Severe Thunderstorm Warning 193, NWS Fort Worth, TX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
633 PM CDT FRI MAY 8 2009

.AVIATION...
VFR CONDITIONS SHOULD CONTINUE ACROSS ALL TAF SITES THROUGH LATE
EVENING WITH THE MAJORITY OF THUNDERSTORM ACTIVITY REMAINING WEST
OF THE INTERSTATE 35 CORRIDOR IN THE AREA OF BEST INSTABILITY.
THUNDERSTORM CHANCES SHOULD INCREASE OVERNIGHT AS A COLD FRONT
MOVES ACROSS THE RED RIVER. THERE IS A GOOD CHANCE THAT A CONVECTIVE
COMPLEX COULD DEVELOP OVERNIGHT WITH SEVERAL HOURS OF RAIN AND
THUNDERSTORMS THROUGH SUNRISE. FOR NOW WILL KEEP A TEMPO GROUP AT
THE METRO SITES BETWEEN 05Z AND 9Z WITH PREVAILING -TSRA BETWEEN
09 AND 15Z. MVFR CEILINGS SHOULD ARRIVE WITH THE FRONT LATE THIS
EVENING AND PREVAIL THROUGH SATURDAY. A SOUTH WIND AROUND 15 KNOTS
THIS EVENING WILL BACK TO THE EAST/NORTHEAST OVERNIGHT WITH THE
PASSAGE OF THE FRONT. WIND SPEEDS WILL RANGE FROM 9 TO 14 KNOTS.

WACO SHOULD REMAIN SOUTH AND EAST OF THE EXPECTED THUNDERSTORMS
TONIGHT/SATURDAY MORNING...BUT MVFR CEILINGS WILL ARRIVE AROUND
06Z AND REMAIN THROUGH SATURDAY.

79

&&

.UPDATE...
QUICK UPDATE TO INCLUDE TORNADO WATCH 272 FOR WESTERN PORTIONS OF
NORTH TEXAS THROUGH TONIGHT. THUNDERSTORMS HAVE RAPIDLY DEVELOPED
ALONG WHAT APPEARS TO BE THE SOUTHERN EXTENT OF A COLD
FRONT...ALTHOUGH TRUE COOLER AIR AND MORE DISTINCT BOUNDARY IS
STILL UP IN SOUTHERN OKLAHOMA. ATMOSPHERE WHERE STORMS ARE
DEVELOPING IS CHARACTERIZED BY MIXED LAYER CAPE IN EXCESS OF
4000 J/KG WITH MINIMAL INHIBITION. STORMS WILL BE SEVERE WITH
GIANT HAIL LIKELY AND STRONG WINDS. ALTHOUGH SHEAR IS NOT THAT
IMPRESSIVE...EXTREME INSTABILITY MAY ALLOW STORMS TO EFFECTIVELY
USE WHAT IS AVAILABLE...LEADING TO A TORNADO THREAT. STORMS WILL
MOVE EAST THROUGH THE EVENING. WILL CONTINUE TO TWEAK POPS THROUGH
THE EVENING.

91/DUNN

&&

.PREV DISCUSSION... /ISSUED 323 PM CDT FRI MAY 8 2009/
LITTLE CHANGE TO PREVIOUS FORECAST THIS PACKAGE...AS WE AWAIT TO SEE
IF INTENSE HEATING JUST ALONG FRONTAL WAVE JUST OFF NW COUNTIES CAN
CONTINUE TO WEAKEN CINH/CONVECTION INHIBITION AND ALLOW FOR RAPID/
ISOLATED SUPERCELL DEVELOPMENT ALONG/W OF A BOWIE-MINERAL WELLS LINE
...WHERE MSAS MOISTURE CONVERGENCE HAS BEEN INTENSIFYING WITH SOME
SLOW BACKING OF SFC WINDS TO SELY AT BRECKENRIDGE/BOWIE/MINERAL
WELLS/AND GRAHAM. 0-1KM/0-6KM SHEAR WILL BE AMPLE ON SRN FRINGE OF
WLY/ZONAL FLOW ALOFT ACROSS THIS AREA TO KEEP STORMS GOING AFTER
DARK AND THEN PROPAGATE ESE ACROSS NE COUNTIES THROUGH SAT MORNING
PER MEAN CORFIDI VECTORS AND COMPONENT FLOW. EARLY ON...VERY LARGE
HAIL...LOCALIZED DAMAGING WINDS AND A BRIEF TORNADO COULD OCCUR
DURING DISCRETE STAGES OF ACTIVITY...BEFORE BECOMING A LEWP/LINEAR
MCS TYPE OF SYSTEM WITH DAMAGING WINDS/ LOCALLY HEAVY RAINFALL
BETWEEN 1-2 INCHES BEING THE MAIN THREATS...WITH SOME MARGINALLY
SEVERE HAIL POSSIBLE.

