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

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FXUS64 KFWD 221841
AFDFWD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
141 PM CDT TUE JUL 22 2014

.AVIATION...

FOR THE 18Z TAFS...VFR CONDITIONS ARE EXPECTED THROUGH THE VALID
FORECAST PERIOD.

THE PRIMARY AVIATION WEATHER CONCERNS OVER THE NEXT 24 TO 30 HRS
ARE WIND DIRECTION AT AREA AIRPORTS...AND THEN A SMALL CHANCE OF
THUNDERSTORMS TOWARDS THE END OF THE DFW TAF.

WITH REGARDS TO THE WIND DIRECTION...THE 12Z UPPER AIR ANALYSIS
IDENTIFIED AN ANTICYCLONE AT THE 850 MB LEVEL CENTERED ROUGHLY
OVER CHILDRESS...TX. THIS CAUSED 850 MB WINDS TO SWITCH FROM THE
SOUTH TO THE EAST-NORTHEAST OVER THE PAST 12 TO 18 HRS. THE
SURFACE PRESSURE GRADIENT HAS BECOME EXTREMELY WEAK TO NEARLY NON-
EXISTENT ACROSS NORTH TEXAS...ALLOWING THE WIND DIRECTION/SPEEDS
FROM ALOFT TO LARGELY DETERMINE THE VECTOR OF THE SURFACE WINDS.

AS A RESULT...SURFACE WINDS THAT WERE EXPECTED TO REMAIN
SOUTHEASTERLY HAVE MORE OR LESS MIRRORED THE 850 MB WINDS EARLY
THIS AFTERNOON. WINDS ARE EXPECTED TO REMAIN LIGHT...AROUND 5 MPH
OR LESS THROUGH THIS EVENING...BUT PROBABLY WILL HOLD ON TO A EAST
OR NORTHEASTERLY COMPONENT. WINDS WILL PROBABLY BECOME SOUTHERLY
AGAIN AFTER MIDNIGHT TONIGHT AS THE NOCTURNAL INVERSION
STRENGTHENS...LIMITING THE ABILITY FOR WIND DIRECTION ALOFT TO
STRONGLY INFLUENCE THE SURFACE WINDS. THE SURFACE PRESSURE
GRADIENT SLIGHTLY FAVORS A SOUTHEAST WIND...SO WENT AHEAD WITH
THAT AFTER MIDNIGHT. VERY LIGHT WINDS WILL LIKELY CONTINUE
THROUGHOUT THE DAY TOMORROW AS WELL.

WITH REGARDS TO THUNDERSTORM CHANCES LATE WEDNESDAY
AFTERNOON...FORECAST SOUNDINGS SHOW THAT AIR PARCELS WILL BECOME
CONVECTIVELY UNSTABLE BY 6 PM TOMORROW AFTERNOON. THERE WILL BE
SOME LIFT MOVING INTO THE AREA...BUT FROM THE NORTHEAST AND
PROBABLY AFTER SUNSET. LEFT THUNDERSTORMS OUT OF THE END OF THE
DFW TAF FOR NOW BECAUSE LIFT IS EXPECTED TO COME IN AFTER THE PEAK
HEATING HOURS OF THE DAY...REDUCING CONFIDENCE IN STORMS IMPACTING
AIRPORTS LATE TOMORROW AFTERNOON. ANY STORMS THAT DEVELOP WILL
LIKELY MOVE INTO THE AREA FROM THE NORTH OR NORTHEAST TO THE SOUTH
OR SOUTHWEST. THIS IS A VERY NON-TRADITIONAL STORM MOTION FOR THIS
AREA...AND IS SOMETHING THAT INTERESTED PARTIES SHOULD BE AWARE OF
FOR FLIGHT PLANNING AND RADAR MONITOR PURPOSES TOMORROW AFTERNOON
AND EVENING.


&&

.UPDATE...
WARM AND MUGGY CONDITIONS THIS MORNING WILL LEAD TO ANOTHER
UNCOMFORTABLE AFTERNOON ACROSS NORTH TEXAS. THOUGH CONDITIONS WILL
REMAIN RATHER HUMID THIS AFTERNOON...THE LOW AND MID 70S DEWPOINTS
CURRENTLY IN PLACE SHOULD AT LEAST FALL INTO THE UPPER 60S THIS
AFTERNOON...KEEPING HEAT INDICES IN THE 100-105 DEGREE RANGE AND
JUST BELOW HEAT ADVISORY CRITERIA. OTHERWISE...AN ISOLATED STORM
OR TWO WILL BE POSSIBLE OVER THE SOUTHEASTERN COUNTIES LATER THIS
AFTERNOON. NO CHANGES TO THE FORECAST ARE ANTICIPATED AT THIS
TIME.

