Severe Thunderstorm Warning 139, NWS Fort Worth, TX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
334 PM CDT THU APR 28 2016

...POTENTIALLY SIGNIFICANT SEVERE WEATHER POSSIBLE FRIDAY...

.DISCUSSION...
IT HAS BEEN A NICE DAY ACROSS NORTH AND CENTRAL TEXAS BUT CHANGES
ARE ON THE WAY AS A VERY MOIST AND UNSTABLE AIR MASS HEADS BACK
INTO THE REGION TONIGHT IN THE WAKE OF A WARM FRONT MOVING UP FROM
THE SOUTH. THIS WILL SET THE STAGE FOR AN ACTIVE DAY TOMORROW WITH
A NOTEWORTHY SEVERE WEATHER POTENTIAL THAT COULD END UP BEING
SIGNIFICANT IF MESOSCALE FEATURES EVOLVE AS DISCUSSED BELOW.

SATELLITE AND SURFACE OBSERVATIONS DEPICT THE RICH MOISTURE WITH
DEWPOINTS IN THE LOW TO MID 70S IN SOUTH AND SOUTHEAST TEXAS THAT
WILL ENTER THE SOUTHERN ZONES THIS EVENING. WARM FRONTS ARE NOT
SURPRISINGLY ASSOCIATED WITH WARM ADVECTION...AND WARM ADVECTION
IS OFTEN SYNONYMOUS WITH LIFTING OR RISING AIR. AS THIS WARM AND
MOIST AIR ENTERS THE CWA...IT WILL BE UNDERCUTTING A COLDER
AIRMASS ALOFT WHICH WILL YIELD HIGH AMOUNTS OF INSTABILITY THAT
WILL BE UNCAPPED. THE WARM ADVECTION ITSELF WILL BE PROVIDING THE
LIFT FOR SCATTERED STORMS TO BLOSSOM. THESE STORMS SHOULD BE
SLIGHTLY ELEVATED ABOVE THE BOUNDARY LAYER WHICH SHOULD LIMIT THE
WIND OR TORNADO POTENTIAL DESPITE WELL ORGANIZED AND IMPRESSIVE
SHEAR PROFILES. HOWEVER THESE STORMS WILL STILL BE CAPABLE OF
LARGE HAIL...PERHAPS UP TO THE SIZE OF GOLFBALLS FOR THE STRONGEST
CELLS. THE ISOLATED TO SCATTERED ACTIVITY IS EXPECTED TO DEVELOP
IN THE SOUTHERN ZONES AROUND MID EVENING...WITH STORMS MOVING
NORTHWARD AND INCREASING IN COVERAGE AND INTENSITY BY THE TIME
THEY REACH THE I-20 CORRIDOR AROUND MIDNIGHT. HIGHEST POPS OF
60-70 PERCENT WILL BE LOCATED OVER THE NORTHERN HALF OF THE
REGION...WITH POPS JUST 30 PERCENT IN THE SOUTHERN ZONES.

WHILE MODEL GUIDANCE IS SOMEWHAT SPLIT ON WHETHER THE OVERNIGHT
ACTIVITY WILL CONTINUE TO REDEVELOP/PERSIST OVER THE CWA LATE
TONIGHT AND INTO FRIDAY MORNING...AM SIDING WITH THE RAP/HRRR/TTU
WRF FORECASTS WHICH KICK THE WARM FRONT AND STORMS NORTH OF THE
RED RIVER BY DAY BREAK. THIS IS BECAUSE THE SOUTHERLY WINDS IN
THE LOW-MID LEVELS SHOULD ALSO PULL SOME WARMER AIR IN FROM SOUTH
TEXAS WHICH SHOULD EFFECTIVELY CAP THE CWA FOR ADDITIONAL
CONVECTION WELL SOUTH OF THE WARM FRONT BY DAYBREAK FRIDAY. THIS
CAP IS NOT FORECAST TO BE VERY STRONG BY ANY OF THE MODELS...AND
AS TEMPS REACH THE UPPER 70S TO LOWER 80S BY MIDDAY FRIDAY IT
SHOULD BREAK.

