Graphic for MPD #0901

MESOSCALE PRECIPITATION DISCUSSION 0901
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
205 AM EDT SUN OCT 22 2017

AREAS AFFECTED...SOUTH-CENTRAL/SOUTHEAST LA...FAR SOUTHWEST MS

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

VALID 220600Z - 221200Z

SUMMARY...SLOW-MOVING TO NEARLY STATIONARY CLUSTERS OF SHOWERS AND
THUNDERSTORMS WITH VERY HEAVY RAINFALL WILL CONTINUE. RUNOFF AND
FLASH FLOODING CONCERNS WILL CONTINUE.

DISCUSSION...THE LATEST NON-OPERATIONAL GOES-16 10.3 MICRON/IR
IMAGERY CONTINUES TO SHOW VERY COLD-TOPPED CLUSTERS OF CONVECTION
OVER AREAS OF SOUTH-CENTRAL LA AND ALSO NEAR THE LA/MS BORDER
SOUTH OF NATCHEZ MS. THE CONVECTION CONTINUES TO DEVELOP WITHIN A
RELATIVELY CONFLUENT BUT VERY MOIST LOW LEVEL FLOW PATTERN AND
WITHIN AN INCREASINGLY DIVERGENT FLOW PATTERN ALOFT. THE UPPER
LEVEL FLOW IS BECOMING INCREASINGLY DIVERGENT TOO BY THE APPROACH
AND AMPLIFICATION OF THE UPSTREAM TROUGH OVER THE SOUTHERN PLAINS
REGION. HOWEVER...THERE HAS BEEN SOME EVIDENCE OF A VERY SMALL
SCALE VORT CENTER/TROUGH OVER CENTRAL/SOUTHERN LA BASED ON THE
GOES-16 RGB AIRMASS AND 7.3 MICRON/WV IMAGERY. THIS SMALL SCALE
ENERGY HAS BEEN BASICALLY ANCHORED OVER THE SAME AREA ALL EVENING
AND CONTINUES TO INTERACT WITH THE MOIST AND RELATIVELY UNSTABLE
BOUNDARY LAYER FOR FOCUSED AREAS OF CONVECTION WITH EXTREMELY
HEAVY RAINFALL RATES.

THE ACTIVITY HAS BEEN HIGHLY FOCUSED OVER AREAS OF SOUTH-CENTRAL
LA WHERE DUAL-POL RADAR ESTIMATES HAVE BEEN AS HIGH AS 6 TO 8
INCHES THROUGH THE EVENING HOURS. RECENT RUNS OF THE HRRR SUPPORT
AN ADDITIONAL 3 TO 6 INCHES OF RAIN AT LEAST LOCALLY THROUGH 12Z
ACROSS SOUTH-CENTRAL LA BUT ALSO PERHAPS ATTEMPTING TO REACH INTO
FAR SOUTHWEST MS. GIVEN THE VERY SLOW CELL MOTIONS AND RAINFALL
RATES OF AS MUCH AS 3 INCHES/HR...THERE WILL CONTINUE TO BE
ADDITIONAL CONCERNS FOR RUNOFF PROBLEMS AND FLASH FLOODING.

ORRISON

ATTN...WFO...JAN...LCH...LIX...SHV...

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

LAT...LON   31869089 31579030 31019016 30329037 29749007
            29068995 28989067 29269149 29449231 29969262
            30479264 30879246 31339209 31699146


Last Updated: 207 AM EDT SUN OCT 22 2017