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

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FXUS64 KEWX 241157 AAA
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
657 AM CDT Sun Sep 24 2017

.AVIATION...
/12Z TAFS/
There are patchy to areas of fog to the north and east of the I-35
sites this morning. Also, there are light showers over the Edwards
Plateau and Rio Grande Plains including KDRT. In addition, some
locations are experiencing cigs of 200 to 600 feet and vbsys as low
as 200 feet. That said, the next 2 to 3 hours will be challenging to
manage with the possibility of LIFR/IFR across the I-35 terminals and
MVFR for KDRT. VFR conditions return by 17Z and remain through late
this evening before MVFR/IFR come back for the area sites. Southeast
winds of 8 to 10 knots are expected to prevail for much of the period
for KAUS, KATT and KSAT while 10 to 15 knots and gusts up to 25 knots
are possible for KDRT this afternoon and early evening.



&&

.PREV DISCUSSION... /ISSUED 504 AM CDT Sun Sep 24 2017/

SHORT TERM (Today through Monday)...
Early morning radar data shows a few showers moving into the coastal
plains, while farther northwest an area of showers is moving across
western Val Verde county. Satellite data also shows a plume of
moisture stretched from the eastern Pacific from Tropical Storm Pilar
across central Mexico into west Texas. An area of subsidence is also
noted over central and east Texas.

For today, the short term models are in good agreement in showing
mainly isolated showers and storms for most areas today. We will
keep rain chances fairly low (20-30%) across most areas given the
mid-level subsidence. The exception will be across western Val Verde
county where deeper moisture and some weak forcing for ascent can be
found. Most of the shower and thunderstorm activity will decrease
with the loss of daytime heating. However, we should see a continued
good chance of showers and storms overnight across Val Verde county
as models show some mid-level shortwaves will move into the lower
Trans-Pecos. This should aid in some overnight convection for the Rio
Grande plains, especially west of Del Rio. On Monday, the mid-level
ridge axis currently in place should begin to slide eastward. This
will allow some stronger mid-level shortwaves to inch closer to the
Rio Grande plains, resulting in a fairly significant increase in rain
chances.

LONG TERM (Monday Night through Saturday)...
The forecast for the early and middle portion of this week continues
to look increasingly active as a longwave trough to our west combined
with plenty of moisture and a cold front impact the region. The
medium range models continue to show the best chance for heavy
rainfall and possible flooding will remain across the Rio Grande
plains and southern Edwards Plateau on Tuesday and Wednesday. The
models have trended a little slower with the southward progression of
the cold front for our central and eastern areas on Wednesday.
However, the models do show the boundary will push southward into
western Texas. As the front encounters the deeper moisture, we
expect additional convection to develop across the southern Edwards
Plateau and Rio Grande plains. If models continue to trend slower
with the front, this would prolong the possibility of heavy rainfall.
For now, we will show the higher rain chances on Tuesday and
Wednesday, but did opt to boost rain chances on Thursday for our
western areas. Some drier air will eventually work in from the north
and this will bring a lowering of rain chances for Friday and
Saturday.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              89  73  88  73  87 /  20  10  20  30  40
Austin Bergstrom Intl Airport  89  71  90  72  88 /  20  10  20  30  40
New Braunfels Muni Airport     88  72  89  73  87 /  30  10  30  30  40
Burnet Muni Airport            87  70  86  70  83 /  20  10  20  30  30
Del Rio Intl Airport           93  75  89  73  86 /  20  50  50  70  70
Georgetown Muni Airport        89  71  89  71  86 /  10  10  20  20  30
Hondo Muni Airport             93  74  93  74  90 /  20  20  40  50  50
San Marcos Muni Airport        90  72  89  72  87 /  20  10  30  30  40
La Grange - Fayette Regional   90  72  90  73  90 /  20  10  20  20  40
San Antonio Intl Airport       89  74  89  75  86 /  30  10  30  30  50
Stinson Muni Airport           89  74  89  75  86 /  30  10  40  30  50

&&

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

$$

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


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