MESOSCALE PRECIPITATION DISCUSSION 0117
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1055 PM EDT SAT MAY 23 2015
 
AREAS AFFECTED...SOUTHEAST OK, NORTHWEST AR, SOUTHWEST MO 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 240254Z - 240854Z
 
SUMMARY...THUNDERSTORMS WITH HOURLY RAIN RATES OF 2"+ SHOULD CAUSE
FLASH FLOODING.

DISCUSSION...A LEWP/QLCS IS MOVING ACROSS NORTHEAST & CENTRAL OK,
WHICH IS BEING HELD UP ON ITS SOUTHERN END BY A MESOSCALE LOW
ALONG THE SYSTEM'S OUTFLOW BOUNDARY.  THE INSTABILITY ENVIRONMENT
JUST AHEAD OF THIS SYSTEM IN TX HAS BEEN COMPLICATED BY A COLD
POOL/ORGANIZED THUNDERSTORM COMPLEX FARTHER SOUTH ACROSS
SOUTH-CENTRAL TX.  MUCAPE VALUES ABOVE 1000 J/KG LIE AHEAD OF MOST
OF THE SYSTEM, WITH PRECIPITABLE WATER VALUES OF 1.75-2" IN ITS
VICINITY.  INFLOW AT 850 HPA IS 40-45 KTS PER VAD WIND PROFILES IN
THE AREA, EXCEEDING THE MEAN 850-400 HPA WIND BY ~10 KTS, WHICH
SHOULD AID PRECIPITATION EFFICIENCY.

THE MESOSCALE QPF GUIDANCE HAS BEEN TOO SLOW WITH THE EASTWARD
PROPAGATION OF THIS SYSTEM, WHICH HAS BEEN ~15 KTS OVER THE PAST
SEVERAL HOURS PER RADAR IMAGERY.  THE 18Z CANADIAN REGIONAL MODEL
HAS DONE THE BEST SO FAR WITH THE SYSTEM'S PROGRESSION.  LOW-LEVEL
INFLOW INTO THE REGION IS EXPECTED TO INCREASE ANOTHER 10+ KTS PER
RECENT RAP GUIDANCE.  THERE IS A CONSISTENT SIGNAL IN THE
MESOSCALE GUIDANCE FOR 3-5" LOCALLY THROUGH 09Z, WHICH ALONG WITH
HOURLY RAIN RATES POTENTIALLY REACHING 2.25", WOULD EXCEED FLASH
FLOOD GUIDANCE VALUES.  THE GREATEST SOURCE OF UNCERTAINTY
REGARDING HEAVY RAIN POTENTIAL IS NEAR GAINESVILLE TX, WHERE
INSTABILITY IS LESS SIGNIFICANT TO THE SOUTH.  FLASH FLOODING IS
CONSIDERED LIKELY IN THIS AREA. 

ROTH

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

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

LAT...LON   36939576 36829361 35289388 34229512 33829712 
            33779903 33849919 34489911 35009763 35809631