Special Weather Statement, NWS Austin/San Antonio, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
716 AM CDT MON APR 18 2016

.UPDATE...
PLEASE SEE THE 12Z AVIATION FORECAST DISCUSSION BELOW.

&&

.AVIATION...
SHOWER AND THUNDERSTORM ACTIVITY CONTINUES TO BE THE MAIN CONCERN
FOR THE EARLY PORTION OF THE FORECAST PERIOD. A WEST TO EAST
ORIENTED LINE OF CONVECTION WILL MOVE LITTLE AND THIS WILL KEEP
THE THREAT OF TSRA AT OUR I-35 SITES THROUGH THIS MORNING. FOR THE
AFTERNOON HOURS...THE HI-RES MODELS GENERALLY AGREE THE LINE OF
CONVECTION WILL PUSH SOUTHWARD AS A COLD FRONT GRADUALLY MOVES IN
FROM THE NORTH. THIS SHOULD LEAD TO A VERY GRADUAL DECREASE IN
COVERAGE THIS AFTERNOON...BUT WILL CONTINUE TO MENTION A TEMPO
GROUP FOR -TSRA THROUGH THIS AFTERNOON. BOUNDARY LAYER COOLING
THIS EVENING SHOULD LEAD TO A RETURN TO IFR CONDITIONS FOR THE
I-35 SITES AFTER 02Z.

&&

.PREV DISCUSSION... /ISSUED 330 AM CDT MON APR 18 2016/

SHORT TERM (TODAY THROUGH TUESDAY)...
A SURFACE BOUNDARY (WEAK COLD FRONT) LINGERS ALONG THE ESCARPMENT
WEST OF I-35 AND NORTH OF HIGHWAY 90 WHILE AN UPPER LEVEL LOW
MEANDERS OVER THE FOUR CORNERS REGION. RADARS SHOW SHOWERS AND
THUNDERSTORMS FROM THE EASTERN HILL COUNTRY ACROSS I-35 INTO
SOUTHEASTERN TEXAS AND OVER THE RIO GRANDE PLAINS. EXPECT AREAS IN
BETWEEN TO FILL IN WITH SHOWERS AND THUNDERSTORMS EARLY THIS
MORNING AS WEAK SHORTWAVE MOVES FROM MEXICO INTO TEXAS. RAINFALL
INTENSITY WILL INCREASE AS STORMS TRAIN OVER THE SAME AREAS AND
THE LOW LEVEL JET IMPINGES ON THE SURFACE BOUNDARY ENHANCING LIFT
WITH PWS AT OR ABOVE 1.5 INCHES. THE HEAVY RAINFALL MAINTAINS THE
FLASH FLOOD AND RIVER FLOOD THREAT ACROSS MUCH OF SOUTH CENTRAL
TEXAS. SOME AREAS HAVE ALREADY HAD UP TO 9 INCHES OF RAIN AND THIS
HAS CAUSED SOME FLOODING ON A FEW RIVERS AND STREAMS. SOILS ARE
SATURATED AND RUNOFF WILL BECOME RAPID LEADING TO FLASH FLOODING
AND IN TURN RIVER FLOODING. THE GREATEST THREAT AREA IS ACROSS OUR
NORTHEASTERN COUNTIES FROM TRAVIS AND WILLIAMSON TO BASTROP...LEE
AND FAYETTE WHERE THE HEAVIEST RAINS HAVE FALLEN. WITH TIME...THE
SURFACE BOUNDARY SAGS SOUTH AND THE UPPER LEVEL TROUGH WEAKENS
WHILE ELONGATING EAST TO WEST OVER THE CENTRAL ROCKIES AND HIGH
PLAINS. SOME MODELS MAINTAIN A HEAVY RAIN THREAT TONIGHT INTO
EARLY TUESDAY ACROSS OUR EASTERN AREAS WHILE OTHERS END THE THREAT
BY THIS AFTERNOON. THUS...THE CONFIDENCE IS A LITTLE LOWER FOR
TONIGHT INTO EARLY TUESDAY. CAPES OF 1500 TO 2000 J/KG AND 0 TO 6
KM SHEAR OF 25 TO 35 KTS INDICATE A SLIGHT THREAT OF STRONG TO
SEVERE STORMS TODAY AND TUESDAY.

LONG TERM (TUESDAY NIGHT THROUGH SUNDAY)...
THE WEAKENING UPPER LEVEL LOW SLOWLY MOVES OUT INTO THE PLAINS MID
WEEK AS THE SURFACE BOUNDARY LINGERS. EXPECT ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS TUESDAY NIGHT THROUGH THURSDAY NIGHT.
CANNOT RULE OUT LOCALLY HEAVY RAINS AND ISOLATED STRONG TO SEVERE
STORMS. THE UPPER LEVEL LOW TRANSITIONS INTO A TROUGH MOVING
ACROSS THE MID WEST AND DRAGS A COLD FRONT ACROSS OUR AREA LATER
THIS WEEK ENDING THE RAINS...EXCEPT FOR SLIGHT CHANCES ALONG THE
RIO GRANDE PLAINS WHERE MOIST SOUTHEASTERLY FLOW PERSISTS FRIDAY
AND SATURDAY. RAIN CHANCES RETURN TO THE REST OF SOUTH CENTRAL
TEXAS ON SUNDAY AS ANOTHER UPPER LEVEL TROUGH APPROACHES.

