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000
FXUS64 KFWD 260435 AAC
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1135 PM CDT SAT MAY 25 2013

.AVIATION...
ISOLATED SHOWERS THAT WERE ABOUT 50 MILES SOUTH OF KGKY
/ARLINGTON/ AT 0430Z...WILL CONTINUE TO MOVE NORTH. HAVE PLACED
6SM SHRA IN THE METROPLEX TAFS FOR THE 06-08Z PERIOD...AND MAY
HAVE TO ADD VCTS OR TSRA IF THE SHOWERS BECOME THUNDERSTORMS.
OTHERWISE... EXPECT SOME MVFR STRATUS TO SPREAD NORTH INTO THE
WACO AREA AROUND 09Z...AND INTO THE METROPLEX AROUND 11Z. THE LOW
CLOUDS WILL SCATTER OUT AFTER 16Z SUNDAY. SOUTH WINDS AROUND 10
KNOTS WILL INCREASE TO AROUND 15 KNOTS BY 16Z SUNDAY AND SOME
GUSTS OVER 20 KNOTS ARE LIKELY SUNDAY AFTERNOON. SOME LOW CLOUDS
ARE EXPECTED TO BRING MVFR CIGS UP INTO WACO AND THE METROPLEX
OVERNIGHT SUNDAY NIGHT /07Z AND 09Z MONDAY RESPECTIVELY/.

58

&&

.UPDATE...
00Z FWD RAOB SHOWS THAT WE ARE ALREADY CAPPED AT THE SURFACE FOR
ADDITIONAL CONVECTION. LATEST AREA RADARS SHOW LITTLE ACTIVITY
WHICH IS LIKELY DUE TO THE CAPPING INVERSION. LOWERED THE 50 POPS
ACROSS THE SE TO 30 FOR THE REST OF THE NIGHT. LATEST HIGH-RES
GUIDANCE ALSO KEEPS THINGS RELATIVELY DRY FOR THE NIGHT...WITH
ONLY ISOLATED TO SCATTERED ACTIVITY FORECASTED.

WE DO ALSO HAVE TO WATCH CONVECTION WHICH IS DEVELOPING IN EASTERN
NEW MEXICO AS IT PROGRESSES EAST LATE THIS EVENING AND OVERNIGHT.
LATEST HRRR BRINGS THE WEAKENING STORMS NEAR OUR WESTERN ZONES
AFTER MIDNIGHT BEFORE DYING OFF. WILL KEEP THE 20 POPS ACROSS THE
WEST TO ACCOUNT FOR THIS POTENTIAL.

HAMPSHIRE

&&

.PREV DISCUSSION... /ISSUED 414 PM CDT SAT MAY 25 2013/

THROUGH TONIGHT...LEFT THE EARLY AFTERNOON UPDATE FORECAST
DISCUSSION ATTACHED BELOW FOR REFERENCE AND MORE DETAILS ON THE
SHORT TERM FORECAST CONCERNS.

CHANGES FROM EARLIER DISCUSSION...THE MCV THAT WAS EXPECTED TO
DEVELOP NEAR SAN ANTONIO WAS APPARENT IN REGIONAL RADAR RETURNS
NEAR AUSTIN AND GONZALEZ AT THE TIME OF THIS DISCUSSION. ASSUMING
THAT THIS IS THE PRIMARY MID-LEVEL LOW/MCV PRODUCED BY THE
PERSISTENT SAN ANTONIO AREA CONVECTION THIS MORNING...ADJUSTED
RAIN CHANCES THIS EVENING AND OVERNIGHT IN LINE WITH ITS EXPECTED
TRAJECTORY. THE 19Z RUN OF THE RAP SEEMS TO HAVE A GOOD HANDLE ON
THE POSITION OF THIS MCV...SO GENERALLY USED THIS MODEL FOR
GUIDANCE OVER THE NEXT 12 TO 18 HRS.

