FXUS64 KEWX 240557

Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1257 AM CDT Fri Mar 24 2017

MVFR CIGs and S Winds 10 to 20 KTs with gusts to 25 KTs will prevail
overnight. A line of SHRA/ISOLD TSRA will accompany a dryline as it
moves across our area later tonight into Friday with winds decreasing
to 10 KTs or less as pressure gradient slackens. Have maintained -RA
at KAUS and VCSH at KSAT/KSSF Friday morning due no changes indicated
in forecast trends. Will monitor radar and forecast trends for
possible updates to TSRA/SHRA at the TAF sites. Clouds become SCT VFR
with winds shifting to SW 10 to 20 KTs across eastern areas and W to
NW 12 to 25 KTs with gusts to 30 KTs across western areas with
passage of the dryline as stronger winds mix to the surface. Winds
decrease to less than 10 KTs Friday evening as airmass decouples and
then shift to NW across all areas Friday night as a weak cold front
moves across our area while skies remain VFR.


.PREV DISCUSSION... /ISSUED 948 PM CDT Thu Mar 23 2017/

The dryline/pre-frontal trough is currently in West Texas and is
kicking off showers and thunderstorms across the Panhandle and into
the Lubbock area. The current forecast is in pretty good shape with
the handling of the PoP configuration and not many updates are
needed. Scattered showers and perhaps some thunderstorms will be
arriving to the northwest CWA around 3 AM and this will continue to
push east through the morning and early afternoon hours. Activity
should be heaviest across the eastern counties in the afternoon,
mainly due to timing when best instability will be realized.

Winds across all areas have fallen below advisory criteria and will
cancel the advisory early. Speeds will still remain in the 15-25 mph
range overnight.

PREV DISCUSSION... /ISSUED 700 PM CDT Thu Mar 23 2017/

Gusty winds will be the main forecast issue as a strong pressure
gradient and strengthening low-level jet ahead of tomorrow's front
keep S-SE winds sustained at 15-25 knots gusting up to 35 knots
through this evening. Wind gusts will fall to 20-25 knots after 6-7Z
as MVFR ceilings return to the I-35 sites and the low-level jet veers
at DRT. A pre-frontal trough will briefly bring northerly winds to
DRT from 10-15Z before they become more W-NW gusting to 25 knots in
the afternoon, with DRT most likely staying VFR through the period.

This pre-frontal trough will cause a brief period of showers at the
I-35 sites between 13-16Z. Thunderstorms are possible, but for now
have left this out of their TAFs as daytime heating and related
instability will be too low to overcome a cap that should suppress
widespread thunderstorm development. However, if this feature is
delayed the chances for thunderstorms will increase. VFR conditions
should return by 18Z at the I-35 sites, with winds becoming SW around
15 knots gusting to 20-25 knots before becoming more W-NW behind the
synoptic front Saturday morning just beyond the TAF period.

PREV DISCUSSION... /ISSUED 334 PM CDT Thu Mar 23 2017/

SHORT TERM (Tonight through Friday Night)...
Strong wind gusts have extended east of the advy area into the I-35
corridor, and sustained winds are on the cusp of reaching advy
criteria. Mixing occurred early along I-35 as opposed to out west, so
perhaps winds are topping out about now. Will leave the advisory as
is and hand off the dilemma to the next shift. Winds are expected to
relax late tonight as the surface low over the high plains to the
north tracks east. Models show good consistency in bringing a broken
line of mostly weak convection through the northern 2/3 of the
forecast area late tonight into Friday. A low CAPE/high shear
environment and a modest amount of moisture for spring standards
should make this round of convection mostly garden variety, but areas
near and to the east of AUS by midday Friday could be able to tap
into slightly deeper moisture and with a more robust afternoon
convection. The SPC outlook remains reasonable for a low end slight
risk day for the eastern counties, but mesoscale model runs such as
the TX Tech WRF suggest the deeper convection and severe threat
should be less than the areas of N-Central & E TX.

Post frontal drying will be efficient with downsloping westerly
winds, but the mid-level low pressure being well to the north may not
mix the gusty winds from aloft to the surface as much as they are
expected to the WFO counties to the north. A Fire Weather Watch is
for now, just north of our counties, and this may need to be reviewed
in more detail as we begin to see the strength of the surface to 850
mb winds in upcoming model runs. The potential for a low-end RFW
event should be mainly NW of a DRT to T82(Fredericksburg) line.

LONG TERM (Saturday through Thursday)...

Good drying from Friday's strong Central Plains storm could leave
Saturday morning with the coolest morning of the next week,
especially over the NW counties. Coastal Plains counties may fail to
lose all the shallow moisutre. Moisture return will resume Sunday but
not fast enough to bring a significant rain chance as a
shallow/smaller upper disturbance passes through the Central Plains
Sunday night. The progressive pattern aloft could keep the nocturnal
jet active, so some low-end convection (primary RW, isolated TRW)
looks reasonable for some northern counties Sunday night. while the
frontal wind shift in the wake of the Sunday system is weak, winds
will not shift to southerly but rather to the east in the advance of
a much deeper trough/upper low that reaches TX by Wednesday. This
system remains poorly agreed upon by deterministic solutions, with
the GFS running slowest/wettest and the CMC running fastest/driest.
Feel a ECM type middle ground solution will narrow the window in
future with a TRW likely type period Wednesday into Wednesday night;
for now will keep with the blended population schemes until the
model trends show more consistency.


Austin Camp Mabry 56 83 59 86 64 / 0 0 0 10 20
Austin Bergstrom Intl Airport 54 82 56 86 63 / 0 0 0 10 20
New Braunfels Muni Airport 54 83 57 86 63 / 0 0 0 - 10
Burnet Muni Airport 50 80 56 84 59 / 0 0 0 10 20
Del Rio Intl Airport 53 86 59 91 59 / 0 0 0 0 -
Georgetown Muni Airport 52 81 56 85 61 / - 0 0 - 20
Hondo Muni Airport 51 86 57 89 60 / 0 0 0 10 20
San Marcos Muni Airport 54 83 57 86 63 / 0 0 0 10 10
La Grange - Fayette Regional 58 82 59 84 66 / 20 0 - 10 20
San Antonio Intl Airport 55 85 59 86 63 / 0 0 0 10 10
Stinson Muni Airport 55 86 59 87 63 / 0 0 0 10 10




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