Severe Thunderstorm Warning 284, NWS Fort Worth, TX

375 
WWUS54 KFWD 182025
SVSFWD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE FORT WORTH TX
325 PM CDT SAT AUG 18 2012

TXC221-251-182100-
/O.CON.KFWD.SV.W.0284.000000T0000Z-120818T2100Z/
HOOD TX-JOHNSON TX-
325 PM CDT SAT AUG 18 2012

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 400 PM CDT
FOR WESTERN JOHNSON AND NORTHEASTERN HOOD COUNTIES...

AT 325 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING QUARTER SIZE HAIL...AND
DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED 6 MILES 
NORTHWEST OF GODLEY...MOVING EAST AT 15 MPH. A NEW UPDRAFT CORE IS 
DEVELOPING JUST WEST OF THE OLD CORE...AND IT MAY BECOME SEVERE AS 
WELL. IT WILL BE MOVING INTO THE WARNED AREA WITHIN 10 MINUTES. 

THE SEVERE THUNDERSTORM WILL BE NEAR...
  GODLEY AROUND 345 PM CDT...
  JOSHUA...CLEBURNE...BURLESON AND KEENE AROUND 400 PM CDT...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

HEAVY RAINS MAY FLOOD LOW LYING AREAS SUCH AS STREETS...DITCHES AND
UNDERPASSES. AVOID THESE AREAS AND DO NOT CROSS FLOODED ROADS AS THEY
MAY BE WASHED OUT.

&&

LAT...LON 3256 9775 3255 9729 3222 9732 3238 9773
      3250 9780
TIME...MOT...LOC 2025Z 276DEG 12KT 3248 9760

$$

787 
WWUS54 KFWD 182041
SVSFWD

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE FORT WORTH TX
341 PM CDT SAT AUG 18 2012

TXC221-251-182051-
/O.CAN.KFWD.SV.W.0284.000000T0000Z-120818T2100Z/
HOOD TX-JOHNSON TX-
341 PM CDT SAT AUG 18 2012

...THE SEVERE THUNDERSTORM WARNING FOR WESTERN JOHNSON AND
NORTHEASTERN HOOD COUNTIES IS CANCELLED...

AT 341 PM CDT THE SEVERE THUNDERSTORM THAT PROMPTED THE WARNING
WEAKENED AND WAS NO LONGER SEVERE...THUS THE WARNING HAS BEEN
CANCELLED.

RADAR INDICATED THAT HEAVY RAIN...SMALL HAIL...AND GUSTY WINDS WERE 
STILL POSSIBLE FROM THE THUNDERSTORM. AN URBAN AND SMALL STREAM 
FLOOD ADVISORY IS IN EFFECT FOR HOOD COUNTY AND PARTS OF JOHNSON 
COUNTY DUE TO THE CONTINUED HEAVY RAIN. 

LAT...LON 3256 9775 3255 9729 3222 9732 3238 9773
      3250 9780
TIME...MOT...LOC 2041Z 276DEG 12KT 3247 9754

$$

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1246 PM CDT SAT AUG 18 2012

.AVIATION...
STORMS CONTINUE ACROSS THE SOUTHERN AREAS NEAR WACO AND WILL
CONTINUE TO MENTION VCTS THROUGH EARLY EVENING. STORMS MAY STILL
BE POSSIBLE AFTER 1Z...BUT WASNT CONFIDENT ENOUGH TO CONTINUE
MENTIONING THUNDER. WILL TEMPO -TSRA FOR THE AFTERNOON HOURS AS
PROBABILITIES FOR SCATTERED CONVECTION IMPACTING KACT IS HIGH.

FOR THE METROPLEX...ONLY 2 THUNDERSTORMS ARE NEAR KFWS AT THIS
TIME. WITH FURTHER DESTABILIZATION AND BETTER LIFT IN OKLAHOMA
MOVING SOUTH...THINK PRECIP CHANCES WILL BE INCREASING. WILL
MENTION VCTS FROM 20Z TO 01Z...BUT DIDNT HAVE THE SAME CONFIDENCE
TO TEMPO -TSRA LIKE WACO. ADDITIONAL PRECIP IS POSSIBLE OVERNIGHT.

A COLD FRONT IS EXPECTED TO BRING A NORTHERLY WIND SHIFT INTO THE
METROPLEX TAF SITES TOMORROW. MOVED IT BACK A COUPLE OF HOURS TO
16Z...AS SOME OF THE MORNING MODEL GUIDANCE IS SUGGESTING A LATER
ARRIVAL.

