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

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FXUS64 KEWX 192122
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
422 PM CDT Tue Sep 19 2017

.UPDATE... /Extended PoPs east thru this evening/

Rapid refresh models are performing poorly in the handling of a
shortwave over West Central TX. Will apply a blend of the rapid
refresh and the gfs to extend PoPs eastward to just west of I-35. All
models indicate decreased rain chances by late tonight.

&&

.PREV DISCUSSION... /ISSUED 314 PM CDT Tue Sep 19 2017/

SHORT TERM (Tonight through Wednesday Night)...
A line of showers and storms that developed west of the Rio Grande
has managed to remain intact and move into the western portion of
Val Verde county as of early this afternoon. So far, the 17Z run of
the HRRR seems to have a good handle on the convection when compared
to current radar data. Given the above, we have increased rain
chances along the Rio Grande through this afternoon. Some strong wind
gusts are possible with the stronger storms, especially across Val
Verde county. In addition, another area of convection is beginning to
develop across the southern Edwards Plateau, including Edwards
county. The HRRR is a little less aggressive with this convection,
but given ongoing trends, we did opt to show a low chance for showers
and storms for the afternoon hours. We will need to monitor
convective trends over west central Texas this evening as some of the
models show a complex of thunderstorms developing this evening. For
now, we will keep a low chance for showers and storms for this
evening for areas generally along and north of a Del Rio to
Rocksprings to Burnet line. If convection does materialize, parts of
the western Hill Country (Llano and Burnet counties) may see some
showers and storms early Wednesday morning. Confidence in this
scenario is low at this time and for now we will not mention in the
latest forecast.

Elsewhere, some convection is ongoing east of the I-35 corridor along
a Cuero to Giddings line. The convection east of I-35 will likely
decrease by early evening with the loss of daytime heating.

Any rain chances on Wednesday will again likely remain confined to
areas east of I-35. Some isolated activity is also possible across
far western Val Verde county. We expect little change in temperatures
through midweek, with highs in the 90s and lows in the 70s.

LONG TERM (Thursday through Tuesday)...
Some weak mid-level shortwave energy moving in from the west on
Thursday should help to generate some isolated to scattered
convection across south central Texas. Rain chances should still be
favored along and east of I-35 where deeper moisture will reside and
we`ll continue to mention 30-40% chances here, with 20% elsewhere.
The forecast for the remainder of the work week into the upcoming
weekend should result in continued isolated afternoon showers and
thunderstorms, mainly along and east of the I-35 corridor. In
addition, we expect above normal temperatures to continue given mid
and upper level ridging along with southerly flow in the low-levels.
The forecast for the early portion of next week could become a little
more active as a longwave trough to our west may ease into the
western half of Texas. This upper trough should help to weaken the
persistent upper ridging and allow a more active southwest flow aloft
to spread into the region. For now, we will only mention low chances
for rainfall as the medium range deterministic models diverge on
handling this upper trough beginning late Monday into Tuesday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              75  94  76  92  74 /  10  -   -   20  10
Austin Bergstrom Intl Airport  75  94  75  91  72 /  10  -   -   20  10
New Braunfels Muni Airport     74  95  75  93  72 /  10  10  10  20  10
Burnet Muni Airport            73  92  74  90  72 /  20  -    0  20  10
Del Rio Intl Airport           79  99  77  97  75 /  20  10  10  20  10
Georgetown Muni Airport        76  94  76  91  73 /  10  -    0  20  10
Hondo Muni Airport             76  99  76  96  74 /  20  -   10  20  10
San Marcos Muni Airport        74  94  75  92  72 /  10  10  10  20  10
La Grange - Fayette Regional   76  93  75  91  73 /  10  20  10  40  10
San Antonio Intl Airport       77  95  77  93  75 /  10  -   10  20  10
Stinson Muni Airport           76  96  77  94  75 /  10  -   -   20  10

&&

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

$$

Mesoscale/Aviation...LH
Synoptic/Grids...Oaks
Public Service/Data Collection...YB


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