Severe Thunderstorm Warning 40, NWS Austin/San Antonio, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
830 PM CDT MON APR 5 2004

.UPDATED DISCUSSION...
A FLASH FLOOD WATCH CONTINUES FOR ALL OF THE FORECAST WARNING COUNTY
AREA THROUGH TONIGHT TO 6 AM TUESDAY MORNING. THE SEVERE
THUNDERSTORMS WATCH THAT WAS IN EFFECT UNTIL 8 PM FOR VAL VERDE
COUNTY HAS EXPIRED.

A REGIONAL SURFACE ANALYSIS SHOWS A WEAK LOW CENTER LOCATED OVER
WESTERN TEXAS JUST NORTH OF THE BIG BEND. DOPPLER RADARS SHOW
CONVECTIVE ACTIVITY DEVELOPING OVER WEST TEXAS IN ASSOCIATION WITH
THIS WEAK LOW CENTER. A LOCAL AREA SURFACE ANALYSIS SHOWS WIDESPREAD
CLOUDINESS WITH TEMPERATURES IN THE 70S...DEW-POINTS IN THE UPPER 50S
TO LOWER 60S AND WINDS FROM THE EAST AND SOUTHEAST. A REGIONAL UPPER
LEVEL ANALYSIS SHOWS A CLOSED LOW LOCATED OVER EASTERN NEW
MEXICO/WESTERN TEXAS...DRIFTING NORTHEAST. THIS FEATURE ALSO SEEN ON
VISIBLE AND WV/IR SATELLITE LOOPS.

AS NOTED ABOVE...THE AREA IS STILL UNDER A FLASH FLOOD WATCH.
WITH THE AMOUNT OF RAIN THAT HAS FALLEN...ANY ADDITIONAL RAINS...
REGARDLESS OF THE AMOUNT WILL CAUSE FLOODING. FLASH FLOOD GUIDANCE
FOR THE WESTERN COUNTIES IS UNDER ONE INCH FOR ONE HOUR RATES...
WITH 1.3 TO 1.9 INCHES FOR THE EASTERN COUNTIES ONE HOUR RATES.
MODEL GUIDANCE FOR THE NGM...MESO ETA...AVN AND UKMET...RAINFALL
ACCUMULATION ANALYSIS FOR SOUTH CENTRAL TEXAS AND THE HILL COUNTRY
FORECAST WARNING AREA SHOW FOR TONIGHT...0.45 TO 1.95 INCHES.
FOR TUESDAY 0.25 TO 0.45 INCHES.

AS NOTED ABOVE...THE WESTERN COUNTY OF VAL VERDE WAS UNDER A
SEVERE THUNDERSTORM WATCH WHICH EXPIRED AT 8PM. THE THREAT OF
SEVERE WEATHER CONTINUES. NCEP SPC CONVECTIVE OUTLOOK HAS THE SOUTH
CENTRAL TEXAS FORECAST WARNING AREA IN A SLIGHT RISK OF SEVERE
THUNDERSTORMS OVER THE WESTERN TWO THIRDS OF THE AREA THROUGH 12Z
TUESDAY MORNING. THE DOPPLER RADARS OVER THE WESTERN SECTIONS OF
TEXAS INDICATE THUNDERSTORM DEVELOPMENT ACROSS THE BIG BEND
EXTENDING NORTHEAST. A EASTWARD MOVEMENT IS INDICATED. NEEDLESS TO
SAY...THUNDERSTORMS WILL BE INCREASING ACROSS THE WESTERN COUNTIES OF
THE HILL COUNTRY AND SOUTH CENTRAL TEXAS THIS EVENING. IT SHOULD
ALSO BE NOTED THAT THE DEL RIO...DRT...00Z RAOD SOUNDING THIS
EVENING HAD A FREEZING LEVEL AT 10 K. WITH CONVECTIVE STORMS
DEVELOPMENT...LOOKS LIKE A GOOD HAIL PRODUCING ATMOSPHERE.

