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

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000
FXUS64 KFWD 241956
AFDFWD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FORT WORTH TX
256 PM CDT FRI APR 24 2015

.DISCUSSION...

FOR TODAY...OUR THINKING HAS NOT CHANGED SIGNIFICANTLY FROM THE
LATE MORNING FORECAST UPDATE/DISCUSSION...THEREFORE THE PREVIOUS
DISCUSSION HAS BEEN LEFT BELOW. MOST OF THE DETAILS REGARDING THE
EXPECTATIONS FOR THUNDERSTORMS THROUGH TONIGHT ARE STILL VALID
FROM THE LATE MORNING DISCUSSION.

CHANGES FROM LATE THIS MORNING: A TORNADO WATCH HAS BEEN ISSUED
FOR MUCH OF NORTH AND CENTRAL TEXAS THROUGH 10 PM CDT. A FLASH
FLOOD WATCH IS IN EFFECT FOR LOCATIONS ALONG AND NORTH OF THE
INTERSTATE 20 CORRIDOR...GENERALLY EAST OF WEATHERFORD...THROUGH 7
PM CDT.

CLOUDS CLEARED OUT JUST ENOUGH TO ALLOW FOR SOME SURFACE BASED
STORMS TO DEVELOP WEST OF NORTH TEXAS. THESE STORMS ARE EXPECTED
TO MOVE EAST THIS AFTERNOON...AND THE THERMODYNAMIC AND KINEMATIC
ENVIRONMENT IN PLACE ACROSS NORTH AND CENTRAL TEXAS IS EXPECTED TO
REMAIN FAVORABLE TO MAINTAIN THE STRUCTURE OF THESE STORMS AS THEY
MOVE EAST. SUPERCELL THUNDERSTORMS ARE EXPECTED AS THE INITIAL
STORM MODE...WITH STORM MERGERS AND COLD POOL CONSOLIDATION MORE
LIKELY TO LEAD TO UPSCALE GROWTH TO A QLCS EARLY THIS EVENING. THE
WARM FRONT IS EVENTUALLY EXPECTED TO LIFT SLOWLY NORTH ACROSS THE
METROPLEX...BUT WAS NOT MOVING MUCH AS OF 2 PM.

WHEREVER SUPERCELLS INTERACT WITH THE WARM FRONT...THE THREAT FOR
TORNADOES IS EXPECTED TO BE HIGHEST...SO THE POSITION OF THE WARM
FRONT WILL BE AN IMPORTANT FEATURE TO TRACK THROUGH THIS EVENING.
OTHER THAN TORNADOES...SUPERCELLS WILL BE CAPABLE OF PRODUCING
LARGE HAIL AND DAMAGING WINDS. IF UPSCALE GROWTH INTO A QLCS
OCCURS AS EXPECTED...THE MAIN THREAT WOULD TRANSITION OVER TO
DAMAGING STRAIGHT LINE WINDS. FLASH FLOODING REMAINS MOST LIKELY
ALONG AND NORTH OF THE WARM FRONT...SO NO CHANGES TO THE FLASH
FLOOD WATCH AREA WILL BE MADE AT THIS TIME.

TONIGHT AND SATURDAY...ONCE STORMS MOVE EAST AWAY FROM NORTH AND
CENTRAL TEXAS...A PACIFIC TYPE COLD FRONT IS EXPECTED TO SEND MUCH
DRIER AIR INTO THE REGION FOR SATURDAY. WITH DRY AIR IN PLACE
DURING THE DAY ON SATURDAY...SKIES ARE EXPECTED TO BE MOSTLY CLEAR
AND HIGHS ARE EXPECTED TO CLIMB INTO THE MID 80S.

