MESOSCALE PRECIPITATION DISCUSSION 0192
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1027 PM EDT MON MAY 09 2016
 
AREAS AFFECTED...PORTIONS OF IA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 100225Z - 100825Z
 
SUMMARY...SLOW-MOVING CONVECTION IS EXPANDING IN COVERAGE ACROSS
WESTERN IA.  HOURLY RAIN RATES UP TO 1.5", WITH LOCAL AMOUNTS OF
2-4", COULD LEAD TO FLASH FLOODING.

DISCUSSION...SATELLITE IMAGERY REVEALS A CONVECTIVE BLOB NEAR THE
IA/NE/MO/KS BORDER, WHICH HAS FORMED IN A FAVORABLE LOCATION ALOFT
(WITH ANTICYCLONIC FLOW) NORTHEAST OF A MID-LEVEL SHORTWAVE  NEAR
THE KS/OK BORDER AND SOUTHWEST OF AN UPPER LOW IN SD. 
PRECIPITABLE WATER VALUES ARE NEAR 1.1" PER GPS VALUES AND RAP
FORECAST FIELDS.  MUCAPE OF 1000-2000 J/KG EXISTS ACROSS THIS
REGION.  SOUTHEAST FLOW AT 850 HPA IS NEAR 30 KTS PER VAD WIND
PROFILES.

THE EXPECTATION IS FOR THE CONVECTION TO REMAIN SLOW-MOVING AS
LOW-LEVEL INFLOW BACKS WITH TIME, WHICH WOULD COUNTER ITS NORMAL
TENDENCY TO PROPAGATE NORTHEAST PARALLEL TO THE 1000-500 HPA
THICKNESS LINES.  EXISTING MOISTURE IN THE REGION SUPPORTS HOURLY
RAIN RATES UP TO 1.5", IMPLYING LOCAL AMOUNTS IN THE 2-4" RANGE
ARE POSSIBLE.  RECENT HRRR AND RAP RUNS HAVE SOME INDICATION OF
THIS ACTIVITY, THOUGH IT IS OCCURRING MORE NORTHERLY IN IA THAN
THEY ANTICIPATED.  CONSIDERING THE LOW FLASH FLOOD GUIDANCE
VALUES, FLASH FLOODING IS CONSIDERED POSSIBLE, PARTICULARLY WITHIN
URBAN AREAS.  LOWERING LOW-LEVEL INFLOW AND INSTABILITY WITH TIME
SHOULD LEAD TO A DECLINING HEAVY RAIN THREAT AFTER 07Z.  COVERAGE
OF HEAVY RAINFALL WITHIN THE DEFINED AREA IS EXPECTED TO BE BELOW
AVERAGE FOR AN MPD DUE TO A MARGINAL MOISTURE SUPPLY.

ROTH

ATTN...WFO...DMX...EAX...FSD...GID...OAX...TOP...

ATTN...RFC...MBRFC...NCRFC...

LAT...LON   43719529 43049428 42349355 40769327 40039398 
            39719454 39589574 39909642 40419703 41519769 
            42609735 43469623