THE NE HALF OF NORTH TEXAS WILL BE THE GROUNDS FOR INCREASE STORM
ACTIVITY THROUGH SATURDAY...AS FRONT LOSES PUSH AND HANGS UP JUST
SOUTH OF I-20. WITH HEATING EACH DAY THROUGH SUNDAY AND THE ZONAL
FLOW CREEPING NWD...BEST RAIN CHANCES THROUGH MONDAY WILL BE ACROSS
THE NORTH...WITH MORE ISOLATED ACTIVITY SOUTH. EACH DAY COULD SEE
SOME LOCALIZED SEVERE WEATHER...BUT PROBABLY NOT AS INTENSE AS
TONIGHT THROUGH THE WEEKEND. ALSO...TEMPERATURES WILL BE TEMPERED
WITH INCREASING RAIN/CLOUD COVER WITH VALUES A GOOD 15 DEG F OR
BETTER COOLER. DECIDED TO FORGO FFA/FLASH WATCH ISSUANCE OVER NE CWA
FOR NOW...WITH PROGRESSIVE FORWARD MOTION OF MCS TONIGHT EXPECTED
AND UNCERTAINTY ON FRONTAL POSITION AND CONCENTRATED RAINFALL NEXT
48-72 HOURS. FUTURE SHIFTS WILL NEED TO REASSESS.

MON NIGHT-WEDNESDAY MORNING WILL BE ANOTHER RESPITE AND WAA/LLJ
SHOOT OLD FRONT NORTH OF THE RED RIVER WITH APPROACH OF NRN ROCKIES
UPPER TROUGH. HOWEVER ANOTHER FRONT WILL APPROACH THE RED RIVER LATE
WEDNESDAY INTO THURSDAY AND HAVE INTRODUCE LOW CHANCE POPS FOR
MAINLY AREA ALONG/ NORTH OF I-20 ONCE AGAIN. SOME DISCREPANCIES
EXIST WITH MED RANGE MODELS AND WILL NEED TO BE FINE TUNED WITH
BETTER MODEL AGREEMENT BY THE END OF THE WEEKEND.

FRIDAY INTO SATURDAY...HAVE LEFT DRY WITH WNW FLOW COMPONENT AND SFC
FOCUS LACKING.

05/

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  70  75  58  75  60 /  50  40  30  20  50
WACO, TX              72  85  64  83  63 /  10  20  20  10  20
PARIS, TX             68  72  60  73  59 /  70  50  50  40  50
DENTON, TX            67  72  56  71  59 /  60  40  40  30  50
MCKINNEY, TX          67  74  57  73  58 /  70  40  40  30  50
DALLAS, TX            71  77  60  74  62 /  60  40  30  20  50
TERRELL, TX           72  78  62  78  60 /  50  40  30  20  40
CORSICANA, TX         71  83  65  81  64 /  30  30  30  10  30
TEMPLE, TX            71  86  66  83  65 /  10  10   5  10  20

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

79/91

HAZARDOUS WEATHER OUTLOOK FOR NORTH TEXAS
NATIONAL WEATHER SERVICE FORT WORTH TX
331 PM CDT FRI MAY 8 2009

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-091000-
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-
331 PM CDT FRI MAY 8 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH TEXAS.

.DAY ONE...LATE THIS AFTERNOON AND TONIGHT.
THERE IS A CHANCE OF SEVERE THUNDERSTORMS WITH LARGE HAIL AND
DAMAGING WINDS...AND POSSIBLY ISOLATED TORNADOES...BEGINNING
BEFORE SUNSET OVER THE NORTHWEST COUNTIES AND MOVING EAST
SOUTHEAST THROUGH THE EVENING HOURS. IN THE OVERNIGHT HOURS...
THESE THUNDERSTORMS MAY FORM INTO A COMPLEX THAT WILL MOVE ACROSS
NORTH-CENTRAL AND NORTHEAST TEXAS WITH LARGE HAIL...DAMAGING
WINDS...AND LOCALLY HEAVY RAINFALL THAT MAY RESULT IN LOCALIZED
FLASH FLOODING IN AREAS THAT RECEIVED VERY HEAVY RAINFALL LAST WEEK.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.
THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS THIS WEEKEND AND
INTO MONDAY...MAINLY OVER THE NORTHERN HALF...AS THE COLD FRONT
FLUCTUATES AROUND NORTH TEXAS. THE MAIN SEVERE WEATHER THREATS
WILL BE LARGE HAIL...DAMAGING WINDS...AND LOCALLY HEAVY RAINFALL.
THERE WILL BE ANOTHER CHANCE OF THUNDERSTORMS WEDNESDAY THROUGH
THURSDAY.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS LIKELY BY THIS EVENING GENERALLY NORTH OF
INTERSTATE 20.

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