MESOSCALE PRECIPITATION DISCUSSION 0098
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
810 PM EDT SUN MAY 17 2015
 
AREAS AFFECTED...MID-MISSISSIPPI VALLEY 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 180009Z - 180609Z
 
SUMMARY...WIDELY SCATTERED THUNDERSTORMS ARE BEGINNING TO DEVELOP
WITHIN A REGION OF SIGNIFICANT MOISTURE, INSTABILITY, AND CLOUD
BASE INFLOW.  CONSIDERING RECENT RAINS, FLASH FLOODING IS POSSIBLE.

DISCUSSION...NEARBY MESOSCALE BOUNDARIES ALONG WITH AVAILABLE
MIXED LAYER CAPES OF 1000-2000 J/KG AND 30-40 KTS OF 850 HPA
INFLOW (NEAR THE MAGNITUDE OF THE 850-400 HPA MEAN WIND) HAVE LED
TO WIDELY SCATTERED THUNDERSTORMS ACROSS PORTIONS OF AR AND
SOUTHEAST MO WHICH ARE SHOWING ENHANCEMENT PER RECENT SATELLITE
AND RADAR IMAGERY.  SO FAR, ORGANIZED THUNDERSTORM ACTIVITY ACROSS
LA DOES NOT APPEAR TO BE HAMPERING THEIR DEVELOPMENT. 
PRECIPITABLE WATER VALUES OF 1.75" EXIST ACROSS THE REGION.

ACTIVITY HAS BEEN MOVING NORTHEAST AT A GOOD CLIP.  ONCE THE
STORMS ORGANIZE, EAST-NORTHEAST FORWARD PROGRESSION IS ANTICIPATED
AT CLOSE TO 20 KTS.  THE AVAILABLE MOISTURE SUPPORTS HOURLY RAIN
RATES UP TO 2", OUTSIDE OF CELL MERGERS WHERE RAIN RATES COULD
SIGNIFICANTLY INCREASE.  CELL TRAINING IS THE MAIN CONCERN. 
DESPITE THE POOR PERFORMANCE OF THE MESOSCALE QPF GUIDANCE ACROSS
TX AND LA, THERE HAS BEEN A CONSISTENTLY MODERATE SIGNAL FOR HEAVY
RAINFALL ACROSS THE MID-MISSISSIPPI VALLEY, WITH THE LOWER BIASED
GUIDANCE INDICATING LOCAL AMOUNTS OF 2-4" OVER THE NEXT SIX HOURS,
AND SOME OF THE HIGHER BIASED GUIDANCE INDICATING 6"+ BEING
POSSIBLE LOCALLY.  CONSIDERING HEAVY RAINS SO FAR THIS MONTH AND
CURRENT FLASH FLOOD GUIDANCE VALUES, HEAVY RAINFALL FROM THESE
STORMS COULD CAUSE FLASH FLOODING.

ROTH

ATTN...WFO...JAN...LSX...LZK...MEG...PAH...SGF...

ATTN...RFC...ABRFC...LMRFC...NCRFC...OHRFC...

LAT...LON   38358904 38328823 37658786 36238856 34559008 
            33759115 34509166 35209256 36479197 37759058