Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Austin/San Antonio Texas
1155 PM CDT Tuesday Sep 16 2014
Aviation... /issued for 06z tafs/
tropical moisture continues to fill in over south central Texas
both from advection and precipitation processes. Heavy rainfall
near abia will likely result in spotty IFR conditions or possibly
worse at times overnight in light surface flow. Model projections
continue to be more and more pessemistic for for this area
Thursday evening...so will opt for prevailing thunderstorms and rain and IFR
conditions. Conditions do not appear as dire for Sat/ssf with
mainly MVFR conditions and more intermittent IFR conditions and
storm chances. Driest conditions are reserved for drt with
MVFR conditions and no mention of thunderstorms and rain in the tafs for now.
Chances could potentially go up for drt and down for aus...but
will not stray far from the consensus of the finer model
Previous discussion... /issued 953 PM CDT Tuesday Sep 16 2014/
shower activity is on the down trend with only an isolated
thunderstorm over the southern part of Gillespie County.
With abundant tropical moisture in place...expect isolated to
scattered showers overnight mainly across the coastal plains...
southeast and southern counties. Good rain chances are anticipated
for Wednesday and Thursday across most areas. Locally heavy rain
and minor flooding expected mainly across the eastern half of
south central Texas.
Previous discussion... /issued 642 PM CDT Tuesday Sep 16 2014/
Aviation... /00z taf update/
convection just outside the abia vicinity to the north and east will
have a chance to impact the terminal over the next 1-2 hours.
Overall...convective trends are decreasing...no tempo groups are
mentioned for the remaining taf sites over the next several hours.
A more uniform southeasterly wind is expected in the lower levels
tonight...and the CIRA simulated low cloud product suggests more
continuous MVFR to possibly IFR ceilings to develop over the
Escarpment late tonight. There will also be a good chance of
streamer showers as indicated in the NAM and higher resolution
forecasts. Later in the day...more convection is possible with
high precipitable water environments along I-35 suggesting a good chance of
storms for much of the afternoon and evening. Given an outflow
boundary dominated environment...will leave the chances as prob30
groups from 18z to 00z Thursday.
Previous discussion... /issued 340 PM CDT Tuesday Sep 16 2014/
Short term (tonight through Wednesday night)...
16/12z radiosonde observation data across southern Texas shows plenty of deep layer
moisture in place...with precipitable water values of 2.5" at kcrp
and 1.8" at kdrt. The latest water vapor loop also shows plenty of
middle and upper level moisture from /Odile/ moving in from the west.
Otherwise...the latest radar imagery shows scattered showers and
storms ongoing across south central Texas. Chances for rainfall
will remain highest along the coastal plains where deeper moisture
will be found. Most activity will be tied closely to diurnal
heating...so a general decreasing trend is anticipated during the
late evening and overnight hours. However... given plenty of
moisture in place...can/T completely rule out additional showers
overnight. On Wednesday...moisture levels should increase slightly
across the region. Meanwhile...an increase in middle-level shortwave
activity embedded in the northwest flow aloft is anticipated. Rain
chances will remain favored for areas generally north of I-10 and
the coastal plains. Based on the latest round of model
guidance...we have increased rain chances on Wednesday and
Long term (thursday through tuesday)...
on Thursday...deep layer moisture and northwest flow aloft remain
intact across south central Texas. Rain chances will again be
favored for locations generally north of I-10 and the coastal
plains. Despite the relatively weak flow aloft...the models
suggest good potential for several rounds of rainfall on
Thursday...especially along and north of Highway 71. Locally
heavy rainfall will continue to remain a concern... especially for
locations that see multiple rounds of moderate to heavy rainfall.
We/ll continue to mention this in the latest hazardous weather
outlook. We/ll continue to mention rain chances into Friday and
based on the latest guidance...have increased probability of precipitation for areas east
of Highway 83. Moisture levels will be slow to decrease through
the upcoming weekend as the middle-level subtropical ridge axis is
expected to be weaker than previously anticipated. This will lead
to additional rain chances for the upcoming weekend and we have
included mainly 20-30% probability of precipitation for now. By early next week... a cold
front is expected to move Ino the region. The latest European model (ecmwf) has
backed off considerably on the strength of this cold front and is
now closer to the GFS solution. For now...we will not make any
significant changes to the forecast and await future model runs
for some consistency with this front.
Preliminary point temps/pops...
Austin Camp Mabry 74 89 74 88 71 / 30 50 60 60 30
Austin Bergstrom international Airport 72 89 71 87 70 / 40 50 60 60 30
New Braunfels Muni Airport 73 90 73 89 72 / 30 50 40 50 30
Burnet Muni Airport 72 87 72 87 70 / 30 50 60 60 30
del Rio International Airport 75 89 74 89 76 / 20 30 20 20 20
Georgetown Muni Airport 74 88 74 86 71 / 30 50 60 60 30
Hondo Muni Airport 73 90 73 91 73 / 20 40 30 30 20
San Marcos Muni Airport 73 89 73 87 71 / 30 50 50 50 30
La Grange - Fayette regional 74 89 74 87 73 / 40 60 60 60 20
San Antonio International Airport 76 90 76 90 75 / 20 50 40 40 30
Stinson Muni Airport 75 91 75 91 75 / 30 40 40 40 30