Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
816 PM CDT Tuesday Jul 26 2016
shower and thunderstorm coverage has waned considerably this
evening with only sparse locations with returns on radar. Hi-res
model suite continues to indicate a quiet night for south central
Texas. Can't rule out a potential isolated cell to develop
overnight so included iso mention in the wx grid for overnight in
the south. Looking at Storm Prediction Center mesoanalysis, at least some instability
still exists just south of the County Warning Area border east of I-37. It
currently is the only area to still have lightning activity but
also looks like it will continue to wane over the next hour.
Thus, have trimmed back pops from the original forecast and
attempted to massage the hourly T/TD grids due to the precip
cooling effects from this afternoon. Will likely need to stay on
these edits each hour to capture the correct trends.
Previous discussion... /issued 705 PM CDT Tuesday Jul 26 2016/
patches of -ra along with isolated rain showers/thunderstorms and rain are currently slowly
decreasing across south central Texas. This trend is expected to
continue as the atmosphere stabilizes. Due to a moist airmass and
weak cyclonic flow, could see some rain showers/thunderstorms and rain redevelopment toward
morning with scattered development during the day on Wednesday as
airmass destabilizes from solar heating. Surface boundaries from
earlier rain showers/thunderstorms and rain will also force development. There is
uncertainty on locations of best upward forcing. For now, have
left precip mention out of tafs. However, expect later updates to
mention based on radar and model trends. VFR skies are expected
this evening. Stratus with MVFR ceilings will develop overnight into
early morning and have mentioned 08z-17z in the tafs. Patchy IFR
ceilings and br with IFR/MVFR vsbys are possible due to surface
moisture from recent rains. Chances are low at the taf sites and
have left mention out for now. VFR skies return in the afternoon,
except brief IFR/MVFR ceilings/visibilities are expected in shra/tsra. S to
southeast winds around 10 kts or less will prevail. Wind gusts up to 40
kts are possible in/near the stronger shra/tsra.
Previous discussion... /issued 305 PM CDT Tuesday Jul 26 2016/
Short term (tonight through Wednesday night)...
26/12z upper air data shows a moist atmosphere in place with
precipitable water values near 1.9" and kdrt with near 2.1" at
kcrp. Given the well above normal moisture and daytime heating,
we expect another round of showers and thunderstorms this afternoon
and evening, especially along and south of the Highway 90 corridor.
Similar to yesterday, some of the stronger thunderstorms will be
capable of producing locally heavy rainfall and wind gusts to 50
miles per hour. Some minor flooding may also develop given well above normal
moisture and slow moving storms. A few spots could pick up a quick
2-3 inches of rainfall, especially if several storms move over the
same region. Otherwise, rainfall amounts should average 1/4 to 3/4
of an inch for most locations.
On Wednesday, deep layer moisture persists over the region with
most areas expected to remain around 2". We'll continue to see
some fairly broad cyclonic flow in the mid-levels and with daytime
heating, we expect another round of scattered showers and
thunderstorms during the afternoon and evening hours. Similar to
today, can't rule out a some pockets of locally heavy rainfall
across the region and we will continue to mention this in the
hazardous weather outlook.
Long term (thursday through tuesday)...
the atmosphere begins to dry out late this week (friday and
saturday) and we'll begin to show a decrease in rain chances from
west to east across south central Texas. We'll keep a 20-30%
chance for rain across all areas on Thursday, with chances then
limited to areas mainly east of I-35 on Friday and Saturday.
Temperatures will also begin to increase, with near normal
readings expected Thursday and above normal for Friday and
The subtropical ridge axis will then gradually build into early
next week across all areas. While most areas will likely remain
dry with above normal temperatures, prefer to hang on to a low
chance for convection near the coastal plains.
Preliminary point temps/pops...
Austin Camp Mabry 76 96 76 97 76 / 20 40 20 20 10
Austin Bergstrom Intl Airport 75 94 75 96 75 / 20 40 20 20 20
New Braunfels Muni Airport 74 95 75 96 75 / 20 40 20 20 10
Burnet Muni Airport 74 93 75 95 75 / 20 40 20 30 10
del Rio Intl Airport 77 97 78 98 78 / 20 30 20 20 10
Georgetown Muni Airport 75 93 76 95 76 / 20 40 20 30 20
Hondo Muni Airport 75 93 75 96 74 / 20 40 20 20 10
San Marcos Muni Airport 74 93 75 96 75 / 20 40 20 20 10
La Grange - Fayette regional 76 93 77 96 76 / 20 50 20 30 20
San Antonio Intl Airport 76 93 77 95 76 / 20 40 20 20 10
Stinson Muni Airport 76 95 77 98 76 / 20 40 20 20 10
public service/data collection...33