THE MCV IS EXPECTED TO MOVE GENERALLY IN A NORTHEASTERLY DIRECTION
THROUGH TONIGHT...TAKING IT FROM ITS CURRENT LOCATION TO JUST
NORTHEAST OF TYLER BY SUNRISE SUNDAY. THE GFS INDICATES THAT THE
UPPER TROUGH THAT WAS ANALYZED IN THE 12Z RAOB ANALYSIS TO THE
WEST OF THE CWA WILL INTERACT WITH THIS MCV FAVORABLY AND RESULT
IN WIDESPREAD THUNDERSTORM ACTIVITY GENERALLY EAST OF I-35 AND
SOUTH OF I-20 AFTER MIDNIGHT...SPREADING NORTHEAST INTO THE
ARKLATEX AREA JUST AFTER SUNRISE. BOTH OF THESE FEATURES
EXIST...SO THIS SOLUTION IS VIABLE...HOWEVER THE FORCING FOR
ASCENT ADVERTISED BY THE GFS IS GREATLY ENHANCED BY CONVECTIVE
FEEDBACK. THAT IS...MODEL GENERATED STORMS COOL OFF LOCATIONS
DOWNSTREAM /NORTHEAST/ ALLOWING WARM AIR ADVECTION TO ARTIFICIALLY
RAMP UP RESULTING IN THE GENERATION OF MORE STORMS. IN SHORT...A
MODEL GENERATED FEEDBACK LOOP. THIS LOOP MAY VERIFY AND RESULT IN
A HEAVY RAINFALL EVENT EAST OF I-35 TO THE ARKLATEX AREA TONIGHT
THROUGH SUNDAY MORNING. HOWEVER THERE IS NOT REALLY ANY HIGH
RESOLUTION MODEL OUTPUT SUPPORT FOR THIS SOLUTION AT THIS
TIME...THEREFORE CONFIDENCE IS SOMEWHAT LOW IN A WIDESPREAD HEAVY
RAIN EVENT.

THAT SAID...MANY FACTORS ARE IN PLACE TO SUPPORT A LOCALIZED HEAVY
RAINFALL EVENT ANYWHERE STORMS EXIST OVER THE NEXT 12 TO 18 HRS.
PRECIPITABLE WATER VALUES ARE ABOVE THE 75TH PERCENTILE OF
HISTORICAL PRECIPITABLE WATER VALUES FOR THIS REGION IN LATE MAY.
MID-LEVEL LAPSE RATES ARE POOR BUT THE ENVIRONMENT IS
UNCAPPED...IN SHORT A FAVORABLE ENVIRONMENT FOR VERY TALL RAIN
SHOWERS WITH LITTLE LIGHTNING ACTIVITY AND ONLY WEAK GENERATION OF
OUTFLOW BOUNDARIES. WEAK OUTFLOW MEANS THAT STORMS CAN REMAIN IN
ONE PLACE FOR A LONGER PERIOD OF TIME INCREASING THE CHANCES FOR
TRAINING OF STORMS AND A LOCALIZED FLOODING THREAT. AT THIS TIME
WENT WITH A MENTION OF LOCALIZED HEAVY RAIN AND FLOODING IN THE
HAZARDOUS WEATHER OUTLOOK AND WORDED FORECAST.

WITH WEAK WIND SHEAR IN THIS THERMODYNAMIC ENVIRONMENT STORMS ARE
EXPECTED TO BEHAVE IN A NEARLY TROPICAL NATURE WITH EFFICIENT
RAINFALL PRODUCTION. THEREFORE CHANCES OF SEVERE WEATHER APPEAR TO
BE VERY SMALL TONIGHT. WE WILL HAVE TO KEEP A CLOSE EYE ON THE
EVOLUTION OF A LOCALIZED FLOODING EVENT...ESPECIALLY WITH MANY
PEOPLE LIKELY CAMPING OUTDOORS IN FLOOD PRONE AREAS THROUGH
TONIGHT.

