Austin / Travis County and South Central Texas Weather Statement #1
Prepared by UT University/Incident Meteorologist Troy Kimmel
1120am CT – Saturday / 29 April 2017

.. Enhanced Severe Thunderstorm Risk This Afternoon into Tonight with Cold Frontal Passage ..


NWS WATCHES / ADVISORIES / WARNINGS:
There are no current NWS watches, advisories and/or warnings in effect for our IH35
corridor counties..
Based on the NWS/Storm Prediction Center outlook, I feel as though a severe weather watch,
from the NWS/Storm Prediction Center, is likely for parts or all of our area between 3pm today
and 9pm tonight as the dynamics (atmospheric instability and lift), associated with a passing
upper air low pressure area and a rather strong surface cold front, increase and peak over our area.

SYNOPTIC/FORECAST REASONING:
A strong upper level low pressure area and an associated cold front will move from west to
east across the area later today into early tonight. The best dynamics (instability and lift) will
be overhead and to our north.

Current NWS/Weather Prediction Center rainfall guidance suggests that rainfall should remain in
the 1/2 to 1 inch range.. therefore the risk of any flooding is very low. Urban and small stream
flooding is possible during the periods of heavier rain over these respective areas.

The cold frontal passage will occur locally by early evening tonight with any severe
weather risk and rain chances diminishing thereafter.

THREAT(S) FOR AUSTIN METRO AND IH35 CORRIDOR COUNTIES:
Severe weather threat probability –
Geographic area: The IH35 corridor of south central Texas
Time Period: 4pm today to 10pm tonight
Main severe weather hazards expected:
Larger hail.. potential of strong straight line thunderstorm wind and isolated tornadoes…
***REMEMBER, DANGEROUS CLOUD-TO-GROUND LIGHTNING SHOULD BE EXPECTED
TO OCCUR WITH ANY THUNDERSTORMS THAT DEVELOP OR MOVE INTO OUR AREA***

MY FORECAST CONFIDENCE:
Weather system evolution: Very high
Precipitation chances: High
Liquid precipitation (rain) chances: High
Thunderstorm/lightning chances: High
Flash flood potential: Very Low to Low
Severe thunderstorm chances: ENHANCED 
(Main risks being large hail.. straight line thunderstorm wind and isolated tornadoes)
Freezing precipitation (freezing rain/freezing drizzle) chances: None
Frozen precipitation (snow/ice pellets-sleet) chances: None

LATEST OBSERVATIONS AND MY THOUGHTS:
At 1100am, the surface cold front extends from east of Tulsa, OK southwestward
to near Sherman/Denison, TX (and then to about 60 miles west of the DFW Metroplex)
to near Brownwood then to near Sonora and to west of Del Rio and then into Mexico.
Temperatures have warmed into the 80s (and dew points in the 60s to near 70 degrees F)
ahead of the front with temperatures falling back in the 50s in the wake of the front at
Wichita Falls and Abilene with the 40s over the panhandle. At 1100am, there is little in
the way of precipitation immediately ahead of the front as the result of a layer of warmer,
more stable air aloft (referred to as a “temperature inversion”).
Short range high resolution data suggests that this “temperature inversion” will be overcome
by increased atmospheric lift and daytime heating in the next hour or two and, as a result,
a broken north to south line of thunderstorms will quickly develop over north Texas in the
next hour or two and move eastward; as it does, the line will develop further southward
through central Texas with the guidance suggesting that the thunderstorms make their closest
approach locally with the frontal passage locally around 5 to 6pm. The guidance suggests that
the line will further solidify well southward once it passes the Austin area and the IH35 corridor
by early evening. Given this current scenario, it is possible that some people west of the IH35
corridor may not even receive any rainfall while other areas, primarily to the east of the IH35
corridor will see the stronger thunderstorms and the heavier rains. This system will be quite
progressive.. that is, it will move steadily through the area.. so the time period for thunderstorms
will remain fairly short for any given location.

AVIATION INFORMATION FOR THE AUSTIN/BERGSTROM
INTERNATIONAL AIRPORT (KAUS) AERODROME:
There is a ENHANCED large hail.. strong straight line thunderstorm wind.. and
isolated tornado threat this afternoon into tonight. Scattered to numerous
rain showers and thunderstorms will affect the AUS aerodrome as the cold front
passes by early evening. Deadly cloud-to-ground lightning will accompany
thunderstorms. The thunderstorm/rain chances slowly decreasing after 10pm
tonight…

Current KAUS Terminal Aerodrome Forecast (TAF) – Updated 291532z ..

FTUS44 KEWX 291532 AAA
 TAFAUS
 TAF AMD
 KAUS 291532Z 2916/3018 15014G24KT P6SM BKN025 BKN035
      FM291700 16016G26KT P6SM VCSH BKN035
      FM300100 34018G28KT P6SM SHRA BKN035
       TEMPO 3001/3004 TSRA SCT010 BKN035CB
      FM300600 34012KT P6SM FEW025 BKN070
      FM301500 29014KT P6SM FEW090=

. For Our DAL/DFW Hub Aerodromes ..
… Delays / Diversions Likely This Afternoon into this Evening …
Current NWS public forecasts indicates a 70% chance of rain showers and
thunderstorms this afternoon diminishing slowly to 60% tonight. There is a SLIGHT to
ENHANCED risk of severe thunderstorms this afternoon with larger hail.. strong
damaging straight line thunderstorm winds and isolated tornadoes. The cold front, with
associated wind shift (and airport approach/departure “turn around”) is forecast to move
through the aerodromes by mid afternoon. Given this scenario, it is likely that we’ll see
at least some delays and diversions from individual aerodromes and the ZFW center air
space as the strongest thunderstorms affect the area through early this evening.

For Our HOU/IAH Hub Aerodromes ..
… Delays / Diversions Possible Late Tonight and Again First Thing in the Morning …
Current NWS public forecasts indicates a 20% chance of rain showers and
thunderstorms this afternoon.. increasing to 40% by 9pm tonight.. then
increasing to 70% after midnight tonight and continuing through the overnight hours
with rain chances decreasing by daybreak tomorrow. There is a SLIGHT risk of severe
thunderstorms later tonight into the 4am time period tomorrow with larger hail.. strong
damaging straight line thunderstorm winds and isolated tornadoes. The cold front is
forecast to cross the IAH and HOU aerodromes in the 3am to 4am time frame early
tomorrow. Even though this is a quieter operational commercial aircraft period for the
aerodromes, there is still a possibility of delays and diversions from individual aerodromes
and the ZHU center air space overnight tonight as the upper air low pressure system
and front moves across Texas.

Current FAA National Airspace Status

CALL TO ACTION:

Please remain “weather aware” and listen for the latest weather statements,
advisories, watches and warnings from the National Weather Service.

Make sure that your NOAA All Hazards Weather Radio is operational and are
set to alarm in case of severe and inclement weather watches and/or warnings.

FOLLOWUP STATEMENTS:

I will continue to keep you informed regarding this severe/inclement weather
event. Any questions, please let me know at [email protected]

GENERAL WEATHER INFORMATION LINKS:

NWS/Austin-San Antonio Current Statements/Advisory/Watches/Warnings
NWS/Austin-San Antonio Web Page
NWS/Storm Prediction Center (Outlooks)
NWS/Storm Prediction Center (Mesoscale Discussions – Severe Weather & Snow)
NWS/Storm Prediction Center (Severe Thunderstorm/Tornado Watches)
NWS/Weather Prediction Center (Mesoscale Discussions – Heavy Rain & Flooding)
NWS/National Hurricane Center

tk