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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS64 KFWD 211628 AAD
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1128 AM CDT TUE MAY 21 2013

.UPDATE...
-- Changed Discussion --
THE MAIN TORNADO THREAT WILL BE WITH DISCRETE CELLS OUT AHEAD OF
THE SQUALL LINE THIS AFTERNOON. THE SQUALL LINE IS BEGINNING TO
ORGANIZE AND IS MOVING SOUTHEAST AT 20-25 MPH. EXTRAPOLATION PLACES
IT ALONG A SHERMAN TO EASTLAND LINE AROUND 2 PM AND ALONG AN EMORY
TO LAMPASAS LINE BY 5 PM. LEAD STORMS ALONG THE LINE COULD STILL
PRODUCE TORNADOES...BUT THOSE CELLS WITHIN THE LINE WILL BE MORE
LIKELY TO PRODUCE DAMAGING STRAIGHT LINE WINDS FROM BOW ECHOES AND
LARGE HAIL.

HAVE HIGHEST POPS ARE ASSOCIATED WITH THE LINE AS IT MOVES
THROUGH THE REGION. THE CONVECTION WILL EXIT THE SOUTHEAST
COUNTIES EARLY THIS EVENING.  TEMPERATURES ARE ALREADY FALLING
BEHIND THE COLD FRONT WHICH HAS PUSHED INTO THE NORTHWEST
COUNTIES. 75
-- End Changed Discussion --

&&

.AVIATION...
THUNDERSTORM TIMING STILL PROBLEMATIC...WITH RAP/NAM FORECASTING
15Z TSRA ARRIVAL AT METRO AIRPORTS AND HRRR/OUN WRF INDICATING
18Z. WRF ARW FAVORS 20Z AND TTU WRF IS THE LATEST WITH A 21Z
ARRIVAL. ELEVATED CONVECTION IN OKLAHOMA HAS SHOWN NO TENDENCY TO
MOVE SOUTH YET...BUT THE BOUNDARY CAN BE SEEN NEAR THE FREDERICK
RADAR MOVING SOUTH. WILL TIME THE VCTS IN FOR 16Z AND THE TSRA IN
FOR 18Z FOR THESE TAFS...BUT STILL SUBJECT TO CHANGE ONCE
CONVECTION FIRES NEAR THE FRONT AND CAN BE TIMED.

TODAY HAS THE POTENTIAL TO BECOME A HIGH END EVENT...WITH LARGE
HAIL THE GREATEST THREAT TO AVIATION INTERESTS. A SIGNIFICANT
PERCENTAGE OF THE SUPERCELLS THAT DEVELOP WILL LIKELY PRODUCE
HAIL...AND SHOULD A HAIL CORE MOVE OVER AN AIRPORT THE POTENTIAL
FOR DAMAGE IS HIGH. THE TORNADO THREAT WILL BE INCREASING DURING
THE MORNING...AND REMAIN FAIRLY HIGH UNTIL THE DISCRETE SUPERCELLS
EVOLVE INTO A SQUALL LINE DURING THE MID- LATE AFTERNOON...LIKELY
NEAR OR SOUTH OF WACO.

STORM TIMING AT WACO WILL BE A COUPLE OF HOURS AFTER METROPLEX
ARRIVAL...AND HAVE CURRENTLY INDICATED 20Z. WACO IS ALSO IN THE
MODERATE RISK AREA WITH ALL THE ATTENDANT HAZARDS. 84


&&

.PREV DISCUSSION... 
-- Changed Discussion --
/ISSUED 357 AM CDT TUE MAY 21 2013/
ISOLATED SHOWERS CONTINUE TO POP UP ACROSS THE AREA EARLY THIS
MORNING...WITH THUNDERSTORM ACTIVITY REMAINING NORTH OF THE
REGION OVER OKLAHOMA IN THE VICINITY OF A SLOW MOVING FRONT. THE
WEATHER SHOULD REMAIN RELATIVELY QUIET IN THE SHORT TERM...BUT THE
INGREDIENTS APPEAR TO BE COMING TOGETHER FOR A SEVERE WEATHER
OUTBREAK ACROSS NORTH TEXAS LATER TODAY.