IN SUMMARY...FOR TONIGHT...
LOOKING FOR THUNDERSTORMS TO CONTINUE THIS EVENING WITH ADDITIONAL
DEVELOPMENT TONIGHT. CURRENT ACTIVITY OCCURRING OVER THE WESTERN
COUNTIES NEAR THE UPPER PORTIONS OF THE RIO GRANDE RIVER AND THE
BIG BEND WILL SLIDE EASTWARD INTO THE CENTRAL COUNTIES OF SOUTH
CENTRAL TEXAS LATER TONIGHT AND THEN BE INFLUENCED BY A MID LEVEL JET
WHICH WILL INTENSIFY THE STORMS MOVING ACROSS THE AREA AS THEY SPREAD
NORTHEAST. WITH THE SATURATED ATMOSPHERE UP TO 10K...HEAVY RAINFALL
LOOKS TO BE THE MAIN THREAT. BUT THE FREEZING LEVEL AT 10.8K WILL
PROVIDE A FOCUS FOR HAIL DEVELOPMENT. BUT THE MAIN EVENT IS BELIEVED
TO BE A HEAVY RAIN SITUATION. FLOODING WILL LIKELY OCCUR AS THE
GROUND IS ALREADY SATURATED DUE TO THE RAINS THAT HAVE ALREADY
FALLEN OVER THE PAST FEW DAYS. RAINFALLS EXPECTED TONIGHT WILL
RANGE IN THE ONE-HALF TO TWO INCHES WITH ISOLATED AMOUNTS OF TWO TO
FOUR INCHES POSSIBLE IN THE STRONGER STORMS.

FOR TUESDAY...LOOK FOR THE UPPER LOW TO TRACK NORTHEAST THROUGH
THE DAY WITH RAIN ENDING FROM THE WEST AND PROGRESSING EASTWARD
THROUGH THE DAY.

WILL UPDATE THE 4PM FORECAST PACKAGE...REMOVING THE SEVERE
THUNDERSTORM WATCH HEADER AND ADJUST WEATHER ELEMENTS TO BE MORE
INLINE WITH THE ONGOING WEATHER TRENDS. FLASH FLOOD WATCH WILL
CONTINUE THROUGH THE NIGHT.

&&

.PREV DISCUSSION...
TONIGHT...AS NEXT WAVE OF STRONG EARLY SPRING...RAIN MAKING ENERGY
COMES WITH THE LOW ALOFT.  TREND SHOWS DECREASING CHANCE OF RAIN
FROM THE WEST EVOLVING ON TUESDAY AND CONTINUING THROUGH THE
LATE AFTERNOON AND EVENING.  MOST OF THE RAIN IS EXPECTED TO BE EAST
OF THE AREA BY LATE TUESDAY TO PREDAWN HOURS OF WEDNESDAY MORNING.
WILL CONTINUE THE FLASH FLOOD WATCH THROUGH 6 AM CDT TUESDAY MORNING.
HEAVIEST RAIN AND HIGHEAST CHANCE OF SHOWERS OR THUNDERSTORMS IS
EXPECTED OVER THE NORTHERN PART OF THE AREA.  AS LOW PULLS OFF TO
THE EAST...NORTH OF SOUTH CENTRAL TEXAS...EXPECTED MORE STABLE
CONDITONS TO COME ACROSS THE AREA FROM THE WEST AND SOUTHWEST
IN THE AFTERNOON ON TUESDAY.  WILL KEEP FLASH FLOOD WATCH UP DUE
TO RECENT RAINS...AND EXPECTED ADDITIONAL RAIN TONIGHT.

ON WEDNESDAY...THE WEATHER PATTERN SHOWS A PARTLY CLOUDY TO
MOSTLY SUNNY DAY.  THURSDAY LOOKS LIKE A PARTLY CLOUDY DAY...
WITH A SLIGHT CHANCE OF SHOWERS OR THUNDERSTORMS OVER THE
NORTHWEST PART OF THE AREA.