30

&&

.PREV DISCUSSION... /ISSUED 349 AM CDT TUE JUL 22 2014/
WATER VAPOR SHOWS THE WELL ADVERTISED UPPER LEVEL ANTICYCLONE
GAINING STRENGTH OVER EASTERN NEW MEXICO...BUT ALSO OF INTEREST IS
A DEVELOPING TUTT LOW CENTERED OVER MOBILE. 850MB ANALYSIS
DEPICTS WHAT COULD BE ARGUED AS A COLD FRONT THAT IS DRAPED ALONG
THE LOUISIANA COASTLINE TO NEAR MOBILE. LATEST SATELLITE ACTUALLY
CONFIRMS THE PRESENCE OF A LOW LEVEL CONVERGENCE BOUNDARY
INDICATED BY A BAND OF CLOUDS WHICH BEGINS ACROSS THE PALESTINE
AREA AND EXTENDS SOUTHEAST TO THE GULF COAST WHERE VIGOROUS
CONVECTION HAS DEVELOPED OVERNIGHT. SINCE THIS WEAK BOUNDARY
SHOULD HANG ACROSS THE SOUTHEAST COUNTIES TODAY...WILL MAINTAIN A
MENTION OF ISOLATED CONVECTION THERE THIS AFTERNOON AND EVENING.
ACROSS THE REMAINDER OF NORTH TEXAS...STRONG SUBSIDENCE FROM THE
INTENSIFYING UPPER LEVEL HIGH TO OUR NORTHWEST AND LIMITED DEEP
LAYER MOISTURE WILL ENSURE A DRY AND HOT FORECAST.

MODEL GUIDANCE KEEPS LOW LEVEL THICKNESS VALUES NEARLY STEADY
THROUGH THE NEXT 2 TO 3 DAYS...SO EXPECT HIGHS TO STAY FAIRLY
CLOSE TO YESTERDAY/S READINGS WITH JUST A SLOW DAILY WARMING
TREND. ALSO DEWPOINTS SHOULD MIX OUT A FEW MORE DEGREES THIS
AFTERNOON...SO THE HEAT INDEX SHOULD BE A BIT LOWER THAN MONDAY.

ON WEDNESDAY A SHORTWAVE TROUGH WILL DROP DOWN THE EASTERN FRINGE
OF THE UPPER HIGH AND THROUGH THE OZARKS. THERE IS GOOD MODEL
AGREEMENT THAT THIS WILL SET OFF CONVECTION WEDNESDAY AFTERNOON
ACROSS ARKANSAS AND EASTERN OKLAHOMA. WITH 30KT NORTHEASTERLY FLOW
AT 500MB...THIS ACTIVITY WILL MAKE A RUN AT THE CWA WEDNESDAY
EVENING. MOST MODEL GUIDANCE NOW INDICATES SOME QPF OVER THE
NORTHEAST HALF OF THE CWA WEDNESDAY EVENING...AND THEREFORE WILL
MAINTAIN THE FORECAST OF 30 PERCENT POPS IN THE NORTHEAST ZONES
TAPERING DOWN TO 20 PERCENT OR LESS FARTHER TO THE SOUTHWEST.

ON THURSDAY THE AFOREMENTIONED TUTT LOW WILL MOVE WEST AND INTO
SOUTH TEXAS...PROVIDING SOME WEAK LIFT FOR AN ENHANCEMENT OF
ISOLATED DIURNAL CONVECTION. MOISTURE WILL BE BEST FOR AREAS EAST
OF I-35 AND THIS IS WHERE 20 POPS WILL BE ADVERTISED. LOW LEVEL
MOISTURE WILL BE A LITTLE HIGHER THURSDAY WHICH WILL INCREASE THE
CHANCE THAT HEAT INDEX VALUES WILL REACH 105 FOR MORE LOCATIONS.

THE UPPER LEVEL HIGH WILL BEGIN TO SHIFT SLIGHTLY EASTWARD BY
FRIDAY AND SUBSIDENCE INCREASES OVER THE REGION...RESULTING IN
FURTHER WARMING OF LOW LEVEL THICKNESS VALUES. HIGHS SHOULD BE
AROUND 100 DEGREES FOR MOST OF NORTH TEXAS FRIDAY INTO SUNDAY.
DEWPOINTS WILL LIKELY REMAIN HIGH ENOUGH TO PUT HEAT INDEX VALUES
IN THE 103 TO 108 DEGREE RANGE DURING THE AFTERNOON. A HEAT
ADVISORY WILL PROBABLY BE REQUIRED FOR SOME PORTION OF THE CWA BY
THIS TIME.

THE UPPER LEVEL HIGH WILL BACK OFF TO THE WEST BY MONDAY AS A
TROUGH DEEPENS OVER THE EASTERN US. THIS WILL ALLOW FOR A WEAK
COLD FRONT TO MOVE INTO THE REGION EARLY NEXT WEEK. TEMPERATURES
SHOULD COOL SLIGHTLY...AND THE FRONT MAY RESULT IN A SLIGHT CHANCE
OF RAIN MONDAY. WITH NORTHWEST FLOW ALOFT DEVELOPING BY TUESDAY OR
WEDNESDAY OF NEXT WEEK...IT IS POSSIBLE THAT OUR RAIN CHANCES MAY
INCREASE A BIT MORE IN 8 OR 9 DAYS...BUT NO PROMISES AT THIS TIME.

TR.92



&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  76  99  78  99  78 /   0   5  20  10  10
WACO, TX              72  98  72  99  74 /   5   5  10  10  10
PARIS, TX             70  96  73  97  73 /   5  20  30  20  10
DENTON, TX            72  97  72  99  73 /   0   5  20  10  10
MCKINNEY, TX          71  97  73  99  75 /   0  10  30  20  10
DALLAS, TX            77  98  79  99  79 /   0   5  20  10  10
TERRELL, TX           73  98  74  99  76 /   5  10  20  20  10
CORSICANA, TX         72  97  74  98  75 /   5  10  20  20  10
TEMPLE, TX            72  98  71  99  73 /   5   5  10  10  10
MINERAL WELLS, TX     72 100  72 100  73 /   0   5  10  10  10

&&

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

&&

$$

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