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

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FXUS64 KEWX 150550 AAA

Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
1250 AM CDT Tue May 15 2018

/06Z TAFS/
MVFR cigs are expected to spread across the coastal plains area and
then over the I-35 sites around 07Z. By 09Z, GFS LAMP and MOS
guidance in addition to area forecast soundings suggest for upper end
IFR conditions through 13Z Tuesday. Then, MVFR conditions are
expected to prevail through 16Z across the I-35 terminals. VFR
conditions are forecast for the afternoon into the evening period.
South to southeast winds of 5 to 10 knots to prevail through the
forecast period.

MVFR cigs are forecast for KDRT around 11Z/12Z time frame and remain
through 14Z Tues. VFR conditions are expected for the remainder of
the forecast period. Southeast winds of 5 to 10 knots are expected to
prevail with occasional gusts of 15 to 17 knots during the afternoon


.PREV DISCUSSION... /ISSUED 901 PM CDT Mon May 14 2018/

Convection is ongoing across portions of Texas, but presently our
region is staying clear. A severe-warned cell making its way into
Mason County in San Angelo`s CWA will need to be monitored to see if
it will reach Llano County. Convection is also ongoing out west in
Mexico east of the Sierra Del Burros, but these storms should
dissipate before crossing the Rio Grande as the 00z observed
sounding at DRT shows a fairly substantial cap in place. Convection
allowing models suggest some shower activity making its way into our
western counties, but this will most likely be confined to primarily
along the Rio Grande. These models also show any shower activity
coming to an end shortly after midnight, so have updated the grids to
lower POPs to below 20 percent out west after 1 am Tuesday morning.
The rest of the forecast seems to be on track, with overnight lows in
the lower 70s (with upper 60s across the Hill Country) and patchy
fog developing early Tuesday morning across the coastal plains east
of the Interstate 35 corridor.

PREV DISCUSSION... /ISSUED 616 PM CDT Mon May 14 2018/

A repeat pattern is expected at KAUS/KSAT/KSSF with VFR skies
becoming MVFR overnight, then VFR late Tuesday morning through
evening. S to SE winds 6 to 15 KTs will prevail.

There is a possibility of SHRA/TSRA at KDRT this evening and have
maintained TEMPO 01Z-05Z. Otherwise, VFR skies becoming MVFR early
morning, then VFR afternoon. SE winds 5 to 12 KTs will prevail.

PREV DISCUSSION... /ISSUED 305 PM CDT Mon May 14 2018/

SHORT TERM (Tonight through Tuesday Night)...
Afternoon temperatures are generally in the 80s and lower 90s across
most areas, except for a few 70s across the southern Edwards Plateau
where persistent cloud cover has kept afternoon temperatures cooler
than surrounding areas. South central Texas is currently free from
any convection. However, we are beginning to see some storms fire
over the higher terrain of Mexico, west of the Rio Grande. Continued
storm development is also noted over Brewster and Pecos counties in
southwest Texas.

Through late this afternoon, most of the hi-res models show good
agreement in convection continuing to flourish over southwest Texas
and the higher terrain west of the Rio Grande. By late afternoon/
early evening, some of this convection will begin moving into western
Val Verde county. By that time, the mid-level capping inversion
should be eroded given strong heating in the low-levels. With the cap
eroded, this will aid in continued storm development through most of
the evening hours across the Rio Grande plains. SPC continues to
maintain a Marginal risk area for the Rio Grande plains and we have
continued to mention this in the latest Hazardous Weather Outlook.
The main severe weather hazards with any storms that manage to
become strong to severe will be damaging wind gusts and large hail.

Some of the hi-res models show enough cold-pool generation to
promote continued thunderstorm development farther east into the Hill
Country. While we can`t completely rule this out, we should begin to
see atmospheric stabilization during the late evening hours, with
increasing convective inhibition. At this time, suspect most activity
will tend to weaken as it approaches the Highway 83 corridor, or
roughly a Concan to Carrizo Springs line.

On Tuesday, a fairly active west-southwest flow aloft remains to our
west. This along with another round of strong afternoon surface
heating should yield some isolated to scattered convection across the
Rio Grande plains into portions of the western Hill Country. It is
unclear if this convection will manage to push into the I-35
corridor, but we did include a low chance for storms across Llano,
Burnet and Williamson counties. The ECMWF is the most aggressive with
the convection, but we would prefer to see a little more continuity
before increasing rain chances. Otherwise, look for another hot and
humid day on Tuesday with highs mainly in the 90s.

LONG TERM (Wednesday through Monday)...
For mid to late this week, look for above normal temperatures and
dry conditions as the mid-level subtropical ridge axis builds over
northern Mexico and western Texas. Increased mixing in the low-levels
should yield lower dewpoints in the afternoons. This along with a
strengthening low-level thermal ridge will allow temperatures to warm
to well above normal levels for Wednesday through Friday. We expect
highs mostly in the 90s, with near 100 along the Rio Grande. At this
time, heat index values are not expected to be much higher than the
daily high temperatures due to increased mixing/lower dewpoints in
the afternoon hours.

For the upcoming weekend into early next week, the subtropical ridge
axis begins to shift eastward as a broad upper trough moves into the
desert southwest. This should allow temperatures to drop slightly,
but we still expect above normal heat and dry conditions for most
areas. The one exception could be out west along the Rio Grande in
Val Verde county where some isolated convection may move in from the
higher terrain of Mexico.


Austin Camp Mabry              70  94  69  95  70 /  10  -   -   -   -
Austin Bergstrom Intl Airport  66  92  67  94  69 /  10   0  -   -   -
New Braunfels Muni Airport     67  93  67  94  68 /  10   0  -   -    0
Burnet Muni Airport            68  92  67  93  69 /  20  -   10  -   -
Del Rio Intl Airport           73  98  71 100  73 /  20  -   -   -    0
Georgetown Muni Airport        69  93  68  94  69 /  10  -   -   -   -
Hondo Muni Airport             68  94  66  96  67 /  10   0  -   -    0
San Marcos Muni Airport        67  93  67  94  68 /  10   0  -   -    0
La Grange - Fayette Regional   68  93  68  94  69 /  10   0  -   -    0
San Antonio Intl Airport       70  93  69  95  70 /  10   0  -   -    0
Stinson Muni Airport           69  94  69  96  70 /  10   0  -   -    0




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