National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS64 KFWD 171723 AAB
AFDFWD

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1223 PM CDT FRI MAY 17 2013

.AVIATION...
CONCERNS...RETURN OF MVFR CIGS LATE TONIGHT.

CURRENT MVFR CIGS ACROSS THE METROPLEX SHOULD GO SCT030-040 FOR
MOST TAF SITES EARLY THIS AFTERNOON WHILE KFTW/KAFW MAY REMAIN
BKN030 THROUGH 20Z. AFTERWARD...VFR CONDITIONS WITH SOUTHERLY
WINDS 13-20KTS. EXPECT ANOTHER ROUND OF STRATUS LATE TONIGHT
08-10Z THAT WILL PERSIST UNTIL 15Z. VFR SKIES LATE MORNING THROUGH
LATE SATURDAY AFTERNOON. SURFACE WINDS SHOULD BE SEVERAL KNOTS
HIGHER ON SATURDAY AFTERNOON THAN THIS AFTERNOON.

AS FOR CONVECTION...MIDDAY CONVECTION BETWEEN KCRS-KLFK-KUTS WILL
PERSIST SEVERAL MORE HOURS AS THE CELLS PROPAGATE SOUTHEAST.
OTHERWISE...FORECAST SOUNDINGS SHOW ALL FWD TAF SITES REMAINING
STRONGLY CAPPED THROUGH THE FORECAST PERIOD. HOWEVER...FAR TO THE
WEST...A DRYLINE WILL NEAR A KCDS-KABI- KSJT LINE THIS AFTERNOON
AND SHOULD BE ABLE TO PRODUCE SEVERAL SUPERCELL THUNDERSTORMS
BETWEEN 21-23Z. NONE ARE EXPECTED TO AFFECT OUR TAF SITES. 75

&&

.UPDATE...
12Z FWD SOUNDING DEPICTS NEARLY DRY ADIABATIC LAPSE RATES FROM
850MB UP TO 500MB. CURRENTLY A WEAK SHORTWAVE WAS MOVING ACROSS
NORTH TEXAS IN NORTHWEST FLOW ALOFT AND WAS RESPONSIBLE FOR THE
ELEVATED CONVECTION OCCURRING OVER THE SOUTHEAST ZONES THIS
MORNING. THESE STORMS HAVE PRODUCED HAIL UP TO GOLF BALL SIZE AND
ARE A TESTAMENT TO THE STEEP LAPSE RATES ALOFT. THIS SHORTWAVE
WILL CONTINUE TO MOVE SOUTHEAST AND OUT OF THE AREA BY MIDDAY.

STRONG SURFACE HEATING ACROSS THE WESTERN ZONES WILL HELP PUSH
TEMPERATURES TO NEAR THE CENTURY MARK THIS AFTERNOON. A DRY LINE
WILL REACH A LINE FROM GRAHAM TO COMANCHE TO LLANO. SHORT TERM
MODELS DEPICT DEWPOINTS IN THE LOW TO MID 70S AHEAD OF THE DRY
LINE...BUT THIS IS PROBABLY TOO HIGH. BELIEVE DEWPOINTS WILL MIX
OUT INTO THE UPPER 60S. NONETHELESS...THIS WILL CONTRIBUTE TO
EXTREME INSTABILITY WITH SURFACE BASED CAPE VALUES ABOVE 4000
J/KG. UNLIKE THE EVENT ON WEDNESDAY...THE CAP WILL BE MUCH
STRONGER TODAY AND WILL REQUIRE STRONG HEATING AND THE MESOSCALE
FORCING PROVIDED BY A DRY LINE TO BE OVERCOME. GIVEN A REASONABLE
FORECAST TEMP/DEWPOINT COMBINATION OF 99 OVER 68 AHEAD OF THE DRY
LINE...THIS SHOULD BE SUFFICIENT FOR THE CAP TO BREAK.

SEVERAL OF THE HI-RES CONVECTION ALLOWING MODELS AND THE LAST 2
RUNS OF THE NAM ARE SHOWING STORM INITIATION LATE THIS
AFTERNOON...AND ARE FOCUSING IN ON THE AREA NEAR THE LLANO
UPLIFT...WHICH WOULD AFFECT OUR SW ZONES AND ALSO ANOTHER AREA
NEAR GRAHAM AND BRECKENRIDGE. DEEP LAYER SHEAR IS NOT OVERLY
STRONG AND IS ON THE LOW END OF THE ALLOWABLE LEVEL FOR
SUPERCELLS. HOWEVER THE HIGH INSTABILITY WILL LIKELY COMPENSATE
AND ALLOW FOR SUPERCELL MODES. SUPERCELL STORM MOTION TECHNIQUES
BASED ONLY ON WIND PROFILES ARE EAST AT 10KT...BUT IN CASES OF
HIGH INSTABILITY AND WEAK FLOW...THESE SUPERCELLS WILL LIKELY HEAD
SLOWLY SOUTHEAST OR EVEN DUE SOUTH. GIANT HAIL...PERHAPS GREATER
THAN BASEBALLS WILL BE POSSIBLE WITH ANY SUPERCELL STORM.

