Flash Flood and Flooding in Texas, April 17 to 19, 2010

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1236 PM CDT SAT APR 17 2010

.AVIATION...
INTERESTING CHANGE IN CONDITIONS ACROSS NORTH TEXAS DURING THE
LAST HOUR HAS RESULTED IN SIGNIFICANT CHANGES TO THE TAFS FOR THE
AFTERNOON HOURS. SURFACE LOW IS CURRENTLY LOCATED NEAR EASTLAND
COUNTY WITH HEAVIEST RAIN LOCATED JUST EAST AND NORTHEAST OF THE
LOW. TO THE EAST OF THIS SURFACE LOW /ALONG AND EAST OF INTERSTATE
35/ DRIER AIR FROM THE SOUTHEAST HAS RESULTED IN LIFTING CLOUD
BASES TO VFR CONDITIONS. FOR THE AFTERNOON HOURS...THINK THAT MOST
OF THE RAIN WILL REMAIN WEST OF INTERSTATE 35 CLOSER TO THE
SURFACE LOW. HOWEVER...AS THE SURFACE LOW SLOWLY MOVES EAST THIS
AFTERNOON...RAIN CHANCES WILL SHIFT EAST AND HIGHER RAIN CHANCES
OVER THE TAF SITES WILL OCCUR BEGINNING LATE AFTERNOON. UNTIL
THEN...VFR WILL PREVAIL AT KDAL WITH MVFR AT THE REMAINING TAF
SITES. ON AND OFF RAIN SHOWERS THROUGH MID AFTERNOON WILL BE MOST
LIKELY AT KAFW AND KFTW.

EXPECT CONDITIONS TO DETERIORATE AGAIN TONIGHT AND OVERNIGHT WITH
ALL SITES FALLING BACK TO LOW END IFR AND POSSIBLY LIFR. RAIN WILL
BE ENDING AT KACT TONIGHT AS THE SURFACE LOW MOVES THROUGH AND THE
RAIN WILL LIKELY END BY LATE MORNING ON SUNDAY IN THE METROPLEX.
TRUE COLD FRONT WILL PUSH THROUGH SUNDAY AFTERNOON RESULTING IN
STRONGER NORTHEAST WINDS.

82/JLD

&&

.UPDATE...
FORECAST ON TRACK AS OUR MID-LVL DISTURBANCE CENTERED NEAR HASKELL/
THROCKMORTON CONTINUES IT'S SLOW DRIFT NWD TOWARD WICHITA FALLS
AND VERNON THE REMAINDER OF THE DAY. MOST WIDESPREAD LIGHT TO
MODERATE RAIN...WITH ISOLATED POCKETS OF HEAVIER RAIN WILL REMAIN
CONCENTRATED FROM WRN D/FW METRO...NWWD TOWARD BOWIE...GRAHAM...
AND JACKSBORO. AS EXPECTED...SOME HIGHER TOTALS TO 2-3 INCHES UP
OVER YOUNG/JACK COUNTIES...BUT THIS HAS BEEN OVER THE PAST 24
HRS...AND NOT SHORT-FUSED. NO FLOODING PROBLEMS AS OF YET OUTSIDE
OF DRAINAGE DITCHES FILLING UP AND SOME MINOR STREET FLOODING.

NAM/GFS HAVE BEST RAINS FOCUSED TO FAR NW OVER SW OK/SE TX
PANHANDLE THIS AFTN...WHILE THE GEM/CANADIAN IS TOO HEAVY OVER SW
COUNTIES WHERE SOME DRIER AIR IS ENTRAINING IN FROM THE SW
RELATIVELY SPEAKING. ECMWF/RUC HAVE BEST HANDLE ON PLACEMENT
THROUGH AFTERNOON/EARLY EVE WITH HPC QPF IN GENERAL AGREEMENT.

MADE SOME MINOR TWEAKS ON POPS/QPF...BUT CURRENT FLOOD WATCH
COVERAGE LOOKS TO BE ON TARGET WITH NO CHANGES PLANNED. FRONT
STILL TECHNICALLY NW OF CWA...BUT SFC LOW NEAR COMANCHE/CISCO IS
TRAINING IN SOME CAA ACROSS FAR NW COUNTIES AND TWEAKED HIGHS A
BIT. UPDATE ON THE WAY.

