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

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FXUS64 KFWD 040504 AAC
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1204 AM CDT SAT JUL 4 2015

.AVIATION...
SEVERAL OF THE HIGH RESOLUTION COMPUTER MODELS...GENERATE SHOWERS
AND THUNDERSTORMS NEAR AND NORTH OF THE I-20 CORRIDOR OVERNIGHT
TONIGHT. CONFIDENCE IN THEIR SOLUTIONS IS NOT HIGH GIVEN BUT
GIVEN AN ADVANCING SHORTWAVE...IT IS POSSIBLE. THUS HAVE
ADDED VCSH IN THE METROPLEX TAF SITES FOR THE 08-15Z PERIOD...
BUT HAVE NOT MENTIONED THUNDERSTORMS. WE WILL MONITOR FOR POSSIBLE
DEVELOPMENT AND UPDATE AS NEEDED.

OTHERWISE...EXPECT MOSTLY VFR CONDITIONS IN THE METROPLEX
THROUGH THE FORECAST PERIOD. SOME STRATUS SHOULD SPREAD NORTH
FROM SOUTH TEXAS INTO THE WACO AREA BEFORE DAYBREAK...THUS
HAVE PLACED BKN015 IN THE WACO TAF FOR THE 10-16Z PERIOD.

SOUTHERLY WINDS AROUND 10 KNOTS WILL PREVAIL FOR THE 36 HOURS.


58

&&

.UPDATE...
LATE AFTERNOON CONVECTION HAS DIMINISHED CONSIDERABLY OVER NORTH
TEXAS OVER THE LAST HOUR AS WEAK BOUNDARY APPEARS TO HAVE BECOME
QUITE A BIT MORE DIFFUSE. THERE ALSO APPEARS TO BE AT LEAST SOME
WEAK SUBSIDENCE IN PLACE AS ANY ACTIVITY THAT DOES TRY TO DEVELOP
QUICKLY DIMINISHES. IN THE IMMEDIATE SHORT TERM...HAVE LOWERED
POPS TO 20-30 PERCENT THROUGH THE REMAINDER OF THE EVENING BUT
WILL CONTINUE TO MONITOR UPSTREAM ACTIVITY. THERE IS ANOTHER
SHORTWAVE MOVING THROUGH THE CENTRAL PLAINS THAT WILL PROVIDE
ASCENT OVERNIGHT TO OUR NORTH. ANY SHOWER AND THUNDERSTORM
ACTIVITY THAT CAN GET ORGANIZED TO OUR NORTH MAY PUSH INTO NORTH
TEXAS LATER TONIGHT. OTHER THAN SOME MINOR ADJUSTMENTS TO POPS
THROUGH THE NEXT 6 HOURS...NO MAJOR CHANGES MADE AT THIS TIME.

DUNN

&&

.PREV DISCUSSION... /ISSUED 320 PM CDT FRI JUL 3 2015/

FROM THE EARLY AFTERNOON FORECAST DISCUSSION...THE PRIMARY SHORT
TERM FORECAST CONCERN CONTINUES TO CENTER ON THE CHANCES FOR NEW
THUNDERSTORMS DEVELOPING ALONG A WEAK FRONTAL BOUNDARY LOCATED
JUST SOUTH OF THE RED RIVER. 2 PM SURFACE OBSERVATIONS INDICATED
THAT THE WEAK FRONT WAS IN PLACE ROUGHLY ALONG A BOWIE TO MCKINNEY
TO EMORY LINE. THE FRONT HAS REORIENTED ITSELF FROM EAST TO WEST
EARLIER THIS MORNING TO NORTHWEST TO SOUTHEAST THIS AFTERNOON.
WATER VAPOR SATELLITE IMAGERY CONTINUES TO TRACK ONE WEAK
SHORTWAVE MOVING AWAY FROM THE SOUTHERN PLAINS...WITH A SECOND...
SLIGHTLY STRONGER...SHORTWAVE TROUGH MOVING SOUTH-SOUTHEAST OVER
WESTERN NEBRASKA.

