Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX

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000
FXUS64 KFWD 011128 AAA
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
628 AM CDT MON SEP 1 2014

.AVIATION...
/12Z TAFS/

CONCERNS...MVFR CIGS THIS MORNING.

MVFR STRATUS SURGED NORTH OVERNIGHT BUT IS NOW LOCATED MAINLY EAST
OF THE TAF AIRPORTS. KDAL AND KACT MAY SEE PERIODS OF BKN CIGS
THROUGH 14-15Z BUT THE REMAINING TAF SITES WILL LIKELY REMAIN
IN VFR CATEGORY. WILL TEMPO FOR BKN020 AT KDAL AND KACT FROM
12-14Z. HOWEVER...A BRIEF PERIOD OF BKN MVFR CIGS CANNOT BE RULED
OUT AT KDFW...KAFW...KFTW...AND KGKY.

EXPECT SOUTH TO SOUTH-SOUTHEAST WINDS BETWEEN 13-18 KTS FOR MOST
OF THE PERIOD WITH GUSTS UP TO 25 KTS POSSIBLE. WIND SPEEDS WILL
DIMINISH TO AROUND 10 KTS TUESDAY MORNING.

82/JLD

&&

.PREV DISCUSSION... /ISSUED 337 AM CDT MON SEP 1 2014/

08Z/3AM REGIONAL RADARS AND SURFACE OBSERVATIONS SHOWED A COLD
FRONT/CONSOLIDATED OUTFLOW BOUNDARY LOCATED NEAR THE KANSAS AND
OKLAHOMA BORDER...SINKING SLOWLY SOUTH PRIMARILY DUE TO ONGOING
THUNDERSTORM ACTIVITY ACROSS SOUTHEASTERN KANSAS. 00Z UPPER AIR
ANALYSIS SHOWED WEAK UPPER LEVEL RIDGING EXTENDING FROM FAR WEST
TEXAS EASTWARD OVER THE SOUTHEASTERN CONUS AT THE 500 MB LEVEL.
MID-LEVEL ANALYSIS SHOWED WINDS OUT OF THE SOUTH-SOUTHWEST WHILE
LOW-LEVEL WINDS WERE DIRECTED OUT OF THE SOUTH TO SOUTH-SOUTHEAST
ALONG THE TX GULF COAST. EARLY MORNING WATER VAPOR SATELLITE
IMAGERY SHOWED A SHORTWAVE TROUGH OVER THE CENTRAL PLAINS MOVING
TO THE EAST-NORTHEAST TO THE NORTH OF THE RIDGE IN PLACE OVER THE
SOUTH PLAINS. TO THE SOUTH OF OUR UPPER RIDGE...A PLUME OF
MOISTURE AND LOOSELY ORGANIZED THUNDERSTORM ACTIVITY WAS OBSERVED
ALONG THE BELIZE/MEXICO BORDER ON THE YUCATAN PENINSULA. THIS
ACTIVITY IS ASSOCIATED WITH WHAT THE NATIONAL HURRICANE CENTER IS
CALLING DISTURBANCE 1...WHICH THEY INDICATE HAS A HIGH CHANCE OF
DEVELOPING INTO A TROPICAL DEPRESSION WITHIN THE NEXT 48 HOURS.

TODAY...WITH UPPER LEVEL RIDGING IN PLACE...EXPECT DRY CONDITIONS
TO HOLD AS WEAK LARGE SCALE FORCING FOR SUBSIDENCE WILL CONTINUE
TO PROVIDE A CAP OVER THE REGION FOR THUNDERSTORMS. THE 00Z FWD
RAOB OBSERVED AN 850 MB DEW POINT OF 15 DEG C...WHILE SURFACE
OBSERVATIONS SHOWED DEW POINTS IN THE UPPER 60S TO LOW 70S FOR
MOST LOCATIONS. WHILE THIS IS INDICATIVE OF GOOD TROPICAL MOISTURE
IN PLACE IN THE LOWER ATMOSPHERE OVER THE REGION...THE SUBSIDENCE
ASSOCIATED WITH THE TROUGH...COMBINED WITH DRY MID-LEVEL
TRAJECTORIES OUT OF THE SOUTH-SOUTHWEST ARE EXPECTED TO CONTINUE
TO MAINTAIN THE FAIRLY STRONG CAP IN PLACE OVER THE CWA TODAY. AS
A RESULT...EXPECT TODAY TO BE A NEAR CARBON COPY OF YESTERDAY WITH
HIGHS IN THE MID TO UPPER 90S UNDER MOSTLY SUNNY SKIES.

