Special Weather Statement, NWS Austin/San Antonio, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
847 PM CDT FRI APR 29 2016

.MESOSCALE UPDATE...
SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR MOST OF THE AREA
AND WILL TRY TO EXPLAIN LATEST CONVECTIVE THINKING FOR THE NEXT
SEVERAL HOURS. FIRST...THINGS HAD BEEN SLOW GOING FOR MOST OF THE
AFTERNOON. THE DRYLINE HAD BEEN NEARLY STATIONARY AND THUS
CONVECTION HAD A HARD TIME DEVELOPING WITH THE LACK OF SURFACE
FOCUS. A COUPLE OF STRONG TO SEVERE STORMS DID DEVELOP NEAR BURNET
COUNTY WHERE THE DRYLINE WAS ABLE TO BULGE OUTWARD. FARTHER
SOUTH...THERE HAS BEEN A STATIONARY BOUNDARY BETWEEN HONDO AND
CASTROVILLE THAT COULD BE SEEN ON VISIBLE SATELLITE. SEVERAL
SHOWERS DEVELOPED ALONG THIS BOUNDARY IN THE LATE AFTERNOON HOURS.
ABOUT TWO HOURS AGO...THE WIND AT HONDO TURNED TO THE WEST AND
AFTER THIS OCCURRED...STRONGER UPDRAFTS DEVELOPED WITH THE
INCREASE OF LOW-LEVEL CONVERGENCE. THE RESULTANT SUPERCELL HAS
BEEN ONGOING FOR THE PAST HOUR AND HAS MOVED INTO NORTHERN BEXAR
COUNTY.

THERE HAVE BEEN A COUPLE OF ROTATIONAL SIGNATURES WITHIN THIS CELL
BUT THESE HAVE QUICKLY BEEN OVERCOME BY A SURGING RFD. THE
ENVIRONMENT IS NOT OVERLY CONDUCIVE FOR TORNADOES TONIGHT. THERE
IS SOME VEERING IN THE LOW-LEVELS OF THE ATMOSPHERE BUT SPEED
SHEAR IS LACKING AS SPEEDS REMAIN NEAR 20 KNOTS. THIS IS EQUATING
TO 0-3 HELICITY VALUES NEAR 100. CANT RULE OUT A BRIEF TORNADO BUT
OVERALL...THE POTENTIAL IS LOW.

WITH THE LESSER AMOUNT OF ACTIVITY THIS AFTERNOON...THE ATMOSPHERE
IS PRIMED FOR POSSIBLE CONVECTION OVERNIGHT WHEN THE FRONT MAKES
IT TO THE CWA. THIS FRONT WILL SERVE AS A FOCUS FOR THUNDERSTORM
INITIATION. WE HAD CAPE VALUES NEAR 4000 J/KG ALL AFTERNOON BUT
UNTIL SOMETHING FORCES PARCELS UPWARD...NONE OF THIS CAPE WILL
EVER BE REALIZED. WITH THE INSTABILITY STILL AROUND
OVERNIGHT...GIVEN THE ABNORMALLY HIGH DEWPOINTS IN THE MIDDLE
70S...THINK THERE COULD BE SOME STRONG UPDRAFTS FOR HAIL
PRODUCTION WHEN THE BOUNDARY MAKES IT INTO THE CWA LATER TONIGHT.
WITH THE WEAKER WIND SPEEDS IN THE LOWER LEVELS OF THE
ATMOSPHERE...THE THREAT FOR STRAIGHT LINE WINDS IS A BIT
LOWER...BUT ANY DOMINATING COLD POOLS COULD LEAD TO SEVERE WIND
GUSTS.

&&

.PREV DISCUSSION... /ISSUED 637 PM CDT FRI APR 29 2016/

AVIATION...
HAVENT SEEN TOO MUCH NEAR THE TERMINALS THIS AFTERNOON BESIDES A
FEW SHOWERS WEST OF SAN ANTONIO. WILL BEGIN THE SAN ANTONIO SITES
WITH VCSH TO COVER THIS ACTIVITY. WITH LITTLE CONVECTION THIS
AFTERNOON...THERE WILL BE THE POTENTIAL FOR STORMS OVERNIGHT ONCE
THE FRONT COMES INTO THE AREA AND SERVES AS A FOCUS FOR
THUNDERSTORM DEVELOPMENT AS IT FORCES AIR PARCELS UPWARDS. SOME OF
THE HIGH-RES GUIDANCE IS DIFFERING ON THIS SOLUTION BUT THE HRRR
SEEMS TO HAVE A BETTER HANDLING ON INITIALIZATION AND THINK ITS
SOLUTION OF THUNDERSTORMS OVERNIGHT IS PLAUSIBLE. WILL MENTION
VCTS FROM 7Z-11 FOR THE I-35 TAF SITES. MAY NEED TO UP THAT TO
PREVAILING OR TEMPO GROUPS LATER IF CONFIDENCE INCREASES. MVFR/IFR
CEILINGS ARE EXPECTED OVERNIGHT BEFORE BECOME VFR TOMORROW MORNING
AS LIGHT NORTHERLY FLOW CLEARS THINGS OUT.

