Severe Thunderstorm Warning 307, NWS Fort Worth, TX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
125 AM CDT WED JUN 20 2007

.UPDATE...
UPDATED FORECASTS ARE BEING SENT TO INCLUDE SEVERE THUNDERSTORM WATCH
426 THAT IS IN EFFECT UNTIL 9 AM CDT. POPS/WX/QPF GRIDS WERE ALSO
ADJUSTED UPWARD FOR THE THUNDERSTORM COMPLEX OVER SOUTHERN OKLAHOMA
THAT IS BARRELING SOUTHWARD. #58

&&

.DISCUSSION...

&&

.PREV DISCUSSION... /ISSUED 1147 PM CDT TUE JUN 19 2007/

AVIATION...
1147 PM.
WE/LL BE UPDATING KDFW TRACON TAF SITES TO INCLUDE TSRA 12-15Z AS
OKLAHOMA CONVECTION CONTINUES TO MOVE SOUTH AT 21KT OVERNIGHT AS LLJ
FEEDS THE SYSTEM.  OTHER THAN SOME MORNING STRATUS AT KACT...MOST
VFR CONDITIONS ARE EXPECTED OUTSIDE OF CONVECTION.  LOW LEVEL FLOW
WILL REMAIN GENERALLY SOUTHEAST AT 6-12KT.  75

UPDATE...
1100 AM.
THUNDERSTORM COMPLEX IN CENTRAL OKLAHOMA CONTINUES TO MOVE SOUTH
AROUND 20 MPH. THE STORMS ARE STILL GOING STRONG AND CURRENT VAD
SHOWS ABOUT 25 KNOTS OF MOIST INFLOW.  HAVE DECIDED TO BE A LITTLE
MORE AGGRESSIVE WITH THE FORECAST WITH RESPECT TO THUNDERSTORM
CHANCES AND THE FLOODING POTENTIAL.  WILL BE ISSUING A FLASH FLOOD
WATCH FOR THE COUNTIES OF COOKE...GRAYSON...DENTON AND WISE THROUGH
MIDDAY WEDNESDAY.  ADDITIONAL RAINFALL AMOUNTS OF ONE TO TWO INCHES
IN A RELATIVELY SHORT TIME PERIOD WILL MOST CERTAINLY HAVE A HIGH
IMPACT IN THE FLASH FLOOD WATCH AREA. SINCE STORMS SHOULD NOT REACH
THE RED RIVER UNTIL ABOUT 3 OR 4 AM.  WILL LET THE NEXT SHIFT
REASSESS THE NEED FOR A WATCH FURTHER SOUTH ON WEDNESDAY.

ONLY OTHER CHANGE WILL BE TO BUMP OVERNIGHT LOWS DOWN A BIT IN THE
NORTH TO ACCOUNT FOR RAIN COOLED AIR.

79

UPDATE...
940 PM
IMPRESSIVE CONVECTIVE COMPLEXES DEVELOPING OVER OKLAHOMA AND THE
TEXAS PANHANDLE THIS EVENING.  THE BIG QUESTION IS WHAT DIRECTION
THESE STORMS WILL MOVE OVERNIGHT. IT APPEARS THAT A SOUTHWESTWARD
PROPAGATION IS MOST LIKELY BASED ON THE FORECASTED LOW LEVEL JET AND
CORFIDI VECTORS.  HOWEVER... THE LINE IS FILLING IN FAR ENOUGH EAST
THAT SOME STORMS WILL MOVE INTO NORTH TEXAS BEFORE SUNRISE
WEDNESDAY. THE BEST CHANCE FOR SEVERE STORMS AND HEAVY RAINFALL WILL
BE GENERALLY WEST OF A GAINESVILLE TO EASTLAND LINE. THE HEAVY
RAINFALL COULD LEAD TO FLOODING ISSUES AGAIN...ESPECIALLY IF THE
COMPLEX MOVES SLIGHTLY MORE SOUTHERLY. WE WILL INCREASE POPS IN THE
NORTH OVERNIGHT.  WE WILL ALSO INCREASE POPS ON WEDNESDAY DUE TO
WEAKENING STORM COMPLEX AND LEFT OVER OUTFLOW BOUNDARIES.

NO OTHER MAJOR CHANGES WITH THIS UPDATE.

AVIATION...
534 PM.
KDFW/KACT TRACONS ARE TO REMAIN VFR EXCEPT 12-15Z WHEN A STRATUS
DECK MAY ADVECT OVER THE SITES. AS EARLIER STATED...TONIGHT/S LLJ
WILL BE WEAKER...THUS THERE IS LESS OF A POTENTIAL FOR
STRATUS...HOWEVER WE/LL CARRY A BRIEF TEMPO TO COVER THE EVENT.
SOUTHERLY FLOW WILL CONTINUE THROUGH THE PERIOD WITH SKIES BECOME
SKC THIS EVENING. EXPECT SOME CIRRUS DEBRIS FROM WEST TEXAS AFTER
MIDNIGHT...AND SCATTERED CUMULUS WEDNESDAY LATE MORNING AND
AFTERNOON. HOT AND VERY HUMID WEDNESDAY AFTERNOON. 75

PREV DISCUSSION...
422 PM CDT
INTENSE HUMIDITY PREVAILS...WITH DEW POINTS IN THE 70S AREAWIDE.
ACARS DATA SHOWING LITTLE IN THE WAY OF CAPPING...BUT CU SHOWING
LITTLE VERTICAL EXTENT IN AN IMMENSELY UNSTABLE ENVIRONMENT. HEIGHTS
ALOFT ARE RISING WITH DEEP SUBSIDENCE. IN THE CAPE VS. CAP
BATTLE...CAP APPEARS TO BE WINNING.