NEXT CHANCE OF RAIN AFTER FRIDAY APPEARS TO BE OVER THIS
WEEKEND...ASSOCIATED WITH A COOL FRONT.  THE PATTERN THIS WEEKEND IS
FORECAST BY MEDIUM RANGE PREDICTIONS TO DIFFER FROM LAST WEEKEND.
NORTHERN BRANCH OF WESTERLIES APPEARS TO MERGE...LINK IN PHASE WITH
SOUTHERN STREAM WESTERLIES.  THIS PATTERN IS SHOWN BY BOTH THE ECMWF
AND GFS ENSEMBLE MEAN.  THESE TRENDS SHOW A LITTLE COOLER WEATHER IS
COMING OVER THE WEEKEND AND IN THE EARLY PART OF NEXT WEEK.  THE
PATTERN LOOKS MORE LIKE A MARCH OR LATE FEB PATTERN IN A MID APRIL
TIME FRAME.  THE RESULT OF THIS IS A CHANCE OF RAIN OR SHOWERS
SATURDAY AFTERNOON OR LATE SATURDAY TO SUNDAY...ASSOCIATED
WITH A COLD FRONT...AND A FAST MOVING WEATHER SYSTEM ALOFT.
ECMWF...00Z GFS AND GFS ENSEMBLE MEAN ALL SHOW 2ND QUICK MOVING 500
HPA TROF AND 2ND SURGE OF COOL AIR MOVING ACROSS AREA SUNDAY
NIGHT...ASSOCIATED WITH CHC OR SLGT CHC OF RAIN.  IN WAKE OF THESE
MID APRIL COOL FRONTS...A COOL MORNING IS EXPECTED MONDAY OF NEXT
WEEK...FOLLOWED BY MILD TO WARM AFTERNOON AFTERNOON ON MONDAY APRIL
12.  ANOTHER COOL NIGHT FOR MID APRIL IS EXPECTED THE NIGHT OF THE
12TH AND EARLY MORNING OF APRIL 13.  DRY CONDITIONS IN THE EARLY TO
MID PART OF NEXT WEEK ARE FORECAST BY MEDIUM RANGE FCSTS...TO BE
FOLLOWED BY ANOTHER RAIN MAKING WEATHER SYSTEM LATE NEXT WEEK TO THE
FOLLOWING WEEKEND...IN THE APR 16 TO 21 TIME FRAME.

&&

.EWX WATCHES/WARNINGS/ADVISORIES...FLASH FLOOD WATCH IS IN EFFECT FOR
ALL OF THE COUNTRY WARNING AREA THROUGH 6AM TUESDAY MORNING.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
400 PM CDT MON APR 5 2004

TXZ171>173-183>194-202>209-217>225-228-061000-
ATASCOSA-BANDERA-BASTROP-BEXAR-BLANCO-BURNET-CALDWELL-COMAL-DEWITT-
DIMMIT-EDWARDS-FAYETTE-FRIO-GILLESPIE-GONZALES-GUADALUPE-HAYS-KARNES-
KENDALL-KERR-KINNEY-LAVACA-LEE-LLANO-MAVERICK-MEDINA-REAL-TRAVIS-
UVALDE-VAL VERDE-WILLIAMSON-WILSON-ZAVALA-
400 PM CDT MON APR 5 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH CENTRAL TEXAS.

.DAY ONE...TODAY AND TONIGHT.
A FLASH FLOOD WATCH REMAINS IN EFFECT UNTIL 6 AM CDT TUESDAY MORNING.
ADDITIONAL HEAVY RAINFALL TONIGHT WILL AVERAGE ONE HALF TO NEAR 2
INCHES WITH ISOLATED AMOUNTS OF 2 TO 4 INCHES.

THERE IS ALSO A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS ALL OF
THE TEXAS HILL COUNTRY AND SOUTH CENTRAL TEXAS LATE THIS EVENING AND
INTO THE EARLY MORNING HOURS.  LARGE HAIL NEAR 2 INCHES IN DIAMETER
AND WINDS GUSTS TO NEAR 60 MPH WILL BE THE PRIMARY SEVERE WEATHER
THREAT.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.
THE THREAT OF HEAVY RAIN WILL DECREASE TUESDAY AFTERNOON AND END
TUESDAY NIGHT AS THE UPPER LEVEL STORM SYSTEMS MOVES OFF TO THE
NORTHEAST.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE REQUIRED THIS THIS EVENING.