SUNDAY...SUNDAY MORNING WE WILL LIKELY HAVE SOME REMNANT POCKETS
OF HEAVY RAIN ALONG A SULPHUR SPRINGS TO PALESTINE LINE...LIKELY
MOVING NORTHEAST TOWARDS THE ARKLATEX REGION THROUGHOUT THE
MORNING HOURS. FROM THE WEST...THE HRRR HAS CONSISTENTLY INDICATED
THAT A SQUALL LINE WILL ORGANIZE OVER THE SOUTHERN HIGH PLAINS/TX
PANHANDLE TONIGHT AND MOVE EAST TOWARDS OUR WESTERN CWA EARLY
SUNDAY MORNING. WE WILL HAVE TO KEEP AN EYE ON THIS...NOT SO MUCH
FROM A SEVERE WEATHER STAND POINT BUT FROM ANOTHER POTENTIAL
SOURCE FOR MCV PRODUCTION. WITH THE SAN ANTONIO AREA MCV AND
LARGER UPPER TROUGH MOVING EAST...SUBSIDENCE WILL LIKELY DOMINATE
ANY MCV MOVING OFF THE HIGH PLAINS AND THRU NORTH TX TOMORROW.
HOWEVER UNTIL WE GET SOME DRIER AIR IN OVER THE REGION CAPPING OFF
THE ATMOSPHERE FOR THUNDERSTORM DEVELOPMENT...WILL HOLD ON TO A
BROAD BRUSHED MENTION OF SHOWERS AND THUNDERSTORMS IN THE FORECAST
ACROSS ALL OF NORTH TX THROUGH SUNDAY.

NEXT WEEK...BEGINNING MONDAY A WESTERN CONUS TROUGH IS EXPECTED TO
ORGANIZE SENDING THE WEAK UPPER LEVEL RIDGE AND ENTRAPPED MCV
FEATURES OFF TO THE EAST OF THE REGION. THIS IS EXPECTED TO RESULT
IN SOUTHWEST FLOW ALOFT OVER NORTH TX ON MONDAY WHICH SHOULD HELP
TO ADVECT A RELATIVELY STOUT CAP IN PLACE OVER THE REGION BY
MONDAY AFTERNOON. THIS CAP IS EXPECTED TO HOLD IN PLACE THROUGH
THE WEEK UNLESS THE DRYLINE OR A STRONG SHORTWAVE TROUGH CAN LIFT
THE CAP AND RESULT IN THUNDERSTORM INITIATION DURING THE WEEK
AHEAD.

WE ARE EXPECTED TO HAVE RELATIVELY PERSISTENT...BREEZY SOUTH
WINDS IN PLACE BELOW THE CAP THROUGH THE WEEK. THIS WILL HELP KEEP
GOOD GULF MOISTURE IN PLACE UNDER THE CAP PROVIDING PLENTY OF
POSITIVE CAPE FOR THUNDERSTORM DEVELOPMENT IF ANYTHING CAN REMOVE
THE CAP. WITHOUT STORMS...WE WILL LIKELY SEE HIGHS HOLD IN THE
UPPER 80S WITH LOWS IN THE LOWER TO MID 70S EACH DAY. THE GFS AND
ECMWF BOTH INDICATE THAT A STRONG SHORTWAVE TROUGH WILL MOVE OVER
THE SOUTH PLAINS WEDNESDAY THROUGH WEDNESDAY EVENING. THE ECMWF
REMAINS FURTHER SOUTH WITH THIS TROUGH WHICH IS WHAT WE WILL NEED
TO LIFT THE CAP AND RESULT IN STORMS ACROSS THE CWA WEDNESDAY
AFTERNOON AND EVENING. THE GFS INDICATES THE BEST FORCING STAYS
NORTH OF THE CWA. WENT AHEAD WITH 20 TO 30 POPS WEST OF INTERSTATE
35...CLOSEST TO THE UPPER TROUGH WEDNESDAY AFTERNOON THROUGH
WEDNESDAY NIGHT AS RESULT. REMOVED POPS THEREAFTER WITH ALL
GUIDANCE INDICATING SUBSIDENCE BEHIND THIS UPPER TROUGH ON
THURSDAY.

CAVANAUGH




&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  69  84  67  86  69 /  30  20  10   0   0
WACO, TX              68  86  67  88  69 /  30  20  10   0   0
PARIS, TX             69  82  65  84  67 /  30  30  10   0   0
DENTON, TX            66  83  66  85  68 /  30  20  10   0   0
MCKINNEY, TX          68  82  66  86  68 /  30  20  10   0   0
DALLAS, TX            71  83  70  88  72 /  30  20  10   0   0
TERRELL, TX           70  82  67  87  69 /  30  30  10   0   0
CORSICANA, TX         69  83  68  88  69 /  30  20  10   0   0
TEMPLE, TX            68  85  67  87  69 /  30  20  10   0   0
MINERAL WELLS, TX     67  86  66  87  68 /  20  20  10   0   5

&&

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

&&

$$

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