85/NH

&&

.UPDATE...

INCREASED PRECIPITATION CHANCES ACROSS MUCH OF NORTH AND CENTRAL
TEXAS FOR THIS AFTERNOON.

MORNING ANALYSIS REVEALED A FEW FEATURES THAT WILL SUPPORT RAIN
SHOWER AND THUNDERSTORM CHANCES ACROSS THE REGION THIS AFTERNOON.
THE EASIEST FEATURE TO ANALYZE IS A COLD FRONT WHICH CONTINUES TO
RESIDE OVER OKLAHOMA LATE THIS MORNING. THIS FRONT IS MOVING
SLOWLY SOUTH AND LOOKS ON PACE TO MOVE INTO NORTH TX LATE TONIGHT
INTO SUNDAY MORNING. SOUTH OF THIS FRONT A FAIRLY WELL ORGANIZED
LINE OF SHOWERS AND THUNDERSTORMS IS EVIDENT AND ADVANCING SOUTH
TOWARDS THE RED RIVER. THIS LINE OF PRECIPITATION SEEMS TIED TO A
BAND OF MORE FOCUSED LARGE SCALE FORCING FOR ASCENT ASSOCIATED
WITH A SHORTWAVE TROUGH DIVING SOUTH THROUGH THE CENTRAL PLAINS
THIS MORNING. THIS ACTIVITY IS EXPECTED TO CONTINUE TO MAINTAIN
SOME LOOSE ORGANIZATION AS IT MOVES SOUTHEAST INTO NORTH TX THIS
AFTERNOON.

ASIDE FROM THIS LINE OF PRECIPITATION...BROAD ISENTROPIC LIFT OR
WARM AIR ADVECTION REMAINS IN PLACE OVER ALMOST ALL OF NORTH AND
CENTRAL TX. OVERNIGHT THUNDERSTORMS AROUND AND SOUTHEAST OF THE
WACO AREA HAS LEFT A RELATIVELY COOL AIRMASS IN PLACE OVER THE
SOUTHERN THIRD OF THE FORECAST AREA. THIS HAS ACTUALLY SERVED TO
LOCALLY STEEPEN LOW LEVEL ISENTROPIC SURFACES...THEREBY ENHANCING
LOW LEVEL FORCING FOR ASCENT LATE THIS MORNING. BASICALLY ONGOING
THUNDERSTORM ACTIVITY HAS ACTUALLY CREATED MORE FAVORABLE
CONDITIONS FOR ADDITIONAL STORMS THIS AFTERNOON. AS A RESULT WENT
AHEAD AND BUMPED POPS UP TO 60 PERCENT FOR THE SOUTHERN PORTIONS
OF THE FORECAST AREA..INCLUDING WACO AND KILLEEN/TEMPLE
METROPOLITAN AREAS. THIS ACTIVITY IS EXPECTED TO REMAIN SOMEWHAT
ELEVATED IN NATURE AND THEREFORE PRESENTS A RELATIVELY LOW SEVERE
WEATHER THREAT FOR THIS AFTERNOON.

THE LAST FEATURE TO MENTION IS THE OUTFLOW BOUNDARY MOVING
SOUTHWEST THROUGH NORTH TX THAT HAD SEVERAL VISIBLE EMBEDDED
GRAVITY WAVES LATE THIS MORNING AS IT MOVED OVER THE DFW
METROPLEX. THIS BOUNDARY AND THESE WAVES HAVE HELPED SET OFF SOME
ELEVATED THUNDERSTORM ACTIVITY ALONG THE INTERSTATE 35 CORRIDOR
JUST SOUTH OF TARRANT AND DALLAS COUNTIES. WHILE THIS ACTIVITY IS
NOT OVERLY STRONG AT THIS TIME...THE LONGER IT PERSISTS...THE MORE
LIKELY IT IS TO ENHANCE LOW LEVEL WARM AIR ADVECTION AND
ISENTROPIC LIFT. THIS MAY RESULT IN THE DEVELOPMENT OF NUMEROUS
ELEVATED THUNDERSTORMS SIMILAR TO WHAT WAS HAPPENING OVER THE
SOUTHERN CWA LATE THIS MORNING.

