.
Areas along and west of I-35 could see 2 to 4 inches.
3) There remains uncertainty in the forecast track of Harvey across
Texas. Small changes to the track or forward speed of Harvey will
result in large changes to impacts across South Central Texas. If
the the track of Harvey shifts to the west or the system stalls, then
much higher amounts will be possible.

Now, the short term forecast period. Scattered showers and isolated
thunderstorms are possible the rest of this afternoon and evening as
a weak frontal boundary stalls across the area. Some of the HiRes
models suggest for the boundary to push to the north and generates
isolated to scattered showers and isolated thunderstorms across the
Hill Country overnight into Thursday.

&&

.LONG TERM (Friday through Wednesday)...
More on Harvey and expected weather conditions through the extended
forecast period.
A weakening upper level ridge across the desert southwest will pull
to the northwest and allows Harvey to approach the middle Texas coast
and make landfall late Friday into early Saturday. The system is
expected to slowly move to the north and into the Hill Country and
possibly stalls as an upper level trough digs down across the Central
Plains Saturday into Sunday. With the operational GFS, GFSensemble
and ECMWF models agree on this solution this far out, we urge you to
closely monitor the weather conditions for the next few days as
changes will be made to the forecast and updated information will be
shared for situational awareness and preparedness before, during and
after the event. There is a good chance for a Flash Flood Watch to go
out later tonight as we continue to adjust upward rainfall amounts,
mainly across the Tropical Storm Watch area.

The upper level ridge above mentioned is expected to rebuild across
the Intermountain West late Sunday into Monday and then push to the
east. Also, an upper level trough is expected to swing across the
Ohio Valley and help Harvey to move to the northeast. This
combination will allow Harvey to curve to the northeast and away from
the area with rain chances ending Tuesday. The rest of the week
looks dry and cooler with highs in the lower 90s....


&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              76  95  76  93  75 /  30  50  30  40  40
Austin Bergstrom Intl Airport  74  95  74  93  74 /  40  50  30  40  50
New Braunfels Muni Airport     74  95  74  93  75 /  30  40  30  40  50
Burnet Muni Airport            73  90  72  89  71 /  30  50  30  30  40
Del Rio Intl Airport           77  97  76  95  76 /  30  30  20  30  20
Georgetown Muni Airport        74  92  74  91  73 /  30  50  30  40  40
Hondo Muni Airport             73  95  73  95  74 /  30  40  20  40  30
San Marcos Muni Airport        75  95  74  93  74 /  30  40  30  40  50
La Grange - Fayette Regional   75  96  75  93  75 /  40  40  30  50  80
San Antonio Intl Airport       76  95  76  93  74 /  30  50  20  40  50
Stinson Muni Airport           75  95  75  93  75 /  30  40  20  40  50

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
Tropical Storm Watch for the following counties: De Witt...
Fayette...Gonzales...Karnes...Lavaca...Wilson.

&&

$$

Mesoscale/Aviation...Treadway
Synoptic/Grids...17


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