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Area forecast discussion
National Weather Service Austin/San Antonio Texas
1202 am CDT Fri may 26 2017

Aviation...
MVFR ceilings are in place across the i35 sites at the present time
and should arrive to drt within the next several hours. Cloud bases
should continue to lower and possibly reach IFR later tonight.
Conditions will be slow to improve in the late morning hours, but VFR
should return in the afternoon. Southerly flow will continue with
speeds in the 8-15 knot range.

&&

Previous discussion... /issued 339 PM CDT Thu may 25 2017/

Short term (tonight through Friday night)...
an increase in southerly flow in the low-levels will lead to
increased moisture and a return of low clouds across south central
Texas tonight. Overnight low temperatures will be much warmer when
compared to the last couple of nights. Given the increase in moisture
and cloud cover, we expect low temperatures in the 70s tonight. We
could see a few light showers develop east of the I-35 corridor early
tomorrow morning. For now, confidence in measurable precipitation is
low and we will keep the forecast dry. Another warm, humid and breezy
day is on tap for Friday, with highs generally in the 90s. The warm
temperatures along with humid conditions could push afternoon heat
index values to near 103 degrees along the I-35 corridor to near 108
degrees across the Rio Grande plains south of del Rio. Warm and humid
conditions are in store Friday night, with lows in the 70s.

Long term (saturday through thursday)...
another hot and humid day is in store for Saturday with highs in the
90s and maximum heat index values of 103-105 along I-35, with 105 to
108 degrees along the Rio Grande. Given the strong heating, we can't
completely rule out some strong to possibly severe thunderstorm
development along and north of a del Rio to Llano line. Chances of
the cap breaking appear low at this time, so we will keep rain
chances low. Should a few storms manage to develop, the main severe
weather concern will be large hail and damaging winds.

The weather pattern becomes increasingly active on Sunday as a cold
front begins to move into south central Texas during the late
afternoon and early evening hours. Overall instability should be
lower than Saturday, but given the cold front and an increase in
mid-level shortwave troughs, we should see some strong to severe
thunderstorms over the southern Edwards Plateau and western Hill
Country during the late afternoon and evening hours. The front
continues to slowly drop southward Sunday night and with the boundary
intersecting the higher terrain west of the Rio Grande, additional
thunderstorms will develop across the Rio Grande plains. Given the
fairly weak 0-6km winds along with southeast-easterly upslope flow in
the low levels, the pattern appears favorable for some locally heavy
rainfall. The exact location for heavy rainfall is tough to
determine at this time, but would initially favor the Rio Grande
plains and southern Edwards Plateau Sunday night. As the front drops
southward late Sunday night into Monday morning, we could also see
some pockets of locally heavy rainfall spread into The Hill Country
and I-35 corridor. The frontal boundary becomes increasingly diffuse
by late Monday and this should result in a lower, but continued rain
chances.

The forecast for the middle of the upcoming work week appears wet,
as a series of mid-level shortwave troughs move overhead in the
active southwest flow aloft. The remnant frontal boundary or
convective outflow boundaries will also aid in shower and
thunderstorm development. It will be tough to time the best chance
for activity to develop, so we will keep rain chances generally in
the 30-50% range through the remainder of the forecast.

&&

Preliminary point temps/pops...
Austin Camp Mabry 76 95 76 92 69 / 10 10 10 30 60
Austin Bergstrom Intl Airport 77 95 75 92 70 / 10 10 10 30 60
New Braunfels Muni Airport 76 95 76 93 70 / 10 10 10 20 60
Burnet Muni Airport 75 93 74 90 66 / - 10 20 40 60
del Rio Intl Airport 78 97 77 93 72 / - 10 20 40 70
Georgetown Muni Airport 76 94 75 91 67 / 10 10 10 30 60
Hondo Muni Airport 77 96 76 94 71 / 10 10 10 20 60
San Marcos Muni Airport 77 95 76 93 70 / 10 10 10 20 60
La Grange - Fayette regional 77 94 77 93 72 / 10 10 10 20 40
San Antonio Intl Airport 77 96 77 93 71 / 10 10 10 20 60
Stinson Muni Airport 77 97 77 94 72 / 10 10 10 20 60

&&

Ewx watches/warnings/advisories...
none.
&&

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