MESOSCALE PRECIPITATION DISCUSSION 0240
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1214 AM EDT THU MAY 31 2018

AREAS AFFECTED...NWRN TO CTRL OKLAHOMA

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

VALID 310413Z - 310900Z

SUMMARY...A LINE OF THUNDERSTORMS SHOULD BEGIN TO ACCELERATE INTO
NORTHWEST AND CENTRAL OKLAHOMA. HEAVY RAIN RATES COULD PRODUCE
LOCALIZED FLASH FLOODING... PARTICULARLY ALONG THE SOUTHERN END OF
THE LINE WHERE STORMS MAY DEVELOP INTO A TRAILING LINE AND PROLONG
THE DURATION OF HEAVY RAINFALL. LOCALIZED TOTALS OF 3-5 INCHES
WILL BE POSSIBLE.

DISCUSSION...KVNX AND KAMA RADARS SHOWED AN INCREASINGLY ORGANIZED
FORWARD-PROPAGATING MCS ADVANCING INTO NORTHWEST OKLAHOMA ROUND
04Z...AND CONVECTION ALLOWING MODELS GENERALLY SHOW THIS
CONTINUING TO PROPAGATE IN AN EASTERLY DIRECTION FOR AT LEAST
ANOTHER FEW HOURS. THERE IS EVIDENCE FOR INCREASING FORWARD
PROPAGATION IN OKLAHOMA MESONET SITES JUST BEHIND THE DEVELOPING
BOW ECHO...WITH SURFACE TEMPERATURES FALLING WELL INTO THE 60S AND
RISING PRESSURES...INDICATIVE OF A STRONG COLD POOL. THE FORWARD
PROPAGATING NATURE OF THIS CONVECTIVE LINE WOULD TEND TO BE A
MITIGATING FACTOR AGAINST FLASH FLOOD POTENTIAL...AS WOULD THE
RELATIVELY HIGH FLASH-FLOOD GUIDANCE FIGURES ACROSS MOST OF THE
NORTHWEST QUADRANT OF OKLAHOMA. THE LINE SHOULD GENERALLY
PROPAGATE EAST OR EAST-SOUTHEAST ALONG THE CUSP OF A WELL-DEFINED
LOW-MID LEVEL THERMAL RIDGE AND ELEVATED MIXED LAYER OVER THE NEXT
FEW HOURS.

HOWEVER...HEAVIER RAIN RATES AND A GREATER LONGEVITY OF CONVECTION
MAY BE EXPECTED ALONG THE SOUTHERN FLANK OF THE ADVANCING LINE.
THIS WOULD OCCUR WHERE AN INCREASING LOW-LEVEL JET WOULD INTERCEPT
THE STRENGTHENING COLD POOL AND NEW CELL GROWTH WOULD BE POSSIBLE
ON THE UPSHEAR FLANK. THE HRRR AND EXPERIMENTAL HRRR TEND TO SHOW
THIS WELL...WITH THE HEAVIEST QPF ALONG AND SOUTH OF THE APEX OF
THE DEVELOPING BOW. IN GENERAL...HI-RES MODELS KEEP MAXIMUM TOTALS
BELOW 5 INCHES...WITH LOCALIZED SWATHS AROUND 3-4 INCHES WHERE
CELL TRAINING CAN BE SUSTAINED FOR AROUND 1-2 HOURS. THIS MAY BE
SUFFICIENT TO PRODUCE LOCALIZED HEAVY RAINFALL...DEPENDING ON THE
EXACT CONVECTIVE EVOLUTION AND RAIN RATES. IF THE LINE REMAINS IN
TACT AND ON A RELATIVELY CONSISTENT COURSE...THESE HEAVIER RAIN
RATES COULD BE CLOSER TO THE NWRN AND NRN SIDES OF THE OKC METRO
AREA (WHERE FFG IS A LITTLE LOWER) CLOSER TO 07Z...BUT THAT IS
MORE UNCERTAIN.

LAMERS

ATTN...WFO...AMA...DDC...ICT...OUN...TSA...

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

LAT...LON   37119962 37109851 36929689 36399622 35659617
            35229712 35249830 35529960 36070056 36890011