MESOSCALE PRECIPITATION DISCUSSION 0018
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
304 PM EDT WED MAR 25 2015
 
AREAS AFFECTED...PORTIONS OF OK, KS, MO, AR 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 251901Z - 260101Z
 
SUMMARY...INCREASING INSTABILITY, LOW-LEVEL INFLOW, AND MOISTURE
INTERACTING WITH A FRONTAL ZONE AHEAD OF A MID-LEVEL SHORTWAVE
SHOULD LEAD TO HOURLY RAIN RATES OF 1.5", WHICH COULD LEAD TO
FLASH FLOODING IN AREAS WHERE CELLS BACKBUILD AND/OR TRAIN.

DISCUSSION...A SHORTWAVE ALOFT ENTERING WESTERN OK HAS BEEN ACTING
TO HELP TRIGGER ELEVATED SEVERE THUNDERSTORMS ACROSS SOUTHEAST KS
AND SOUTHWEST MO OVER THE PAST COUPLE HOURS.  PRECIPITABLE WATER
VALUES (PWS) IN THE AREA HAVE JUST EXCEEDED AN INCH, WITH
LOW-LEVEL INFLOW OF 30-35 KTS NOTED IN REGIONAL VAD WIND PROFILES,
CLOSE IN MAGNITUDE TO THE 850-400 HPA MEAN WINDS.  CAPE VALUES OF
1500-3000 J/KG LIE WITHIN THE WARM SECTOR OF THIS SYSTEM, PER SPC
RECENT MESOANALYSES.  RECENT SATELLITE IMAGERY HAS SHOWN AN
EROSION OF LOW STRATUS CLOUDS NEAR AND SOUTH OF THE FRONTAL
BOUNDARY, INDICATING AN EROSION OF LOCAL CIN NEAR AND SOUTH OF THE
FRONT.  TEMPERATURES AT 700 HPA ARE ROUGHLY 3-4C IN THIS REGION,
BELOW VALUES NORMALLY ASSOCIATED WITH A CAPPING INVERSION IN MARCH.

SOON AFTER 19Z, THE GUIDANCE INDICATES A COMPLETE EROSION OF CIN
NEAR THE FRONT WHICH SHOULD LEAD TO SURFACE-BASED THUNDERSTORM
ACTIVITY IN NORTHEAST OK AND NEAR THE WESTERN AR/MO BORDER WHICH
TRIES TO WORK SLIGHTLY INTO THE COLD SECTOR. AN INCREASE OF
LOW-LEVEL INFLOW, POSSIBLY REACHING 50 KTS BY THE END OF THE
PERIOD, SHOULD BRING LOCAL PWS INTO THE 1.25-1.50" RANGE, NEAR THE
LOWER THRESHOLD FOR FLASH FLOODING AND NEARLY DOUBLE WHAT IS
NORMAL FOR LATE MARCH.  THIS DEGREE OF MOISTURE SHOULD ALLOW FOR
HOURLY RAINFALL RATES UP TO 1.5" IN STRONGER STORMS.  THE FLOW IN
THE REGION SHOULD BECOME UNIDIRECTIONAL BY LATE THIS AFTERNOON AND
THIS EVENING, WITH WET BULB ZEROES RISING TO AROUND 10,000 FT,
WHICH COULD LEAD TO WARM RAIN PROCESSES.

INITIAL THUNDERSTORMS IN NORTHEAST OK COULD BACKBUILD IN RESPONSE
TO THE STRENGTHENING LOW-LEVEL INFLOW, WHICH WOULD AID SIGNIFICANT
RAINFALL PRODUCTION.  THE MEAN FLOW COMBINED WITH LOCAL COOL POOLS
FROM DEVELOPING CONVECTION AND A NORTHWARD MOVING WARM FRONT
SHOULD LEAD TO STORM MOTIONS TO THE EAST TO EAST-NORTHEAST WITH
TIME -- CELL TRAINING IS THE MAIN CONCERN ACROSS SOUTHERN MO. 
HOWEVER, THE DEGREE OF BULK SHEAR EXPECTED IN RAP MASS FIELDS
INDICATES THAT SUPERCELLS ARE EXPECTED, WHICH COULD PREVENT A
SOLID WARM ADVECTION THUNDERSTORM BAND FROM MATERIALIZING ACROSS
NORTHEAST OK AND SOUTHERN MO -- THE SUPERCELLS COULD CREATE BOWS,
LEWPS, AND/OR A MORE QLCS STRUCTURE WITHIN THE WARM ADVECTION
THUNDERSTORM BAND AND PERHAPS BREAK IT APART WITHIN 2-4 HOURS OF
ITS FORMATION.  REGIONAL MESOSCALE GUIDANCE INDICATES LOCAL
AMOUNTS OF 2-3" BY 01Z, WHICH COULD OCCUR WITHIN TWO HOURS AT ANY
PARTICULAR LOCATION.  FLASH FLOODING IS CONSIDERED POSSIBLE.

ROTH

ATTN...WFO...EAX...ICT...LSX...LZK...MEG...OUN...PAH...SGF...

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

LAT...LON   38199296 38069176 37528999 36668998 36309030 
            36199162 36229313 36269449 35469708 35859785 
            36249764 36839710 37699543 38129377