SEA BREEZE ACTIVITY ABOUT 50 MILES SOUTHEAST OF CWA...MAKING
MINIMAL PROGRESS INLAND (INTO SUBSIDENT AREA). FRONTAL CONVECTION
IN ARKANSAS IS BUILDING WEST...BUT SHOULD FAIL TO REACH AS FAR
WEST AS NE CWA. MOISTURE SURGING WEST INTO WEST TEXAS...BUT WITH
EASTERLY WINDS PREVAILING ACROSS WEST TEXAS AND NEW MEXICO...
MOISTURE CONVERGENCE IS LESS THAN WHAT THE DEW POINT GRADIENT
WOULD IMPLY. REGARDLESS...CONVECTION HAS BEGUN FROM EASTERN NEW
MEXICO INTO THE BIG BEND REGION. THIS ACTIVITY WILL STAY WELL WEST
OF THE AREA.

BEYOND THE THREAT OF SPONTANEOUS CONVECTION ACROSS THE AREA THIS
AFTERNOON/EVENING...NEXT BEST CHANCE FOR PRECIP WILL BE FROM MCS
PLUNGING SOUTH FROM ONGOING CONVECTION IN KANSAS. MODELS DESIRE TO
STEER MCS SOUTHWESTWARD TOWARD BEST (THOUGH MEAGER) INFLOW. DEW
POINTS OF 60 TO 70F ON HIGH TERRAIN IS CONSIDERABLY BUOYANT...AND
WILL REMAIN SO THROUGHOUT THE NIGHT...PERHAPS AIDED BY ONGOING
AFTERNOON/EVENING STORMS. EXPECT MCS WILL BE MORE LIKELY TO HEAD
SOUTH OR EVEN SOUTHEAST THAN TRY TO PENETRATE RIDGE AT NIGHT.
WILL CARRY LOW END POPS IN NORTHERN FRINGE OF CWA FOR LATE NIGHT
TIME PERIOD. WILL CERTAINLY BEAR WATCHING.

EFFECTS OF RIDGE WILL BE SHORT-LIVED...AS UPPER HIGH WILL EASE
BACK WEST. NORTHERLY FLOW THIS WEEKEND COULD ALLOW FOR SOME
NOCTURNAL EVENTS...BUT THINK RIDGE WILL STILL BE DOMINANT. SOME
DISAGREEMENT NEXT WEEK...BUT TEXAS MAY FIND ITSELF IN THE TROPICAL
EASTERLIES SOUTH OF THE SUBTROPICAL RIDGES. WILL NOT INTRODUCE
POPS UNTIL THERE IS BETTER RUN-TO-RUN CONSISTENCY. 25

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  76  94  75  94  75 /  10  10  10  10  10
WACO, TX              73  94  73  94  73 /  10  10  10  10  10
PARIS, TX             73  93  72  94  73 /  20  10  10  10  10
DENTON, TX            73  94  74  95  73 /  10  10  10  10  10
MCKINNEY, TX          72  94  72  95  72 /  10  10  10  10  10
DALLAS, TX            77  95  77  95  76 /  10  10  10  10  10
TERRELL, TX           73  95  73  95  74 /  20  10  10  10  10
CORSICANA, TX         74  93  73  94  73 /  20  10  10  10  10
TEMPLE, TX            74  93  73  93  73 /  10  10  10  10  10

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH UNTIL 1 PM CDT THIS AFTERNOON FOR THE
FOLLOWING ZONES: TXZ092-093-102-103.

&&

58/58

HAZARDOUS WEATHER OUTLOOK FOR NORTH TEXAS...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1104 PM CDT TUE JUN 19 2007

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-201000-
ANDERSON-BELL-BOSQUE-COLLIN-COMANCHE-COOKE-CORYELL-DALLAS-DELTA-
DENTON-EASTLAND-ELLIS-ERATH-FALLS-FANNIN-FREESTONE-GRAYSON-HAMILTON-
HENDERSON-HILL-HOOD-HOPKINS-HUNT-JACK-JOHNSON-KAUFMAN-LAMAR-LAMPASAS-
LEON-LIMESTONE-MCLENNAN-MILAM-MILLS-MONTAGUE-NAVARRO-PALO PINTO-
PARKER-RAINS-ROBERTSON-ROCKWALL-SOMERVELL-STEPHENS-TARRANT-VAN ZANDT-
WISE-YOUNG-
1104 PM CDT TUE JUN 19 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH TEXAS.

.DAY ONE...
A FLASH FLOOD WATCH IS IN EFFECT FOR COOKE...GRAYSON...WISE AND
DENTON COUNTIES THROUGH NOON WEDNESDAY. A LINE OF STRONG THUNDERSTORM
IN OKLAHOMA WILL MOVE ACROSS THE RED RIVER BEFORE DAYBREAK. THE MAIN
THREATS WILL BE LOCALIZED FLOODING...DAMAGING WIND AND CLOUD TO
GROUND LIGHTNING.

.DAYS TWO THROUGH SEVEN...
SCATTERED THUNDERSTORMS WILL BE POSSIBLE WEDNESDAY OVER ALL OF NORTH
TEXAS. THE MAIN THREAT WITH THESE STORMS WILL BE LOCALIZED FLOODING
AND CLOUD TO GROUND LIGHTNING.

.SPOTTER INFORMATION STATEMENT...
LIMITED SPOTTER ACTIVATION MAY BE REQUESTED AFTER 2 AM.