Scientific Forecaster Discussion
fxus64 kewx 191115
Area forecast discussion
National Weather Service Austin/San Antonio Texas
615 am CDT Thu Sep 19 2019
VFR conditions are prevailing across the area this morning with just
some passing mid-level clouds. Winds are light and variable and
should be mostly out of a southerly direction later today. There will
be a chance of showers and thunderstorms for this afternoon and early
evening for the i35 sites. Will prevail vcsh for these sites but
mention a tempo group for -tsra for aus who has a slightly greater
probability to see a thunderstorm than the San Antonio sites. Some of
these storms today could produce brief heavy rainfall and perhaps
some gusty winds as well.
Previous discussion... /issued 405 am CDT Thu Sep 19 2019/
Short term (today through friday)...
area radars show showers east of Bastrop into southeastern Texas.
These showers are in the tail end of a moisture convergence zone
feeding into tropical depression Imelda as it drifts north across
eastern Texas. This zone lingers today into tonight from The Hill
Country across I-35/I-37 corridors to the coastal plains. Showers
and thunderstorms gradually spread west across this zone with
heating. Pws of 1.6 to 2 inches which are 120 to 140 percent of
normal for this time of year are indicated by satellite imagery. As a
result, locally heavy rainfall is possible and may cause minor
flooding, especially if rain cells train over the same areas. The
weakness in the subtropical ridge caused by Imelda should allow
showers and thunderstorms to linger further into this evening and
overnight before dissipation with loss of heating. As Imelda drifts
further to the north on Friday, the subtropical ridge gradually
regains influence with increasing subsidence. Deeper moisture remains
east of US 281 on Friday keeping chances of showers and
thunderstorms across that area with heating. Temperatures remain well
above normal, though "cooler" than last few days in the rainy areas.
Long term (friday night through wednesday)...
the subtropical ridge is the dominant influence this weekend into
next week as mid level shortwaves pass well north of our area with no
significant impacts to our area. The exception to this would be any
upper level moisture from eastern Pacific tropical cyclones Lorena
and mario moving over the top of the ridge to bring enhanced moisture
levels. However, the chances for this are very low as models show a
fujiwara pattern of interaction between the two cyclones. For now,
will maintain low chances of showers and thunderstorms mainly across
eastern areas each day with heating. The enhanced moisture mentioned
above would bring low chances of showers and thunderstorms to mainly
far western areas.
There are potentially higher chances of showers and thunderstorms for
middle to late next week as models show a deeper upper level trough
developing across the western states eventually dislodging the ridge.
However, there remains disagreement among the models on the evolution
of this trough. Also, it seems the models have finally given up on
any cold fronts moving into south central Texas and The Hill Country
for the remainder of September.
Preliminary point temps/pops...
Austin Camp Mabry 94 76 96 76 93 / 40 30 30 - 20
Austin Bergstrom Intl Airport 94 75 95 73 92 / 50 30 30 - 20
New Braunfels Muni Airport 96 75 97 73 91 / 40 30 30 - 20
Burnet Muni Airport 93 73 94 73 90 / 30 30 20 - 10
del Rio Intl Airport 101 77 97 76 97 / - 10 - - -
Georgetown Muni Airport 93 75 93 73 92 / 40 30 30 - 20
Hondo Muni Airport 100 75 98 75 96 / 20 20 10 - 10
San Marcos Muni Airport 95 74 96 73 92 / 50 30 30 - 20
La Grange - Fayette regional 93 75 93 74 92 / 50 40 40 10 30
San Antonio Intl Airport 97 77 97 76 93 / 30 30 20 - 20
Stinson Muni Airport 100 77 99 76 96 / 20 20 20 - 20