&&

.PRELIMINARY POINT TEMPS/POPS...
AUSTIN CAMP MABRY              74  65  78  67  80 / 100  80  60  40  40
AUSTIN BERGSTROM INTL AIRPORT  74  64  78  65  81 / 100  80  60  40  40
NEW BRAUNFELS MUNI AIRPORT     76  65  79  67  81 / 100  80  60  30  40
BURNET MUNI AIRPORT            71  62  77  64  79 /  90  70  40  40  40
DEL RIO INTL AIRPORT           76  63  82  67  85 /  80  40  20  30  20
GEORGETOWN MUNI AIRPORT        72  64  77  65  79 / 100  80  50  40  40
HONDO MUNI AIRPORT             77  65  81  66  83 /  90  60  30  40  30
SAN MARCOS MUNI AIRPORT        74  65  78  66  80 / 100  80  60  30  40
LA GRANGE - FAYETTE REGIONAL   76  68  78  68  81 / 100  90  60  30  40
SAN ANTONIO INTL AIRPORT       76  65  80  68  81 / 100  70  40  30  40
STINSON MUNI AIRPORT           77  67  81  69  82 / 100  70  40  40  40

&&

.EWX WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH THROUGH TUESDAY MORNING FOR THE FOLLOWING
COUNTIES: ATASCOSA...BANDERA...BASTROP...BEXAR...BLANCO...BURNET...
CALDWELL...COMAL...DE WITT...EDWARDS...FAYETTE...FRIO...GILLESPIE...
GONZALES...GUADALUPE...HAYS...KARNES...KENDALL...KERR...KINNEY...
LAVACA...LEE...LLANO...MEDINA...REAL...TRAVIS...UVALDE...VAL
VERDE...WILLIAMSON...WILSON.

&&

MESOSCALE/AVIATION...24
SYNOPTIC/GRIDS...04
PUBLIC SERVICE/DATA COLLECTION...30

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
515 AM CDT MON APR 18 2016

TXZ171>173-183>194-202>209-217>225-228-191015-
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-
515 AM CDT MON APR 18 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH CENTRAL TEXAS.

.DAY ONE...TODAY AND TONIGHT.

ADDITIONAL HEAVY RAINFALL WILL LIKELY LEAD TO AREAS OF RIVER AND
FLASH FLOODING ACROSS SOUTH CENTRAL TEXAS TODAY AND TONIGHT...
INCLUDING BOTH THE AUSTIN AND SAN ANTONIO METRO AREAS. AN
ADDITIONAL 1 TO 3 INCHES OF RAINFALL IS EXPECTED...WITH ISOLATED
HIGHER AMOUNTS OF 4 TO 6 INCHES POSSIBLE. IT IS NOT IMPOSSIBLE FOR
LOCATIONS TO RECEIVE RAINFALL TOTALS SINCE SUNDAY OF UP TO 15
INCHES. IMPACTS WILL BE GREATER IN THE AREAS THAT HAVE ALREADY
RECEIVED HEAVY RAINS AND FLOODING MAINLY EAST OF HIGHWAY 281 AND
NORTH OF INTERSTATE 10. HOWEVER...IMPACTS ARE POSSIBLE ACROSS THE
REMAINDER OF SOUTH CENTRAL TEXAS AND THE HILL COUNTRY.

IN ADDITION TO THE THREAT OF HEAVY RAINFALL...THERE IS A SLIGHT
RISK FOR SEVERE THUNDERSTORMS. LARGE HAIL AND DAMAGING WIND GUSTS
ARE THE MAIN SEVERE WEATHER THREATS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY.

THE STORM COMPLEX RESULTING IN HEAVY RAINS WILL LINGER INTO
TUESDAY MORNING. ANY ADDITIONAL HEAVY RAINFALL WILL LEAD TO RAPID
FLASH FLOODING OR WORSEN ANY ONGOING FLOODING THAT MAY DEVELOP
TODAY.

IN ADDITION TO THE THREAT OF HEAVY RAINFALL...THERE IS A SLIGHT
RISK FOR SEVERE THUNDERSTORMS TUESDAY AND WEDNESDAY. DAMAGING
WIND GUSTS AND LARGE HAIL ARE THE MAIN SEVERE WEATHER THREATS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY AND TUESDAY.

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