05

&&

.PREV DISCUSSION... /ISSUED 404 AM CDT SAT APR 17 2010/
A WET WEATHER PATTERN WILL CONTINUE ACROSS NORTH TEXAS THROUGH
SUNDAY AS A WEAK UPPER LEVEL TROUGH AND COLD FRONT MOVES SLOWLY
ACROSS THE REGION. ABUNDANT MOISTURE AND RELATIVELY LOW MID LEVEL
WIND SPEEDS WILL KEEP A THREAT OF HEAVY RAINFALL WITH ONLY
ISOLATED THUNDERSTORM CHANCES. IT APPEARS THAT THE HEAVIEST
RAINFALL TODAY AND TONIGHT WILL BE CONFINED TO ABOUT THE WESTERN
HALF OF THE REGION WHERE THE BEST ISENTROPIC LIFT IS EXPECTED.
THEREFORE...WE WILL KEEP THE FLOOD WATCH IN EFFECT THROUGH SUNDAY
AFTERNOON ACROSS THE WESTERN TWO THIRDS OF NORTH TEXAS. DRIER AIR
WILL BEGIN TO WORK INTO THE REGION SUNDAY AS THE UPPER TROUGH AXIS
SHIFTS TO THE EAST AND SURFACE HIGH PRESSURE BUILDS SOUTHWARD.
AVERAGE RAINFALL TOTALS IN THE WATCH AREA WILL RANGE FROM 2 TO 4
INCHES WITH SOME HIGHER AMOUNTS.

DRIER AIR AND BUILDING UPPER LEVEL HIGH PRESSURE MONDAY THROUGH
WEDNESDAY WILL BRING AN END TO THE PRECIP CHANCES. LOW LEVEL
MOISTURE WILL BE ON THE INCREASE WEDNESDAY NIGHT AS LOW PRESSURE
DEEPENS IN THE WEST. THERE IS A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS THURSDAY AS LARGE SCALE LIFT AND INSTABILITY
INCREASE WITH THE APPROACH OF A STRONG LOW PRESSURE SYSTEM. BOTH
THE GFS AND ECMWF AGREE THAT THE BEST CHANCE FOR STORMS WILL BE
FRIDAY WHEN A DRY LINE SWEEPS ACROSS THE REGION. WILL LEAVE POPS
ON THE LOW SIDE DUE TO THE TIMING ISSUES THAT FAR OUT IN THE FORECAST.

ABUNDANT CLOUD COVER AND RAIN WILL HOLD AFTERNOON TEMPS DOWN THE
NEXT COUPLE OF DAYS. EXPECT TEMPERATURES TO WARM NEXT WEEK WITH THE
RETURN OF THE SUN AND INCREASING LOW LEVEL MOISTURE.

79

&&

.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX  71  56  62  50  68 / 100  90  70  30  10
WACO, TX              73  56  67  51  70 /  90  80  60  20  10
PARIS, TX             71  53  60  48  70 /  70  70  90  30  10
DENTON, TX            68  55  60  49  70 / 100  90  70  30  10
MCKINNEY, TX          71  55  61  47  68 /  90  80  80  40  10
DALLAS, TX            71  57  62  50  68 / 100  90  70  30  10
TERRELL, TX           75  57  62  49  70 /  80  80  80  40  10
CORSICANA, TX         74  57  65  52  69 /  90  80  70  40  10
TEMPLE, TX            73  56  68  52  67 /  80  70  60  20  10

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH THROUGH SUNDAY EVENING FOR TXZ091>093-100>104-
115>119-129>134-141>145-156>160-174.

&&

82/05

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE FORT WORTH TX
1013 AM CDT SAT APR 17 2010

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-181200-
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-
1013 AM CDT SAT APR 17 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH TEXAS.

.DAY ONE...TODAY AND TONIGHT.
A FLOOD WATCH IS IN EFFECT FOR THE WESTERN HALF OF NORTH TEXAS...
WHERE LOCALIZED MODERATE TO HEAVY RAINFALL MAY PRODUCE MINOR
FLOODING OF POOR DRAINAGE AREAS...DITCHES...CREEKS AND ROADS.

ISOLATED THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND EVENING
SOUTH OF INTERSTATE 20.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.
THE FLOOD WATCH WILL CONTINUE THROUGH 7 PM SUNDAY. THE RAIN AND
ISOLATED THUNDERSTORMS WILL GRADUALLY SHIFT INTO EAST TEXAS SUNDAY
NIGHT.

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS TUESDAY. MORE WIDESPREAD
THUNDERSTORM CHANCES WILL RETURN THURSDAY AND FRIDAY.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION IS NOT ANTICIPATED. HOWEVER...RAINFALL REPORTS
AND REPORTS OF ANY FLOODING TO THE NATIONAL WEATHER SERVICE OFFICE
IN FORT WORTH ARE ENCOURAGED.

05/