FOR THE BIG PICTURE...WITH ALL OF THESE FACTORS COMBINED THOUGHT
IT WAS NECESSARY TO BUMP UP POPS FOR MOST OF NORTH AND CENTRAL TX
THIS AFTERNOON. BECAUSE MOST ACTIVITY IS EXPECTED TO BE ELEVATED
IN NATURE THROUGH EARLY THIS AFTERNOON...THE THREAT FOR SEVERE
WEATHER SEEMS LOW. OUR BIGGEST THREAT IS GOING TO BE FROM SLOW
MOVING STORMS THAT PRODUCE COPIOUS AMOUNTS OF RAINFALL WHICH MAY
LEAD TO LOCALIZED FLOODING PROBLEMS. WILL NOT ISSUE A FLASH FLOOD
WATCH AT THIS TIME AS CURRENT THINKING IS THAT FLASH FLOODING WILL
BE A LOCALIZED THREAT BEST HANDLED WITH LOCAL STATEMENTS AND
WARNINGS AT THIS TIME.

LASTLY...WITH REGARDS TO HIGH RESOLUTION MODEL GUIDANCE...HERE ARE
SOME OBSERVATIONS WITH REGARDS TO SHORT TERM SCIENTIFIC FORECAST
CONCERNS FOR THUNDERSTORM EVOLUTION THIS AFTERNOON. NEARLY ALL
HIGH RESOLUTION MODEL GUIDANCE INDICATES THAT THE LINE OF
THUNDERSTORMS ORGANIZING ACROSS OKLAHOMA WILL GROW INTO A LINEAR
MCS CONTAINING SOME RESPECTABLE WINDS (AROUND 40 KTS SUSTAINED)
WITHIN ITS SUSTAINED OUTFLOW. HIGH RESOLUTION GUIDANCE BRINGS THIS
SYSTEM ACROSS THE RED RIVER BY 20Z WHICH SHOULD SIGNIFY AN
ENHANCED STRAIGHT LINE WIND THREAT FOR OUR NORTHERN CWA ONCE IT
ARRIVES. SHORTLY THEREAFTER GUIDANCE INDICATES THAT THIS COMPLEX
EFFECTIVELY DISSIPATES ALLOWING COLD OUTFLOW TO GREATLY
OUTDISTANCE SIMULATED REFLECTIVITY CORES. THIS MAY SEEM COUNTER-
INTUITIVE WITH GENERALLY WARMER AIR TO THE SOUTH OF THIS LINE OF
STORMS BUT SEEMS SUPPORTED BY A CLOSER LOOK AT SURFACE ANALYSIS
FIELDS. HOURLY SURFACE ANALYSIS OF THETA-E COURTESY OF DAVE BARBER
INDICATES A GENERAL INCREASE OF THETA-E SOUTHEAST OF THE OKLAHOMA
LINE OF STORMS. BARBERS ANALYSIS ALSO LOOKS AT THE GRADIENT OF
SURFACE THETA-E AND SHOWS THAT THE THETA-E GRADIENT SOUTHEAST OF
NORTH TX IS TIGHTER THAN THE GRADIENT ACROSS THE CWA. THE THETA-E
GRADIENT IS ONCE AGAIN HIGHER ACROSS OKLAHOMA WITH THE INFLUENCE
OF THE COLD FRONT AND CONSOLIDATED OUTFLOW BOUNDARIES FACTORED IN.
THIS LEAVES NORTH TX WITHIN A POSITIVE LAPLACIAN IN THE LOW LEVEL
THETA-E FIELD.

THIS THERMODYNAMIC CONSIDERATION COMBINED WITH WEAKER DEEP LAYER
SHEAR IN PLACE ACROSS NORTH TX SEEMS TO SUPPORT THE HIGH
RESOLUTION MODEL GUIDANCE SOLUTION THAT A LINEAR MCS WOULD HAVE
TROUBLE CONTAINING ITS SYSTEM RELATIVE OUTFLOW AS IT MOVES INTO
THE CWA THIS AFTERNOON. SO BOTTOM LINE...THIS SEEMS TO SIMPLY
REINFORCE LOW CONFIDENCE IN AN ORGANIZED SEVERE WEATHER EVENT
ACROSS NORTH TX THIS AFTERNOON. DEEP LAYER SHEAR IS EXPECTED TO
INCREASE AFTER 00Z AS THE CENTRAL PLAINS SHORTWAVE MOVES CLOSER TO
THE SOUTHERN PLAINS. IF THERE IS SUFFICIENT INSTABILITY LEFT THIS
MAY RESULT IN A SLIGHT INCREASE IN SEVERE WEATHER CHANCES THIS
EVENING ACROSS NORTH TX. WILL CONTINUE TO MONITOR THIS POTENTIAL
THROUGHOUT THE AFTERNOON HOURS AND UPDATE THE FORECAST IF THE
SEVERE WEATHER THREAT LOOKS TO INCREASE SUBSTANTIALLY.