WHILE A DRY LINE WILL BE APPROACHING FROM THE WEST AND REACHES OUR
WESTERN CWA BORDER FRIDAY AFTERNOON...IT IS MORE LIKELY THAT
CONVECTION WILL SPONTANEOUSLY DEVELOP WELL EAST OF THE DRY LINE IN
AN AXIS OF WARM ADVECTION AND MOISTURE CONVERGENCE ALONG THE I-35
CORRIDOR AROUND OR JUST AFTER MIDDAY. THIS IS ADVERTISED BY
SEVERAL OF THE HIGH-RES MODELS...AND ALL OF THE GLOBAL MODELS ARE
DROPPING THE HIGHEST QPF AND UPWARD MOTIONS EAST OF I-35 BETWEEN
18Z-00Z. THUS THERE IS HIGH CONFIDENCE THAT STORMS WILL NOT NEED
THE DRY LINE OR PEAK DAY TIME HEATING TO DEVELOP. IN SHORT THIS
EVENT DOES NOT LOOK LIKE IT IS GOING TO BE THE TYPICAL DRYLINE DAY
WHERE WE WAIT UNTIL LATE AFTERNOON FOR STORMS TO FIRE OUT WEST.

INSTEAD THE INITIATION OVER THE I-35 CORRIDOR COULD LEAD TO
NUMEROUS STORMS IF THE CAP IS TOO WEAK AND PERHAPS A MESSY
CONVECTIVE EVOLUTION THAT DOES NOT LET ANY ONE STORM HAVE ALL OF
THE INSTABILITY TO THEMSELVES. THIS WOULD LOWER THE OVERALL SEVERE
WEATHER POTENTIAL. HOWEVER IF CONVECTION IS NOT AS NUMEROUS THERE
IS A GREATER POTENTIAL FOR SIGNIFICANT SEVERE WEATHER OCCURRING
GIVEN SURFACE BASED CAPE VALUES INCREASING TO 2500 TO 3500 J/KG
BY EARLY AFTERNOON. THIS INSTABILITY WILL ALSO BE OCCURRING IN THE
PRESENCE OF WELL ORGANIZED SHEAR PROFILES...MORE THAN ENOUGH TO
SUPPORT SUPERCELLS AND ENOUGH LOW LEVEL SHEAR TO BE CONCERNED
ABOUT TORNADOES...ESPECIALLY GIVEN THE UNUSUALLY HIGH LOW LEVEL
INSTABILITY COMPLEMENTS OF LOWER 70S DEWPOINTS. FURTHERMORE IF
ACTIVITY DOES DEVELOP ALONG THE I-35 CORRIDOR BY MIDDAY AS
EXPECTED...IT IS LIKELY TO TRAIN OVER THE SAME REGION WITH JUST A
GRADUAL EASTWARD SHIFT. THIS COULD LEAD TO EXCESSIVE MULTI-INCH
RAINFALL IN LOCALIZED AREAS. SINCE THIS FLOODING POTENTIAL IS
HIGHLY DEPENDENT ON MESOSCALE FEATURES DEVELOPING IN THE RIGHT
PLACE AND TIME...WE THOUGHT IT WOULD BE BEST TO LET LATER SHIFTS
MAKE THE CALL WHETHER TO INCLUDE PART OF THE AREA IN A WATCH.

BELIEVE THAT FRIDAY/S THUNDERSTORM ACTIVITY SHOULD SLOWLY SHIFT
EASTWARD DURING THE AFTERNOON HOURS...AND LIKELY INTO EAST TEXAS
BY MIDNIGHT. MOST MODELS SUGGEST THAT THE EFFECTIVE COLD FRONT
WILL SET UP EAST OF THE CWA ON SATURDAY WHICH MEANS ANY ADDITIONAL
CONVECTION SATURDAY AFTERNOON WOULD DEVELOP EAST OF THE REGION.
HAVE RETAINED LOW POPS OVER THE EASTERN ZONES IN CASE THE
FRONT/DRY LINE SETS UP A LITTLE FARTHER WEST THAN EXPECTED.
BEHIND THE FRONT/DRY LINE OVER MOST OF THE AREA IT SHOULD BE
MOSTLY SUNNY AND DRY WITH HIGH TEMPERATURES WARMING INTO THE MID
TO UPPER 80S. A STRONGER PUSH OF COOLER AIR WILL ARRIVE SATURDAY
NIGHT...SO THIS WILL ASSUREDLY RESULT IN A SUNNY AND NICE DAY
SUNDAY WITH TEMPS COOLING INTO THE MID 70S TO LOWER 80S FOR HIGHS.

