Flash Flood Warning 3, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
345 AM CDT SUN APR 30 2000

WILL FOLLOW CLOSELY TO THE ETA MODEL...AND TO AN EXTENT THE
AVN...THIS FORECAST PACKAGE BASED MAINLY ON HANDLING OF SURFACE
FRONT PROGD TO ENTER AREA TODAY FROM THE NORTHWEST. WHERE THIS
BOUNDARY ENDS UP LATE TODAY THROUGH EARLY MONDAY WILL HAVE PROFOUND
IMPACT ON BOTH SEVERE POTENTIAL THROUGH THIS EVENING AND EXCESSIVE
RAINFALL AREA TONIGHT AND EARLY MONDAY. AGREE AND WILL FOLLOW
REASONING GIVEN BY SPC SWODY1 AND HPC QPFPFD DISCUSSIONS. FLY IN THE
OINTMENT WILL BE MESOSCALE INFLUENCES LATER IN FIRST PERIOD AND
BEYOND. DUE TO THE COMPLEX ISSUE OF FUTURE MESOSCALE FEATURES...WILL
NOT ISSUE FLASH FLOOD WATCH ATTM. WILL HOWEVER MENTION HEAVY
RAINFALL TONIGHT INTO EARLY MONDAY IN ZONE GROUPINGS THAT RUN
ROUGHLY ALONG I-44 NORTHWARD. GREATEST THREAT FOR SIGNIFICANT SEVERE
WEATHER LATER TODAY WILL BE OVER OUR WESTERN NORTH TEXAS ZONES AND
PORTIONS OF SOUTHWEST OKLAHOMA. ALL OF THIS WILL BE DISCUSSED IN
THUNDERSTORM OUTLOOK AND A SPECIAL WEATHER STATEMENT OR FLOOD
POTENTIAL OUTLOOK THAT WILL BE ISSUED TOWARD 6 AM THIS MORNING.
DAY SHIFT WILL MONITOR SEVERE AND FLOOD POTENTIALS AS SMALLER SCALE
INFLUENCES BECOME CLEARER.

IN A NUTSHELL...WITH UPPER LOW HANGING AROUND AND MAIN SURFACE
BOUNDARY MAKING AN ENTRANCE...LIKELY TO CATEGORICAL POPS ARE CALLED
FOR THROUGH SHORT TERM PERIODS. TEMPS WILL BE A LITTLE TRICKY AND
WILL GO ON THE COOLER SIDE FOR HIGHS WITH EXPECTED RAINFALL AND
CLOUD COVER. OVERALL...NO SIGNIFICANT CHANGES FROM YESTERDAYS
AFTERNOON PACKAGE.

NOT A WHOLE LOT OF TIME TO LOOK AT EXTENDED...SO WILL NOT MAKE ANY
MAJOR CHANGES THERE.

COORD WITH ICT.

FCSTID = 11
PRELIM CCF NUMBERS...
OKC   72  62  69  57 /  80  80  70  60
HBR   75  61  70  55 /  80  80  70  50
SPS   78  63  73  58 /  80  80  60  50
GAG   67  53  65  52 / 100  80  60  60
PNC   72  6e0  67  56 /  70  80  70  60
DUA   72  63  72  61 /  40  60  70  60

.OUN...
OK...NONE.
TX...NONE.

OKZ004>048-050>052-TXZ083>090-301346-

THUNDERSTORM OUTLOOK
NATIONAL WEATHER SERVICE NORMAN OK
646 AM CDT SUN APR 30 2000

THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING...ACROSS PORTIONS OF WESTERN NORTH TEXAS...ALONG AND SOUTH
OF A LINE FROM QUANAH...TO WICHITA FALLS...TO HENRIETTA. NORTH OF
THIS AREA...A SLIGHT RISK EXISTS THROUGH TONIGHT...FOR THE REMAINDER
OF WESTERN NORTH TEXAS...AND ALL OF WESTERN AND CENTRAL OKLAHOMA...
EXCEPT THE FAR SOUTHEAST...INCLUDING ARDMORE...ADA...AND DURANT.

DISCUSSION...AS OF EARLY THIS MORNING...A SLOW MOVING WARM FRONT WAS
LOCATED JUST SOUTH OF THE RED RIVER...EXTENDING WESTWARD TO AN AREA
OF LOW PRESSURE NEAR LUBBOCK. WHILE SOUTH OF THIS LOW PRESSURE
AREA...A DRY LINE EXTENDING SOUTHWARD INTO MEXICO. THUNDERSTORMS
DEVELOPING NORTH OF THE WARM FRONT THIS MORNING...WILL BE CAPABLE OF
PRODUCING LARGE HAIL NEAR THE OKLAHOMA...TEXAS BORDER...BEFORE THEY
ENCOUNTER MORE STABLE AIR FARTHER EAST.

LATE THIS AFTERNOON AND EVENING...INCREASED INSTABILITY FROM DAYTIME
HEATING...AND GREATER CONVERGENCE ALONG THE WARM FRONT AND
DRY LINE...WILL CONTRIBUTE TO MORE THUNDERSTORM DEVELOPMENT ACROSS
THE MODERATE RISK AREA. FAVORABLE VERTICAL WIND PROFILES WILL
ALLOW THESE STORMS TO BECOME SUPERCELLS...CAPABLE OF PRODUCING VERY
LARGE HAIL...PERHAPS BASEBALL SIZE OR LARGER...AND POSSIBLY A FEW
TORNADOES. NORTH OF THE WARM FRONT...INTO WESTERN AND CENTRAL
OKLAHOMA...THUNDERSTORM DEVELOPMENT IS LIKELY AS WELL...BUT LESS
INSTABILITY AND WEAKER WINDS ALOFT...SUGGESTS THE PRIMARY THREAT WILL
BE LARGE HAIL.

A LARGE AMOUNT OF RAIN IS ALSO EXPECTED THROUGH MONDAY...ACROSS MUCH
OF WESTERN AND NORTHERN OKLAHOMA...AND WESTERN NORTH TEXAS...MAINLY
ALONG AND NORTH OF INTERSTATE 44. ALTHOUGH NO FLASH FLOOD WATCHES
HAVE YET BEEN ISSUED...WATCHES MAY BE ISSUED LATER TODAY OR
TONIGHT...AS FACTORS CONTRIBUTING TO THE POTENTIAL FOR HEAVY RAIN
BECOME MORE CLEAR.

EMERGENCY MANAGERS AND STORM SPOTTER GROUPS ACROSS WESTERN NORTH
TEXAS...AND WESTERN AND CENTRAL OKLAHOMA...SHOULD BE PREPARED FOR
POSSIBLE ACTIVATION TODAY AND TONIGHT.

JAMES