CAVANAUGH

&&

.PREV DISCUSSION... /ISSUED 415 AM CDT SAT AUG 18 2012/
WATER VAPOR LOOP SHOWS A LARGE UPPER LEVEL CYCLONE DROPPING
SOUTHEAST OUT OF CANADA AND INTO THE MIDWEST THIS MORNING. THE
UPPER LEVEL FLOW OVER OUR REGION IS ACQUIRING CYCLONIC CURVATURE
AROUND THE UPPER LOW AND THIS WILL RESULT IN 3-5DM 500MB HEIGHT
FALLS TODAY AS DYNAMIC LIFTING OCCURS. CONVECTION DEVELOPED
OVERNIGHT ALONG A LINE FROM GAINESVILLE TO DALLAS TO PALESTINE
ALONG A LINGERING ELEVATED THERMAL BOUNDARY THAT IS DRAPED ACROSS
THE REGION. WARM ADVECTION AND ISENTROPIC LIFT ACROSS THE BOUNDARY
ON THE 310K SURFACE /NEAR 750-800MB/ IS OCCURRING IN A REGION OF
CONDITIONAL ELEVATED INSTABILITY. MODEL GUIDANCE IS IN AGREEMENT
THAT THESE LOW LEVEL WINDS WILL WEAKEN SUBSTANTIALLY DURING THE
DAY...AND THUS THE CURRENT BAND OF CONVECTION SHOULD DISSIPATE BY
MID-LATE MORNING. HOWEVER EXPECT ADDITIONAL SCATTERED AIRMASS
CONVECTION TO DEVELOP WITH HEATING DURING THE AFTERNOON GIVEN THE
FAVORABLE UPPER LEVEL PATTERN THAT IS PROMOTING ASCENT. WILL SHOW
HIGHEST POPS IN THE NORTH AND EASTERN ZONES PRIMARILY TO ACCOUNT
FOR THE EARLY MORNING ACTIVITY. HIGH TEMPS ARE DIFFICULT AND
DEPENDENT ON CLOUD COVER...BUT GENERALLY EXPECT MORE SUN OVER THE
SOUTHWEST HALF OF THE CWA TODAY. AN ISOLATED SEVERE STORM WILL BE
POSSIBLE...BUT CATEGORICAL SLIGHT RISK FORECAST FROM SPC MAY BE A
BIT AGGRESSIVE GIVEN THE MORE LIMITED INSTABILITY EXPECTED TODAY.

TONIGHT A SHORTWAVE TROUGH AND 500MB SPEED MAX WILL BE DROPPING
INTO NORTH TEXAS FROM THE NORTH. ALREADY THERE IS SOME EVIDENCE OF
THIS FEATURE MOVING THROUGH EASTERN COLORADO AND WESTERN KANSAS
WHERE ELEVATED STORMS HAVE FORMED. A FEW OF THE HI-RES MODELS
ADVERTISE A CONVECTIVE COMPLEX MOVING IN FROM THE NW AROUND
SUNSET. THESE MODELS WEAKEN THIS CONVECTION ACROSS THE NORTHERN
ZONES IN THE EVENING...AND THEREFORE WILL SHOW HIGHEST POPS IN THE
NORTH TONIGHT. IN THE WAKE OF THE SHORTWAVE...FRONTOGENESIS WILL
OCCUR AND NORTHERLY WINDS WILL BEGIN TO ORGANIZE BY SUNDAY
MORNING. DRIER AND MORE STABLE AIR WILL FILTER INTO THE REGION
DURING THE DAY ON SUNDAY...AND POPS WILL END FROM NORTH TO SOUTH.
FAIRLY IMPRESSIVE COLD ADVECTION FOR MID AUGUST IS EXPECTED...AND
HIGHS WILL BE SLIGHTLY BELOW NORMAL SUNDAY AND MONDAY DESPITE THE
AUGUST SUNSHINE. LOW TEMPS WILL ALSO FALL INTO THE 60S.

