Flash Flood Watch 27, NWS Austin/San Antonio, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
1148 PM CDT MON JUL 30 2007

.AVIATION...
ISOLATED SHOWERS ARE DEVELOPING OVER THE RIO GRANDE VALLEY AS AN
OUTFLOW BOUNDARY MAKES ITS WAY NORTHWEST TO THE EDWARDS PLATEAU.
SHOWERS WILL BECOME MORE NUMEROUS VCNTY KDRT BY 09Z. MVFR CIG OVER
THE HILL COUNTRY WILL SPREAD TO ALL TERMINALS AND LOWER TO IFR
LEVELS ARND 09Z. SOME RADIATION FOG KAUS TO KSSF WILL BRING VSBY
TO MVFR LEVELS. THE RAIN WILL CONTINUE OVER KDRT THRU 17Z WHILE
CIGS AND VSBY IMPROVE TO VFR LEVELS KSSF TO KAUS. BY 17Z RAIN MAY
HAVE ENDED AT KDRT LEAVING VFR CONDITIONS WHILE ISOLATED SHOWERS AND
TSTMS DEVLOP ACROSS THE REST OF SOUTH CENTRAL TEXAS AND MOVE
NORTHWEST TOWARD KSSF, KSAT, KHY AND KAUS. THIS ACTIVITY WILL
DISSIPATE WITH LOSS OF DAYTIME HEAT LEAVING VFR CONDITIONS AT ALL
TERMINALS.

&&

.PREV DISCUSSION... /ISSUED 1015 PM CDT MON JUL 30 2007/

UPDATE...
A MOIST AIRMASS REMAINS ACROSS SOUTH CENTRAL TEXAS WITH PWS AT DRT
AT 2.2 INCHES, HOWEVER SOME DRYING NOTED ALONG PORTIONS OF THE
TEXAS COAST WITH PWS AROUND 1.9 INCHES DOWN FROM 2.2 THIS MORNING
AS SMALL UPPER RIDGE EASES INTO SOUTHERN TEXAS. HAVE UPDATED TO
REMOVE POPS FROM EASTERN AREAS DUE TO SOME DRYING AND SUBSIDENCE.
OUT WEST, HAD CONSIDERED A FLASH FLOOD WATCH FOR WESTERN AREAS DUE
TO A MOIST AND UNCAPPED AIRMASS, HOWEVER, UNLIKE THE LAST COUPLE
OF NIGHTS, CONVECTION REMAINS OVER THE SIERRA MADRE AND SO FAR HAS
NOT DEVELOPED ALONG THE RIO GRANDE. WILL NOT ISSUE A FLASH FLOOD
WATCH FOR NOW, ALTHOUGH THE NEXT SHIFT MAY HAVE TO ISSUE ONE
SHOULD RADAR TRENDS INDICATE. REGARDLESS, HAVE SLIGHTLY INCREASED
POPS ALONG THE RIO GRANDE AND LOWER PECOS VALLEYS. HAVE DROPPED
FORECAST LOWS ALONG THE RIO GRANDE AS TEMPERATURES ALREADY AT
ONGOING FORECAST LEVELS. OTHERWISE, ONGOING FORECASTS ON TRACK.

PREV DISCUSSION... /ISSUED 648 PM CDT MON JUL 30 2007/

AVIATION...
MOST TERMINAL ARE VFR THIS EVENING. HOWEVER KDRT HAS VARIOUS
LEVELS OF CLOUD COVER DUE TO VCNTY OF SHOWER ACTIVITY. BY 06Z KDRT
WILL HAVE RAIN AT THE TERMINAL WITH MVFR CIGS. MVFR CIGS WILL FORM
FARTHER EAST FROM KSSF TO KAUS ARND 09Z AND LOWER TO IFR CIGS WITH
MVFR FOG ARND 11Z. KDRT WILL VARY FROM MVFR TO IFR CONDITIONS THRU
21Z DUE TO OCCASIONAL RAIN. KSSF TO KAUS WILL LIFT TO VFR BY 17Z.
ISOLATED AFTERNOON TSTMS WILL MOVE INLAND FROM THE COASTAL
PLAINS, APPROACHING TO KSSF TO KAUS CORRIDOR ARND 20Z. KDRT CUD
BREAK OUT OF THE RAIN BY 21Z.