SUNDAY...MODELS INDICATE THAT A STRONG UPPER LEVEL TROUGH
CURRENTLY OFF THE COAST OF WESTERN CANADA WILL DIG SOUTH OVER THE
SOUTHWESTERN CONUS SATURDAY NIGHT INTO SUNDAY. THIS FEATURE IS
EXPECTED TO SPREAD STRONG LARGE SCALE FORCING FOR ASCENT OVER THE
SOUTHERN HIGH PLAINS...RESULTING IN RELATIVELY STRONG LEE SIDE
CYCLOGENESIS OVER THE TX PANHANDLE. THIS SHOULD BRING LOW-LEVEL
MOISTURE BACK ACROSS NORTH AND CENTRAL TEXAS RAPIDLY ON SUNDAY.
WITH MOISTURE BACK IN PLACE...AND STRONG UPPER LEVEL DIFFLUENCE
ALOFT OVER THE DRYLINE...EXPECT STORMS WILL DEVELOP ALONG THE
DRYLINE LATE SUNDAY AFTERNOON. IF THE DRYLINE IS CLOSE ENOUGH TO
THE CWA...SEVERE THUNDERSTORMS WOULD LIKELY DEVELOP NEAR THE
DRYLINE AND MOVE EAST SUNDAY EVENING. CONFIDENCE IN THE EXACT
POSITION OF THE DRYLINE IS NOT HIGH AT THIS TIME...SO ONLY WENT
WITH A MENTION OF 30 POPS WEST OF INTERSTATE 35 IN THIS FORECAST.
IF STORMS DO DEVELOP WEST OF INTERSTATE 35...THEY WOULD LIKELY BE
SUPERCELLS AND CAPABLE OF PRODUCING LARGE HAIL AND DAMAGING WINDS.

MONDAY...THE UPPER TROUGH IS EXPECTED TO BECOME A CUT-OFF LOW AND
THEN MOVE SLOWLY EAST TOWARDS NORTH TEXAS. THE STRONG LARGE SCALE
FORCING FOR ASCENT ASSOCIATED WITH THE UPPER LOW WOULD LIKELY LEAD
TO WIDESPREAD THUNDERSTORM ACTIVITY ACROSS NORTH AND CENTRAL TEXAS
ON MONDAY. THE SEVERE WEATHER CHANCES ON MONDAY WILL LIKELY BE
VERY DEPENDENT UPON HOW FAST STORMS DEVELOP AND MOVE ACROSS THE
AREA MONDAY MORNING. DEEP LAYER SHEAR VALUES ARE EXPECTED TO BE
STRONG ENOUGH TO SUPPORT AN ORGANIZED STORM MODE...BUT THE AMOUNT
OF THERMODYNAMIC ENERGY AVAILABLE FOR FREE CONVECTION IS UNCERTAIN
AT THIS TIME. IF STORMS WERE TO HOLD OFF UNTIL THE LATE AFTERNOON
HOURS OF THE DAY...THERE WOULD LIKELY BE ENOUGH INSTABILITY AND
SHEAR IN PLACE TO ONCE AGAIN SUPPORT A SUPERCELL STORM MODE MONDAY
AFTERNOON. IF STORMS DEVELOP DURING THE MORNING HOWEVER...THE
MORNING CONVECTION MAY STABILIZE THE ENVIRONMENT TOO MUCH FOR ANY
SIGNIFICANT SEVERE THUNDERSTORM THREAT MONDAY AFTERNOON.

TUESDAY...DEPENDING ON THE SPEED OF THE UPPER LOW...IF IT IS OVER
NORTH TEXAS...OR TO OUR EAST...TUESDAY WILL LIKELY BE DRY. IF THE
UPPER LOW IS OVER THE CWA OR JUST OFF TO THE WEST...MORE
THUNDERSTORM ACTIVITY IS POSSIBLE DURING THE DAY ON TUESDAY. AT
THIS TIME SIMPLY LEFT THE 20 TO 30 PERCENT CHANCE OF STORMS IN THE
FORECAST TO ACCOUNT FOR UNCERTAINTY REGARDING THE SPEED OF THIS
UPPER LOW. WE WILL BE ABLE TO REFINE THUNDERSTORM CHANCES ON
TUESDAY ONCE THE UPPER LOW IS OVER THE SOUTHWESTERN CONUS AND ITS
EASTWARD TRACK IS RESOLVED BETTER BY FORECAST GUIDANCE.

REMAINDER OF THE WEEK...A COLD FRONT IS EXPECTED TO MOVE ACROSS
THE REGION BEHIND THE UPPER LOW...LEAVING DRIER AND COOLER AIR IN
PLACE. DRY CONDITIONS LOOK TO HOLD FROM WEDNESDAY THROUGH THE END
OF THE WEEK AT THIS TIME WITH WEAK UPPER LEVEL RIDGING BUILDING IN
OVER THE REGION BEHIND THE UPPER LOW.

CAVANAUGH

&&

.PREVIOUS UPDATE FROM 11 AM...