ANOTHER SHORTWAVE WILL MOVE ACROSS THE REGION IN NW FLOW ALOFT ON
TUESDAY. LOW LEVEL MOISTURE/INSTABILITY LOOKS ABSENT WHEN THIS
FEATURE ARRIVES AND THEREFORE WILL KEEP POPS AT 10 PERCENT AND OUT
OF THE WORDED FORECAST. ENOUGH MID LEVEL MOISTURE EXISTS FOR A
MENTION OF MORE CLOUD COVER AND PERHAPS A FEW SPRINKLES ACROSS THE
NORTH. THE CLOUD COVER SHOULD PROVIDE US ANOTHER DAY OF BELOW NORMAL
TEMPS DESPITE RETURNING SOUTHERLY WINDS. TEMPS WILL REBOUND A BIT
BY MIDWEEK AS SOUTH WINDS BRING WARM/MOIST AIR BACK INTO THE
REGION. ANOTHER SHORTWAVE IS POSSIBLE LATE IN THE WEEK...AND
THEREFORE WILL SHOW SLIGHT CHANCE POPS ON FRIDAY.

TR.92

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  92  75  90  67  88 /  60  50  30   5   0
WACO, TX              97  73  93  69  91 /  60  50  40  10   0
PARIS, TX             89  72  86  62  86 /  60  60  30   5   0
DENTON, TX            90  71  89  61  88 /  60  60  30   5   0
MCKINNEY, TX          89  72  89  61  87 /  60  60  30   5   0
DALLAS, TX            92  76  90  67  88 /  60  50  30   5   0
TERRELL, TX           90  73  90  65  88 /  60  50  40  10   0
CORSICANA, TX         94  74  93  68  90 /  60  50  40  10   0
TEMPLE, TX            95  73  94  68  92 /  60  50  40  10   0
MINERAL WELLS, TX     93  70  89  62  88 /  50  60  30   5   0

&&

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

&&

85/85

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FORT WORTH TX
441 AM CDT SAT AUG 18 2012

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-191200-
MONTAGUE-COOKE-GRAYSON-FANNIN-LAMAR-YOUNG-JACK-WISE-DENTON-COLLIN-
HUNT-DELTA-HOPKINS-STEPHENS-PALO PINTO-PARKER-TARRANT-DALLAS-
ROCKWALL-KAUFMAN-VAN ZANDT-RAINS-EASTLAND-ERATH-HOOD-SOMERVELL-
JOHNSON-ELLIS-HENDERSON-COMANCHE-MILLS-HAMILTON-BOSQUE-HILL-NAVARRO-
FREESTONE-ANDERSON-LAMPASAS-CORYELL-BELL-MCLENNAN-FALLS-LIMESTONE-
LEON-MILAM-ROBERTSON-
441 AM CDT SAT AUG 18 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH TEXAS.

.DAY ONE...TODAY AND TONIGHT.

SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED ACROSS MUCH OF
NORTH TEXAS TODAY. ACTIVITY WILL GENERALLY BE CONFINED TO AREAS
EAST OF INTERSTATE 35 THROUGH THE MORNING HOURS...THEN SCATTERED
STORMS WILL DEVELOP THROUGHOUT THE REST OF NORTH TEXAS BY LATE
AFTERNOON AND PERSIST INTO THE NIGHTTIME HOURS. AN ISOLATED SEVERE
STORM CAN BE EXPECTED WITH DAMAGING WINDS AND QUARTER SIZE HAIL.
FREQUENT CLOUD TO GROUND LIGHTNING AND LOCALLY HEAVY RAINFALL CAN
ALSO BE EXPECTED WITH ANY STORMS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

THERE IS A CHANCE OF THUNDERSTORMS ACROSS ALL OF NORTH TEXAS ON
SUNDAY WITH RAIN CHANCES ENDING FROM NORTH TO SOUTH BY LATE IN THE
DAY. FREQUENT CLOUD TO GROUND LIGHTNING AND LOCALLY HEAVY RAINFALL
WILL BE THE MAIN THREATS.

THERE IS A CHANCE OF THUNDERSTORMS ACROSS ALL OF NORTH TEXAS
FRIDAY AND FRIDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUESTED AT TIMES TODAY THROUGHOUT
NORTH TEXAS.

DUNN