MESOSCALE PRECIPITATION DISCUSSION 0057
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
556 AM EDT TUE MAY 21 2013
AREAS AFFECTED...CENTRAL AND EASTERN OK...NORTHWEST AR
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 210955Z - 211255Z
SUMMARY...A SOLIDIFYING LINE OF CONVECTION HAS DEVELOPED FROM
CENTRAL INTO EASTERN OK AND HAS BEGUN TO TRAIN. THIS COULD LEAD
TO FLASH FLOODING.
DISCUSSION...A LINE OF CONVECTION HAS FORMED ABOUT 100 MILES NORTH
OF AN OUTFLOW BOUNDARY WHICH HAS BEEN STUCK ACROSS NORTHEAST TX
OVERNIGHT. COOL AIR ALOFT UNDER THE BASE OF A WEAK SHORTWAVE
ACROSS KS COMBINED WITH BACKING 850 HPA INFLOW OVERRIDING THE
OUTFLOW BOUNDARY HAS LED TO ITS DEVELOPMENT. THE PRESENCE OF CIN
NEAR THE OUTFLOW BOUNDARY HAS FORCED THE CONVECTION TO BE ELEVATED
IN NATURE. DIVERGENCE ALOFT IS BEING AIDED BY A STRONGER UPPER
LEVEL DISTURBANCE DRIFTING ACROSS CENTRAL AND EASTERN NM. THE 12Z
MESOSCALE GUIDANCE HAD THIS INDICATED THIS SOLUTION ON MONDAY,
BEFORE THE 00Z GUIDANCE BACKED OFF WITHIN THEIR QPF FIELDS. EVEN
SO, THE RAP INDICATED THE POSSIBILITY OF THIS OVERNIGHT WITHIN ITS
MASS FIELD FORECASTS. THE LINE IS ALIGNED WITH THE
CORFIDI/PROPAGATION VECTORS, AND IS EXPECTED TO PERSIST FOR A FEW
HOURS BEFORE IT ESCAPES AS A WHOLE TO THE EAST-NORTHEAST INTO AR,
POSSIBLY ORGANIZING AS A BOW ECHO IT DOES SO, SIMILAR TO THE LINE
THAT BRIEFLY FORMED BETWEEN 04-07Z ACROSS SOUTHERN OK. THREE HOUR
FLASH FLOOD GUIDANCE VALUES -- FFGS -- ARE ON THE ORDER OF 2.5
INCHES/3 HOURS. PRECIPITABLE WATER VALUES -- PWS -- OF 1.50-1.75
INCHES LIE WITHIN THIS REGION. RAINFALL RATES OF 1-2 INCHES PER
HOUR WOULD EXCEED THIS THRESHOLD, THOUGH THE LINE IS EXPECTED TO
DRIFT NORTHWARD THIS MORNING AT A SLOW RATE OF SPEED. LOCAL
RAINFALL AMOUNTS OF 3-5 INCHES ARE POSSIBLE, WHICH COULD LEAD TO
FLASH FLOODING. CONFIDENCE IS MODEST IN FLASH FLOODING DUE TO ITS
NORTHWARD DRIFT, HENCE THE POSSIBLE WORDING.
ROTH
ATTN...WFO...TSA...OUN...
LAT...LON 34889894 35959721 36399602 36459422 35409407 35099501
34869756 34889894