Severe Thunderstorm Warning 237, NWS Fort Worth, TX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
114 PM CDT SUN OCT 24 2010

.AVIATION...
/18Z TAFS/

CONCERNS...STRATUS AT WACO...CROSSWINDS MONDAY.

DRYLINE SURGE IS APPROACHING METROPLEX. BOUNDARY WILL MAKE SOME
ADDITIONAL PROGRESS TO THE EAST BEFORE SLOWING DOWN. CU NEAR MKN
APPEARS ROOTED IN THE BOUNDARY LAYER...BUT CONSIDERABLE DRY
ADVECTION HAS OCCURRED ABOVE THE BOUNDARY LAYER IN ADVANCE OF THE
DRYLINE. AS A RESULT...DO NOT EXPECT THOSE OR ANY OTHER SURFACE-
BASED PARCELS TO CONVECT MUCH FURTHER. CONVECTIVE INITIATION HAS
ALREADY BEGUN EAST OF DALLAS...AND SEVERE STORMS WILL BE POSSIBLE
IN EASTERN PORTIONS OF FWD CWA...BUT CONVECTION SHOULD STAY EAST
OF TAF SITES.

DRYLINE WILL RETREAT TONIGHT...ALLOWING MORNING STRATUS TO RETURN
TO WACO. DALLAS MAY BE NEAR WESTERN EDGE OF CLOUD BANK...BUT WILL
REFRAIN FROM INTRODUCING ANY MENTION NOW.

850MB WINDS MAY APPROACH 50KTS MONDAY AFTERNOON. DEEP MIXING WILL
RESULT IN SUSTAINED SURFACE WINDS IN EXCESS OF 20KTS. OCCASIONAL
GUSTS OVER 30KTS ARE LIKELY. FROM 190 DEGREES...THIS WOULD RESULT
IN SOME CROSSWIND ISSUES ON 31 L/R AT DFW/DAL.

25

&&

.UPDATE...

15Z SFC OBS INDICATE THAT A VERY MOIST AND UNSTABLE AIRMASS IS
SETTING UP OVER AREAS SOUTHEAST OF A CANTON TO TEMPLE LINE FOR
THIS AFTERNOON. DEW POINTS ARE IN THE UPPER 60S TO 70 DEGREES IN
SOME LOCATIONS WHILE VISIBLE SATELLITE IMAGERY INDICATES BROKEN
CLOUDS IN PLACE WHICH WILL ALLOW ENOUGH SUNSHINE THRU FOR A QUICK
WARM UP THROUGH THE EARLY AFTERNOON HRS. 15Z WATER VAPOR IMAGERY
INDICATES A RELATIVELY STRONG SHORTWAVE TROUGH IS OVER THE TX
PANHANDLE...MOVING EAST TOWARDS NORTH TX. THIS TROUGH WILL SPREAD
LARGE SCALE FORCING FOR ASCENT OVER THE FORECAST AREA WITHIN THE
NEXT COUPLE OF HRS. THIS WAVE HAS ALSO ALLOWED THE LOW LVL WINDS
TO VEER AROUND TO THE WEST ACROSS WEST CENTRAL TX WHICH HAS CAUSED
A DRYLINE TO BEGIN SURGING EAST TOWARDS NORTH TX. THE 14Z RUC
INDICATES THAT THE 0-6 KM BULK SHEAR VECTOR WILL BE ORIENTED OUT
OF THE WEST NORTHWEST AT 40 KTS ALONG THE DRYLINE THIS AFTERNOON.
A BULGE IN THE DRYLINE IS EXPECTED TO SURGE INTO THE SOUTHERN HALF
OF NORTH TX AFTER 18Z. BY 21Z THE DRYLINE IS EXPECTED TO BE
ORIENTED ROUGHLY ALONG A DFW TO TEMPLE LINE. THIS EXPECTED
NORTHEAST TO SOUTHWEST ORIENTATION OF THE DRYLINE WILL ALLOW THE
0-6 KM BULK SHEAR VECTOR TO BE POSITIONED NEARLY PERPENDICULAR TO
THE DRYLINE. ASSUMING THE DRYLINE WILL BE IMPORTANT IN
THUNDERSTORM INITIATION THIS AFTERNOON...A DISCRETE STORM MODE
WOULD BE FAVORED. FORECAST SOUNDINGS INDICATE ENVIRONMENTAL MIXED
LAYER CAPE WILL BE IN EXCESS OF 2000 J/KG OUT AHEAD OF THE
DRYLINE. THE EXPECTED CAPE/SHEAR COMBINATION THIS AFTERNOON
COMBINED WITH AN ANTICIPATED DISCRETE STORM MODE FAVOR SUPERCELLS
AS THE PRIMARY STORM MODE ASSUMING STORMS DEVELOP.