WATER VAPOR IMAGERY INDICATES A SHORTWAVE OVER NEW MEXICO MOVING
SOUTHEAST TOWARDS NORTHWEST TEXAS. THIS FEATURE WILL CONTINUE TO
SWING SOUTHEAST INTO NORTH TEXAS LATER TODAY...PROVIDING LIFT FOR
SHOWER AND THUNDERSTORM DEVELOPMENT LATER THIS MORNING AND
THROUGH THE AFTERNOON. AT THE SURFACE...AN OUTFLOW BOUNDARY
APPEARS TO BE LOCATED JUST SOUTH OF THE RED RIVER. THIS BOUNDARY
WILL PROVIDE FOCUS FOR DEVELOPMENT AS LIFT INCREASES AHEAD OF THE
SHORTWAVE. HI-RESOLUTION MODEL DATA SHOWS DEVELOPMENT BEGINNING
OVER THE NORTHERN COUNTIES AROUND DAYBREAK NEAR THE REMNANT
BOUNDARY. ADDITIONAL STORM DEVELOPMENT WILL LIKELY OCCUR ALONG THE
SYNOPTIC FRONT AS IT ADVANCES SOUTH TOWARDS THE RED
RIVER...ESSENTIALLY OVERTAKING THE MESOSCALE BOUNDARY LATER THIS
MORNING.

SHOWERS AND STORMS SHOULD ADVANCE SLOWLY SOUTHEAST ALONG THE SLOW
MOVING COLD FRONT. SURFACE HEATING WILL ALLOW THE ATMOSPHERE TO
DESTABILIZE MID AND LATE MORNING AHEAD OF THE FRONT AND ONGOING
STORMS. THIS SHOULD LEAD TO THE DEVELOPMENT OF STRONG TO SEVERE
STORMS AROUND MIDDAY. THESE STORMS WILL LIKELY BE IN THE FORM OF
DISCRETE CELLS...MOST LIKELY OCCURRING ALONG THE INTERSTATE 20
CORRIDOR INCLUDING DALLAS-FORT WORTH AND SURROUNDING AREAS.
SEVERAL OF THESE STORMS WILL QUICKLY BECOME SEVERE WITH LARGE
HAIL...DAMAGING WINDS...AND TORNADOES ALL POSSIBLE DURING THE
AFTERNOON. WITH THE SLOW MOVING SURFACE BOUNDARY IN PLACE...THE
POTENTIAL FOR LONG-TRACK TORNADOES WILL EXIST OVER CENTRAL AND
EASTERN PORTION OF THE REGION AS INDICATED BY SPC DAY 1 MODERATE
RISK AREA.

BY LATE AFTERNOON...STORMS SHOULD FORM INTO A SQUALL
LINE...SHIFTING THE MAIN SEVERE THREAT TO DAMAGING WINDS AND HAIL
DURING THE EVENING HOURS. THIS LINE OF STORMS WILL PUSH EAST OF
THE REGION TONIGHT AS THE SHORTWAVE TROUGH CONTINUES EAST AND
HEADS FOR THE MS VALLEY....BRINGING OVERALL QUIET WEATHER TO THE
REGION WEDNESDAY. THE SYNOPTIC SCALE COLD FRONT WILL HANG UP NEAR
THE I-20 CORRIDOR TODAY BEFORE GRADUALLY LIFTING NORTH OF THE AREA
WEDNESDAY AND WEDNESDAY NIGHT.

AN UPPER RIDGE WILL BUILD OVERHEAD WEDNESDAY THROUGH THE END OF
THE WEEK. MODEL DATA CONTINUES TO HINT AT STORM DEVELOPMENT
NORTHWEST OF THE REGION AROUND THE PERIPHERY OF THE RIDGE...WITH
ACTIVITY PROPAGATING SOUTHEAST TOWARDS THE AREA. WILL CONTINUE
WITH LOW POPS ACROSS THE NORTHWESTERN THIRD OF THE REGION DURING
THE EVENING AND OVERNIGHT HOURS WEDNESDAY AND THURSDAY...WITH
LINGERING POPS NORTH OF I-20 FRIDAY MORNING. THE UPPER RIDGE IS
PROGGED TO INTENSIFY THIS WEEKEND...WHICH WOULD BRING SUMMER-LIKE
TEMPERATURES FOR MEMORIAL DAY.     30
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
DALLAS-FT. WORTH, TX  82  65  87  68  89 /  70  30  10  10  10
WACO, TX              87  67  89  68  89 /  60  40  10  10  10
PARIS, TX             79  64  85  63  85 /  80  30  10  10  10
DENTON, TX            80  62  87  65  88 /  80  20  10  20  10
MCKINNEY, TX          81  63  87  64  86 /  80  30  10  10  10
DALLAS, TX            83  66  88  69  90 /  70  30  10  10  10
TERRELL, TX           84  65  86  65  87 /  80  30  10  10  10
CORSICANA, TX         87  67  87  68  88 /  80  40  10  10  10
TEMPLE, TX            88  68  89  68  88 /  60  50  20  10  10
MINERAL WELLS, TX     81  61  88  65  90 /  80  20  10  20  10
-- End Changed Discussion --

&&

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

&&

$$

 /75