Flash Flood and Hail in Texas, May 16, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CORPUS CHRISTI TX
656 PM CDT SUN MAY 16 2010

.DISCUSSION...UPDATED FOR AVIATION
&&

.AVIATION...LIGHT WINDS AND HIGH DEWPOINTS WILL LEAD TO FOG
FORMATION OVERNIGHT. HOWEVER THIS EVENING DEBRIS CLOUDS FROM
STRONG THUNDERSTORMS TO THE SOUTHWEST WILL AFFECT ALI AND CRP.
CONVECTION CONTINUES TO BUILD NORTHWARD...SLOWLY...IN DUVAL
COUNTY ALONG OLD SEA BREEZE AND OUTFLOW FROM STRONG THUNDERSTORMS THAT
FORMED SOUTH OF HEBBRONVILLE. DUE TO THE RICH UNSTABLE MOISTURE
AXIS (CAPE 3000 J/KG) AND SURFACE CONVERGENCE OVER DUVAL AND JIM WELLS
COUNTIES HAVE INCLUDE A TEMPO FOR THUNDERSTORMS AND ERRATIC GUSTY WINDS
FOR ALI. OUTFLOW FROM DUVAL SHOULD REACH ALI. THERE IS A 20 PERCENT
CHANCE THAT LRD WILL BE AFFECT BY CONVECTION LIFTING NORTHWARD AS
WELL...AND THERE IS GOOD SURFACE CONVERGENCE BANKED IN THE RIO
GRANDE VALLEY JUST SOUTH OF LRD. OTHERWISE CONVECTION SHOULD
GRADUALLY DIMINISH THIS EVENING WITH MARGINAL UPPER SUPPORT WITHIN
THE WEAK WEST TO NORTHWEST FLOW ALOFT. HOWEVER WILL HAVE TO WATCH
WESTERN AREAS AS INSTABILITY AND WESTERLY STEERING FLOW ARE PRESENT
OVERNIGHT. HAVE KEPT THE MVFR FOG IN FOR ALI AND VCT...SHOULD BE
WORSE AT ALI ONCE CLEARING SETS IN. WEAK OFFSHORE LAND BREEZE
SHOULD FORM FOR VCT WHICH MAY LIMIT FOG. MODEL TIME HEIGHT SECTION
ALSO DEPICT LOW STRATUS IN MFVR FOR LRD AFTER 09Z. FOR CRP THE
LIKELY SCENARIO IS VFR BUT A COUPLE HOURS OF MVFR FOR CEILING AND
LIGHT FOG PROBABLE. 20 PERCENT CHANCE FOR LIFR CONDITIONS AT CRP
AND VCT AND HAVE INCLUDED TEMPO FOR LIFR AT ALI.

&&

.PREV DISCUSSION... /ISSUED 622 PM CDT SUN MAY 16 2010/

DISCUSSION...DID A QUICK UPDATE FOR ON-GOING CONVECTION WHICH
WILL LIKELY LINGER ANOTHER HOUR OR TWO BEFORE ENDING. NO OTHER
CHANGES AT THIS TIME.

PREV DISCUSSION... /ISSUED 330 PM CDT SUN MAY 16 2010/

SHORT TERM (TONIGHT THROUGH MONDAY NIGHT)...WEAK CONVECTION
FINALLY STARTING TO GET GOING INLAND BETWEEN FREER AND CORPUS
CHRISTI. RUC ANALYZED THE CWA UNDER WEAK NVA FOR MUCH OF THE
MORNING AND EARLY AFTERNOON...BUT THIS IS FINALLY STARTING TO
SHIFT EAST. WITH NVA SHIFTING EAST AND INSTABILITY APPROACHING
3500 J/KG ACROSS MUCH OF THE CWA...SHOULD CONTINUE TO SEE ISOLATED
CONVECTION DEVELOP THROUGH THE REMAINDER OF THE AFTERNOON AND
EARLY EVENING. LACK OF FORCING AND WEAK LOW LEVEL FLOW SHOULD
PREVENT COVERAGE FROM INCREASING BEYOND ISOLATED...WITH MOST
COVERAGE ALONG AND SOUTHWEST OF I-37. AFTER SUNSET PRECIP SHOULD
QUICKLY END. THERE IS A WEAK SHORTWAVE THAT APPROACHES THE RIO
GRANDE AFTER MIDNIGHT...SO A FEW ELEVATED SHOWERS OR THUNDERSTORMS
MAY BE POSSIBLE ACROSS THE RIO GRANDE PLAINS AND BRUSH COUNTRY
06Z-12Z. WINDS WILL BECOME VERY LIGHT AFTER MIDNIGHT...AND
FORECAST SOUNDINGS SUGGEST POSSIBLE SHALLOW FOG AGAIN TONIGHT
ACROSS THE INLAND COASTAL PLAINS AND PORTIONS OF THE BRUSH
COUNTRY. TOMORROW...INSTABILITY WILL REMAIN HIGH AGAIN WITH PWS
POOLED AROUND 1.7-1.8". HOWEVER...AGAIN LACK OF FORCING AND WEAK
FLOW SHOULD LIMIT COVERAGE OF ANY CONVECTION TO ISOLATED.

MODELS HAVE BEEN ADVERTISING A STRONGER SHORTWAVE CROSSING THE
SIERRA MADRE MONDAY NIGHT AND POSSIBLY INTERACTING WITH SIERRA
MADRE CONVECTION AND DEEPER POOL OF MOISTURE UP THE RIO GRANDE TO
PRODUCE ORGANIZED CONVECTION. WILL CONTINUE THE INHERITED CHANCE
POPS GOING IN THE FORECAST FOR MONDAY NIGHT ACROSS THE RIO GRANDE
PLAINS AND PORTIONS OF THE BRUSH COUNTRY.

