Severe Thunderstorm Warning 490, NWS Fort Worth, TX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
904 AM CDT TUE OCT 6 2009

.UPDATE...
WE WILL BE CANCELING THE DENSE FOG ADVISORY AS OF 9 AM. THE COLD
FRONT EXTENDED SOUTHEAST OF AN ARDMORE OKLAHOMA... WICHITA FALLS
LINE OF 9 AM. WINDS BEHIND THE FRONT ARE A LITTLE STRONGER THAN
EARLIER EXPECTED...SO HAVE BUMPED UP THE WINDS FOR LATE MORNING
AND AFTERNOON BEHIND THE FRONT. UPDATES HAVE BEEN SENT.

58

&&

.AVIATION...
610 AM
COMPLICATED TAFS. WARM FRONT NOW SLIDING NORTH OF
METROPLEX...CEILINGS/VISIBILITIES HAVE RISEN AS WINDS HAVE PICKED UP
INTO THE 10-15 MPH RANGE. HAVE FORECAST IFR THIS MORNING UNTIL
FROPA...BUT THEY COULD TICK UP AND DOWN INTO THE MVFR RANGE. WACO
MORE LIKELY TO SEE HIGHER CEILINGS BEING FARTHER AWAY FROM THE
FRONT. COLD FRONT NOW NEARING WICHITA FALLS...AND SHOULD HIT
METROPLEX NEAR 18Z/1 PM. TSTMS NOW AHEAD OF FRONT ALSO EXPECTED TO
SLIDE SOUTHEAST AND SHOULD MAKE METROPLEX TAF SITES NEAR 15Z/10 AM.
CEILINGS SHOULD IMPROVE TO VFR AFTER THE RAIN...BUT WILL LIKELY
DECREASE TO MVFR/IFR BEFORE WEDNESDAY MORNING.    84

&&

.PREV UPDATE...
.UPDATE...
610 AM
WILL DISCONTINUE DENSE FOG ADVISORY FOR ALL BUT NORTHERN COUNTIES AS
VISIBILITIES HAVE IMPROVED WITH WARM FROPA.

.AVIATION...
610 AM
COMPLICATED TAFS. WARM FRONT NOW SLIDING NORTH OF
METROPLEX...CEILINGS/VISIBILITIES HAVE RISEN AS WINDS HAVE PICKED UP
INTO THE 10-15 MPH RANGE. HAVE FORECAST IFR THIS MORNING UNTIL
FROPA...BUT THEY COULD TICK UP AND DOWN INTO THE MVFR RANGE. WACO
MORE LIKELY TO SEE HIGHER CEILINGS BEING FARTHER AWAY FROM THE
FRONT. COLD FRONT NOW NEARING WICHITA FALLS...AND SHOULD HIT
METROPLEX NEAR 18Z/1 PM. TSTMS NOW AHEAD OF FRONT ALSO EXPECTED TO
SLIDE SOUTHEAST AND SHOULD MAKE METROPLEX TAF SITES NEAR 15Z/10 AM.
CEILINGS SHOULD IMPROVE TO VFR AFTER THE RAIN...BUT WILL LIKELY
DECREASE TO MVFR/IFR BEFORE WEDNESDAY MORNING.    84

&&

.PREV DISCUSSION... /ISSUED 610 AM CDT TUE OCT 6 2009/
500 AM
PRIMARY FORECAST CONCERNS ARE TSTM CHANCES FOR THE REMAINDER OF
THE WEEK AND THEN EARLY MORNING FOG ACROSS NORTH TX.

VISIBILITIES BEGAN DROPPING QUICKLY AROUND 07-08Z EARLY THIS
MORNING SO WENT AHEAD WITH A DENSE FOG ADVISORY WITH MANY 08Z
VISIBILITIES REPORTING IN AROUND 1 SM. SINCE THEN VISIBILITIES
ACRS THE AREA HAVE BEEN IMPROVING AS SOUTHERLY WINDS PICK UP IN
INTENSITY. UNCERTAIN IF VSBYS WILL DROP AGAIN...BUT FOR NOW WILL
LET THE DENSE FOG ADVISORY GO THROUGH SUNRISE AT LEAST AND SEE HOW
VSBYS ACRS THE AREA RESPOND. LIGHT MIST/DRIZZLE WAS OBSERVED
FALLING OUT OF THE LOW STRATUS DECK...SO SOME REDUCED VISIBILITIES
WILL LIKELY STILL AFFECT THE MORNING COMMUTE.