PREV DISCUSSION... /ISSUED 244 PM CDT MON JUL 30 2007/

DISCUSSION...
THE PRESENCE OF A MOIST AND UNSTABLE AIRMASS ALOFT HAS BECOME QUITE
APPARENT AS SCATTERED SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ACROSS
MOST OF THE STATE. A BROAD AREA OF LIGHT TO MODERATE RAIN WITH EMBEDDED
HEAVY DOWNPOURS HAS BEEN PERSISTENT ACROSS THE RIO GRANDE PLAINS AND
WESTERN EDWARDS PLATEAU. ADDITIONAL SHOWERS AND THUNDERSTORMS HAVE
DEVELOPED ACROSS THE COASTAL PLAINS ALONG THE SEA BREEZE BOUNDARY.
BOTH AREAS OF ACTIVITY WILL CONTINUE THROUGH THE AFTERNOON AND
EVENING HOURS. ONCE DIURNAL HEATING IS LOST...THE SEA BREEZE
ENHANCED STORMS WILL DISSIPATE QUICKLY. HOWEVER...WILL CONTINUE
WITH CHANCE POPS OUT WEST THROUGH THE LATE EVENING HOURS AS
LINGERING INSTABILITY FROM THE UPPER LOW TO THE WEST COULD BE
ENOUGH TO KEEP RAIN IN THE PICTURE THROUGH MIDNIGHT.

A SIMILAR DAY IS EXPECTED TOMORROW...WITH THE BEST CHANCE FOR RAIN
CENTERED ALONG THE WESTERN EDWARDS PLATEAU AND SEA BREEZE ACTIVITY
DEVELOPING BY EARLY AFTERNOON. WEAK RIDGING WILL BUILD INTO THE
REGION THROUGH WEDNESDAY WITH A MORE SEASONAL SUMMER DAY EXPECTED
WITH 20-30 POPS AND HIGHS IN THE MID 90S. THESE CONDITIONS WILL BE
SHORT LIVED, THOUGH AS A WEAK MID LEVEL SHEAR AXIS ENTERS THE
REGION ON THURSDAY. ATTM...MODELS INDICATE THE BEST CHANCE FOR
RAIN WILL BE NORTH OF THE HILL COUNTRY AND EXTEND INTO THE BIG
BEND AREA. DESPITE ONLY CHANCE POPS DURING THIS TIME FRAME...THERE
WILL BE A POTENTIAL FOR FLASH FLOODING FROM LOCALLY HEAVY RAINFALL
DUE TO AMPLE MOISTURE THROUGH THE ATMOSPHERE.

LONGER RANGE MODELS INDICATE WEAK RIDGING WILL BUILD ACROSS THE
REGION OVER THE WEEKEND. THIS WILL LEAD TO A WARMING TREND WITH
NEAR-NORMAL EARLY AUGUST TEMPERATURES AND POPS FOR THE BEGINNING
OF NEXT WEEK.

&&

.PRELIMINARY POINT TEMPS/POPS...
AUSTIN CAMP MABRY              75  96  76  94  75 /  10  20  20  30  20
AUSTIN BERGSTROM INTL AIRPORT  74  95  73  94  73 /  10  20  20  30  20
DEL RIO INTL AIRPORT           71  90  76  94  77 /  40  40  30  30  30
SAN ANTONIO INTL AIRPORT       76  93  76  92  75 /  10  20  20  30  20

&&

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

04/06

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
828 AM CDT MON JUL 30 2007

TXZ171>173-183>194-202>209-217>225-228-311100-
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-
828 AM CDT MON JUL 30 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH CENTRAL TEXAS.

.DAY ONE...TODAY AND TONIGHT...
SHOWERS AND THUNDERSTORMS ARE LIKELY TODAY ACROSS THE RIO GRANDE
VALLEY AND EDWARDS PLATEAU. LOCALLY HEAVY RAINFALL IS
POSSIBLE...LEADING TO FLASH FLOODING.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY...
NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL NOT BE NEEDED.