MESOSCALE PRECIPITATION DISCUSSION 0250
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
349 AM EDT FRI JUN 01 2018

AREAS AFFECTED...PORTIONS OF NRN AR INTO FAR WRN TN/NWRN MS

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

VALID 010746Z - 011300Z

SUMMARY...LOCALIZED HEAVY RAINFALL MAY LEAD TO FLASH FLOODING
ACROSS PORTIONS OF NORTHERN AR INTO FAR WESTERN TN/NORTHWESTERN MS
THROUGH THE EARLY MORNING. BY 13Z...ADDITIONAL RAINFALL OF 3-4
INCHES MAY OCCUR IN A COUPLE OF LOCATIONS.

DISCUSSION...SURFACE OBSERVATIONS PLACED AN OUTFLOW BOUNDARY FROM
WEST-CENTRAL TN INTO NORTH-CENTRAL AR AS OF 07Z...WITH LITTLE TO
NO MOVEMENT OBSERVED FOR THE WESTERN PORTION OF THE BOUNDARY.
REGIONAL RADAR HAS SHOWN A HISTORY OF LOCALIZED TRAINING FROM
NORTHWEST TO SOUTHEAST ACROSS NORTHERN AR...FOLLOWING THE AVERAGE
FLOW BETWEEN THE LFC AND EL. THE SPC MESOANALYSIS PAGE SHOWED AN
ABUNDANCE OF MUCAPE STILL AVAILABLE TO THE SOUTH OF THE OUTFLOW
BOUNDARY IN THE VICINITY OF THE OK/AR BORDER WITH ROUGHLY
1000-2000+ J/KG PRESENT. MEANWHILE...850 MB FLOW WAS ROUGHLY 25 KT
AT KSRX AND KLZK AS MEASURED BY VAD WIND DATA...OVERRUNNING THE
SURFACE OUTFLOW BENEATH STRONGLY DIFFLUENT FLOW ALOFT.

WHILE THE RAP FORECAST IS FOR SLIGHT WEAKENING OF 850 MB FLOW
THROUGH 13Z...THE ORIENTATION OF WIND VECTORS AT 850 MB IS
EXPECTED TO BECOME A LITTLE MORE ALIGNED WITH THE ORIENTATION OF
THE OUTFLOW BOUNDARY. GIVEN THE UNIDIRECTIONAL FLOW OF FORECAST
SOUNDINGS ALOFT IN THE VICINITY OF NORTHEASTERN AR...THE POTENTIAL
EXISTS FOR SMALL CORES OF VERY HEAVY/TRAINING RAINFALL GIVEN
SUFFICIENT CAPE AND PRECIPITABLE WATER VALUES NEAR 1.7 INCHES PER
RECENT GPS OBSERVATIONAL DATA. RECENT RUNS OF THE HRRR AND
EXPERIMENTAL HRRR...AS WELL AS OTHER 00Z HI-RES MODEL
GUIDANCE...SUPPORT THE IDEA OF 3-4 INCHES OF ADDITIONAL RAINFALL
IN NORTHERN TO NORTHEASTERN AR INTO PERHAPS FAR WESTERN
TN/NORTHWESTERN MS THROUGH 13Z. THESE VALUES WOULD BE NEAR FLASH
FLOOD GUIDANCE VALUES AND COULD SUPPORT LOCALIZED FLASH FLOODING
OVER THE NEXT SEVERAL HOURS.

OTTO

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

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

LAT...LON   36629324 36469195 36058964 34878994 34489109
            35109265 35999362