LONG TERM (TUESDAY THROUGH SUNDAY)...THE MODELS CONTINUE TO
STRONGLY SUGGEST THAT EITHER AN ONGOING MCS OR THE REMNANTS OF AN
MCS WL AFFECT THE CWA ON TUE AS IT PROPAGATES EWD. THIS WL BE MOSTLY
DRIVEN BY A QUICK MOVING SRN STREAM S/WV MOVING ACROSS THE CWA ON
TUE.  GUIDANCE POPS REMAIN QUITE PALTRY DESPITE THE MOISTURE FIELDS
AND THE PRESENCE OF UPR SUPPORT.  FOR NOW...WL GO WITH BLANKET LOW
CHC POPS FOR TUE GIVEN THE PREVIOUSLY MENTIONED FACTORS AND THE
UNCERTAINTY OF HOW FAR TO THE EAST THIS CONVECTION WL MOVE.  BY TUE
EVENING...A S/WV RDG AXIS WL BUILD INTO THE CWA AND PCPN SHOULD END
RATHER QUICKLY AS THE AIRMASS QUICKLY STABILIZES.  FOR WED AND
BEYOND...THE CAP IS EXPECTED TO STRENGTHEN AS SOUTHERLY FLOW ADVECTS
DRIER AND WARMER AIR FROM MEXICO AND DEEP SOUTH TX.  700 MB TEMPS
ARE EXPECTED TO AVERAGE BETWEEN 11 AND 13 DEGS CELSIUS BETWEEN WED
AND THE WEEKEND. MEANWHILE...THE MAIN FORCING WL LIFT NWD AS WELL AS
A MEAN RDG AXIS PREVAILS ALOFT.  A S/WV WL MOVE INTO KANSAS...
OKLAHOMA AND NORTH TX BY THU.  HOWEVER...THE MAIN CONVECTION ASSCTD
WITH THIS SYSTEM SHOULD REMAIN WELL TO OUR NORTH AND NORTHEAST.  SO
AS A RESULT...WL KEEP A DRY..CAPPED AND WARM FCST FOR THE MAJORITY
OF THE EXTENDED FCST EXCEPT FOR TUE.

&&

.PRELIMINARY POINT TEMPS/POPS...
CORPUS CHRISTI    69  88  71  87  73  /  10  10  10  30  10
VICTORIA          69  88  69  87  70  /  10  20  10  30  10
LAREDO            74  99  72  94  75  /  20  20  40  30  10
ALICE             70  91  71  90  71  /  10  20  20  30  10
ROCKPORT          72  87  74  85  75  /  10  10  10  30  10
COTULLA           70  92  68  90  71  /  10  20  40  30  10
KINGSVILLE        71  92  71  89  72  /  10  20  10  30  10
NAVY CORPUS       73  86  74  85  75  /  10  10  10  30  10

&&

.CRP WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.

&&

AT/15...SHORT TERM/AVIATION

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE CORPUS CHRISTI TX
502 AM CDT SUN MAY 16 2010

GMZ230-235-250-255-270-275-TXZ229>234-239>247-171015-
BAYS AND WATERWAYS FROM BAFFIN BAY TO PORT ARANSAS-
BAYS AND WATERWAYS FROM PORT ARANSAS TO PORT O'CONNOR-
COASTAL WATERS FROM BAFFIN BAY TO PORT ARANSAS OUT 20 NM-
COASTAL WATERS FROM PORT ARANSAS TO MATAGORDA SHIP CHANNEL OUT
20 NM-WATERS FROM BAFFIN BAY TO PORT ARANSAS FROM 20 TO 60 NM-
WATERS FROM PORT ARANSAS TO MATAGORDA SHIP CHANNEL FROM 20 TO
60 NM-LA SALLE-MCMULLEN-LIVE OAK-BEE-GOLIAD-VICTORIA-WEBB-DUVAL-
JIM WELLS-KLEBERG-NUECES-SAN PATRICIO-ARANSAS-REFUGIO-CALHOUN-
502 AM CDT SUN MAY 16 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH TEXAS AND THE MIDDLE
TEXAS COASTAL WATERS.

.DAY ONE...TODAY AND TONIGHT

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED
TODAY...HOWEVER NO ORGANIZED SEVERE WEATHER IS ANTICIPATED AT
THIS TIME.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

ISOLATED TO SCATTERED THUNDERSTORMS WILL REMAIN POSSIBLE THROUGH
THE PERIOD...BUT THE GREATEST CHANCES APPEAR TO BE MONDAY NIGHT
INTO TUESDAY. NO ORGANIZED SEVERE WEATHER IS EXPECTED AT THIS TIME.
HOWEVER..A FEW STRONG TO POSSIBLY SEVERE THUNDERSTORMS WILL BE
POSSIBLE MAINLY IN THE AFTERNOON THROUGH THE NIGHTTIME HOURS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED.

TE/TMT

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE CORPUS CHRISTI TX
738 PM CDT SUN MAY 16 2010

TXZ239-170130-
WEBB-
738 PM CDT SUN MAY 16 2010

...A STRONG THUNDERSTORM WAS AFFECTING WEBB COUNTY...

AT 735 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM OVER LAREDO...MOVING NORTH AT 5 MPH.

MOTHBALL SIZE HAIL...AND WINDS AROUND 40 MPH ARE EXPECTED WITH THIS
STORM. THE STORM WILL ALSO HAVE FREQUENT CLOUD TO GROUND LIGHTNING
AND VERY HEAVY RAIN. RAINFALL OF 1 TO 2 INCHES MAY CAUSE STREET
FLOODING.

TARDY