ASIDE FROM MORNING FOG ASSOCIATED WITH THE WARM FRONT LIFTING
NORTH...TSTM ACTIVITY HAS FINALLY DEVELOPED ALONG AND AHEAD OF THE
COLD FRONT DIVING SOUTH INTO THE SOUTHERN PLAINS EARLY THIS
MORNING. THE FRONT LOOKS TO MOVE THRU NORTH TX A BIT FASTER THAN
EXPECTED YESTERDAY...WITH THE FRONT ENTERING THE NORTHWESTERN
PORTIONS OF THE FORECAST AREA AROUND OR JUST AFTER SUNRISE.
FORECAST SOUNDINGS INDICATE SOMEWHERE IN THE VICINITY OF 1500 J/KG
OF CAPE OUT AHEAD OF THE FRONT...WITH A SUFFICIENT SHEAR PROFILE
TO SUPPORT ORGANIZED THUNDERSTORMS...POSSIBLY SOME ELEVATED
SUPERCELLS. WITH THE LLJ VEERED ALONG THE FRONTAL BOUNDARY...H850
ANALYSIS INDICATING 20 DEG C DEW POINT VALUES TO THE
SOUTHWEST...AND FORECAST SOUNDINGS BRINGING PWAT VALUES ABOVE 2
INCHES...THERE IS ALSO SOME POTENTIAL FOR HEAVY RAINFALL WHICH MAY
LEAD TO LOCALIZED FLOODING PROBLEMS. THIS BEING SAID...IF THE
FRONT KEEPS MOVING...FLOODING IS SOMEWHAT LESS OF AN ISSUE
TODAY...BUT SOMETHING TO WATCH AS THIS SYSTEM EVOLVES. HAVE GONE
WITH 60 TO 80 POPS ALONG THE FRONTAL BOUNDARY TODAY...BUT THERE IS
STILL THE CONCERN THAT TSTM COVERAGE WILL BE LIMITED BY H900-H800
WARM LAYER/CAP AS THE FRONT MOVES THRU. ONGOING ACTIVITY IN
SOUTHERN OK RAISES CONFIDENCE THAT TSTMS WILL BE NUMEROUS ALONG
THE COLD FRONT. UNLESS WE BREAK OUT OF THE LOW STRATUS
TODAY...WOULD ANTICIPATE THE PRIMARY SVR WX THREATS TO BE LARGE
HAIL AND FREQUENT LIGHTNING...AND OF COURSE LOCALIZED FLOODING AS
MENTIONED ABOVE. IF WE WERE TO BREAK OUT AND GET A COUPLE OF HRS
OF SUNSHINE AT THE SFC...WOULD BECOME VERY CONCERNED ABOUT THE
WIND THREAT AS WELL...BUT FOR NOW STRATUS LOOKS TO HOLD IN ACRS
THE REGION FOR THE REMAINDER OF THE DAY.

TONIGHT THRU WEDNESDAY NIGHT...00Z MODEL GUIDANCE INDICATES THAT
THE COLD FRONT WILL MOVE SOUTH THROUGH THE ENTIRE FORECAST AREA
TONIGHT...EFFECTIVELY TAKING THE BEST TSTM CHANCES WITH IT.
ELEVATED INSTABILITY REMAINS OVER THE SOUTHERN HALF OF NORTH TX
DURING THE PERIOD...SO CANNOT RULE OUT REDEVELOPING TSTM ACTIVITY
ASSOCIATED WITH ANY WEAK SHORTWAVE TROUGH EMBEDDED IN THE
WEST/SOUTHWEST FLOW ALOFT. THIS FRONT LOOKS TO LIFT NORTH
WEDNESDAY NIGHT AS ANOTHER STRONG UPPER LVL SYSTEM MOVES INTO THE
SOUTHWESTERN CONUS BRINGING FAIRLY STRONG LEE SIDE CYCLOGENESIS
OVER THE HIGH PLAINS. THIS WILL LIKELY CAUSE A NEAR REPEAT OF
CONDITIONS THAT OCCURRED EARLY THIS MORNING ACROSS NORTH TX...WITH
INCREASING TEMPERATURES DURING THE OVERNIGHT HRS AND THE ONSET OF
LOW STRATUS AND FOG.