TUESDAY...MODELS CONTINUE TO INDICATE THAT TROPICAL DISTURBANCE 1
WILL DEEPEN AS IT MOVES OVER THE FAR SOUTHWESTERN GULF OF MEXICO
AND BAY OF CAMPECHE OVER THE NEXT 24 TO 48 HOURS. MOST DYNAMICAL
MODELS TAKE THIS TROPICAL SYSTEM NORTHWEST AND MOVE IT BACK OVER
LAND OVER NORTHERN MEXICO BY TUESDAY AFTERNOON...SO THIS SYSTEM IS
VERY UNLIKELY TO IMPACT NORTH OR CENTRAL TEXAS DIRECTLY OVER THE
NEXT SEVERAL DAYS. HOWEVER...ASSUMING THIS SYSTEM DOES BECOME AT
LEAST WEAKLY ORGANIZED...MOST MODELS INDICATE THAT THIS WILL BE
SUFFICIENT TO ALTER THE MID-LEVEL WIND FIELD TO CHANGE THE
TRAJECTORIES OVER THE REGION FROM DRY/SOUTH-SOUTHWESTERLY TO MOIST
/SOUTH-SOUTHEASTERLY.

THE CONSENSUS OF GUIDANCE FAVORS THIS CHANGE IN MID-LEVEL WINDS BY
LATE TUESDAY MORNING...AND MOST MODELS SEND A SLUG OF DEEPER
TROPICAL MOISTURE NORTHWEST FROM THE GULF COAST UP OVER THE
SOUTHEASTERN CWA BY TUESDAY AFTERNOON. THIS RESULTS IN
PRECIPITABLE WATER VALUES INCREASING BY ABOUT A QUARTER INCH
ACROSS THE CWA ON TUESDAY. WHILE DEEPER MOISTURE CERTAINLY SEEMS
TO IMPROVE OUR PRECIPITATION CHANCES...THE MAIN INGREDIENT MISSING
FOR WIDESPREAD PRECIPITATION OR STORMS IS LIFT. DESPITE THE SURGE
OF DEEPER MOISTURE ON TUESDAY...THERE IS NO OBVIOUS FORCING
MECHANISM THAT WILL PROVIDE LIFT OVER THE AREA TUESDAY AFTERNOON.

AS A RESULT...MAINTAINED 20 POPS OVER LOCATIONS GENERALLY ALONG
AND SOUTHEAST OF A LINE FROM SULPHUR SPRINGS TO KILLEEN TUESDAY
AFTERNOON AND EVENING. IF SOME FORM OF LIFT BECOMES OBVIOUS IN
LATER FORECASTS... POPS MAY HAVE TO BE BUMPED UP AND EXPANDED IN
COVERAGE AS IT WOULD NOT TAKE MUCH TO GET STORMS TO DEVELOP WITH
DEEP TROPICAL MOISTURE IN PLACE. WENT AHEAD AND LOWERED HIGHS BY A
COUPLE OF DEGREES ON TUESDAY FROM MONDAY...SIMPLY WITH THE
EXPECTATION THAT WE WILL HAVE MORE AFTERNOON CLOUDS TO SLOW DOWN
THE HEATING A BIT.

WEDNESDAY THROUGH FRIDAY...MOST MODEL GUIDANCE CONTINUES TO TRACK
THE TROPICAL DISTURBANCE NORTHWEST OVER NORTHERN MEXICO THROUGH
THIS PERIOD. BY WEDNESDAY...THE BEST FETCH OF TROPICAL MOISTURE IS
EXPECTED TO MOVE WEST OF THE CWA WITH THE NORTHWESTWARD MOVING
TROPICAL DISTURBANCE. AS A RESULT...LEFT WEDNESDAY AFTERNOON DRY
FOR NOW DESPITE THE INCREASE IN TROPICAL MOISTURE OVER THE REGION
ON TUESDAY. THE MAIN REASON FOR THIS IS THE PERSISTENCE OF THE
RIDGE ALOFT IN MODEL GUIDANCE. IN THE ABSENCE OF LIFT...SUBSIDENCE
ASSOCIATED WITH THE RIDGE ALOFT WILL SLOWLY WORK AWAY AT THE
TROPICAL MOISTURE FROM THE TOP DOWN...FAVORING A DRY FORECAST FOR
MID TO LATE IN THE WEEK.