RAIN CHANCES RETURN ON MONDAY AS ANOTHER SHORTWAVE TROUGH MOVES
ACROSS THE REGION. THE FORCING WITH THIS SYSTEM WILL BE STRONG BUT
WILL OCCUR ON THE COLD SIDE OF THE FRONTAL BOUNDARY WHICH MEANS NO
SEVERE WEATHER IS EXPECTED. WILL SHOW A CHANCE OF RAIN AND
SEASONABLY COOL TEMPS MONDAY WITH HIGHS IN THE MID 60S WEST TO MID
70S EAST.

FOR MID TO LATE NEXT WEEK...UPPER LEVEL RIDGING WILL PREVAIL AND
IT LOOKS LIKE WE WILL STRING A FEW DRY AND PLEASANT DAYS TOGETHER.
HIGHS WILL BE NEAR 80 WITH LOWS IN THE 50S.

TR.92

&&

.AVIATION...
/ISSUED 118 PM CDT THU APR 28 2016/
/18Z TAFS/

VFR WITH SE WINDS 10-15 KTS WILL PREVAIL THROUGH 03Z. CHALLENGES
ARRIVE AFTERWARD WITH REGARD TO TIMING CIGS/CONVECTION THROUGH
12Z. WAA AND LARGE SCALE ASCENT ASSOCIATED WITH A SURFACE WARM
FRONT AND LEAD SOUTHERN ROCKIES SHORTWAVE ALOFT WILL INCREASE
DURING THE OVERNIGHT HOURS. ISOLATED-SCATTERED STRONG-SEVERE TSRA
WILL BE POSSIBLE FOR A TIME WINDOW BETWEEN 03Z-09Z...WHEN THE
WARM FRONT LIFTS RAPIDLY NORTH IN RESPONSE TO A 30-40 KT LLJ. WITH
CONVECTIVE ACTIVITY BEING FAIRLY DISCRETE...WE WILL ONLY INTRODUCE
VCTS IN THE FCST AT ALL NORTH TX AIRPORTS DURING THIS 6-HR WINDOW.
BEST WAA AND POTENTIAL FOR STORMS WILL SHIFT INTO OK/AR BY 12Z AND
AFTER.

WE DO LOOK FOR A RELATIVELY QUIET PERIOD 12Z-18Z FRIDAY...AS A
SHORTWAVE EXITS THE AREA AND SUBSIDENCE TAKES HOLD. IN ADDITION...
WAA WILL WEAKEN SOMEWHAT. HOWEVER...IFR/MVFR CIGS WILL PREVAIL AND
LIMIT ARRIVALS TO AREA AIRPORTS WITH SE WINDS 15-20 KTS AND GUSTY
PREVAILING.

THE MAIN SHORTWAVE TROUGH WILL BEGIN LIFTING OUT OF THE SOUTHERN
ROCKIES IN THE 18Z FRIDAY-00Z SATURDAY TIME FRAME... WITH A DRYLINE
MOVING CLOSE TO...OR INTO WESTERN NORTH TX. MORE NUMEROUS SHRA AND
TSRA WILL DEVELOP AND RACE NORTHEAST WITH THE MEAN FLOW FRIDAY
AFTERNOON...SOME SEVERE WITH LARGE HAIL...DAMAGING WINDS...AND A
FEW TORNADOES POSSIBLE. THE BULK OF THIS ACTIVITY WILL MOVE EAST
OF THE AIRPORTS BY NIGHTFALL FRIDAY EVENING. HAVE ADDED A 24-30 HR
PERIOD BEGINNING AT 20Z FRIDAY TO INTRODUCE VCTS AND CONVECTIVE
POTENTIAL INCREASING ACROSS NORTH TX FOR DFW AIRPORT.

