MESOSCALE PRECIPITATION DISCUSSION 0480
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
825 PM EDT SUN SEP 06 2015
 
AREAS AFFECTED...IA...SOUTHEAST NEB...NORTHEAST KS...NORTHWEST MO 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 070015Z - 070600Z
 
SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS WILL EXPAND IN COVERAGE
OVER THE NEXT FEW HOURS. INTENSE RAINFALL RATES OF UP TO 2.5
INCHES/HR AND TRAINING CELLS MAY RESULT IN FLASH FLOODING.

DISCUSSION...NUMEROUS SHOWERS AND THUNDERSTORMS HAVE BEEN
DEVELOPING ALONG AND JUST AHEAD OF A COLD FRONT PUSHING INTO THE
MIDWEST THIS EVENING AS THE CAPPING INVERSION WHICH HAD PERSISTED
THROUGH THE AFTERNOON HAS NOW ERODED AWAY AND IS ALLOWING FOR
SURFACE-BASED CONVECTION TO EXPAND IN COVERAGE. THE FRONTAL ZONE
IS INTERACTING WITH A VERY MOIST AND UNSTABLE
AIRMASS...CHARACTERIZED BY PWATS OF 1.8 TO 2 INCHES...AND MLCAPE
VALUES OF 3000 TO 3500 J/KG AND LOCALLY HIGHER.

THE CONVECTION IS EMBEDDED WITHIN A DEEPER LAYER SOUTHWESTERLY
FLOW REGIME THAT IS NEARLY PARALLEL TO THE BOUNDARY...AND THE
CONCERN OVER THE NEXT SEVERAL HOURS WILL BE THE INCREASED
POTENTIAL FOR TRAINING AND BACKBUILDING CELLS AS CONVECTION
CONTINUES TO ORGANIZE AND EXPAND IN COVERAGE AND INTENSITY.

CONSECUTIVE RUNS OF THE HRRR SUGGEST THE SHORT-TERM THREAT FOR
TRAINING CELLS WILL BE TO SOUTHEAST NEB AND ESPECIALLY ACROSS
SOUTHWEST/CENTRAL AND NORTHEAST PORTIONS OF IA AHEAD OF THE
SLOW-MOVING FRONT. HOWEVER...BY MID TO LATE EVENING...EXPECT THERE
TO BE SOME POTENTIAL FOR BACKBUILDING AND TRAINING CONVECTION NEAR
THE FRONT FOR PARTS OF NORTHEAST KS AND NORTHWEST MO AS THE LOW
LEVEL JET INCREASES TO AT OR ABOVE 30 KTS AND SUSTAINS A FAVORABLE
THERMODYNAMIC ENVIRONMENT WHILE ALSO INTERACTING POTENTIALLY WITH
A CONVECTIVE COLD POOL.

THE CIRA LAYERED PWAT PRODUCT SHOWS A RATHER ROBUST CONCENTRATION
OF MOISTURE IN THE 700MB TO 500MB LAYER WHICH IS COINCIDING WITH
THE CURRENT AXIS OF CONVECTION AND IS JUSTAPOSED WITH THE FRONTAL
ZONE. THE DEEP AND HIGH CONCENTRATION OF MOISTURE OVERALL IS
EXPECTED TO LEAD TO EFFICIENT RAINFALL PRODUCTION AND ENHANCED
RAINFALL RATES THAT MAY REACH UP TO 2.5 INCHES/HR. LOCALIZED
RAINFALL AMOUNTS MAY EXCEED 5 INCHES THIS EVENING CONSIDERING THE
THE BACKBUILDING AND TRAINING POTENTIAL...AND THUS SOME FLASH
FLOODING WILL BE POSSIBLE.

ORRISON

ATTN...WFO...ARX...DMX...DVN...EAX...GID...OAX...TOP...

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

LAT...LON   43559284 43479195 42839113 42039137 41339216 
            40089407 39329573 39579715 40259759 41079675 
            41949549 42929409