MESOSCALE PRECIPITATION DISCUSSION 0481
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
407 AM EDT THU JUL 19 2018

AREAS AFFECTED...CENTRAL IA, NORTHEAST MO, & VICINITY

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 190806Z - 191406Z

SUMMARY...SHOWERS AND THUNDERSTORMS ARE INCREASING IN COVERAGE AND
INTENSITY TO THE EAST OF A WEAK THERMAL BOUNDARY.  HOURLY RAIN
TOTALS TO 2" WITH LOCAL AMOUNTS TO 4" ARE POSSIBLE THROUGH 14Z.

DISCUSSION...SATELLITE IMAGERY REVEALS A COUPLE UPPER LEVEL
SHORTWAVES THAT ARE LEADING TO AN UPTICK IN CONVECTION FROM
CENTRAL IA INTO NORTHEAST MO WITHIN A MOISTURE AND INSTABILITY
GRADIENT TO THE EAST OF A WEAK THERMAL BOUNDARY.  THE WEAKER
SHORTWAVE IS TO THE NORTH ACROSS SOUTHEAST MN, WHILE A STRONGER
NEGATIVELY-TILTED SHORTWAVE IS APPROACHING FROM WESTERN IA. 
PRECIPITABLE WATER VALUES OF 1.5-1.8" EXIST IN THIS AREA.  INFLOW
AT 850 HPA IS CONVERGENT AT 15-25 KTS PER VAD WIND PROFILES, WHICH
EXCEEDS THE MEAN 850-400 HPA WIND.  EFFECTIVE BULK SHEAR IS 20-30
KTS PER SPC MESOANALYSES.  MU CAPE VALUES UPWIND ARE 500-1000
J/KG, AND INCREASING.

WITH MINIMAL MOVEMENT EXPECTED WITH NEARBY BOUNDARIES AT THE
SURFACE AND 850 HPA OVER THE NEXT SEVERAL HOURS, AND SOME
ADDITIONAL INCREASE IN THE 850 HPA INFLOW POSSIBLE, BELIEVE
PRECIPITATION RATES SHOULD INCREASE WITH TIME AS INSTABILITY
INCREASES.  THE 0Z HREF PROBABILITIES OF 1"+ IN AN HOUR INDICATE
AN UPTICK IN RAIN RATES, PEAKING IN THE 10-13Z TIME FRAME.  WHILE
THE 00Z NMMB GUIDANCE IS DOING QUITE WELL THUS FAR, THE 00Z AND
06Z NAM CONEST APPEAR TO HAVE VALUE.  HOURLY RAIN TOTALS SHOULD
PEAK IN THE 2" RANGE WITH LOCAL AMOUNTS OF 4"+ POSSIBLE.  THIS
WOULD CHALLENGE THE THREE HOUR FLASH FLOOD GUIDANCE VALUES IN THIS
REGION.

ROTH

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

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

LAT...LON   42999328 41789147 40629082 39139093 39149197
            40079290 42849456