MESOSCALE PRECIPITATION DISCUSSION 0088
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
437 AM EDT FRI APR 06 2018

AREAS AFFECTED...PORTIONS OF EASTERN OK AND SOUTHERN AR

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

VALID 060836Z - 061436Z

SUMMARY...SHOWERS AND THUNDERSTORMS ARE GROWING IN COVERAGE AND
INTENSITY ACROSS THE REGION. HOURLY TOTALS TO 1.75" WITH LOCAL
AMOUNTS TO 3" ARE EXPECTED.

DISCUSSION...A SHORTWAVE MOVING ACROSS WESTERN OK AND THE TX
PANHANDLE HAS SPURRED THE DEVELOPMENT OF SHOWERS AND THUNDERSTORMS
TO THE NORTH OF A STATIONARY FRONT AND RED RIVER CONVERGENCE ZONE
DURING THE PAST 2-2.5 HOURS, WITH COVERAGE AND INTENSITY COMING UP
SINCE 0730Z.  PRECIPITABLE WATER VALUES OF 1-1.25" LIE ACROSS THE
REGION PER GPS VALUES.  A POOL OF 500-1500 J/KG OF MU CAPE LIES
ACROSS SOUTHWEST AR AND SOUTHERN OK, WHOSE NORTHWARD MOVEMENT HAS
SLOWED AS OF LATE.  INFLOW AT 850 HPA OFF THE INSTABILITY POOL IS
OUT OF THE WEST-SOUTHWEST AT 20-30 KTS, NEAR THE MAGNITUDE AND
DIRECTION OF THE MEAN 850-400 HPA WIND.  EFFECTIVE BULK SHEAR OF
25-35 KTS LIES ACROSS THE REGION PER SPC MESOANALYSES. 

PORTIONS OF THIS AREA HAVE SEEN ABOVE NORMAL PRECIPITATION OVER
THE PAST COUPLE WEEKS WHICH HAS LED TO MODEST FLASH FLOOD GUIDANCE
VALUES. RECENT RADAR REFLECTIVITY APPEARS SUPPORTIVE OF THE WETTER
00Z WRF NSSL, 00Z 4 KM NAM CONEST, A SOUTHWARD ADJUSTED 00Z
CANADIAN REGIONAL, AND 06Z RAP GUIDANCE WITH A BETTER DEPICTION OF
THE RECENT CONVECTIVE RAMP UP, WITH HRRR/HRRR EXPERIMENTAL RUNS
DECIDEDLY DRIER AND LAGGING BEHIND.  CONVECTIVE COVERAGE AND
INTENSITY IS EXPECTED TO CONTINUE GROWING OVER THE NEXT SEVERAL
HOURS AS THE BREADTH AND INTENSITY OF THE 850 HPA INFLOW
INCREASES.  THE MAIN CULPRITS FOR HEAVY RAINFALL IN THE PATTERN
APPEAR TO BE CELL MERGERS BETWEEN MORE ORGANIZED ACTIVITY MOVING
EAST TO EAST-SOUTHEAST, AND LESS ORGANIZED ACTIVITY AND ACTIVITY
WITHIN THE INSTABILITY POOL ITSELF MOVING EAST-NORTHEAST, ALONG
WITH SHORT PERIODS OF CELL TRAINING.  HOURLY RAIN TOTALS UP TO
1.75", WITH LOCAL AMOUNTS TO 3" ARE EXPECTED. 

ROTH

ATTN...WFO...FWD...JAN...LZK...OUN...SHV...TSA...

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

LAT...LON   35669610 35269438 34629276 33929159 33379183
            33289271 33459528 33699703 33819721 34539734
            35339705