MESOSCALE PRECIPITATION DISCUSSION 0433
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
505 AM EDT SUN AUG 09 2015
 
AREAS AFFECTED...EXTREME SOUTHEAST NEB...IA...NORTHERN
MO...WESTERN IL 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 090900Z - 091400Z
 
SUMMARY...A STRONG MCS WILL CONTINUE TO IMPACT THE MIDWEST THIS
MORNING...WITH HEAVY SHOWERS AND THUNDERSTORMS FOSTER THE
POTENTIAL FOR FLASH FLOODING DUE TO TRAINING CELLS AND INTENSE
RAINFALL RATES.

DISCUSSION...A VERY COLD-TOPPED MCS IS IMPACTING AREAS OF FAR
SOUTHEAST NEB..CENTRAL AND SOUTHERN IA..NORTHERN MO AND INTO PARTS
OF WESTERN IL WITH VERY HEAVY RAINS. THE CONVECTION IS BEING
FOSTERED BY THE APPROACH OF A SHORTWAVE TROUGH ENTERING THE
NORTHERN PLAINS AND WITH A WAVE OF LOW PRESSURE MOVING EAST ALONG
A FRONTAL ZONE SITUATED ACROSS NORTHERN KS AND NORTHERN MO. AHEAD
OF THE SURFACE WAVE IS A WELL-DEFINED SOUTHWESTERLY LOW LEVEL JET
WHICH BASED ON AREA VWPS IS ON THE ORDER OF 40 TO 45 KTS. THIS IS
HELPING TO TRANSPORT A VERY MOIST AND UNSTABLE AIRMASS OVER THE
FRONTAL ZONE AND PROVIDING STRONG ISENTROPIC ASCENT.

DEEP LAYER FORCING IS EXPECTED TO PERSIST OVER THE NEXT SEVERAL
HOURS AND THE MAIN CONCERN WILL BE ADDITIONAL TRAINING AND
BACKBUILDING CONVECTION NEAR AND JUST NORTH OF THE WARM FRONT
WHERE LOW LEVEL FORCING/CONVERGENCE WILL COINCIDE WITH THE BEST
DEEP LAYER FORCING/DYNAMICS ASSOCIATED WITH THE APPROACHING
SHORTWAVE. THE LATEST IR SATELLITE IMAGERY SHOWS A RATHER
WELL-DEFINED CONVECTIVE WEDGE SIGNATURE WITH THE STRONGEST CELLS
IMPACTING FAR SOUTHEAST NEB AND AREAS ALONG THE IA/MO BORDER...AND
THESE AREAS SHOULD SEE THE HIGHEST RISK FOR FLASH FLOODING SINCE
THE LOW LEVEL JET IS EXPECTED TO VEER WITH TIME THIS MORNING
ACROSS THIS AREA AND THAT WILL ONLY ENHANCE THE RISK OF TRAINING
CONVECTION NEAR THE FRONT.

PWATS REMAIN NEAR 2 INCHES AND WITH ENHANCED MOISTURE POOLED ALOFT
BASED ON THE LATEST CIRA LAYERED PWAT ANALYSIS. THIS WILL ENHANCE
RAINFALL RATES WHICH MAY APPROACH 2.5 INCHES/HR...ESPECIALLY ALONG
THE SOUTHERN FLANK OF THE MCS WHERE THE STRONGEST CORES ARE NOTED.
THE 00Z ARW/00Z NMMB AND THE 07Z HRRR ALL SUGGEST SOME
SOUTHEASTWARD PROPAGATION OF THE MCS INTO NORTHEAST MO AND WESTERN
IL OVER THE NEXT FEW HOURS. LOCALLY AS MUCH AS 3 TO 5 INCHES OF
ADDITIONAL RAINFALL IS POSSIBLE BASED ON THE HIRES GUIDANCE
THROUGH MID-MORNING...AND THIS WILL THERE FOR ENHANCE THE RISK FOR
FLASH FLOODING.

ORRISON

ATTN...WFO...DMX...DVN...EAX...ILX...LOT...LSX...OAX...

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

LAT...LON   42229249 42049098 41889030 41618961 41098892 
            40338879 39718932 39449011 39409113 39569275 
            39989457 40359570 40419595 40739659 41059693 
            41369672 41359616 41029477 41199388 41589367 
            42109347