WATER VAPOR SATELLITE IMAGERY SHOWS A STRONG SHORTWAVE TROUGH
OVER FAR WEST TEXAS...MOVING NORTHEAST OVER EASTERN NEW MEXICO.
THIS TROUGH IS EXPECTED TO CONTINUE NORTHEAST THROUGHOUT THE DAY
TODAY...SPREADING RELATIVELY STRONG LARGE SCALE FORCING FOR ASCENT
OVER THE REGION. 12Z UPPER AIR ANALYSIS SHOWED A PLUME OF DEEP
MOISTURE IN PLACE OVER THE SOUTHERN PLAINS WITH STRONG SPEED AND
DIRECTIONAL SHEAR FROM THE SURFACE TO 500 MB. AT THE 850 MB LEVEL
A RELATIVELY STRONG TROUGH WAS ANALYZED OVER THE HIGH
PLAINS...DOWNSTREAM OF THE SHORTWAVE TROUGH MOVING NORTHEAST OVER
THE REGION. AT THE SURFACE...ONGOING THUNDERSTORM ACTIVITY LEFT A
SOMEWHAT MESSY ANALYSIS IN PLACE...BUT BASED ON THE 15Z ANALYSIS
THERE WAS A WARM FRONT LOCATED JUST SOUTH OF THE INTERSTATE 20
CORRIDOR ACROSS THE DFW AREA...MORE OR LESS ATTACHED TO A SURFACE
LOW LOCATED IN SOUTHERN PALO PINTO COUNTY.

15Z REGIONAL RADARS SHOWED SCATTERED CONVECTION NEAR THE SURFACE
LOW...AND ALL ALONG AND NORTH OF THE WARM FRONT. VISIBLE SATELLITE
IMAGERY SHOWED THAT THE THICK MORNING CLOUD COVER WAS BEGINNING TO
CLEAR OUT FROM CLEBURNE SOUTHWEST TO GOLDTHWAITE...AND SOUTH ALONG
THE INTERSTATE 35/35W CORRIDORS. FROM GRANBURY TO CLEBURNE
SOUTHWEST TOWARDS HAMILTON...LOCALLY CALCULATED CONVECTIVE
PARAMETERS WERE HIGHLIGHTING A LOCAL MAXIMA OF LOW-LEVEL (0-3 KM)
CAPE OF AROUND 100 TO 150 J/KG...AND A LOW-LEVEL EHI OF JUST UNDER
2. BOTH OF THESE PARAMETERS FAVOR THE POTENTIAL FOR STRONG LOW-
LEVEL UPDRAFTS AND THE POTENTIAL TO TILT LOW-LEVEL HORIZONTAL
VORTICITY INTO THE VERTICAL. THE PRIMARY MISSING INGREDIENT TO
ACCOMPLISH THIS THUS FAR HAS BEEN WELL ORGANIZED CONVECTION/STRONG
UPDRAFTS.

WHILE DEEP MOISTURE WAS ANALYZED ON THE 12Z UPPER AIR MAPS...THERE
WERE NO STRONG OR STEEP MID-LEVEL LAPSE RATES ANALYZED UPSTREAM OF
NORTH AND CENTRAL TEXAS. WHILE DEEP MOISTURE VALUES APPEAR TO BE
AT NEAR RECORD LEVELS FOR THIS TIME OF YEAR...THIS DEEP MOISTURE
ALSO INDICATES THAT THERE IS NO STRONG THETA-E CHANGE WITH
HEIGHT...LEADING TO A THERMODYNAMIC PROFILE CHARACTERIZED BY TALL
AND SKINNY CAPE. WHILE THIS IS A VERY FAVORABLE PROFILE FOR
THUNDERSTORM CHANCES AND EFFICIENT RAINFALL IN GENERAL...IT COULD
LIMIT THE STRENGTH OF INITIAL UPDRAFTS TODAY. IF STORMS CAN
MAINTAIN UPDRAFTS LONG ENOUGH TO INGEST SOME OF THE RELATIVELY
STRONG HORIZONTAL VORTICITY INDICATED BY CALCULATED PARAMETERS...
SUPERCELLS WILL BECOME MORE LIKELY. IF A SUPERCELL CAN BECOME
ESTABLISHED...THE INTERNAL DYNAMICS OF THE SUPERCELL WILL PROMOTE
A MUCH STRONGER UPDRAFT THAN WHAT WOULD BE SUPPORTED BY
THERMODYNAMICS ALONE.

