Flash Flood Warning 71, NWS Austin/San Antonio, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
1156 AM CDT MON SEP 11 2006

.AVIATION...
MOIST UNSTABLE TROPICAL AIRMASS OVER S CENTRAL TX AND THE HILL
COUNTRY WILL RESULT IN WIDESPREAD SHRA/TSRA WITH IFR CIGS AND
VSBYS POSSIBLE THRU 00Z. AFTER 00Z SHRA/TSRA WILL DECREASE AND
BECOMING SCT SHRA/TSRA AS A COLD FRONT IN CENTRAL TEXAS MOVES SEWD
ACROSS THE HILL COUNTRY BETWEEN 00Z AND 06Z...AND S CENTRAL TX
BETWEEN 12Z AND 18Z. MVFR AND OCCASIONALLY IFR CIGS WILL
WIDESPREAD AHEAD OF THE FRONT...QUICKLY LIFTING TO VFR BEHIND THE
FRONT.

&&

.PREV DISCUSSION... (ISSUED 952 AM CDT MON SEP 11 2006)

UPDATE...
BROAD AREA OF CONVECTION MOVING NORTH OUT OF SOUTH TEXAS IS
HOLDING TOGETHER RATHER WELL, AND LOOKS LIKE IT WILL BRING SOME
MUCH-NEEDED RAIN TO SOUTH CENTRAL TEXAS TODAY AHEAD OF THE COLD
FRONT. QUICK UPDATE TO INCREASE NEAR-TERM POPS, MAINLY ALONG AND
SOUTH OF THE I-35 CORRIDOR.

PREV DISCUSSION... (ISSUED 446 AM CDT MON SEP 11 2006)

DISCUSSION...
SCATTERED SHOWERS WILL SPREAD INTO MUCH OF SOUTH CENTRAL TEXAS
FROM THE SOUTH AS ENERGY LIFTS OUT OF MEXICO TODAY. HOW MUCH
ENERGY IS QUESTIONABLE, WITH THE NAM AND GFS SHOWING CONSIDERABLE
POP DIFFERENCES OF 30-50 PERCENT. THE PATTERN FOR THE PAST COUPLE
MORNINGS HAVE ME FAVORING THE DRIER ETA MOS FOR TODAY, BUT THE
FORECAST SHOWS MORE OF A SPLIT OF THE TWO. THE CURRENT ACTIVITY ON
THE MORNING RADAR LOOP LOOKS TO FAVOR THIS SPLIT WITH LIGHT
SHOWERS AND LOW QPF AMOUNTS DUE TO MORE MORNING CLOUD COVER
EXPECTED TODAY THAN WAS SEEN SUNDAY. THE INCREASED MID-LEVEL
CLOUDINESS HAS CURBED FOG DEVELOPMENT OVER ALL BUT THE EASTERN
COUNTIES, AND WILL LIKELY CURB SIGNIFICANT FOG DEVELOPMENT HERE TOO
AS THE CLOUDS CONTINUE TO BUILD FROM WEST TO EAST.

THE COLD FRONT EXPECTED TO REACH SOUTH CENTRAL TX TONIGHT WILL
HELP TAP INTO ALL THE PACIFIC MOISTURE IN PLACE TO WARRANT
INCREASED POPS FOR TONIGHT INTO TUESDAY. HOWEVER, WILL CONTINUE TO
SHOW MORE CONSERVATIVE NUMBERS THAN THE GFS BASED MOS SINCE
FRONTAL WIND CONVERGENCE WILL BE LIGHT, AND ANTICYCLONIC FLOW WILL
CONTINUE AT 700 MBS THROUGH THE NEXT COUPLE DAYS. THE STABLE WIND
FLOW ALOFT SHOULD ALSO HELP KEEP THUNDERSTORMS FROM BECOMING
SEVERE. WITH THIS IN MIND, WILL STAY ON THE DRY SIDE OF GUIDANCES,
SWITCHING TO THE MAV GUIDANCE. QPF AMOUNTS THROUGH THIS PERIOD ARE
ADMITTEDLY UNDERSOLD A BIT, BUT THIS IS DUE TO THE CONTINUED WET
BIAS AND DROUGHT CONDITIONS. MOST AREAS SHOULD SEE SOME MEASURABLE
RAIN BETWEEN NOW AND 00Z WEDNESDAY, WITH AMOUNTS TO AVERAGE AROUND
1/4 INCH.

IN THE MEDIUM RANGE, THE GFS AND DGEX MODELS DIFFER ON WHAT TO DO
WITH A WEAK APPROACHING UPPER LOW, CURRENTLY CAUGHT IN LIGHT FLOW
ALOFT OVER CA. THE GFS/ECMWF LOOKS MORE REASONABLE HERE WITH
A MOIST SW FLOW ALOFT TO CONTINUE OVER S TX WHILE A LARGE UPPER
TROUGH PULLS THE DISTURBANCE INTO THE CENTRAL PLAINS. A CONSENSUS
SOLUTION OF THE MEDIUM RANGE MODELS POINTS TO A PERSISTENCE
PATTERN OF SW FLOW ALOFT TAPPING INTO PACIFIC MOISTURE PLUMES.
THIS WEEKEND, THE GFS APPEARS TO BE A REASONABLE MIDDLE GROUND
BETWEEN THE WETTER CANADIAN AND ECMWF AND THE DRIER DGEX.

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

25/01

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
514 AM CDT MON SEP 11 2006

TXZ171>173-183>194-202>209-217>225-228-121000-
LLANO-BURNET-WILLIAMSON-VAL VERDE-EDWARDS-REAL-KERR-BANDERA-
GILLESPIE-KENDALL-BLANCO-HAYS-TRAVIS-BASTROP-LEE-KINNEY-UVALDE-
MEDINA-BEXAR-COMAL-GUADALUPE-CALDWELL-FAYETTE-MAVERICK-ZAVALA-
FRIO-ATASCOSA-WILSON-KARNES-GONZALES-DE WITT-LAVACA-DIMMIT-
514 AM CDT MON SEP 11 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH CENTRAL TEXAS.

.DAY ONE...TODAY AND TONIGHT
THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS. THE MAIN THREAT IS
LOCALLY HEAVY DOWNPOURS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY
THERE IS A GOOD CHANCE OF SHOWERS AND THUNDERSTORMS TUESDAY AND
TUESDAY NIGHT. THE MAIN THREAT IS LOCALLY HEAVY DOWNPOURS.

THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS THURSDAY
THROUGH SUNDAY.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS NOT ANTICIPATED.