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

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FXUS64 KEWX 151503

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1003 AM CDT Sat Jun 15 2019

Visible satellite imagery and area radars show streamer showers
developing near Fayette and Lavaca Counties this morning and have
done a quick update to add a mention of showers through the remainder
of the morning hours. Also increased thunderstorm chances for Val
Verde County during the late afternoon hours where dryline convection
is expected to propagate. Afternoon dew point depressions of 25-30
degrees across portions of the lower Trans-Pecos will create an
environment capable of gusty downburst winds. Latest ARW/NMM/HRRR
/TTU-WRF guidance remains consistent in adverstising cold pools
associated with these downbursts allowing for some of this activity
to move into Val Verde County late this afternoon and evening.
Otherwise, expect highs in the upper 80s to low 90s in the Hill
Country, increasing to near 100 in the Rio Grande Plains.


.PREV DISCUSSION... /ISSUED 657 AM CDT Sat Jun 15 2019/

Please see the 12Z aviation forecast discussion below.

MVFR cigs will continue along the I-35 corridor through most of the
morning hours. Gusty south winds can also be expected from mid-
morning through the afternoon. At DRT, mid and high level cloud cover
has hindered the formation of low clouds and given satellite trends
and the latest forecast soundings, we will not mention any MVFR cigs
this morning. We could see some convection approach DRT during the
evening hours and have opted to only mention VCSH at this time as
coverage should be isolated.

PREV DISCUSSION... /ISSUED 336 AM CDT Sat Jun 15 2019/

SHORT TERM (Today through Sunday)...
Humidities increase today along with afternoon heat indices. Mid-
level ridging maintains a capping inversion over most of South
Central TX today, while a shortwave moving into N TX brings enough
energy into the Trans Pecos region to generate a few strong storms
that could move into our srn Edwards Plateau counties this evening.
Deep layer moisture is suggested to be lacking for good coverage and
continued eastward propagation into the more stable region of the
I-35 corridor, but the 00Z GFS does suggest a more aggressive push
to where moisture is deeper over the Hill Country. Will defer to the
more stable ECM solution that maintains a stronger cap, but we will
need to monitor trends given some of the steeper mid level lapse
rates that will move into N TX. The ECM which is more stable for
today than the GFS then becomes the more unstable model for Sunday
afternoon along and east of I-35 as the base of the low amplitude
shortwave amplifies slightly over E TX. Will again favor the more
stable solution and choose the flatter mid-level pattern of the GFS
of the 2nd period. Prefer the more conservative solutions mainly due
to the much more unstable conditions farther north that will be aided
by a sharper dry-line this evening and later on, outflow boundaries.
Nevertheless, a broad low chance for isolated strong to severe
storms is in place for the northern half of the area Sunday, with
best PoPs at around 40 percent over our far eastern counties.

LONG TERM (Sunday Night through Friday)...
For Sunday night into Monday, prefer the NAM/ECM solutions which
do not tie up all the vorticity into convective feedback over
eastern OK as is done by the 00z GFS. This period might bring the
best the chance of rain but is still favored for the eastern half of
the forecast area. While the convective focus is expected to push
through our eastern counties early in the day, would not be surprised
to see a few strong storms in the early afternoon hours Monday east
of I-35. South of Hwy 90 mostly stable conditions will continue and
heat index values should continue to be elevated, but convective
debris clouds should keep the higher values mainly in the 100 to 105
range. Tuesday trends are drying due to the slightly amplified s/w
trough to the east, and we may need to reconsider mentioning elevated
heat index values. For now, will stick with Wednesday and Thursday
as the days the models show the low level thermal ridge expanding
east from West TX the most. HI values of 102 to 110 should be
considered and there could be a need for a heat advisory. Mid level
height fields are forecast to lower on Friday with cooler 850 mb
temps suggesting max temps and heat indices lowering slightly.


Austin Camp Mabry              93  75  93  74  93 /  10  10  30  30  30
Austin Bergstrom Intl Airport  93  75  93  74  93 /  10  10  30  30  30
New Braunfels Muni Airport     94  74  93  73  93 /  10  10  20  20  30
Burnet Muni Airport            92  73  91  72  93 /  -   10  20  30  30
Del Rio Intl Airport           94  74  95  74  97 /  10  10  10  20   0
Georgetown Muni Airport        93  75  93  73  93 /  -   10  20  30  40
Hondo Muni Airport             96  74  96  74  98 /  -   10  -   20  10
San Marcos Muni Airport        94  74  93  73  94 /  10  10  30  30  30
La Grange - Fayette Regional   93  77  91  75  93 /  20  10  40  30  40
San Antonio Intl Airport       94  75  94  74  95 /  10  10  10  20  20
Stinson Muni Airport           96  75  95  74  97 /  10  10  10  20  20




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