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

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FXUS64 KEWX 231155 AAA
AFDEWX

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
655 AM CDT Sat Sep 23 2017

.AVIATION...
/12Z TAFS/
Cigs are expected to be between MVFR and IFR categories along the
I-35 terminals for the next several hours before they lift to VFR
late this morning. Patchy to areas of fog have developed to the south
and east of the I-35 sites this morning and expected to lift within
the next couple of hours. Wind should stay from the southeast at 8 to
12 knots with gusts up to 25 knots along the Rio Grande. Isolated
showers and storms are expected east of the I-35 with no impact to
the area terminals.

&&

.PREV DISCUSSION... /ISSUED 508 AM CDT Sat Sep 23 2017/

SHORT TERM (Today through Sunday)...
Early morning surface observations show plenty of low-level moisture
in place with dewpoint temperatures currently in the upper 60s and
lower 70s for most areas. Winds are also fairly light east of I-35
and this has allowed some patchy fog to develop. The fog will
continue through mid-morning, then dissipate quickly as daytime
heating and mixing commence. We will likely see a few showers early
this morning given plenty of moisture along with the presence of a
low-level jet. The Texas Tech WRF and HRRR models are consistent in
showing the better rain chances this morning along Highway 83. For
the afternoon hours, look for high temperatures near climatological
normals along with a low chance for showers and thunderstorms. Any
showers and storms should dissipate fairly quickly with the loss of
daytime heating. The one exception to this could be out west along
the Rio Grande where some convection across the lower Trans-Pecos may
impact western Val Verde county. The weather pattern will change
little on Sunday and we should see another round of mainly isolated
afternoon convection across the region along with near normal
temperatures.

LONG TERM (Sunday Night through Friday)...
Early next week, a broad upper trough will gradually approach from
the west. Ahead of this trough, we will continue to see a strong
southeasterly flow in the low-levels and this will help maintain or
increase moisture levels across the region. In the mid and upper
levels, we will continue to see an increasingly active southwest
flow as an upper trough remains to our west. In addition, a cold
front will move in either late Tuesday or Wednesday. The GFS and
ECMWF are beginning to show some agreement with regards to timing,
with the GFS trending toward the faster ECMWF solution with the
front. The cold front is expected to slow it`s southward progress or
perhaps even stall over the region Wednesday or Wednesday night.
This pattern still remains favorable for a heavy rainfall event
across portions of south central Texas. At this time, it appears
areas along the Rio Grande and southern Edwards Plateau will see the
heaviest rainfall totals late Tuesday and Wednesday. However, the
potential for heavy rainfall could persist well into Thursday. Model
QPF amounts are quite impressive along the Rio Grande. While these
totals are likely too high, am still concerned about the heavy
rainfall and flooding threat along the Rio Grande and southern
Edwards Plateau during the middle of the upcoming week. The GFS
ensemble plumes along with MOS guidance numbers continue to show
good confidence for some heavy rainfall and we will continue to
mention this in the Hazardous Weather Outlook. For the remainder of
south central Texas, we do expect a decent chance of rain, but should
see lesser amounts as the main source of lift should remain focused
along the Rio Grande.

Some drier air is expected to move in behind the front on Friday and
we will see decreasing rain chances.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              91  73  90  73  89 /  20  -   20  10  20
Austin Bergstrom Intl Airport  91  72  90  72  89 /  20  -   20  10  20
New Braunfels Muni Airport     90  72  90  72  89 /  20  10  30  10  30
Burnet Muni Airport            89  70  87  70  85 /  10  -   10  10  20
Del Rio Intl Airport           93  75  91  74  89 /  20  20  30  50  50
Georgetown Muni Airport        91  71  90  71  88 /  10  -   10  10  20
Hondo Muni Airport             94  73  94  73  93 /  20  10  30  10  30
San Marcos Muni Airport        91  72  91  72  89 /  20  10  30  10  20
La Grange - Fayette Regional   91  72  91  72  90 /  20  -   20  10  20
San Antonio Intl Airport       90  74  89  74  88 /  20  20  30  10  30
Stinson Muni Airport           89  74  89  74  89 /  20  10  30  10  30

&&

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

$$

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



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