THROUGH THIS EVENING...NEITHER OF THESE TROUGHS IS IN A POSITION
TO SPREAD LIFT ACROSS NORTH TEXAS...SO THINK THAT THE WEAK FRONTAL
BOUNDARY WILL CONTINUE TO BE THE SOURCE OF ANY NEW RAIN SHOWER OR
THUNDERSTORM DEVELOPMENT. THINK THAT THE COVERAGE OF STORMS NEAR
THIS BOUNDARY WILL REMAIN SCATTERED IN NATURE...SO DO NOT THINK
ANY EVENING INDEPENDENCE DAY RELATED FESTIVITIES WILL BE A
COMPLETE WASH OUT. DELAYS WILL BE POSSIBLE...AND MOST LIKELY NEAR
THE FRONTAL BOUNDARY. AT THIS TIME THE FRONTAL BOUNDARY HAS NOT
REALLY MADE ANY PROGRESS DUE SOUTH TOWARDS DOWNTOWN DALLAS OR FORT
WORTH...SO RAIN CHANCES THIS EVENING WERE HELD IN THE 20 TO 30
PERCENT RANGE. KEPT POPS IN THE 50 TO 60 PERCENT RANGE CLOSE TO
THE FRONTAL BOUNDARY.

ANY STORMS THAT DEVELOP THROUGH THIS EVENING WILL BE CAPABLE OF
PRODUCING CLOUD TO GROUND LIGHTNING STRIKES...LOCALLY HEAVY
RAINFALL...AND LOCALLY STRONG WIND GUSTS. WHILE SEVERE WEATHER IS
NOT EXPECTED FOR MOST STORMS...IT IS DIFFICULT TO RULE OUT A
DAMAGING MICROBURST FROM A FEW STORMS THROUGH THIS EVENING.
LOCALLY CALCULATED PARAMETERS INDICATE THAT CAPE IS ON THE ORDER
OF 1500 TO 2000 J/KG...WITH DEEP LAYER SHEAR OF 15 TO 20 KTS.
REGIONAL MORNING RAOB ANALYSIS INDICATED THAT MID-LEVEL LAPSE
RATES WERE SOMEWHAT MEAGER...AND THE KFWS RAOB HAD A PRECIPITABLE
WATER OF 1.90 INCHES. THESE PARAMETERS SUPPORT PRIMARILY A SINGLE
TO MULTI-CELL STORM MODE CAPABLE OF PRODUCING THE THREATS
MENTIONED ABOVE. WIDESPREAD SEVERE WEATHER IS NOT A THREAT AT
THIS TIME. FLOODING IS EXPECTED TO REMAIN LOCALIZED...BUT COULD
BECOME A LARGER SCALE THREAT IF THE COVERAGE OF STORMS IS GREATER
THAN ANTICIPATED. THE WEAK FORCING ALONG THE FRONT SUGGESTS THAT
THE COVERAGE WILL REMAIN SCATTERED TO ISOLATED IN
NATURE...LIMITING THE POTENTIAL FOR WIDESPREAD HEAVY RAIN AND
FLOODING.

OVERNIGHT INTO TOMORROW MORNING...THE WESTERN NEBRASKA SHORTWAVE
TROUGH IS EXPECTED TO CONTINUE TO MOVE SOUTH-SOUTHEAST OVERNIGHT
BEFORE SWINGING EAST TOMORROW MORNING. THIS TROUGH WILL SPREAD
SOME DECENT LIFT ACROSS THE SOUTHERN PLAINS TONIGHT...AND WILL
HELP INCREASE DEEP LAYER SHEAR A BIT AS WELL. AS A RESULT...THINK
THAT THE 12Z NAM SOLUTION FOR THUNDERSTORM CHANCES HAS A GOOD
CHANCE OF VERIFYING. THIS SOLUTION INDICATES THAT A MULTI-CELLULAR
CLUSTER WILL DEVELOP ACROSS EASTERN OKLAHOMA AFTER MIDNIGHT
TONIGHT AND MOVE DUE SOUTH TOWARDS NORTH TEXAS.