PREV DISCUSSION... /ISSUED 337 PM CDT FRI APR 29 2016/

SHORT TERM (TONIGHT THROUGH SATURDAY NIGHT)...
LATE AFTERNOON SURFACE OBSERVATIONS SHOW A DRYLINE IN PLACE FROM
NEAR SONORA BACK INTO NORTHWESTERN VAL VERDE COUNTY. TRAILING BEHIND
THE DRYLINE IS A PACIFIC COLD FRONT LOCATED ROUGHLY ALONG AN OZONA
TO DRYDEN LINE. CONVECTION CONTINUES TO SLOWLY DEVELOP TO THE EAST
OF THE DRYLINE AND A MARGINAL TO ENHANCED RISK FOR SEVERE WEATHER IS
IN PLACE ACROSS ALL OF SOUTH CENTRAL TEXAS. HI-RES MODELS CONTINUE
TO INDICATE A LINE OF THUNDERSTORMS WILL DEVELOP AHEAD OF THE
DRYLINE...ALBEIT PERHAPS A LITTLE LATER THAN PREVIOUSLY ANTICIPATED.
ONCE STORMS DEVELOP...THEY WILL LIKELY BECOME SEVERE QUICKLY... WITH
LARGE HAIL...DAMAGING WINDS BEING THE MAIN CONCERNS. CAN/T RULE OUT
SOME ISOLATED TORNADOES AS WELL...ESPECIALLY WHERE WINDS BECOME
LOCALLY BACKED. SOME LOCALLY HEAVY RAINFALL IS ALSO POSSIBLE...
ESPECIALLY FOR AREAS EAST OF I-35 GIVEN WELL ABOVE NORMAL MOISTURE
LEVELS. ONCE WE LOOSE PEAK HEATING...A GRADUAL DECREASE IN
CONVECTION IS EXPECTED. THE EXCEPTION COULD BE ALONG AND EAST OF THE
I-35 CORRIDOR LATE TONIGHT INTO SATURDAY MORNING AS THE PACIFIC COLD
FRONT MOVES IN FROM THE WEST. SOME OF THE HI-RES MODELS ARE SHOWING
ANOTHER LINE OF CONVECTION DEVELOPING ALONG AND EAST OF THIS
BOUNDARY DURING THE ABOVE MENTIONED TIME FRAME. LATE SATURDAY
NIGHT... A MORE NORTHERN STREAM COLD FRONT MOVES IN AND THIS SHOULD
SHIFT THE FOCUS FOR CONVECTION SOUTHWARD INTO THE COASTAL PLAINS.

LONG TERM (SUNDAY THROUGH FRIDAY)...
ON SUNDAY...A COLD FRONT WILL LIKELY BE STALLED ACROSS THE SOUTHERN
RIO GRANDE PLAINS INTO THE COASTAL PLAINS. WITH MOISTURE POOLING
ALONG THIS FRONT...RAIN CHANCES WILL BE FAVORED ACROSS THE MENTIONED
AREAS. ANOTHER SURGE OF SURFACE HIGH PRESSURE MOVES IN SUNDAY NIGHT
AND WITH INCREASED ISENTROPIC ASCENT...RAIN CHANCES WILL BE ON THE
INCREASE. RAIN CHANCES SHOULD INCREASE ON MONDAY AS A SUBTROPICAL
JET MOVES ACROSS SOUTHERN TEXAS. RAIN CHANCES WILL BEGIN TO EASE ON
TUESDAY AS MID-LEVEL RIDGING BEGINS TO BUILD IN FROM THE WEST. WE/LL
GO WITH A DRY FORECAST FOR THE REMAINDER OF THE UPCOMING WORK WEEK
AS MID-LEVEL RIDGING CONTINUES TO BUILD IN FROM THE WEST.

&&

.PRELIMINARY POINT TEMPS/POPS...
AUSTIN CAMP MABRY              67  88  65  82  63 /  60  20  10  20  50
AUSTIN BERGSTROM INTL AIRPORT  67  87  65  81  64 /  60  20  10  20  50
NEW BRAUNFELS MUNI AIRPORT     67  88  66  82  65 /  60  30  10  30  40
BURNET MUNI AIRPORT            62  86  62  79  60 /  40  10  10  10  40
DEL RIO INTL AIRPORT           61  91  68  86  64 /  20  -   20  30  50
GEORGETOWN MUNI AIRPORT        64  85  63  81  62 /  60  20  10  10  50
HONDO MUNI AIRPORT             64  91  67  84  66 /  40  10  10  30  40
SAN MARCOS MUNI AIRPORT        67  86  66  83  64 /  60  30  10  30  50
LA GRANGE - FAYETTE REGIONAL   70  84  69  83  67 /  80  40  20  30  50
SAN ANTONIO INTL AIRPORT       68  88  67  82  65 /  50  20  10  30  40
STINSON MUNI AIRPORT           70  90  69  83  67 /  50  20  10  30  40

&&

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

MESOSCALE/AVIATION...HAMPSHIRE
SYNOPTIC/GRIDS...HAMPSHIRE
PUBLIC SERVICE/DATA COLLECTION...TREADWAY

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE AUSTIN/SAN ANTONIO TX
357 AM CDT FRI APR 29 2016

TXZ171>173-183>194-202>209-217>225-228-300900-
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-
357 AM CDT FRI APR 29 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTH CENTRAL TEXAS.

.DAY ONE...TODAY AND TONIGHT.

SCATTERED THUNDERSTORMS ARE EXPECTED THIS AFTERNOON AND EVENING
NEAR AND EAST OF A MASON TO KERRVILLE TO PEARSALL LINE. LARGE
HAIL AND DAMAGING STRAIGHT-LINE WINDS ARE THE MAIN THREATS.
ISOLATED TORNADOES CANNOT BE RULED OUT. SOME ISOLATED POCKETS
OF 2-4 INCHES OF RAIN COULD RESULT IN LOCALIZED FLOODING...MAINLY
EAST OF THE I-35 CORRIDOR.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

ISOLATED STRONG TO SEVERE STORMS ARE POSSIBLE MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ENCOURAGED TO RELAY REPORTS THIS AFTERNOON AND
EVENING.

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