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

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FXUS64 KFWD 220241 AAB
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
941 PM CDT MON JUL 21 2014

.UPDATE...
THE PREVIOUS FORECAST IS IN GOOD SHAPE. HAVE JUST MADE SOME
CHANGES TO THE HOURLY GRIDS FOR ON-GOING TRENDS.

58

&&

.AVIATION...
/ISSUED 704 PM CDT MON JUL 21 2014/
/00Z TAFS/

CONCERNS...STRATUS POTENTIAL.

AS THE SUN SETS...THE AFTERNOON CU FIELD WILL GIVE WAY TO CLEAR
SKIES...WHICH SHOULD PREVAIL MUCH OF THE NIGHT. FEW OR SCATTERED
CLOUDS MAY DEVELOP NEAR THE TOP OF THE NOCTURNAL BOUNDARY LAYER
(1000-2000FT AGL) NEAR SUNRISE TUESDAY...LINGERING THROUGH MID-
MORNING...BUT MVFR CEILINGS LOOK UNLIKELY.

SYNOPTIC-SCALE MOS GUIDANCE WAS CONFOUNDED BY DEW POINTS IN
THE MID-70S DURING JULY...BUT THE 00Z NAM SUNDAY EVENING DID KEY
ON THE LIKELIHOOD FOR LOW CEILINGS MONDAY MORNING. DESPITE
CONSIDERABLE MOISTURE REMAINING IN PLACE...THE CURRENT MOS OUTPUT
IS VFR FOR TUESDAY MORNING. THE LATEST RAP PERFECT PROGS SUGGEST
THE BEST POTENTIAL FOR A THIN LAYER OF TROPICAL STRATUS WOULD BE
EAST OF THE I-35 CORRIDOR. IT IS IMPORTANT TO NOTE THAT THIS
POTENTIAL STRATUS SCENARIO DEPENDS ON THE ABILITY OF THE LAYER TO
DEVELOP IN THE VICINITY OF OUR TAF SITES...NOT ON THE ADVECTION OF
UPSTREAM STRATUS. SURFACE RIDGING OVER THE GULF SHOULD VEER THE
LOW-LEVEL WINDS UPSTREAM...EFFECTIVELY CLOSING OFF THE GULF FROM
ADDITIONAL MOIST ADVECTION OVERNIGHT. BUT OUR BOUNDARY LAYER
MOISTURE IS ALREADY IN PLACE AND...WITH NEGLIGIBLE ADVECTION...IS
LIKELY TO REMAIN UNCHANGED BY DAYBREAK TUESDAY. WILL CONTINUE TO
MONITOR MESOSCALE OUTPUT THIS EVENING...BUT DO NOT ANTICIPATE
NEEDING TO INTRODUCE CEILINGS WITH THE 03Z AMENDMENTS OR 06Z
ROUTINE TAFS.

25


&&



.PREV DISCUSSION... /ISSUED 311 PM CDT MON JUL 21 2014/
SUMMER HEAT HAS QUICKLY RETURNED TO NORTH TEXAS TODAY WITH HOT AND
HUMID CONDITIONS AREA-WIDE. TEMPERATURES IN THE 90S COMBINED WITH
DEWPOINTS IN THE LOWER TO MIDDLE 70S HAVE CREATED HEAT INDICES IN
THE 100-105 RANGE IN MANY LOCATIONS THIS AFTERNOON. ABOVE-NORMAL
TEMPERATURES CAN BE EXPECTED FOR THE REST OF THE WEEK DUE MAINLY
TO THE STRENGTHENING OF A MID AND UPPER LEVEL RIDGE OVER MUCH OF
THE REGION. THE RIDGE AXIS IS CENTERED OVER COLORADO AND NEW
MEXICO BUT STRETCHES EASTWARD ACROSS THE SOUTHERN PLAINS AND NORTH
TEXAS...WITH LITTLE OVERALL CHANGE IN POSITION EXPECTED THIS WEEK.

