MESOSCALE PRECIPITATION DISCUSSION 0059
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1101 AM EDT THU MAY 07 2015
 
AREAS AFFECTED...PORTIONS OF NORTHERN TX/SOUTHWEST OK 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 071501Z - 072101Z
 
SUMMARY...CONVECTION IS EXPANDING IN COVERAGE NEAR A SURFACE
BOUNDARY WITH SUFFICIENT MOISTURE AND INSTABILITY.  CELL TRAINING
COULD LEAD TO FLASH FLOODING OVER THE NEXT SEVERAL HOURS.

DISCUSSION...SCATTERED THUNDERSTORMS HAVE RECENTLY DEVELOPED
ACROSS THE TX PANHANDLE AHEAD OF A SHORTWAVE ENTERING WEST-CENTRAL
TX.  THE ENVIRONMENT HAS 25-30 KTS OF 850 HPA INFLOW --
APPROACHING THE MEAN 850-400 HPA WIND -- PER VAD WIND PROFILES
NEAR A BAROCLINIC TROUGH/WEAK THERMAL GRADIENT.  PRECIPITABLE
WATER VALUES PER GPS INFORMATION ARE CLOSE TO 1.25", NEAR THE
LOWER THRESHOLD FOR A BROADER FLASH FLOOD CONCERN.  SURFACE BASED
CAPE VALUES OF 2000-4000 J/KG LIE NEARBY AND UPSTREAM PER THE MOST
RECENT SPC REANALYSIS -- A HINT THAT FORWARD PROPAGATION IS
EXPECTED.  

AREA SOUNDINGS FROM 12Z ALONG WITH RAP-DERIVED SOUNDINGS INDICATE
DECENT DIRECTIONAL SHEAR ACROSS THE REGION, WHICH SHOULD ALLOW FOR
PROGRESSION.  THE SURFACE BOUNDARY COULD LIFT SLIGHTLY MORE TO THE
NORTH TODAY.  THE BREADTH OF INFLOW INTO THE SURFACE BOUNDARY
(CURRENTLY AND EXPECTED) IS BROAD ENOUGH TO ALLOW FOR CELL
TRAINING TO BE A POTENTIAL FLASH FLOOD THREAT.  ADDING TO THIS
POSSIBILITY IS THE RECENT THREE HOUR FLASH FLOOD GUIDANCE, WHICH
IS IN THE NEIGHBORHOOD OF 1.5".  THE AVAILABLE MOISTURE IMPLIES
THAT HOURLY RAINFALL RATES COULD REACH 1.5-1.75" AN HOUR IN
STRONGER CELLS OR WHERE CELLS TRAIN -- CELL MERGERS COULD EXCEED
THIS ESTIMATE.  

WHILE CURRENT ACTIVITY IS MOVING EAST-NORTHEAST, ONCE CONVECTION
BETTER ORGANIZES, IT SHOULD TEND TO FOLLOW THE SURFACE BOUNDARY TO
THE EAST-SOUTHEAST, WHICH IS ALSO IMPLIED BY THE 1000-500 HPA
THICKNESS LINES ACROSS THE REGION AND THE CURRENT/EXPECTED SURFACE
CAPE GRADIENT.   THE 00Z NSSL WRF, 12Z NAM CONEST, AND 13Z HRRR
HAVE CAPTURED THE CURRENT CONVECTIVE EVOLUTION THE BEST. 
CONSIDERING RECENTLY SATURATED SOILS AND THE EXPECTED RAINFALL
RATES, FLASH FLOODING IS POSSIBLE.

ROTH

ATTN...WFO...AMA...FWD...LUB...OUN...SJT...

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

LAT...LON   35440002 33919820 33039850 32939947 33190041 
            33480165 33670303 34670176 35380125