MESOSCALE PRECIPITATION DISCUSSION 0121
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
933 PM EDT WED MAY 02 2018

AREAS AFFECTED...CENTRAL OKLAHOMA...NORTH-CENTRAL TEXAS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 030133Z - 030445Z

SUMMARY...LOCALIZED FLASH FLOODING WILL BE POSSIBLE AS A LINE OF
STORMS MOVES THROUGH PARTS OF CENTRAL OKLAHOMA AND NORTH-CENTRAL
TEXAS. HOURLY RAIN RATES HAVE ALREADY BEEN OBSERVED TO BE AS HIGH
AS 2 IN/HR AND RAIN RATES THIS HIGH IN URBANIZED AREAS COULD LEAD
TO FLOODING.

DISCUSSION...A LINE ECHO WAVE PATTERN (LEWP) WAS MOVING THROUGH
PORTIONS OF CENTRAL OKLAHOMA AND NORTH-CENTRAL TEXAS. THE OKLAHOMA
MESONET SITE NEAR MINCO RECENTLY REPORTED AN HOURLY RAIN RATE AS
HIGH AS 2 IN/HR. STORM MOTIONS HAVE BEEN CHAOTIC AND SLOW TO THE
NORTHEAST OF A MORE DOMINANT MESOVORTEX IN THE LEWP CURRENTLY
APPROACHING CHICKASHA. EXTRAPOLATION OF CURRENT TRENDS WOULD TAKE
THIS THROUGH THE OKLAHOMA CITY METRO AREA OVER THE NEXT COUPLE
HOURS. ENHANCED LOW LEVEL INFLOW AND FOCUSED CONVERGENCE JUST
DOWNSTREAM FROM THE MESOVORTEX MAY BE ABLE TO SUSTAIN HEAVY
RAINFALL OVER INDIVIDUAL LOCATIONS FOR OVER AN HOUR...AND WITH
MAXIMUM RAIN RATES ALREADY OBSERVED TO BE JUST OVER 2 IN/HR...THIS
COULD LEAD TO A FEW INCHES OF RAIN IN A VERY SHORT PERIOD OF TIME.
ALTHOUGH FLASH FLOOD GUIDANCE IS QUITE HIGH ACROSS THE
REGION...THESE VERY HIGH RAIN RATES COULD PRODUCE LOCALIZED FLASH
FLOODING IN MORE URBANIZED AREAS THAT MAY REQUIRE LESS RAINFALL TO
PRODUCE FLOODING THAN INDICATED BY FFG. GIVEN THE LOCATION AND
MOTION (NORTHEAST) OF THE MESOVORTEX...THE HIGHEST CHANCES OF
FLASH FLOODING APPEAR TO BE IN THE GENERAL VICINITY OF THE
OKLAHOMA CITY METRO AREA. HOWEVER...FLOODING IS NOT CERTAIN AS A
CONTINUED ACCELERATION OF THE LINE COULD REDUCE THE RESIDENCE TIME
OF HEAVY RAIN AND THUS LIMIT THE RAINFALL TOTALS.

ADDITIONAL STORMS WERE DEVELOPING FURTHER SOUTH IN NORTH-CENTRAL
TEXAS AND WERE ORIENTED IN A NE-SW FASHION AS OF 0130Z. THE
ORIENTATION OF THE LINE ROUGHLY PARALLEL TO CELL MOTION AND THE
FAIRLY STRONG SOUTHEASTERLY LOW-LEVEL INFLOW INTERCEPTING THE
ENTIRE LENGTH OF THE LINE COULD SUSTAIN THIS CONVECTION INTO THE
EVENING AND ALLOW FOR A SWATH OF HEAVY RAINFALL IN THIS AREA.
ALTHOUGH FLASH FLOODING MAY BE LESS LIKELY HERE GIVEN THAT
CONVECTION IS GENERALLY AWAY FROM LARGE METRO AREAS...IT CANNOT BE
RULED OUT IF TRAINING CONVECTION IS SUSTAINED FOR A COUPLE HOURS
OR MORE.

LAMERS

ATTN...WFO...FWD...OUN...SJT...TSA...

ATTN...RFC...ABRFC...WGRFC...

LAT...LON   35939766 35919639 35609603 35099606 34259668
            33129775 32599910 32649981 33099968 33749905
            34309820 34709816 35299826