SURFACE TEMPS WILL LIKELY REACH 105 WEST OF OUR CWA BEHIND THE
DRY LINE...WHICH SHOULD ALLOW A THERMAL SURFACE LOW TO INTENSIFY
TODAY. THIS WILL CAUSE LOW LEVEL WINDS TO BACK OVER THE NORTHERN
PART OF THE CWA...WHICH WILL ENHANCE LOW LEVEL DIRECTION SHEAR
PROFILES ACROSS THE NORTHWEST CWA DESPITE WIND SPEEDS REMAINING
FAIRLY WEAK AND LESS THAN 15KT AT ANY GIVEN LEVEL. STORM RELATIVE
0-3KM HELICITY VALUES BY THE RUC/NAM ARE FORECAST TO BE NEAR
100-150 MS/S2...SIGNIFICANTLY LESS THAN LAST WEDNESDAY...BUT AGAIN
THE HIGHER INSTABILITY CAN OFTEN COMPENSATE TO RAISE THE CONCERN
FOR TORNADOGENESIS. IN ADDITION SHOULD SUPERCELLS IN FACT MOVE
SOUTH...THESE MODEL VALUES OF 0-3 SRH VALUES ARE TOO LOW. HAVE
ADDED A RISK OF ISOLATED TORNADOES TO THE HWO AND GRAPHIC
FORECASTS AS WELL.

I SHOULD STRESS ALL OF THE SEVERE THREAT TODAY IS CONDITIONAL
BASED ON THE CAP BREAKING...WHICH AGAIN IS NOT GUARANTEED BUT IS
PROBABLE. WITH LESS HEATING ACROSS THE I-35 CORRIDOR...THIS SHOULD
KEEP SEVERE CONVECTION CONFINED TO THE WESTERN ZONES WITH THE CAP
TOO STRONG FOR SURFACE BASED CONVECTION IN THE CENTRAL AND EASTERN
ZONES. STILL IT IS POSSIBLE RESIDUAL ELEVATED CONVECTION OR ANVIL
PRECIPITATION MAY ENTER THE CENTRAL ZONES LATE TONIGHT...BUT WILL
KEEP POPS AT 10 PERCENT WITH NO MODEL SUPPORT FOR THIS SCENARIO.

FOR THE UPDATE HAVE LOWERED HIGHS IN THE SOUTHEAST ZONES DUE TO
MORNING RAIN AND CLOUDS. HAVE RAISED POPS IN THE WESTERN ZONES TO
REFLECT THE HIGHER POTENTIAL FOR STORMS THIS AFTERNOON AND EVENING.

TR.92

&&

.PREV DISCUSSION... /ISSUED 354 AM CDT FRI MAY 17 2013/
...A FEW SEVERE STORMS POSSIBLE ACROSS FAR WESTERN NORTH TEXAS BY
EACH EVENING TODAY AND SATURDAY...THEN NORTH OF I-20 LATE SUNDAY...

WEATHER FORECAST REMAINS CHALLENGING TODAY INTO THE WEEKEND. WE
CONTINUED TO SEE A SUBTLE SURFACE BOUNDARY SITUATED ALONG/NORTH OF
HWY 38 THIS MORNING AS EVIDENCED BY THE BACKED/LIGHTER EAST WINDS
AND LOWER SURFACE DEW POINTS THIS MORNING...WHILE STRONGER SSE
WINDS 10 TO 15 MPH WHERE OCCURRING FROM THE I-20 CORRIDOR INTO
CENTRAL TEXAS. SOME PATCHY DENSE FOG WAS OCCURRING ALONG THE RED
RIVER VALLEY...WHILE A SUBTLE DISTURBANCE WAS MOVING ACROSS WITHIN
THE UPPER RIDGE OVER THE TOP OF THE AREA. SOME AC/ACCAS WAS NOTED
ON INFRARED SATELLITE IMAGERY WITH STEEP LAPSE RATES ALOFT ON THE
00Z FWD SOUNDING AND MODELS. ISOLATED...ELEVATED/HIGH-BASED
SHOWERS AND STORMS ARE POSSIBLE THIS MORNING MAINLY ALONG AND
SOUTH OF THE I-20/I-30 CORRIDORS. LIGHTNING WILL BE THE MAIN
THREAT WITH ACTIVITY THIS MORNING WITH VERY LITTLE IN THE WAY OF
MEASURABLE RAINFALL EXPECTED.

