Graphic for MPD #0164

MESOSCALE PRECIPITATION DISCUSSION 0164...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
516 PM EDT SAT APR 29 2017

CORRECTED FOR LAST LINE

AREAS AFFECTED...EASTERN OK, NORTHEAST TX, & SOUTHWEST AR

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 292109Z - 300309Z

SUMMARY...EVOLUTION FROM ELEVATED CONVECTION TO SURFACE BASED
CONVECTION APPEARS TO BE UNDERWAY IN THIS REGION, SHIFTING THE
HEAVY RAIN FOCUS TO THE SOUTH.  HOURLY RAIN RATES TO 2.5", WITH
LOCAL AMOUNTS OF 4-7", COULD LEAD TO FLASH FLOODING.

DISCUSSION...A FRONTAL WAVE NEAR DURANT OK HAS BEEN HELPING
ELEVATED CONVECTION TO FORM/TRAIN ACROSS EASTERN OK OVER THE LAST
SEVERAL HOURS.  HOWEVER, THE TRANSITION TO SURFACE BASED
CONVECTION IS UNDERWAY AS CIN IS NEARLY ERODED ACROSS THE REGION
PER RECENT SIGNS OF CONVECTIVE DEVELOPMENT CLOSER TO SURFACE
BOUNDARIES NOTED ON SATELLITE IMAGERY.  COMPLICATING MATTERS IS
NEW CONVECTION AT THE NORTHERN END OF A 75+ DEW POINT PLUME ACROSS
THE PINEY WOODS OF EAST TX.  PRECIPITABLE WATER VALUES ARE NEAR
2", WELL ABOVE NORMAL FOR THE END OF APRIL.  CONVERGENT LOW-LEVEL
850 HPA INFLOW OF 35-55 KTS IS SEEN EAST OF THE WAVE, NEAR THE
MAGNITUDE OF THE MEAN 850-400 HPA WIND.  MLCAPES OF 3000-4500 J/KG
ARE NEAR AND EAST OF THE WAVE, WITH A BROAD AREA OF 500+ J/KG
REMAINING TO BE EXHAUSTED ACROSS EASTERN OK IN THE COLD SECTOR. 
DIVERGENCE IS SIGNIFICANT AHEAD OF A LARGE UPPER TROUGH.  A WEAK
OUTFLOW JET FROM A COMPLEX ACROSS NORTHWEST LA COULD BE AIDING
WITH THE DIVERGENCE ACROSS THE REGION.

THE EXPECTATION IS FOR THE COLD SECTOR CONVECTION TO EAT UP THE
REMAINING INSTABILITY OVER THE NEXT FEW HOURS WHILE SURFACE-BASED
CONVECTION FORMS CLOSER TO THE RED RIVER OF THE SOUTH AND ACROSS
SOUTHWEST AR.  FORWARD PROPAGATION, OUTSIDE COLD FRONT
PROGRESSION, IS NOT EXPECTED AS CONVECTIVE PROPAGATION VECTORS
FAVOR STORMS MOVING PARALLEL TO THE BOUNDARY SLIGHTLY INTO THE
COLD SECTOR.  THE MESOSCALE GUIDANCE SHOWS A STRONG SIGNAL FOR
3-5" OF RAIN.  CONSIDERING HOURLY RAIN RATES OF 2.5" ARE POSSIBLE
NEAR THE ARKLATEX, BELIEVE LOCAL AMOUNTS OF 4-7" ARE MORE
REALISTIC.  OVERALL, BELIEVE RECENT HRRR/RAP RUNS ARE CAPTURING
THE POTENTIAL RAINFALL PATTERN BETTER THAN THE REMAINDER OF THE
MESOSCALE GUIDANCE.  UP NORTH, LOWER RAIN RATES ARE EXPECTED,
THOUGH SOILS ARE SATURATED, SO THE FLOOD RISK CONTINUES.  WHILE
SOILS ARE SATURATING IN EASTERN OK, THEY ARE DRIER SOUTH OF THE
RED RIVER.  THINK THE POSSIBLE CATEGORY IS A BETTER FIT DOWN SOUTH
FOR THIS REASON.

ROTH

ATTN...WFO...FWD...HGX...ICT...LZK...OUN...SGF...SHV...TSA...

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

LAT...LON   37369409 34459411 32749360 32309369 31799457
            31439559 31939651 32999753 33879796 36009725
            37289598


Last Updated: 516 PM EDT SAT APR 29 2017