WITH STRONG FORCING UPSTREAM...DEEP MOISTURE IN PLACE...AND ALMOST
NO CAPPING INVERSION IN PLACE...THUNDERSTORMS ARE VERY LIKELY
TODAY...AND WILL LIKELY CONTINUE INTO THE AFTERNOON HOURS OF THE
DAY. COPIOUS AMOUNTS OF MORNING CONVECTION CAN OFTEN STABILIZE THE
ENVIRONMENT MAKING IT LESS FAVORABLE FOR STORMS LATER ON. THAT
DOES NOT APPEAR TO BE THE CASE TODAY AS THE LACK OF A STRONG
THETA-E DIFFERENCE WITH HEIGHT NOT ONLY LIMITS UPDRAFT
STRENGTH...BUT IT ALSO LIMITS THE STRENGTH OF RAIN COOLED AIR...
I.E. THE RAIN IS NOT VERY COLD BECAUSE THERE IS NOT MUCH DRY AIR
ALOFT TODAY. THE PRIMARY FORECAST CHALLENGE IN DETERMINING STORM
MODE AND THEN THE ASSOCIATED HAZARDS. HERES WHAT WE`RE WATCHING
CLOSELY:

IN GENERAL...THE KINEMATIC OR WIND SHEAR AND FORCING ENVIRONMENT
ARE FAVORABLE FOR SUPERCELL THUNDERSTORMS AND TORNADOES TODAY. THE
THERMODYNAMIC ENVIRONMENT IS MORE QUESTIONABLE. WE CERTAINLY HAVE
AMPLE MOISTURE IN PLACE TO SUPPORT ANY STORM MODE...BUT LAPSE
RATES ALOFT ARE SOMEWHAT MARGINAL...LIMITING UPDRAFT STRENGTH FROM
AIR BEING LIFTED ABOVE ITS LEVEL OF FREE CONVECTION. IT LOOKS LIKE
THE MORE SUNSHINE WE GET THROUGH THIS AFTERNOON...THE MORE LIKELY
WE ARE TO SEE SUPERCELL THUNDERSTORMS. THE MORE CLOUD COVER WE
HANG ON TO...THE MORE LIKELY WE ARE TO SEE NUMEROUS...SOMEWHAT
WEAKER STORMS...THAT POSE MORE OF A HEAVY RAINFALL AND FLOODING
THREAT THAN A LARGE HAIL...DAMAGING WIND AND TORNADO THREAT.

IF WE MAINTAIN THE CLEARING SOUTH-SOUTHWEST OF THE DFW AREA FOR A
FEW HOURS HEADED INTO THIS AFTERNOON...OUR CHANCES OF SEEING A
SUPERCELL STORM MODE INCREASE QUITE A BIT. LOW-LEVEL HEATING WILL
HELP MORE OR LESS MAKE UP FOR THE MARGINAL MID-LEVEL LAPSE RATES
AND INCREASE UPDRAFT SPEED TO THE POINT THAT SUPERCELLS DOMINATE
THE INITIAL STORM MODE. IF WE GET STORMS QUICKLY...OR SIMPLY CLOUD
UP HERE AGAIN BEFORE NOON...A MORE WIDESPREAD STORM COVERAGE MAY
OCCUR WITH WEAKER STORMS IN GENERAL.

IN EITHER CASE...MOST MODEL GUIDANCE FAVORS THUNDERSTORMS GROWING
UPSCALE INTO A SQUALL LINE AND MOVING EAST ACROSS NORTH AND
CENTRAL TEXAS BY LATE THIS AFTERNOON. WITH A NEAR RECORD
PRECIPITABLE WATER VALUE OBSERVED ON THE 12Z FWD
SOUNDING...FLOODING IS ALSO A MAJOR CONCERN TODAY. ONCE DEEP
CONVECTION INITIATES...ANY TRAINING OF STORMS WILL LIKELY RESULT
IN ENOUGH LOCALLY HEAVY RAINFALL TO RESULT IN FLOODING. RAINFALL
RATES OF 2 INCHES PER HOUR ARE VERY LIKELY... AND REALLY THE ONLY
LIMITING FACTOR FOR FLOODING IS THE EXPECTED SPEED OF STORMS.
STORMS ARE EXPECTED TO MOVE EAST OR NORTHEAST AT 35 TO 40 MPH
TODAY...MAKING ANY ONE STORM UNLIKELY TO PRODUCE FLOODING.

