Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Austin/San Antonio Texas
246 PM CDT Friday Jul 29 2016
Short term (tonight through saturday)...
Main highlight will be the low-end rain chances today (20-30%)
that will drop further over the weekend while temperatures and
heat indices rise.
A combination of surface heating-driven instability and a weak
mid- to upper-level shear axis over central Texas is aiding in
isolated to scattered showers in the coastal plains and over the
Edwards Plateau. Earlier this morning a strong outflow boundary
from a previous storm complex in OK is now the focus of new
development in north-central Texas. It is unlikely that this
outflow will make it to south-central Texas. Just north across
Edwards Plateau however, exists scattered thunderstorms where the
shear axis and deeper mid to upper level moisture exist. Feel some
additional activity could develop across The Hill Country and the
southern Edwards Plateau through the afternoon. Coastal plains
storms will persist into the early evening hours and could produce
very localized 1-2 inch amounts. All activity will dissipate
through 8-9pm. Current heat indices are climbing into the 100-105
range as of 3pm and could top out in the 103-108 range through
Clouds will return overnight with lows falling into the low to
mid 70s. Saturday will feature less shower coverage but still a
few isolated showers/storms could develop across the coastal
plains and again over the Edwards Plateau. A weak upper-level
vorticity Max can be seen via water vapor satellite and this could
help increase coverage more than models suggest. Will need to
watch if 20-30% rain chances need to be expanded farther west
across Atascosa and into portions of the Rio Grande plains. Heat
indices will once again rise into the 103-108 range for the
coastal plains on Saturday where rain showers do not occur.
Long term (sunday through friday)...
Generally dry and above normal temperatures are expected through
much of next week with only small pockets of isolated showers and
The weak upper-level low will shift over the mid Rio Grande
Valley by Sunday but mid- to low-level ridging is expected to
strengthen at the same time. This additional suppression should
help quell shower activity more than today and Saturday.
Temperatures will also be ticking up with Metro areas nearing the
100 mark again and del Rio in the low 100s.
Through mid-week, the ridge strengthens further to 594 dm over
Texas and this should firmly place US with little rain and
continued hot temperatures each afternoon. A Special Weather
Statement may be needed during this time for heat indices reaching
into the 105-109 range for a couple hours each afternoon.
By late week, another upper level-low will break off from the jet
stream and become centered over Texas the low to mid level ridging
breaks down. This should allow for slightly better shower coverage
across the coastal plains and inland. One significance of this
ridge breakdown could come into play late next weekend as long
range models are suggesting the possibility of a tropical system
within the Gulf of Mexico. If the ridge breaks down, it could
allow for a tropical system of some type to shift farther north.
It is too far out to determine any details and whether this
solution will play out or not. Please stay through next week on
Preliminary point temps/pops...
Austin Camp Mabry 76 97 76 98 76 / - 10 - - 0
Austin Bergstrom Intl Airport 74 96 75 97 75 / - 10 - - 0
New Braunfels Muni Airport 74 96 75 97 75 / - 10 - - 0
Burnet Muni Airport 74 96 75 97 74 / - 10 - - 0
del Rio Intl Airport 75 98 75 99 76 / 10 10 - - 0
Georgetown Muni Airport 76 96 76 97 76 / - 10 - - 0
Hondo Muni Airport 73 96 74 96 74 / - 10 - - 0
San Marcos Muni Airport 74 95 75 96 75 / - 10 - - 0
La Grange - Fayette regional 76 95 76 96 76 / 10 20 - 10 -
San Antonio Intl Airport 76 95 76 96 76 / - 10 - - 0
Stinson Muni Airport 76 98 76 98 76 / - 10 - - 0
public service/data collection...Williams