MESOSCALE PRECIPITATION DISCUSSION 0045
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1141 PM EDT THU APR 16 2015
 
AREAS AFFECTED...TX PANHANDLE, WESTERN OK, SOUTHERN KS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 170340Z - 170910Z
 
SUMMARY...THUNDERSTORMS WITH HEAVY RAIN RATES OVER WESTERN OK AND
THE TX PANHANDLE ARE SHOWING SLOW MOTION AND RAIN RATES OF 1.5" AN
HOUR.  FLASH FLOODING IS POSSIBLE IN AREAS WITH CELLS THAT TRAIN
OR BACKBUILD FOR AN HOUR OR TWO.

DISCUSSION...AN OUTFLOW BOUNDARY IS SLOWLY EDGING EASTWARD ACROSS
WESTERN OK, FORCED BY A FORMING COLD POOL FROM ONGOING CONVECTION,
WITH ITS WESTERN FLANK STALLING ACROSS THE TX PANHANDLE. 
PRECIPITABLE WATER VALUES ARE 1-1.25" IN THIS REGION, 1.5-2 SIGMAS
ABOVE THE AVERAGE FOR MID-APRIL.  CAPE VALUES OF 1000-2000 J/KG
LIE NEAR AND AHEAD OF THIS BAND.  HOURLY RAIN RATES HAVE EXCEEDED
1.5" PER RADAR IMAGERY, AND SATELLITE IMAGERY SHOWS COOLING CLOUD
TOPS IN ASSOCIATION WITH THE THUNDERSTORM AREA IN THE TX
PANHANDLE.  LOW-LEVEL INFLOW OF 35 KTS IS SEEN ON AREA VAD WIND
PROFILES, WHICH IS IN LINE WITH THE MAGNITUDE OF THE MEAN 850-400
HPA WIND.

WHILE THE MESOSCALE GUIDANCE HAS A SIGNAL FOR HEAVY RAINFALL IN
THIS AREA, IT HAS UNDERESTIMATED THE MAGNITUDE INDICATED BY RADAR
ESTIMATES -- IT IS POSSIBLE THAT THERE IS SOME INFLATION CAUSED BY
HAIL CONTAMINATION.  THE 00Z SPC WRF, WRF4NSSL, AND 02Z RAP SEEM
TO HAVE THIS SITUATION HANDLED THE BEST, INDICATING LOCAL AMOUNTS
OF 2-4" THROUGH 09Z.  HOURLY RAIN RATES OF 1.5" ARE SUPPORTED BY
THE AVAILABLE MOISTURE.  CONVECTIVE PROPAGATION SHOULD BE PARALLEL
TO THE THUNDERSTORM LINE/OUTFLOW BOUNDARY.  THUNDERSTORMS COULD
BECOME MORE ELEVATED DURING THE NEXT HOUR OR TWO DUE TO NOCTURNAL
CIN DEVELOPING, WHICH COULD LEAD TO SOME REPEAT CONVECTIVE
ACTIVITY IN AREAS WHICH RECENTLY RAINED.  THE DEGREE OF LOW-LEVEL
INFLOW AND INSTABILITY ARE EXPECTED TO PERSIST THROUGH 09Z.  FLASH
FLOOD GUIDANCE VALUES HAVE COME DOWN A BIT IN THE TX PANHANDLE --
AN HOUR OR TWO OF CELL TRAINING COULD EXCEED THEM.  FLASH FLOODING
IS CONSIDERED POSSIBLE.

ROTH

ATTN...WFO...AMA...OUN...

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

LAT...LON   36529891 36379827 35809849 35209961 34970072 
            35200167 36100052