THURSDAY THRU FRIDAY...MODELS HAVE BEEN SOMEWHAT INCONSISTENT WITH
THE EXACT TIMING OF THE NEXT COLD FRONT TO AFFECT NORTH TX. GFS
STILL OFFERS A RELATIVELY FAST SOLUTION...BRINGING THE COLD FRONT
THRU MUCH OF THE CWA THURSDAY NIGHT. THE NAM AND ECMWF OFFER A
SLOWER SOLUTION WITH THE FRONT COMING THRU FRIDAY MORNING INSTEAD.
SLOWED THE FRONT DOWN A LITTLE BIT FROM PREVIOUS FORECAST...BUT NO
SIGNIFICANT CHANGES MADE AT THIS TIME. WITH GOOD UPPER LVL SUPPORT
ASSOCIATED WITH THIS FRONT...EXPECT A NEARLY SOLID LINE OF
CONVECTION TO ACCOMPANY THE FRONTAL BOUNDARY AS IT MOVES THRU THE
AREA. ONCE AGAIN PWATS ARE UP AROUND 2 INCHES...AND HEAVY RAINFALL
IS LIKELY WITH THE PASSAGE OF THE FRONT AND THE UPPER LVL SUPPORT.
SUFFICIENT ELEVATED INSTABILITY AND SHEAR EXIST TO SUPPORT
ORGANIZED STORMS ALONG THE FRONT AS WELL. IN TERMS OF FLOODING
POTENTIAL...HEAVY RAINFALL WHICH COULD LEAD TO WIDESPREAD FLOODING
LOOKS TO REMAIN NORTH OF NORTH TX WHERE THE BEST UPPER LVL
DYNAMICS LOOK TO SET UP. THINK THAT POTENTIAL IS THERE FOR
LOCALIZED FLOODING ON THURSDAY NIGHT/FRIDAY...BUT THE SET UP FOR A
MORE WIDESPREAD FLOODING EVENT LOOKS TO HOLD NORTH OF US FOR NOW.
EXACT FLOODING POTENTIAL IS DIFFICULT TO DETERMINE AT THIS
TIME...BUT SOMETHING TO THINK ABOUT AS THIS NEXT SYSTEM
APPROACHES.

THIS WEEKEND...THE COLD FRONT CONTINUES TO BE FORECAST TO MOVE
WELL SOUTH OF NORTH TX FOR THIS WEEKEND...SO HAVE KEPT A DRY AND
SOMEWHAT COOL FORECAST GOING. DO NOT SEE ANY MAJOR SYSTEMS THAT
COULD CAUSE A CHANGE IN THIS THINKING AT THIS TIME...SO CONFIDENCE
IN A DRY FORECAST FOR SATURDAY AFTERNOON THRU SUNDAY IS
INCREASING.

CAVANAUGH

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  79  61  74  70  86 /  80  30  30  20  40
WACO, TX              85  68  79  72  89 /  80  60  30  20  20
PARIS, TX             78  58  73  64  85 /  80  30  20  20  40
DENTON, TX            77  59  74  70  86 /  80  30  30  30  40
MCKINNEY, TX          78  59  74  66  85 /  80  30  20  20  40
DALLAS, TX            80  65  74  72  86 /  80  30  30  20  40
TERRELL, TX           82  63  76  69  86 /  70  40  30  20  30
CORSICANA, TX         85  66  79  72  89 /  80  60  30  20  20
TEMPLE, TX            87  70  79  73  89 /  60  70  30  20  20

&&

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

&&

58/21

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE FORT WORTH TX
1110 AM CDT TUE OCT 6 2009

TXZ092-103-061645-
COOKE TX-DENTON TX-
1110 AM CDT TUE OCT 6 2009

...SIGNIFICANT WEATHER ADVISORY FOR...
  SOUTHEASTERN COOKE COUNTY
  NORTH CENTRAL DENTON COUNTY

AT 1110 AM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
STRONG THUNDERSTORM 5 MILES NORTH OF SANGER...MOVING NORTHEAST AT 35
MPH.

CITIES IN THE PATH OF THIS STORM INCLUDE PILOT POINT...SANGER...RAY
ROBERTS PARK ISLE DU BOIS AND RAY ROBERTS PARK JOHNSON BRANCH.

PEA-SIZED HAIL AND WIND GUSTS TO 40 MPH CAN BE EXPECTED FROM THIS
STORM.

A SEVERE THUNDERSTORM WATCH REMAINS IN EFFECT UNTIL NOON CDT TUESDAY
FOR NORTH CENTRAL TEXAS.

LAT...LON 3343 9694 3342 9688 3330 9723 3348 9733
      3364 9694
TIME...MOT...LOC 1610Z 246DEG 30KT 3343 9718

85/NH

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