MESOSCALE PRECIPITATION DISCUSSION 0090
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
626 PM EDT SAT MAY 16 2015
 
AREAS AFFECTED...PORTIONS OF OK AND NORTHERN TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 162225Z - 170425Z
 
SUMMARY...CONVECTION IS EXPECTED TO INCREASE IN EFFICIENCY AND
COVERAGE ACROSS THE REGION OVER THE NEXT SEVERAL HOURS, WHICH
COULD CAUSE FLASH FLOODING.

DISCUSSION...WHILE AN OUTFLOW BOUNDARY HAS BEEN THE FOCUS FOR
CONVECTION THUS FAR FROM THE TX PANHANDLE ACROSS NORTHWEST OK AND
SOUTHEAST KS, THERE ARE SIGNS THAT A MORE SOUTHERN BOUNDARY COULD
TAKE OVER IN THE NEAR FUTURE.  IT IS A DIFFERENTIAL HEATING
BOUNDARY AT THE LEADING EDGE OF PERSISTENT STRATUS WHICH HAS BEEN
STUCK ACROSS SOUTH-CENTRAL OK THIS AFTERNOON.  THIS BOUNDARY SHOWS
UP IN THE TEMPERATURE OBSERVATIONS AND SPC MESOANALYSIS AS A
SECONDARY SURFACE-BASED CAPE GRADIENT.  PRECIPITABLE WATER VALUES
(PWS) IN THE REGION ARE STARTING OUT NEAR 1.50", WITH 850 HPA
INFLOW OF 30-45 KTS SEEN IN VAD WIND PROFILES.  CAPE VALUES OF
2000-4000 J/KG INHABIT THE REGION.

OVER THE NEXT SEVERAL HOURS, CONVECTION NEAR THE WESTERN EDGE OF
THE DIFFERENTIAL HEATING BOUNDARY SHOULD ORGANIZE AND MOVE EAST TO
EAST-NORTHEAST (PER THE 1000-500 HPA THICKNESS PATTERN) AT NEAR 40
KTS (PER FORWARD PROPAGATING CORFIDI VECTORS).  THE AVAILABLE CAPE
AND SOME TURNING IN THE WIND WITH HEIGHT SHOULD FORCE SOME FORWARD
PROPAGATION IN THE NORTHERN PORTION OF THE AREA.  HOWEVER, WITH
THE MAIN SHORTWAVE LIFTING NORTHEAST, THE VERTICAL WIND PROFILE IS
EXPECTED TO BECOME INCREASINGLY UNIDIRECTIONAL WITH LESS FORWARD
PUSH TO CONVECTION ACROSS TX, AS PWS INCREASE TO 1.75" PER RECENT
RAP FORECASTS.  LOW-LEVEL INFLOW IS FORECAST TO INCREASE FURTHER,
PAST 50 KTS BY THE END OF THE PERIOD, WHICH IS CLOSE TO THE MEAN
850-400 HPA MEAN WIND.   HOURLY RAIN RATES UP TO 2", OUTSIDE OF
LOCATIONS WITH LONGER DURATION CELL TRAINING AND CELL MERGERS, ARE
EXPECTED IN THIS INCREASINGLY MOIST AIR MASS.  THERE IS A SIGNAL
IN THE AVAILABLE MESOSCALE GUIDANCE FOR 2-4" LOCAL AMOUNTS. 
DESPITE THEIR AVAILABLE FLASH FLOOD GUIDANCE VALUES, LOCATIONS IN
SOUTHEAST AND SOUTHERN TX SAW MORE IMPACT THAN YOU WOULD OTHERWISE
EXPECT WITH THESE SORT OF RAIN RATES. CELL TRAINING IS THE MAIN
CONCERN.  FLASH FLOODING IS CONSIDERED POSSIBLE IN A REGION WHICH
HAS SEEN A GREAT DEAL OF RAINFALL IN MAY, SO FAR.

ROTH

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

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

LAT...LON   36049604 35769548 34289606 32809777 32130043 
            34020037 35579824