Flash Flood Warning 11, NWS Norman, OK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORMAN OK
325 AM CDT SAT JUN 17 2000

PRELIMINARY DISCUSSION... FLASH FLOOD WATCH BEING ISSUED.

OVERALL SCENARIO HAS NOT CHANGED MUCH, AND IT WILL NOT CHANGE MUCH
OVER THE NEXT 24 HR OR SO. SURFACE FRONT EXPECTED TO REMAIN NEARLY
STATIONARY FROM SE NM/SW TX NE-WARD TO NEAR RED RIVER IN SE OK, WITH
HIGH POPS CONTINUING NEAR AND N/NW OF SURFACE FRONT. ACTIVE ZONE OF
ELEVATED CONVECTION CURRENTLY ACROSS W/N OK IS ABOUT 100 MI OR SO
FARTHER N THAN WE EXPECTED AT THIS TIME YESTERDAY, BUT IS DEVELOPING
SE. MESONET RAINFALL RATES HAVE INCREASED CONSIDERABLY IN THIS ZONE
SINCE MIDNIGHT, TO 1-2 INCHES/HR LOCALLY. BASED ON CORRENT
INCREASING TREND, WE WILL ISSUE A FLASH FLOOD WATCH FOR MUCH OF
SW/CENTRAL/NCENTRAL OK WHERE 3- AND 6-HOURLY RAINFALL RATES EASILY
MAY APPROACH OR EXCEED CURRENT 2-3 INCH FFG LOCALLY. MAIN RISK MAY
BE THIS MORNING, AS RAINFALL RATES TYPICALLY HAVE BEEN GREATEST AT
NIGHT, BUT WE WILL WORD IT FOR ALL DAY PENDING EVOLUTION OF RAIN
AREAS LATER THIS MORNING.

SOME SMALLER-SCALE DETAILS ALSO NEED TO BE ADDRESSED FOR TONIGHT.
WHILE THE MAIN SHORTWAVE IN THE CENTRAL ROCKIES WILL REMAIN WELL N
TODAY AND TONIGHT, ANOTHER ONE CURRENTLY APPEARS ON SATELLITE
VICINITY OF AZ/NM BORDER AND MAY BECOME A FACTOR TONIGHT. ALSO OF
GROWING CONCERN IS THE PLUME OF HIGH-LEVEL MOISTURE WORKING NE FROM
MEX, SOME OF WHICH IS FROM THE REMNANTS OF PACIFIC TS BUD.
INTERACTION OF THIS SORT OF TROPICAL MOISTURE WITH A SLOW-MOVING
FRONT CAN CAUSE HAVOC HERE IN TERMS OF HEAVY RAIN - USUALLY IN FALL,
BUT SINCE ATMOSPHERE CARES NOT ABOUT CALENDARS, JUNE IS FAIR GAME.
RIGHT ENTRANCE REGION OF 300MB JET OVER GREAT LAKES/UPPER MS VALLEY
ALSO MAY CONTRIBUTE TO LARGE-SCALE LIFT. ALL THIS LEADS TO KEEPING
POPS IN 60-80PCT RANGE TONIGHT, WITH HEAVY RAIN AGAIN POSSIBLE.
RAINFALL TODAY WILL LIKELY LOWER FFG VALUES CONSIDERABLY BY TONIGHT,
SO MORE WATCHES MAY WELL BE NEEDED.

RH GRADUALLY DECREASES INTO SUN, ESPECIALLY N AND W, AND SURFACE
FRONT WEAKENS. THUS POPS WILL DROP OFF TO 40-50PCT RANGE WITH
HIGHEST IN THE SE CLOSER TO LINGERING SURFACE BOUNDARY.

NOT MUCH OPPORTUNITY TO EXAMINE MEDIUM RANGEGUIDANCE THIS MORNING,
SO PLAN TO LEAVE EXTENDED AS IS.

COORD W/ICT, TUL, ABRFC.

NUMBERS WILL BE SENT LATER THIS MORNING.

24

.OUN...
OK...FLASH FLOOD WATCH TODAY MOST OF SW, CENTRAL, N CENTRAL OK -
OKZ007-008-012-013-016>036-038.
TX...NONE.