EAST OF THE RIDGE...A WEAK UPPER LOW CAN BE SEEN ON SATELLITE
GENERATING CONVECTION OVER THE SOUTHEASTERN STATES. THIS LOW WILL
SLOWLY MOVE WEST OVER THE NEXT COUPLE OF DAYS. NORTH TEXAS WILL
RESIDE IN BETWEEN THE RIDGE TO THE WEST AND THE LOW TO THE
EAST...WHICH WILL GENERATE NORTHEAST FLOW ALOFT THROUGH THURSDAY.
A SUBTLE SHORTWAVE IS STILL PROGGED TO ROTATE SOUTHWEST ACROSS THE
ARKLATEX REGION WEDNESDAY NIGHT....BRINGING WITH IT ENOUGH
MOISTURE AND LIFT TO PRODUCE SCATTERED CONVECTION OVER NORTHEAST
PORTIONS OF NORTH TEXAS. THE BEST CHANCES FOR SHOWERS AND STORMS
WILL OCCUR NEAR PARIS...WHERE WE WILL GO AHEAD AND INCLUDE CHANCE
POPS WEDNESDAY NIGHT. SLIGHT CHANCE POPS WILL BE INCLUDED IN
AREAS SOUTHWEST OF LAMAR COUNTY INCLUDING DALLAS/FORT WORTH AND
SURROUNDING LOCALES. THERE IS A CHANCE THAT THUNDERSTORMS WILL
BECOME SOMEWHAT ORGANIZED AS THEY APPROACH FROM THE NORTHEAST LATE
WEDNESDAY...PERHAPS FORMING INTO A SOUTHWEST MOVING MCS. IF THIS
BEGINS TO APPEAR MORE LIKELY IN FUTURE MODEL DATA...HIGHER POPS MAY
BE NEEDED FOR THE NORTHEASTERN THIRD OF THE REGION.

THE NORTHEAST FLOW REGIME WILL ALLOW A WEAK FRONT TO SAG SOUTH
ACROSS THE RED RIVER...BECOMING STATIONARY NORTH OF I-20 ON
THURSDAY. THIS BOUNDARY COULD PROVIDE FOCUS FOR ISOLATED STORMS...
AND WE WILL CONTINUE WITH 20 POPS OVER THE EASTERN HALF OF THE
REGION THURSDAY. WESTERN COUNTIES WILL MOST LIKELY BE TOO HEAVILY
IMPACTED BY SUBSIDENCE FROM THE CO/NM RIDGE FOR THE INCLUSION OF
POPS.

THE HIGH PRESSURE RIDGE WILL EXPAND LONGITUDINALLY LATE THIS WEEK
THROUGH THE WEEKEND...REACHING AS FAR EAST AS THE TENNESSEE VALLEY
FRIDAY. HOT AND RAIN-FREE WEATHER IS EXPECTED AS A RESULT ACROSS A
LARGE PORTION OF TEXAS. THE MAIN WEATHER CONCERN WILL BE THE
DAYTIME TEMPERATURES THIS WEEKEND...WITH CURRENT APPARENT
TEMPERATURE GRIDS PRODUCING HEAT INDICES IN EXCESS OF 105 DURING
THE AFTERNOON HOURS FRIDAY AND SATURDAY. WE WILL MONITOR OUR
FORECAST TEMPERATURE/DEWPOINT TRENDS AS THE WEEKEND APPROACHES...AND
MAY HAVE TO CONSIDER A HEAT ADVISORY IF IT APPEARS THAT THESE
CONDITIONS WILL BECOME FAIRLY WIDESPREAD.

THERE MAY BE SOME RELIEF IN SIGHT EARLY NEXT WEEK...AS MID RANGE
MODELS CONTINUE TO INDICATE A DEEPENING UPPER TROUGH OVER THE
EASTERN HALF OF THE NATION WHILE THE UPPER RIDGE RETROGRADES WEST.
THIS MAY BRING SOME COOLER WEATHER ALONG WITH INCREASED RAIN
CHANCES AS WE MOVE THROUGH NEXT WEEK.

30



&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  77  98  78  99  78 /   0   5   5  10  20
WACO, TX              74  98  74  99  73 /   5   5   5   5  10
PARIS, TX             70  95  72  96  75 /   0   5   5  20  30
DENTON, TX            73  97  74  98  75 /   0   5   5  10  20
MCKINNEY, TX          72  98  73  99  74 /   0   5   5  10  20
DALLAS, TX            78  98  79  99  78 /   0   5   5  10  20
TERRELL, TX           75  98  75  99  75 /   0   5   5  10  20
CORSICANA, TX         75  97  75  98  75 /   5   5   5  10  20
TEMPLE, TX            74  98  73  99  73 /   5   5   5   5  10
MINERAL WELLS, TX     72  99  73 100  73 /   0   5   5   5  20

&&

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

&&

$$

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