THE SURFACE DRYLINE AND ASSOCIATED LOW PRESSURE OVER FAR WEST
TEXAS WILL CONTINUE TO DEEPEN AND SLIDE SLOWLY EAST TOWARD OUR FAR
W/SW COUNTIES LATE THIS AFTERNOON/EVE. STRONG MIXING AND HEATING
ALONG AND JUST AHEAD OF THIS FEATURE WILL HELP HIGHS SOAR WELL
INTO THE 90S WITH A FEW AREAS TOPPING THE CENTURY MARK WEST OF
I-35/I-35W. OUR CAPPING INVERSION WAS ELEVATED AND BASED ABOVE
800MB AND NOT OVERLY STOUT...SO DESPITE THE UPPER RIDGE ARRIVING
OVERHEAD...FEEL THE HOT TEMPS WILL MAKE IT BREAKABLE. HIGH-RES
WRF/ARW/AND HRRR MODELS ALL HINT AT ISOLATED STORM DEVELOPMENT JUST
W/SW OF OUR CWA AT PEAK HEATING AND POTENTIALLY AFFECTING OUR FAR
WSW COUNTIES BETWEEN 4 PM AND SUNSET. INSTABILITY WILL BE VERY HIGH
WITH MODELS SHOWING 3500-5000 J/KG SBCAPE OR POSSIBLY MORE WITH
VERY STEEP MID LEVEL LAPSE RATES OVER 8 DEG C/KM. ANY ISOLATED
STORMS THAT OCCUR WILL LIKELY BE SEVERE WITH VERY LARGE HAIL AND
DAMAGING DOWNBURSTS. DESPITE SURFACE DEW POINTS BEING NEAR 70
DEGREES...THE HOT TEMPERATURES WILL RESULT IN RELATIVELY HIGH
BASES AND A LOWER TORNADO THREAT THAN A FEW DAYS AGO. WITH THE
UPPER RIDGE OVERHEAD...STORMS WILL DIMINISH IN STRENGTH OR
DISSIPATE RAPIDLY AROUND SUNSET WITH LOSS OF HEATING AND THE CAP
INTENSIFYING QUICKLY BY LATE EVENING.

THE UPPER RIDGE SHIFTS EAST OF THE AREA ON SATURDAY WITH LONGWAVE
UPPER TROUGH SNAKING OVER THE ROCKIES INTO THE WESTERN HIGH
PLAINS. THE DRYLINE WILL ACTUALLY MAKE A STRONGER PUSH TOWARD OUR
FAR WESTERN COUNTIES BY EARLY EVENING SATURDAY WITH A LITTLE
BETTER UPPER SUPPORT. INSTABILITY WILL BE VERY STRONG ONCE AGAIN
WITH ISOLATED TO SCATTERED STRONG TO SEVERE STORMS EXPECTED MAINLY
ALONG AND WEST OF HWY 281...THEN DIMINISHING QUICKLY AFTER SUNSET
WITH THE CAP INTENSIFYING ONCE AGAIN. THE UPPER TROUGH DAMPENS
OVER THE CONUS ON SUNDAY WITH STRONG WESTERLY FLOW ALOFT OCCURRING
FROM THE RED RIVER VALLEY NORTH THROUGH THE CENTRAL PLAINS. HAVE
MODIFIED BEST CHANCES TO OCCUR NORTH OF I-20 AND INTO THE RED
RIVER VALLEY...WITH THE CAP BEING MUCH STRONGER OVER THE SOUTH.
DIURNAL SEVERE WEATHER WILL BE POSSIBLE AGAIN...BUT CONFIDENCE IS
LOWER FOR LATE SUNDAY DUE TO UNCERTAINTIES REGARDING CAP STRENGTH
AND SOUTHERN EXTENT OF FORCING. THE BEST SURFACE FOCUS WILL BE
ALONG A COLD FRONT THAT IS EXPECTED TO BE WELL TO THE NORTHWEST OF
THE AREA AS WELL.

OTHERWISE IN THE EXTENDED...STAYED WITH PERSISTENCE WITH THE
PREVIOUS FORECAST WITH LOW POPS RETURNING BY MID WEEK WITH A COLD
FRONT WEAKENING AND STALLING ACROSS THE NORTHWEST COUNTIES. A
SHORTWAVE TROUGH WILL BE MOVING OVER THE CENTRAL AND SOUTHERN
PLAINS AT THIS TIME AS WELL. IT IS TOO EARLY TO ASSESS ANY SEVERE
WEATHER THREAT THIS FAR OUT...BUT WILL CONTINUE TO ASSESS THESE
POSSIBILITIES IN THE COMING DAYS AHEAD.    05/

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  89  72  93  72  88 /  10  10   5  10  10
WACO, TX              91  71  92  71  90 /  10  10   5  10  10
PARIS, TX             82  68  86  69  86 /  10  10  10  10  10
DENTON, TX            86  70  93  71  89 /  10  10  10  10  20
MCKINNEY, TX          84  69  91  69  88 /  10  10   5  10  10
DALLAS, TX            88  72  93  72  90 /  10  10   5  10  10
TERRELL, TX           87  69  90  70  89 /  10  10   5  10  10
CORSICANA, TX         89  70  91  70  89 /  40  10   5  10  10
TEMPLE, TX            91  70  91  71  89 /  10  20  10  10  10
MINERAL WELLS, TX     94  70  96  70  93 /  10  20  10  20  20

&&

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

&&

$$

75/