OUR LOW-LEVEL WINDS ARE EXPECTED TO VEER STRONGLY OUT AHEAD OF
THIS CLUSTER...AND PICK UP IN INTENSITY TO 20 TO 25 KTS. WHILE
THIS IS NOT A SUPER STRONG LOW-LEVEL JET BY ANY MEANS...THE CHANGE
IN DIRECTION AND SPEED IN THE LOWER TROPOSPHERE DOES PROMOTE A
SITUATION WHERE THE PROPAGATION OF NEW STORM DEVELOPMENT WILL BE
JUST AS STRONG IF NOT A BIT STRONGER THAN THE MEAN LAYER OR
ADVECTIVE WINDS. AS A RESULT...THE MULTICELL CLUSTER IS EXPECTED
TO SINK ALMOST DUE SOUTH...WHILE SLOWLY BUILDING OR GENERATING NEW
UPDRAFTS ON THE WESTERN FLANK OF THESE STORMS DRAGGING THE CLUSTER
SOUTH-SOUTHWEST OVER OUR NORTHEASTERN CWA AFTER 09Z. HAVE 60
PERCENT POPS FOR AREAS ALONG AND NORTHEAST OF A GAINESVILLE TO
EMORY LINE LATE TONIGHT THROUGH TOMORROW MORNING TO ACCOUNT FOR
THIS ANTICIPATED STORM MOTION.

THINK THAT THE BACKBUILDING COMPONENT OF THE MULTICELL CLUSTER
WILL WEAKEN AFTER A FEW HOURS OF HEATING HELPS TO MIX OUT THE
HIGHER MOMENTUM AIR WITHIN THE LOW-LEVEL JET. WITH THE SHORTWAVE
TROUGH THEN MOVING EAST OF THE REGION...THE COMBINATION OF
SUBSIDENCE BEHIND THE TROUGH...AND THE LOW-LEVEL JET WEAKENING
SHOULD CAUSE THE ENTIRE COMPLEX OF STORMS TO DISSIPATE JUST
EAST/NORTHEAST OF DALLAS BY 15Z/10AM.

FOR TOMORROW AFTERNOON AND EVENING...WITHOUT ANY OBVIOUS UPSTREAM
SHORTWAVE TROUGH...THUNDERSTORM CHANCES ARE EXPECTED TO REMAIN
TIED TO WHATEVER CONVECTIVE OUTFLOW BOUNDARY REMAINS IN TACT. LEFT
POPS IN THE NORTHEASTERN CWA AS THE OVERNIGHT MULTI-CELL CLUSTER
OF STORMS IS EXPECTED TO DISSIPATE THERE...TO THE NORTHEAST OF THE
DFW AREA TOMORROW MORNING. IF THE CLUSTER DOES NOT PAN OUT AS
EXPECTED...POPS MAY BE ABLE TO BE REMOVED FROM THE FORECAST
TOMORROW. IF THE CLUSTER MOVES FARTHER SOUTHWEST THAN
EXPECTED...WILL PROBABLY NEED TO ADD AT LEAST A SMALL CHANCE OF
POPS TO WHEREVER THE OUTFLOW BOUNDARY GOES TOMORROW. MOST OF THE
OPERATIONAL MODEL GUIDANCE FAVORS A SOLUTION THAT IS SIMILAR TO
THE NAM...SO THINK THAT MOST OF THE AREA WILL REMAIN DRY FOR
EVENING INDEPENDENCE DAY FESTIVITIES TOMORROW.

SUNDAY AND MONDAY...UPPER LEVEL SHORTWAVE RIDGING IS EXPECTED TO
BUILD EAST OVER THE CWA...SO KEPT MOST AREAS DRY WITH HIGHS IN
THE LOWER TO MID 90S AT THIS TIME. ANY OUTFLOW BOUNDARIES THAT
REMAIN IN PLACE OR MOVE INTO THE CWA FROM THE NORTH OR WEST MAY
BECOME A FOCUS FOR STORMS. AT THIS TIME ONLY LEFT SOME LOW POPS IN
THE FORECAST FOR LOCATIONS ALONG AND NORTHEAST OF A SHERMAN TO
EMORY LINE ON SUNDAY AS THIS IS THE MOST LIKELY AREA WHERE A WEAK
OUTFLOW BOUNDARY MAY REMAIN IN PLACE.

