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

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617
FXUS64 KEWX 220609 AAA
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
109 AM CDT Fri Sep 22 2017

.UPDATE...
Please see the 06Z aviation forecast discussion below.

&&

.AVIATION...
Low clouds continue to develop and spread across south central Texas
early this morning. MVFR cigs are already in place along I-35 and
will continue until late morning. Improving conditions are forecast
after 16Z as clouds lift and scatter back to VFR and southeast winds
increase to around 10kts. At DRT, we also expect some MVFR cigs in
the 11-17Z time frame. Clouds scatter to VFR around 17Z as southeast
winds increase to 15kt.

&&

.PREV DISCUSSION... /ISSUED 1037 PM CDT Thu Sep 21 2017/

UPDATE...
Showers and thunderstorms have dissipated across South Central Texas
and expected no additional development this evening. Have left POPs
in for areas between I-35 and the Rio Grande where Hi-Res models show
some development of showers. Only other changes were to reestablish
trends to the temperatures, dewpoints, and winds for the overnight
into early morning. Forecast still looks on track for a potential
locally heavy rain event next week.

PREV DISCUSSION... /ISSUED 243 PM CDT Thu Sep 21 2017/

SHORT TERM (Today through Friday)...
The shortwave that is bringing numerous showers and thunderstorms to
the Houston area this afternoon will continue to push eastward and
weaken through the evening and overnight hours. In its wake weak
isentropic lift combined with the low level jet across west Texas
could produce a few isolated showers/storms over the Edwards Plateau
and Rio Grande Plains through the night.

Friday will see the typical summertime sea breeze showers and storms
as high pressure continues to sit over the ArkLaTex region.
Temperatures will continue to run 2-4 degrees above normal for highs
with afternoon heat index values in the mid to upper 90s due to the
Gulf moisture in place across Central Texas

LONG TERM (Friday Night through Wednesday)...
The high pressure holds on for one more day Saturday, with only
isolated showers and storms possible. By Sunday a large upper trough
digs into the Four Corners region and chances for rain begin to rise.
The trough of low pressure slowly pushes eastward so rain chances
will begin along the Rio Grande Plains Sunday into Monday and then
spread eastward for Tuesday through Thursday. The trough helps to
push a cold front, equally slow moving, down into Texas. While there
is some disagreement between the ECMWF and GFS as to the timing of
the front it will act to only enhance rain chances mid week.
Precipitable Water values will range from 1.75-2.25 inches due to
the continued southerly flow ahead of the trough. The best chances
for rain across South Central Texas look to be Tuesday, Wednesday and
Thursday. With the increased cloud cover and rainfall temperatures
early next week will be kept in the upper 80s with indications of at
least slightly cooler temperatures behind the cold front (whenever it
finally comes through). This far out it is too early to pinpoint
when the heaviest rainfall will occur and where. A lot will depend on
the timing of the cold front, which the models still disagree on.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              91  73  92  72  91 /  20  10  -   -   20
Austin Bergstrom Intl Airport  91  71  92  70  90 /  20  10  -   -   20
New Braunfels Muni Airport     91  72  92  70  91 /  20  -   20  10  30
Burnet Muni Airport            89  71  90  69  88 /  10   0  -   -   10
Del Rio Intl Airport           94  75  93  74  92 /  10  10  10  10  10
Georgetown Muni Airport        91  71  91  70  90 /  10   0  -   -   10
Hondo Muni Airport             94  74  95  72  94 /  10  20  20  10  20
San Marcos Muni Airport        91  72  92  70  91 /  20  10  10  10  20
La Grange - Fayette Regional   91  72  92  71  91 /  20  -   10  -   30
San Antonio Intl Airport       91  74  92  73  91 /  20  10  20  10  20
Stinson Muni Airport           92  74  92  73  91 /  20  10  20  10  20

&&

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

$$

Mesoscale/Aviation...24
Synoptic/Grids...17



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