00Z 4 KM WRF FROM THE NSSL AND NCEP WERE NOT VERY OPTIMISTIC ON
THUNDERSTORM INITIATION FOR THIS AFTERNOON. HOWEVER LOCALLY RUN
12Z 4KM WRF...12Z HRRR AND 14Z RUC ALL INDICATE TSTM INITIATION
ALONG THE DRYLINE IN THE 19 TO 20Z (2-3 PM CDT) TIMEFRAME. CURRENT
THINKING IS TO SIDE WITH THE 12Z HIGH RESOLUTION GUIDANCE AND
EXPECT INITIATION IS LIKELY AFTER 2 PM CDT. IF STORMS DO INITIATE
AS EXPECTED THEY WILL LIKELY BECOME SEVERE AND BE CAPABLE OF
PRODUCING VERY LARGE HAIL AND DAMAGING OUTFLOW WINDS. EXPECT THAT
THE MOST LIKELY AREA FOR TSTMS TO INITIATE WILL BE ALONG A
CORSICANA TO TEMPLE LINE...HOWEVER THIS IS HIGHLY DEPENDENT ON
WHERE THE DRYLINE BULGE ACTUALLY LIES BY 2 PM. THE TORNADO THREAT
IS SOMEWHAT CONDITIONAL. LOW LEVEL WINDS ARE EXPECTED TO BE
VEERED OUT OF THE SOUTHWEST BY 19Z. THIS WOULD MAKE FOR RELATIVELY
STRAIGHT LOW LEVEL HODOGRAPHS WHICH...IN GENERAL...IS NOT
FAVORABLE FOR THE DEVELOPMENT OF TORNADOES. WITH A DISCRETE
SUPERCELL STORM MODE EXPECTED IT IS POSSIBLE THAT A SUPERCELL
ITSELF WILL ALTER ENVIRONMENTAL WINDS AND LOCALLY INCREASE THE
TORNADO THREAT. SO WHILE LOW LEVEL SHEAR PARAMETERS MAY NOT
OVERWHELMINGLY SUGGEST A TORNADO THREAT...CONTINUE TO THINK AN
ISOLATED TORNADO THREAT IS WARRANTED IF A DISCRETE SUPERCELL
DEVELOPS THIS AFTERNOON.

PREVIOUS FORECAST HAD THE SOUTHEASTERN PORTION OF THE CWA
HIGHLIGHTED FOR THE HIGHEST POTENTIAL TO SEE STORMS THIS AFTERNOON
AND THIS CONTINUES TO LOOK ACCURATE SO NO SIGNIFICANT CHANGES TO
POPS PLANNED. THERE IS STILL SOME CHANCE THAT THE DRYLINE WILL
SURGE EAST BEFORE SIGNIFICANT LARGE SCALE FORCING FOR ASCENT
BUILDS OVER THE FORECAST AREA. IF THIS OCCURS LOW LEVEL MOISTURE
WOULD BE SCOURED EAST AND TSTMS WOULD BE LESS LIKELY TO DEVELOP.
WILL KEEP AN EYE ON THIS FOR THE REMAINDER OF THE DAY AND UPDATE
THE FORECAST AS NECESSARY FOR TSTM POTENTIAL.

