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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS64 KFWD 201647 AAA
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1147 AM CDT MON MAY 20 2013

.UPDATE...
-- Changed Discussion --
THE DRYLINE WAS POSITIONED NEAR AN ALTUS OKLAHOMA TO BIG SPRING
LINE AT 10AM WITH A SURFACE LOW SITUATED WEST OF WICHITA FALLS
AND A CU FIELD FORMING WEST OF GRAHAM. CURRENTLY...THE OUTLOOK
FOR A SLIGHT TO MODERATE RISK OF SEVERE THIS AFTERNOON THROUGH MID
EVENING THUNDERSTORMS OVER OUR WESTERN AND NORTHWESTERN COUNTIES
LOOKS GOOD DUE TO THE EXCEPTIONALLY UNSTABLE AIR MASS IN PLACE AND
FORCING THAT WILL TAKE PLACE. CONVECTIVE DEVELOPMENT OVER THE
WESTERN COUNTIES...SOUTH OF I-20...WILL BE CONDITIONALLY
DEPENDENT ON CAP STRENGTH AND WHETHER OR NOT IT HOLDS. EXPECT THE
CAP TO HOLD FIRM GENERALLY EAST OF GAINESVILLE TO WEATHERFORD AND
COMANCHE LINE THIS AFTERNOON.

WITH VERY STEEP MID LEVEL LAPSE RATES...CAPE IN EXCESS OF 2800
J/KG AND BULK SHEAR OF 30-40 KTS...WE EXPECT SUPERCELLS TO DEVELOP
QUICKLY ALONG THE DRYLINE BY MID AFTERNOON. LARGE HAIL TO BASEBALL
SIZE AND DAMAGING WINDS IN EXCESS OF 65 MPH ARE LIKELY. AS FOR
TORNADOES...IF WINDS AROUND NOCONA...GRAHAM AND BRECKENRIDGE BACK
SOUTHEASTERLY OR A DISCRETE SUPERCELL TAKES A RIGHT TURN... THEN
INCREASED HELICITY WOULD INCREASE THE POTENTIAL OF TORNADOGENESIS.

CHANGES MADE TO THE MIDDAY FORECAST...PUSHED POPS WESTWARD A
LITTLE AND REDUCED POPS AROUND THE METROPLEX FOR THIS AFTERNOON.
INCREASED POPS SLIGHTLY AND ADJUSTED COVERAGE FOR TUESDAY AND
TUESDAY EVENING. HEAVY RAIN PRODUCERS ON TUESDAY COULD LEAD TO
SOME FLASH FLOODING EVENTS...MAINLY EAST OF THE I-35 CORRIDOR. WE
WILL EVALUATE THE NEED FOR A FLASH FLOOD WATCH FOR THE EASTERN
CWA LATER TODAY. 75
-- End Changed Discussion --

&&

.AVIATION...
SATELLITE INDICATES STRATUS IS A BIT PATCHY THIS MORNING...SO
CEILINGS MAY VARY. FEEL THAT MVFR CEILINGS ARE LIKELY UNTIL
15Z/10AM WHEN STRONG WINDS AND HEATING SHOULD MIX IT OUT. STRATUS
SHOULD RETURN EARLY TUESDAY MORNING TO ALL TAF SITES.

MODEL GUIDANCE IS A MIXED BAG FOR TSRA ACTIVITY AT METROPLEX THIS
EVENING. TTU WRF...GFS...RUC...AND NAM DISSIPATE THIS EVENING/S
CONVECTION WEST OF TAF SITES...WHILE WRF ARW...4KM WRF...AND EURO
BRING CONVECTION INTO METROPLEX AFTER 00Z. WILL STICK WITH
CURRENT VCTS 00Z-04Z AS BEST COMPROMISE FOR NOW. TSRA THREAT WILL
INCREASE AGAIN TUESDAY AS FRONT PUSHES TO COUNTIES NORTHWEST OF
METROPLEX. ALTHOUGH GUIDANCE DIFFERS FOR METROPLEX...THERE IS
GOOD AGREEMENT ON STORMS ALONG THE DRY LINE WEST AND NORTHWEST OF
TAF SITES AND WEST DEPARTURES WILL LIKELY BE AFFECTED.

WACO WILL HAVE SLIGHT CHANCE POPS OVERNIGHT...AND THE BETTER
THREAT FOR TSRA WILL BE TUESDAY AFTERNOON BEYOND THIS TAF CYCLE.
84

&&

.PREV DISCUSSION... 
-- Changed Discussion --
/ISSUED 337 AM CDT MON MAY 20 2013/
A BROAD UPPER TROUGH REMAINS IN PLACE OVER THE WEST-CENTRAL CONUS
THIS MORNING. SHOWERS AND THUNDERSTORMS CONTINUE TO LIFT
NORTHEASTWARD FROM THE PLAINS TO THE UPPER MIDWEST...AS THE STRONG
SHORTWAVE ASSOCIATED WITH YESTERDAY EVENING/S SEVERE WEATHER ROTATES
NORTHWARD TOWARDS THE CANADIAN BORDER. AT THE SURFACE...A SLOW
MOVING COLD FRONT EXTENDS FROM THE PLAINS SOUTHWESTWARD INTO
NORTHWEST TEXAS...WITH A DRY LINE SOUTH OF THE FRONT FROM BETWEEN
CHILDRESS AND VERNON TO NEAR FORT STOCKTON. THE DRY LINE IS
EXPECTED TO BECOME THE FOCUS FOR THUNDERSTORM DEVELOPMENT OVER
WESTERN COUNTIES OF NORTH TEXAS THIS AFTERNOON. UNTIL
THEN...WARM AND BREEZY CONDITIONS CAN BE EXPECTED AS SOUTH WINDS
OF 15-20 MPH GUSTING TO 35 MPH CONTINUE.

