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

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336
FXUS64 KEWX 241805
AFDEWX

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
105 PM CDT Sat Aug 24 2019

.AVIATION /18Z TAFs/...
The main aviation concern centers around convective initiation this
afternoon. Regional radars show isolated cells developing between BMQ
and SEP, roughly in the vicinity of a remnant outflow boundary.
Closer to the South Central Texas terminals, ascent associated with
a weak trough axis has allowed for a SCT-BKN mid-level deck to
persist near AUS and SAT/SSF. Visible satellite trends have shown
some thinning to this deck near SAT/SSF and additional heating will
allow for lower level cumulus development near the Interstate 35
terminals through the afternoon. Continued heating should provide
additional upscale growth into SHRA or TSRA by late afternoon.
Presence of this mid-level deck has slowed heating somewhat though
and have pushed VCTS onset back into the 21-23Z range with this
package. Should TSRA outside of the terminals produce any kind of
outflow this afternoon, will have to watch for earlier than forecast
terminal impacts. Otherwise, gusty and variable winds and locally
heavy rain leading to visibility restrictions will be possible. Loss
of heating should limit SHRA/TSRA coverage this evening, but
lingering ascent from the trough may allow for a few cells to persist
into the early morning hours. Have not included any mention of this
in the TAFs due to low confidence.

Expect winds to remain below 10 knots, varying between south and
southeast through the period. VFR ceilings are expected to prevail
through the TAF period owing to the presence of the mid-level cloud
deck, but will have to monitor for intermittent MVFR ceiling
development closer to sunrise should this deck clear out faster than
forecast.

&&

.PREV DISCUSSION... /ISSUED 630 AM CDT Sat Aug 24 2019/

AVIATION.../12Z TAFS/
Main concern today will be convection. Expecting to see scattered
convection developing this afternoon and continuing into the
evening. Current VFR cigs (MVFR at KSSF) will prevail outside
convection through the end of this forecast period. Could see a
couple of hours with MVFR cigs through 15Z. With additional mid and
high level clouds tonight will only mention SCT after 07Z for the
I-35 terminals. If we see fewer mid/high level clouds tonight then
MVFR cigs are more likely. Light E/SE winds around 5 knots this
morning will increase to 9-13 knots after 16Z. Winds will be stronger
and gusty in or near SHRA`s/TSRA`s. Currently looks like the
greatest chance for convection impacting the terminals will be during
the 21Z to 03Z period. Once convection initiates then timing issues
can be fine tuned and forecast updated as necessary.

PREV DISCUSSION... /ISSUED 421 AM CDT Sat Aug 24 2019/

SHORT TERM (Today through Sunday)...
Lingering convection across portions of the Hill Country and Rio
Grande plains continues to slowly weaken this morning. Given radar
trends and lightning data, we expect the weakening trend to continue
over the next several hours. Elsewhere, a few showers and
thunderstorms are noted along the middle Texas coast. Some of this
activity may drift northward into the coastal plains through sunrise
and we will keep a low chance for rain in the forecast early this
morning.

A weak upper trough moving in from the northwest along with remnant
outflow boundaries and the sea breeze will bring a chance of showers
and thunderstorms to all of south central Texas today. Hi-res models
tend to favor convection across the southern Edwards Plateau and Hill
Country this afternoon and early evening. As the upper trough moves
through late today into tonight, the flow aloft should be aligned for
this activity to drift east and southeast into portions of the I-35
corridor, mainly south of Austin. With forecast soundings once again
showing a deep inverted-V profile, some gusty winds will certainly
be possible. In addition, any slow-moving storms will be capable of
producing some pockets of locally heavy rainfall. Highs today will be
at or slightly above normal, with highs generally in the 90s, except
near 100 along the Rio Grande.

With the weak upper trough slowly moving through during the
overnight hours, some convection will likely persist well into early
Sunday morning. As of now, this appears to be favored across portions
of the Rio Grande plains. With this in mind we will keep rain
chances in the forecast through tonight for locations generally
along and south of I-10.

As the mid and upper level flow transitions to a more northwesterly
direction on Sunday, moisture levels will begin to decrease from
northwest to southeast. Afternoon shower and thunderstorm activity
will be favored generally along and east of the I-35 corridor.
Temperatures will also warm a degree or two with highs in the mid 90s
to near 105. A few spots east of I-35 may briefly reach Heat Advisory
levels in the late afternoon.

LONG TERM (Sunday Night through Friday)...
Mid and upper level ridging will build across the region during the
early portion of next week. This will bring warming temperatures to
the region Monday through Wednesday, with Monday and Tuesday
currently looking like the warmest days of the forecast period.
Given warming temperatures and persistent southeasterly flow in the
low-levels, heat index values may climb into the Advisory range early
next week.

Confidence in the medium range models in the handling of a cold front
during the middle of the upcoming work week continues to remain low
at this time. For now, we will continue to forecast above normal
temperatures through the period. Most areas should remain dry, except
for possibly the coastal plains where some afternoon convection could
develop along the sea breeze.

&&

.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry              78 100  79 101  79 /  20  20   0   0   0
Austin Bergstrom Intl Airport  77  98  78 100  77 /  20  20   0  -    0
New Braunfels Muni Airport     76  97  77 100  77 /  30  20  -   -    0
Burnet Muni Airport            75  97  76  99  76 /  10  10   0   0   0
Del Rio Intl Airport           77 102  78 105  79 /  30   0   0   0   0
Georgetown Muni Airport        77  99  78 101  78 /  10  20   0   0   0
Hondo Muni Airport             76 101  77 102  77 /  30  20  -    0   0
San Marcos Muni Airport        77  98  77 100  77 /  20  20  -   -    0
La Grange - Fayette Regional   77  99  78 101  78 /  20  30  10  10   0
San Antonio Intl Airport       78  98  79 101  78 /  30  20  -   -    0
Stinson Muni Airport           78  98  79 100  79 /  30  30  -   -    0

&&

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

$$

Aviation...Huffman
Short-Term/Long-Term...Treadway
Public Service/Data Collection...33



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