CAVANAUGH

&&

.PREV DISCUSSION... /ISSUED 433 AM CDT SUN OCT 24 2010/
WATER VAPOR AND SHORT TERM MODEL DATA SHOW THE NEXT UPPER LEVEL
DISTURBANCE IS NOW TRACKING THROUGH NEW MEXICO AND WILL RAPIDLY
MOVE EAST ACROSS NORTH TEXAS LATE THIS AFTERNOON. MODELS INDICATE
500 MB HEIGHT FALLS OCCURRING ACROSS TEXAS TODAY WITH INCREASING
CYCLONIC CURVATURE TO THE MID-UPPER LEVEL HEIGHT FIELDS. THIS IS
INDICATIVE OF STRONG DYNAMIC FORCING WHICH WILL STEEPEN MID LEVEL
LAPSE RATES AND PROVIDE THE LIFT FOR SOME SEVERE STORMS TODAY.

A DRY LINE CURRENTLY ACROSS WEST TEXAS WILL MIX EASTWARD WITH THE
AIDE OF PRONOUNCED SWLY FLOW AND DRY ADVECTION IN THE LOW LEVELS.
DRY LINE WILL BE THE FOCUS FOR STORM INITIATION SOMETIME BETWEEN
2 AND 4 PM...AND THUS ITS LOCATION IS CRITICAL FOR PLACEMENT OF
POPS. MODELS BRING THE DRY LINE TO BONHAM-DALLAS-KILLEEN BUT
SOMETIMES THEY CAN BE TOO AGGRESSIVE WITH THE EASTWARD MOVEMENT.
BELIEVE THE NORTHERN PART OF THE DRY LINE WILL HAVE BETTER
EASTWARD MOMENTUM THAN THE SOUTHERN...WHICH MAY HANG UP ACROSS THE
SW CWA. THUS WILL SHOW LOW POPS THIS AFTERNOON ALONG AND EAST OF
A LINE FROM GAINESVILLE TO GRANBURY TO GOLDTHWAITE TO ACCOUNT FOR
DRY LINE LOCATION UNCERTAINTY. THE BETTER CHANCE OF STORMS/SEVERE
WEATHER TODAY WILL BE FARTHER EAST...GENERALLY EAST OF A BONHAM TO
WAXAHACHIE TO LAMPASAS LINE...WHERE LOW LEVEL MOISTURE BECOMES
PROGRESSIVELY DEEPER AND STORM INITIATION PROBABILITIES INCREASE.

MORNING CLOUDS ARE EXPECTED...BUT DO EXPECT SOME SUNSHINE BY EARLY
AFTERNOON. HIGH TEMPS SHOULD REACH THE MID 80S AREA WIDE WITH DEW
POINTS CLIMBING INTO THE MID-UPPER 60S EAST OF THE DRY LINE. THIS
COMBINED WITH STEEPENING LAPSE RATES/COOLING ALOFT FROM THE UPPER
TROUGH WILL CONTRIBUTE TO CAPE VALUES OVER 2000 J/KG. DEEP LAYER
SHEAR IS AMPLE FOR SUPERCELLS TO DEVELOP...BUT LOW LEVEL FLOW WILL
VEER/WEAKEN THIS AFTERNOON. WHILE A LOW TORNADO THREAT EXISTS...IT
APPEARS THE MAIN THREAT IS VERY LARGE HAIL GIVEN THE FAVORABLE
THERMODYNAMIC ENVIRONMENT...WITH DAMAGING WINDS ALSO POSSIBLE.
UPPER SHORTWAVE WILL PASS THROUGH THE REGION EARLY THIS EVENING
AND EXPECT ALL STORMS TO MOVE EAST AND OUT OF THE CWA BY 9 PM.