STORMS WILL LIKELY DEVELOP IMMEDIATELY AHEAD OF THE DRYLINE LATE
THIS AFTERNOON DURING PEAK HEATING...AIDED BY A SUBTLE DISTURBANCE
PROJECTED TO CROSS FROM NORTHERN MEXICO EAST-NORTHEASTWARD INTO
TEXAS AND THE SOUTHERN PLAINS. THE BULK OF THE THUNDERSTORM COVERAGE
SHOULD BE NORTH OF THE RED RIVER WHERE INSTABILITY LEVELS ARE FORECAST
TO BE HIGHEST. IN FACT SOME OF THE HI-RES MODEL DATA INDICATES
DEVELOPMENT ACROSS OKLAHOMA BY EARLY AFTERNOON ALONG THE QUASI-
STATIONARY FRONT. SOUTH OF THE FRONT...THE DRYLINE SHOULD MIX EAST
TO NEAR THE WESTERN CWA BORDER...INITIATING STORMS BY 00Z/7 PM IF
NOT BEFORE. A NARROW AXIS OF MLCAPE IN EXCESS OF 3000 J/KG AHEAD
OF THE DRYLINE WILL RESULT IN SOME SEVERE STORMS...WITH LARGE
HAIL...DAMAGING WINDS...AND A FEW TORNADOES ALL POSSIBLE. THE
GREATEST THREAT WILL BE IN THE NORTHWESTERN-MOST REGIONS OF NORTH
TEXAS. THIS AREA IS CAPTURED WELL BY SPC DAY 1 CONVECTIVE OUTLOOK.

CELLS WILL MOVE NORTHEASTWARD THROUGH MUCH OF THE EVENING...PERHAPS
TAKING ON MORE OF AN EASTERLY MOTION AS MID LEVEL WINDS VEER LATE
IN THE EVENING. THERE IS THE POSSIBILITY THAT STORMS WILL REMAIN
ONGOING LATE THIS EVENING AND OVERNIGHT AS THE LOW LEVEL JET
BECOMES ESTABLISHED. WILL KEEP HIGHEST POPS OVERNIGHT OVER THE
NORTHERNMOST COUNTIES...WHERE MODELS ARE GENERALLY ROBUST ON QPF
OUTPUT. THE STRONG LLJ WOULD ALSO ALLOW FOR THE POSSIBILITY OF AN
EASTWARD OR SOUTHEASTWARD PROPAGATING MCS DURING THE OVERNIGHT
HOURS OVER THE NORTH AND NORTHEASTERN COUNTIES OF NORTH TEXAS.

THUNDERSTORMS WILL BE A GOOD POSSIBILITY ACROSS MUCH OF THE REGION
ON TUESDAY AS A PRONOUNCED SHORTWAVE SWINGS AROUND THE BASE OF THE
UPPER TROUGH. MESOSCALE SURFACE BOUNDARIES WILL LIKELY BE IN PLACE
FROM THE EXPECTED ACTIVITY MONDAY NIGHT...IN ADDITION TO THE
ACTUAL COLD FRONT WHICH SHOULD HAVE JUST ENOUGH PUSH TO PENETRATE
THE NORTHWESTERN COUNTIES. THESE BOUNDARIES WILL SERVE AS FOCUS
FOR CONTINUED DEVELOPMENT THOUGH THE DAY AS LIFT FROM THE
SHORTWAVE OVERSPREADS THE AREA. ACTIVITY WILL ADVANCE STEADILY
EAST-SOUTHEAST ACROSS NORTH TEXAS THROUGH TUESDAY NIGHT...EXITING
THE AREA TO THE SOUTHEAST BY EARLY WEDNESDAY. INSTABILITY WILL NOT
BE AS HIGH AS THIS EVENING AND TONIGHT...BUT WILL STILL BE
SUFFICIENT FOR A FEW SEVERE STORMS.

AN UPPER RIDGE WILL THEN BUILD OVERHEAD AS THE CENTRAL CONUS
TROUGH HEADS FOR THE THE EASTERN STATES. WILL MAINTAIN THE LOW
POPS OVER THE NORTHWESTERN THIRD OF THE REGION FOR BOTH LATE
THURSDAY AND LATE FRIDAY...WHERE MODELS ARE INDICATING THE
ISOLATED STORM DEVELOPMENT AROUND THE PERIPHERY OF THE
RIDGE...WHICH COULD HOLD TOGETHER LONG ENOUGH TO AFFECT THE
NORTHWEST ZONES. OTHERWISE TEMPERATURES SHOULD BE GENERALLY ABOVE-
NORMAL DURING THE EXTENDED PORTION OF THE FORECAST.    30
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
DALLAS-FT. WORTH, TX  92  72  87  68  89 /  10  40  60  50  10
WACO, TX              91  72  89  68  88 /  10  20  60  60  10
PARIS, TX             89  70  82  65  85 /  10  60  70  50  10
DENTON, TX            92  71  86  64  89 /  10  40  50  40  10
MCKINNEY, TX          90  71  85  64  88 /  10  40  70  50  10
DALLAS, TX            91  72  87  69  89 /  10  40  60  50  10
TERRELL, TX           90  72  86  67  87 /  10  30  70  60  10
CORSICANA, TX         91  72  87  69  87 /  10  20  50  70  10
TEMPLE, TX            91  72  88  69  87 /  10  20  50  60  10
MINERAL WELLS, TX     94  69  87  65  89 /  30  30  40  40  10
-- End Changed Discussion --

&&

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

&&

$$

 /75