WE WILL BE KEEPING A CLOSE EYE ON ALL OF THESE FACTORS HEADED INTO
THE AFTERNOON HOURS...AND WILL ISSUE THE APPROPRIATE WATCHES AS
VARIOUS THREAT LEVELS INCREASE. THERE IS A FAIR AMOUNT OF
UNCERTAINTY REGARDING STORM MODE THIS AFTERNOON...SO IT IS
ADVISABLE TO PAY CLOSE ATTENTION TO THE FORECAST THROUGHOUT THE
DAY AS CONDITIONS COULD BECOME MORE FAVORABLE FOR SUPERCELLS OR
HEAVY RAINFALL AND FLOODING QUICKLY. WE WILL PROVIDE SHORT TERM
FORECAST UPDATES AS QUICKLY AS POSSIBLE AS THESE CONDITIONS
EVOLVE.

CAVANAUGH

&&

.AVIATION...
/ISSUED 105 PM CDT FRI APR 24 2015/

THIS MORNING`S CONVECTION HAS PUSHED EAST OF THE TERMINALS AS OF
1730 Z. AS A RESULT...EXPECT CIGS TO RAISE TO MVFR SHORTLY.
HOWEVER...CONVECTION IS EXPECTED TO REDEVELOP THIS AFTERNOON
ACROSS THE AREA...BUT STORM DEVELOPMENT WILL BE PARTIALLY
DEPENDENT UPON IF WE CONTINUE TO SEE AMPLE CLEARING...WHICH WOULD
LEAD TO THE INCREASED SURFACE HEATING NECESSARY FOR INITIATION.
REGARDLESS...IF STORMS DEVELOP...THESE STORMS WILL BE IN A
FAVORABLE ENVIRONMENT TO BECOME SEVERE...AND ALL FACETS OF SEVERE
WEATHER WOULD BE ON THE TABLE THIS AFTERNOON AND EVENING.

REGARDING WINDS...BECAUSE OF THE COMPLEX SET OF SURFACE
BOUNDARIES CURRENTLY IN PLAY ACROSS THE AREA...WINDS WILL BE
SOMEWHAT VARIABLE. RIGHT NOW THOUGH...A WARM FRONT IS DRAPED
ACROSS THE DFW METROPLEX...SO WINDS NORTH OF THE FRONT ARE
EASTERLY TO NORTHEASTERLY. SOUTH OF THE FRONT...WINDS ARE FROM THE
SOUTH AND SOUTHEAST. THE WARM FRONT APPEARS TO BE MOVING NORTH
NOW...SO EXPECT WINDS AT ALL DFW TERMINALS TO VEER TO THE
SOUTHEAST LATER THIS AFTERNOON. AT KACT...WINDS REMAIN SOUTHERLY.

ONCE THIS SYSTEM CLEARS OUT OF THE REGION LATE TONIGHT...EXPECT
CIGS AND VSBY TO RAISE TO VFR BY THIS EVENING AND PREVAIL THROUGH
SATURDAY. LIKEWISE...WINDS WILL CONTINUE TO VEER AND EVENTUALLY BECOME
NORTHWESTERLY BY TONIGHT AS WELL.

AJS

&&


.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  63  86  61  87  64 /  40   5   5  20  30
WACO, TX              64  87  61  86  65 /  50   5   5  20  30
PARIS, TX             61  84  58  85  58 /  60   5   5  10  30
DENTON, TX            60  86  57  86  61 /  30   0   5  30  30
MCKINNEY, TX          61  85  58  86  61 /  40   5   5  20  30
DALLAS, TX            64  88  63  88  64 /  40   5   5  20  30
TERRELL, TX           66  87  60  86  63 /  60   5   5  20  30
CORSICANA, TX         66  87  63  86  64 /  60   5   5  20  30
TEMPLE, TX            64  89  63  86  65 /  50   5   5  30  30
MINERAL WELLS, TX     58  87  57  86  62 /  10   0   5  30  40

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
FLASH FLOOD WATCH UNTIL 7 PM CDT THIS EVENING FOR TXZ091>095-
102>107-117>123.


&&

$$


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