TUESDAY AND WEDNESDAY...MEDIUM RANGE GUIDANCE IS FAIRLY CONSISTENT
IN INDICATING THAT A STRONG SHORTWAVE TROUGH OVER THE CANADIAN
PACIFIC COAST WILL MOVE SOUTHEAST OVER THE NORTHERN PLAINS MONDAY
THROUGH MONDAY NIGHT. THIS WILL SEND A COLD FRONT SOUTH ACROSS THE
CENTRAL AND SOUTHERN PLAINS MONDAY NIGHT INTO TUESDAY. MODELS ARE
FAIRLY AGGRESSIVE WITH CONVECTION ALONG THIS FRONT AS IT MOVES
SOUTHEAST TOWARDS NORTH TEXAS. HOWEVER...THIS FRONT WILL BE
GETTING FARTHER AND FARTHER AWAY FROM UPPER LEVEL SUPPORT ON
TUESDAY...SO IT MAY STALL OUT BEFORE IT EVER REACHES THE CWA.

THINK THAT THE AGGRESSIVE CONVECTION IN MODEL GUIDANCE IS HELPING
THE FRONT TO MOVE SOUTHEAST INTO NORTH TEXAS FOR TUESDAY AND
WEDNESDAY. THIS STALLED OUT FRONTAL BOUNDARY ACROSS THE AREA
EXPLAINS WHY MOST GUIDANCE IS ADVERTISING 40 TO 60 POPS ACROSS A
LARGE PORTION OF NORTH TEXAS. KEPT SOME PRECIPITATION CHANCES IN
THE FORECAST DURING THIS PERIOD...BUT UNDERCUT GUIDANCE BECAUSE
CONFIDENCE IN THE FRONT MAKING IT ALL THE WAY INTO THE CWA IS LOW
AT THIS TIME. IT IS FAIRLY UNCOMMON FOR A SYNOPTIC COLD FRONT TO
MAKE IT ALL THE WAY INTO NORTH TEXAS IN JULY...SO WILL HEDGE
TOWARDS LOWER RAIN CHANCES AT THIS TIME. IF THE FRONT IS LINED UP
WITH STORMS AS IT MOVES SOUTH...IT DOES HAVE A CHANCE TO MAKE IT
INTO THE CWA AS ADVERTISED. WOULD LIKE TO SEE A SOLID LINE OF
STORMS ON THAT FRONT BEFORE BRINGING IT INTO NORTH TEXAS HOWEVER.
IF IT GETS HERE...WILL DEFINITELY NEED TO INCREASE PRECIPITATION
CHANCES DURING THE PERIOD.

THURSDAY THROUGH NEXT WEEKEND...MOST MODEL GUIDANCE SUGGESTS THAT
UPPER LEVEL RIDGING WILL BUILD OVER NORTH TEXAS. IF WE HAVE 4-5
DAYS OF UPPER LEVEL RIDGING FROM THE END OF NEXT WEEK THROUGH NEXT
WEEKEND...WE MAY START FLIRTING WITH 100 DEGREE HIGHS ACROSS
PORTIONS OF NORTH AND CENTRAL TEXAS. KEPT HIGHS IN THE UPPER 90S
FOR NOW...BUT THIS IS A LARGE SCALE PATTERN THAT TYPICALLY
INCREASES THE HEAT THIS TIME OF YEAR.

CAVANAUGH



&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  76  95  76  92  77 /  30  20  10   5   5
WACO, TX              74  93  74  91  75 /  10  20  10   5   5
PARIS, TX             72  88  73  88  74 /  60  40  20  30  10
DENTON, TX            73  95  74  91  75 /  30  20  10  10   5
MCKINNEY, TX          74  89  75  90  75 /  40  30  20  10   5
DALLAS, TX            77  95  77  93  77 /  30  20  10   5   5
TERRELL, TX           74  89  74  89  74 /  30  30  20  10   5
CORSICANA, TX         74  91  75  91  75 /  20  20  10   5   5
TEMPLE, TX            73  93  73  91  74 /  10  20  10  10   5
MINERAL WELLS, TX     73  93  73  92  74 /  20  10  10   5   5

&&

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

&&

$$

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