A LOT OF THIS FORECAST DEPENDS ON WHAT HAPPENS WITH THIS TROPICAL
SYSTEM OVER THE NEXT COUPLE OF DAYS...AND THEN WHAT HAPPENS WITH
THUNDERSTORM ACTIVITY ON TUESDAY. A STRONGER TROPICAL SYSTEM...OR
A DIFFERENT PATH...WILL CHANGE HOW MUCH TROPICAL MOISTURE WE HOLD
ON TO THROUGH THE END OF THE WEEK. ALSO...IF WE GET PERSISTENT
THUNDERSTORM ACTIVITY ON TUESDAY...THIS MAY LEAVE BOUNDARIES OR A
MID-LEVEL VORTEX BEHIND THAT LEADS TO SOME LOCALIZED LIFT FOR
LATER IN THE WEEK. HOWEVER FOR NOW THE CONSENSUS OF GUIDANCE IS
FOR A DRY FORECAST...SO MAINTAINED THAT IN OUR FORECAST AT THIS
TIME. HIGHS WILL CONTINUE TO TOP OUT IN THE MID TO UPPER 90S EACH
DAY.

SATURDAY AND SUNDAY...MODELS GENERALLY MAINTAIN THE WEAK UPPER
LEVEL RIDGE OVER THE REGION...SO IN A LARGE SCALE SENSE THERE
SHOULD NOT BE MUCH OF A CHANGE IN THE FORECAST FROM LATE THIS WEEK
TO THE WEEKEND. HOWEVER...MODELS CONTINUE TO HINT AT A COLD FRONT
SINKING SOUTH INTO THE REGION THIS WEEKEND...RESULTING IN COOLER
TEMPERATURES AND SCATTERED STORMS EACH DAY. THE MODELS THAT BRING
A FRONT ACROSS NORTH TEXAS DO NOT DO SO WITH STRONG UPPER LEVEL
SUPPORT. THIS IS ALWAYS CAUSE FOR CONCERN THAT THE MODELS MAY BE
OVERDOING THE STRENGTH OF COLD AIR TO OUR NORTH...THEREBY SENDING
THE FRONT MUCH FARTHER SOUTH THAN IT WILL ACTUALLY TRAVEL.
HOWEVER...THERE IS REASON FOR OPTIMISM THAT THE MODELS ARE ON TO
SOMETHING HERE WITH REGARDS TO THE COLD FRONT MAKING IT SOUTH OF
THE RED RIVER.

THE MAIN REASON FOR OPTIMISM IS THAT THE MODELS SINK THE COLD
FRONT SOUTH OF THE RED RIVER AFTER 48 HOURS OF CONVECTION ALONG
THE FRONT ACROSS KANSAS AND OKLAHOMA. THIS IS ESSENTIALLY WHAT IS
HAPPENING ALONG THE KS/OK BORDER EARLY THIS MORNING. IF STORMS
REALLY ARE ACTIVE ALONG THE FRONT FOR A COUPLE OF DAYS...
CONSOLIDATED OUTFLOW CAN HELP PUSH THE FRONT FARTHER SOUTH THAN IT
WOULD TRAVEL UNDER THE INFLUENCE OF UPPER LEVEL DYNAMICS ALONE.
BECAUSE THE MODELS THAT BRING THE FRONT INTO THE AREA DO SO WITH
WIDESPREAD THUNDERSTORMS...WENT AHEAD AND KEPT BROAD BRUSHED 20
POPS OVER THE CWA FOR THE WEEKEND...WITH HIGHS HOLDING AROUND 90
DEGREES FOR MOST LOCATIONS BY SUNDAY AFTERNOON. OF COURSE IF MCS
ACTIVITY REALLY IS THE MECHANISM THAT SENDS THE FRONT SOUTH THIS
WEEKEND...WE WILL NOT KNOW IF IT`S LIKELY TO HAPPEN UNTIL THURSDAY
OR SO WHEN WE CAN WATCH FOR PERSISTENT THUNDERSTORM ACTIVITY TO
OUR NORTH.

CAVANAUGH

&&



.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  96  77  96  77  96 /   5   5  10  10   5
WACO, TX              97  76  96  76  96 /   5   5  10  10   5
PARIS, TX             92  74  91  73  92 /   5   5  10  10   5
DENTON, TX            96  76  95  76  96 /   5   5  10  10   5
MCKINNEY, TX          94  76  94  75  94 /   5   5  10  10   5
DALLAS, TX            96  77  96  77  96 /   5   5  10  10   5
TERRELL, TX           95  76  96  75  95 /   5   5  10  10   5
CORSICANA, TX         96  76  95  74  95 /   5   5  20  20   5
TEMPLE, TX            97  75  96  75  96 /   5   5  20  20  10
MINERAL WELLS, TX     98  74  96  75  96 /   5   5  10  10   5

&&

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

&&

$$

82/69




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