05/

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH    70  81  64  86  58 /  60  80  50  10   5
WACO                71  82  64  87  58 /  40  80  50  10  10
PARIS               64  78  65  83  57 /  70  90  80  30  10
DENTON              66  79  59  86  54 /  60  80  50  10   5
MCKINNEY            67  79  61  84  55 /  70  80  60  10  10
DALLAS              70  81  65  86  59 /  60  80  60  10  10
TERRELL             69  81  66  85  58 /  70  80  70  20  10
CORSICANA           71  83  66  86  61 /  40  80  70  20  10
TEMPLE              72  82  64  88  59 /  30  70  60  20  10
MINERAL WELLS       66  81  56  85  54 /  50  60  30   5   5

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE FORT WORTH TX
318 PM CDT THU APR 28 2016

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-291200-
MONTAGUE-COOKE-GRAYSON-FANNIN-LAMAR-YOUNG-JACK-WISE-DENTON-COLLIN-
HUNT-DELTA-HOPKINS-STEPHENS-PALO PINTO-PARKER-TARRANT-DALLAS-
ROCKWALL-KAUFMAN-VAN ZANDT-RAINS-EASTLAND-ERATH-HOOD-SOMERVELL-
JOHNSON-ELLIS-HENDERSON-COMANCHE-MILLS-HAMILTON-BOSQUE-HILL-NAVARRO-
FREESTONE-ANDERSON-LAMPASAS-CORYELL-BELL-MCLENNAN-FALLS-LIMESTONE-
LEON-MILAM-ROBERTSON-
318 PM CDT THU APR 28 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH AND CENTRAL TEXAS.

.DAY ONE...THROUGH TONIGHT.

THUNDERSTORM CHANCES WILL RETURN LATE THIS EVENING AND THROUGH
THE OVERNIGHT HOURS...AS A WARM FRONT MOVES RAPIDLY NORTH ACROSS
NORTH TEXAS. THE GREATEST CHANCES WILL BE AFTER MIDNIGHT ALONG AND
NORTH OF THE I-20 CORRIDOR. RICH GULF MOISTURE SURGING NORTH WITH
THE WARM FRONT WILL RESULT IN STEADILY INCREASING INSTABILITY...
ESPECIALLY ALOFT. THE INCREASING INSTABILITY WILL COMBINE WITH
STRONG WIND SHEAR WITH HEIGHT FOR ELEVATED SUPERCELL STRUCTURES
CAPABLE OF LARGE HAIL...FREQUENT LIGHTNING AND BRIEF HEAVY
DOWNPOURS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

THUNDERSTORMS MAY BE ONGOING AT DAYBREAK FRIDAY MORNING...
PARTICULARLY ACROSS AREAS ALONG THE RED RIVER VALLEY. LARGE HAIL
WILL CONTINUE TO BE THE PRIMARY CONCERN WITH MORNING STORMS...BUT
BRIEF HEAVY DOWNPOURS COULD RESULT IN MINOR FLOODING ISSUES THAT
MAY IMPACT THE MORNING COMMUTE. THESE STORMS ARE EXPECTED TO COME
TO AN END BEFORE MIDDAY.

A DRYLINE WILL INVADE FROM THE WEST FRIDAY AFTERNOON...AS THE MAIN
UPPER LEVEL DISTURBANCE APPROACHES THE AREA. THE COMBINATION OF
INCREASING LIFT...A VERY UNSTABLE ATMOSPHERE WITH LITTLE CAPPING
IN PLACE AT PEAK HEATING...AND STRONG WIND SHEAR WILL PROMOTE THE
FORMATION OF SEVERE STORMS AND POSSIBLY SUPERCELLS. ANY SUPERCELL
THUNDERSTORMS WILL BE CAPABLE OF PRODUCING LARGE HAIL...DAMAGING
WINDS...AND TORNADOES. THE SEVERE WEATHER THREAT WILL BE ALONG AND
EAST OF INTERSTATE 35 AND WILL CONTINUE FRIDAY NIGHT INTO SATURDAY
MORNING. THUNDERSTORM CHANCES WILL GRADUALLY END FROM WEST TO
EAST LATE ON SATURDAY.

THE NEXT STORM SYSTEM WILL APPROACH EARLY NEXT WEEK. THUNDERSTORM
CHANCES WILL RETURN AS EARLY AS SUNDAY NIGHT AND CONTINUE ON
MONDAY...BEFORE COMING TO AN END ON TUESDAY.

.SPOTTER INFORMATION STATEMENT...
LIMITED SPOTTER ACTIVATION MAY BE REQUESTED OVERNIGHT FOR LARGE
HAIL REPORTS AND ANY LOCALIZED FLOODING.

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