MESOSCALE PRECIPITATION DISCUSSION 0189
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1220 PM EDT WED MAY 23 2018

AREAS AFFECTED...NE OK...NW/NC AR...FAR SW MO...FAR SE KS

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

VALID 231619Z - 232215Z

SUMMARY...THUNDERSTORMS ARE BEGINNING TO INITIATE ACROSS THE
SOUTHERN EXTENT OF THE OZARKS REGION...AND GIVEN WEAK WINDS
THROUGH MUCH OF THE ATMOSPHERE TODAY...MAY BE NEARLY STATIONARY AT
TIMES. THIS SHOULD LEAD TO MAXIMUM RAINFALL RATES AROUND 2 IN/HR
WITH A THREAT OF FLASH FLOODING.

DISCUSSION...CONVECTIVE INITIATION BEGAN ACROSS NORTHEAST OKLAHOMA
BETWEEN 15Z AND 16Z AND NEW UPDRAFTS HAVE RECENTLY FORMED IN
NORTHERN ARKANSAS AS WELL. THESE THUNDERSTORMS WERE FORMING IN A
VERY MOIST ENVIRONMENT WITH CIRA BLENDED TPW...RAP ANALYSIS...AND
A RECENT GPS OBSERVATION INDICATING PRECIPITABLE WATER VALUES
AROUND 1.8 INCHES. THESE VALUES ARE SOMEWHAT ANOMALOUS FOR MAY
RELATIVE TO CLIMATOLOGICAL AVERAGES...AROUND OR JUST ABOVE THE
95TH PERCENTILE. THE ELEVATED PWATS ALSO HAPPEN TO COINCIDE WITH A
MINIMUM (570DM) IN 1000-500 MB THICKNESS... SUGGESTING THEY ARE
ALSO RELATIVELY HIGH FOR THE TEMPERATURE PROFILE IN PLACE ACROSS
THE REGION AND PRODUCING A MEAN 1000-500 MB RH OF AROUND 80-85
PERCENT.

THE NEARLY SATURATED LOW-MID LEVEL ENVIRONMENT ACROSS THE REGION
ALSO COINCIDES WITH VERY WEAK FLOW THROUGH THE DEPTH OF THE
TROPOSPHERE. RAP FORECAST SOUNDINGS FROM NEAR THE NORTHERN OK-AR
BORDER REGION SHOW MEAN LFC-EQL FLOW ON THE ORDER OF 5 KNOTS (FROM
THE SOUTH). THIS SHOULD LEAD TO NEARLY STATIONARY CONVECTIVE
CLUSTERS AT TIMES...WITH PROPAGATION ALSO HEAVILY INFLUENCED BY
CONVECTIVE OUTFLOWS. HOWEVER...GIVEN THE DEEP MOIST PROFILE...IT
ALSO DOES NOT APPEAR THAT COLD POOLS WOULD BE ABLE TO
SIGNIFICANTLY ACCELERATE ANY CONVECTIVE CLUSTERS OR LINES. AND THE
NEARLY SATURATED PROFILE COMBINED WITH A TALL-SKINNY CAPE
DISTRIBUTION SHOULD PROMOTE MORE EFFICIENT RAINFALL PRODUCTION IN
STORMS. THUS SLOW-MOVING OR MERGING CELLS WOULD CERTAINLY POSE A
RISK FOR FLASH FLOODING IF THEY CAN SUSTAIN HEAVY RAINFALL IN A
GIVEN LOCATION FOR OVER AN HOUR...WITH PEAK RAIN RATES LIKELY TO
REACH AROUND 2 IN/HR. THESE SORT OF RAIN RATES HAVE ALREADY BEEN
OBSERVED ON KSRX DUAL POL RADAR ESTIMATES AND MRMS ESTIMATES AS
WELL.

LAMERS

ATTN...WFO...ICT...LZK...MEG...SGF...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...

LAT...LON   37369458 37049336 36729226 36489170 35799129
            35149183 34739274 34759387 35379497 35719581
            36329617 36929620 37289566