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Area forecast discussion 
National Weather Service Austin/San Antonio Texas
632 am CDT Thursday Jul 28 2016

12z aviation update below.


IFR and MVFR ceilings have developed from Sat to near aus and into
The Hill Country. Patchy fog was also producing MVFR visibility
east of I-35. VFR conditions should develop 15z-17z. Isolated to
scattered showers and storms are expected to develop into portions
of the area this afternoon. Favored locations will be east of
I-35, along the Rio Grande, and just north of the County Warning Area across
west-central Texas. Chances are low at the taf sites and have not
included mention of thunderstorms and rain at this time.


Previous discussion... /issued 322 am CDT Thursday Jul 28 2016/

Short term (today through friday)...

Over the next couple days, the weakness in the mid/upper level
ridge will slowly fill in to replace the cyclonic shear axis that
brought some needed rain to much of the area. Today is a
transition day toward more Summer heat with highs probably
reaching near or just below seasonal normals, and isolated to
scattered air mass convection still possible. Weak cyclonic shear
favors slightly better chances for rain over west-central/north-
central Texas and along the northern reaches of our foreast area, and
low/mid level moisture convergence favors another area of
preferred convective initiation over the coastal prairies. The
rest of south central TX will depend on weaker features for
isolated rain chances. As minimal convective activity was seen
overnight, the convection will likely become even more diurnally
driven with no activity expected by this evening. By Friday, rain
chances are shown to have shifted east of I-35, and model trends
suggest this slight chance of rain may be generous. Heat indices
should be on the rise again each day, and ground moisture combined
with light low level wind forecasts will only add to the

Long term (friday night through wednesday)...

The weekend continues to see increasing stability as the GFS and
ecm solutions expand the mid-level ridge east to cover all of
North Texas. Weak onshore flow from the surface through deep into the
mid levels will keep higher pwat values and a slight chance of
weak convection over the southeast counties.

There is a subtle difference in the model solutions over the
weekend in that the GFS shows more convective activity in a northwest
flow pattern aloft over the High Plains, which could send cloud
debris over Texas in the northerly flow aloft. The ecm is weaker with
this feature, and the earlier patterns in the Summer wound up
favoring the GFS with stronger onshore surface winds to keep late
morning dewpoints higher. Meanwhile, the ecm appears to do a
better job of holding higher sfc dewpoints later in the day, which
is favored due to the recent rains. For now, will keep close to
blended guidance for Saturday through Monday, but am concerned
that heat indices and dewpoints could be held up by the impact of
mid-morning cloud cover preserving higher surface moisture
levels. Will continue to mention heat indices in the severe weather potential statement and paint
with a broad brush of 103 to 109 through the extended forecast.

By Monday, the GFS/ecm solutions have trended toward the mid-
level anticyclone to become centered much closer to central Texas
after earlier model cycles kept it farther north. Under this
pattern shift, the deeper moisture over the coastal prairies will
be lower, and extended period rain chances have been dropped after
Sunday. The better part of next week should see a continued
gradual increasing trend in high temps and daytime heat indices
possibly leveling off to persistence as slightly drier low level
air works in each day.


Preliminary point temps/pops...
Austin Camp Mabry 95 76 97 76 98 / 30 10 10 - 10
Austin Bergstrom Intl Airport 94 74 95 75 97 / 30 10 10 - 10
New Braunfels Muni Airport 93 73 95 75 96 / 20 10 10 - 10
Burnet Muni Airport 94 74 96 74 96 / 30 10 10 - -
del Rio Intl Airport 97 77 98 78 100 / 20 10 10 0 0
Georgetown Muni Airport 94 75 95 76 97 / 30 10 10 - -
Hondo Muni Airport 93 74 96 74 97 / 20 10 10 - -
San Marcos Muni Airport 93 74 95 75 96 / 30 10 10 - 10
La Grange - Fayette regional 94 76 95 76 96 / 40 10 20 - 20
San Antonio Intl Airport 93 77 95 77 96 / 20 10 10 - 10
Stinson Muni Airport 95 76 96 76 97 / 20 10 10 - 10


Ewx watches/warnings/advisories...




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