THE DRY LINE WILL LINGER ACROSS NORTH TEXAS THROUGH MONDAY BUT
MOISTURE JUST ABOVE THE SURFACE BECOMES TOO DEPLETED FOR A CHANCE
OF CONVECTION. INSTEAD THE MAIN STORY MONDAY WILL BE STRONG S/SW
WINDS AS A POWERFUL CYCLONE WRAPS UP IN THE PLAINS. A WEAK FRONT
WILL ARRIVE MONDAY NIGHT...WITH PERHAPS A VERY LOW THREAT OF SOME
CONVECTION CLIPPING THE FAR NORTHEAST ZONES WHERE MOISTURE MAY BE
SUFFICIENT. COOLER AND DRIER WEATHER IS EXPECTED FOR TUESDAY.
SOUTHERLY WINDS AHEAD OF THE NEXT FRONT MAY BRING SOME LOW CLOUDS
INTO THE AREA WEDNESDAY. THE FRONT SHOULD PUSH THROUGH WEDNESDAY
NIGHT WITH SOME ELEVATED MOISTURE/FRONTOGENESIS LIFT CONTRIBUTING
TO A FEW SHOWERS ACROSS THE SOUTHERN HALF OF NORTH TEXAS. CLEARING
SHOULD OCCUR AREA WIDE ON THURSDAY WITH SUNNY AND PLEASANT WEATHER
PERSISTING INTO THE WEEKEND. COOL OVERNIGHT LOWS AND MILD-WARM
AFTERNOON HIGHS ARE EXPECTED.

TR.92

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  86  60  88  59  79 /  10  10   5  10   5
WACO, TX              86  62  90  63  82 /  20  10   5   5   5
PARIS, TX             83  61  86  59  78 /  30  30   5  20  10
DENTON, TX            84  56  88  56  77 /  10  10   5  10   5
MCKINNEY, TX          84  58  86  57  78 /  20  10   5  10   5
DALLAS, TX            85  62  88  61  80 /  10  10   5  10   5
TERRELL, TX           85  63  87  62  80 /  30  10   5  10  10
CORSICANA, TX         86  65  87  65  82 /  30  20   5  10   5
TEMPLE, TX            86  62  88  64  83 /  30  10   5   5   5
MINERAL WELLS, TX     86  54  89  55  77 /  10  10   5   5   5

&&

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

&&

25/69

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
750 AM CDT SUN OCT 24 2010

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-242200-
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-
750 AM CDT SUN OCT 24 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH TEXAS.

.DAY ONE...TODAY AND TONIGHT.
THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
NORTH TEXAS THIS AFTERNOON AND THIS EVENING. THE RISK AREA IS
GENERALLY ALONG AND EAST OF INTERSTATE 35. VERY LARGE HAIL...
DAMAGING STRAIGHT LINE WINDS...AND AN ISOLATED TORNADO WILL BE
POSSIBLE. THE SEVERE WEATHER THREAT WILL DIMINISH FROM WEST TO
EAST AFTER SUNSET.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.
WIDELY SCATTERED THUNDERSTORMS ARE EXPECTED ACROSS NORTHEAST
TEXAS MONDAY NIGHT AS A COLD FRONT MOVES THROUGH THE AREA.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION WILL LIKELY BE NEEDED IN THE SLIGHT RISK AREA
AFTER 1 PM THIS AFTERNOON.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE FORT WORTH TX
130 PM CDT SUN OCT 24 2010

TXZ107-122-123-241900-
HOPKINS TX-RAINS TX-VAN ZANDT TX-
130 PM CDT SUN OCT 24 2010

...SIGNIFICANT WEATHER ADVISORY FOR...
  SOUTHWESTERN HOPKINS COUNTY
  RAINS COUNTY
  NORTH CENTRAL VAN ZANDT COUNTY

AT 129 PM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED A
STRONG THUNDERSTORM 6 MILES NORTHEAST OF WILLS POINT...MOVING
NORTHEAST AT 25 MPH.

CITIES IN THE PATH OF THIS STORM INCLUDE COMO...EAST TAWAKONI...
EDGEWOOD...EMORY...SULPHUR SPRINGS AND LAKE TAWAKONI STATE PARK.

PENNY-SIZED HAIL AND WIND GUSTS TO 40 MPH CAN BE EXPECTED FROM THIS
STORM.

LAT...LON 3296 9565 3278 9563 3265 9590 3280 9604
      3285 9599 3286 9594 3288 9596 3321 9561
      3297 9537
TIME...MOT...LOC 1829Z 229DEG 22KT 3278 9589

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