MESOSCALE PRECIPITATION DISCUSSION 0599
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
403 PM EDT THU OCT 22 2015
 
AREAS AFFECTED...PORTIONS OF NORTHERN TX & SOUTHERN OK 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 222001Z - 230201Z
 
SUMMARY...CONVECTION SHOULD SHOW SOME INCREASE IN COVERAGE AND
ORGANIZATION OVER THE NEXT SEVERAL HOURS.  HOURLY RAIN RATES UP TO
2" COULD LEAD TO FLASH FLOODING, PARTICULARLY WITHIN URBAN AREAS.

DISCUSSION...A THERMAL GRADIENT STRETCHES FROM THE TX BIG BEND
THROUGH THE NORTHERN DALLAS/FORT WORTH METROPOLITAN AREA INTO
SOUTHEAST OK.  CIN IS ERODING IN ITS VICINITY BASED ON RECENT SPC
MESOANALYSES.  INFLOW AT 850 HPA INTO/OVER THE BOUNDARY IS 25-40
KTS PER VAD WIND PROFILES, NEAR THE MAGNITUDE OF THE MEAN 850-400
HPA WIND BUT AT A 50 DEGREE ANGLE. PRECIPITABLE WATER VALUES OF
1.5-1.75" LIE ACROSS THE REGION PER GPS INFORMATION, 2-3 SIGMAS
ABOVE THE MEAN FOR LATE OCTOBER.  WHILE CELL MOTION HAS BEEN
NORTH-NORTHEAST AT ~ 35 KTS, THE HEAVY RAIN CORE ALONG THE RED
RIVER HAS BEEN MOVING EAST-NORTHEAST AT ~ 30 KTS, ALONG THE LINES
OF THE FORWARD PROPAGATING CONVECTIVE VECTORS AND PARALLEL TO
1000-500 HPA THICKNESS LINES, LIKELY DUE TO DIRECTIONAL WIND
SHEAR.  MLCAPES OF 500-1000 J/KG EXIST SOUTH OF THE BOUNDARY
ACROSS CENTRAL TX.

RECENT NEW DEVELOPMENT ACROSS NORTH-CENTRAL TX IS EXPECTED TO
INCREASE IN COVERAGE AND INTENSITY OVER THE NEXT SEVERAL HOURS. 
INFLOW AT 850 HPA IS EXPECTED TO INCREASE FROM DALLAS EASTWARD
AFTER ~22Z, WHICH SHOULD ALLOW FOR SOME MAINTENANCE/POSSIBLE
BACKBUILDING NEAR/OVER THE SURFACE BOUNDARY, WHICH SHOULD SAG
SLOWLY SOUTH AND EASTWARD.  THE CAM GUIDANCE ADVERTISES LOCAL
AMOUNTS OF 2-4" WITHIN THIS AREA, WHICH COULD FALL QUICKLY. 
AVAILABLE MOISTURE SUPPORTS HOURLY RAIN RATES UP TO 2".  THE 12Z
WRF4NSSL APPEARS TO BE CAPTURING THE AREA OF HEAVY RAINFALL THE
BEST, WHEN COMPARED TO THE OTHER CAM GUIDANCE.  HOWEVER, SOILS
ACROSS NORTHEAST TX ARE DRY AS THE AREA HAS SEEN LITTLE RAINFALL
SINCE THE DEPARTURE OF T.D. BILL ON JUNE 18 -- AROUND 4" HAS
FALLEN DURING THE PAST 120 DAYS PER SOUTHERN REGIONAL
PRECIPITATION ESTIMATES.  FOR THE MOST PART, THE AREA IS DEALING
WITH A LONGER DURATION RAIN EVENT.  HOWEVER, THE RAIN RATES
EXPECTED WOULD CAUSE URBAN ISSUES IN THE DALLAS/FORT WORTH
METROPOLITAN AREA.  FLASH FLOODING IS CONSIDERED POSSIBLE,
PARTICULARLY WITHIN URBAN AREAS.

ROTH

ATTN...WFO...FWD...LUB...MAF...OUN...SHV...SJT...TSA...

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

LAT...LON   34899702 34459493 33619461 32379634 31200117 
            33230030 34439869