Graphic for MPD #0334

MESOSCALE PRECIPITATION DISCUSSION 0334
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
251 PM EDT SAT JUN 17 2017

AREAS AFFECTED...SOUTHEAST IA, WESTERN IL, & NORTHEAST MO

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

VALID 171850Z - 180050Z

SUMMARY...THUNDERSTORMS ARE ABOUT TO BUILD ACROSS THE REGION. 
HOURLY RAIN RATES UP TO 2", WITH LOCAL AMOUNTS TO 4", ARE EXPECTED.

DISCUSSION...A SAGGING COLD FRONT IS ACTING AS THE FOCUS FOR
TOWERING CUMULI ACROSS SOUTHEAST IA AND NORTHERN IL AT THIS TIME
-- THE MID-LEVEL CAP APPEARS TO BE BREAKING.  A WEAK SHORTWAVE
ALOFT MOVING THROUGH SOUTHEAST SD APPEARS TO BE THE CULPRIT FOR
DIVERGENCE ALOFT, THOUGH A WEAK JET STREAK FROM THE WEAKENING
CONVECTIVE COMPLEX OVER EXTREME SOUTHEAST OK MAY ALSO BE AIDING
DIVERGENCE ALOFT.   MLCAPE VALUES OF 1000-2000 J/KG LURK ACROSS
PORTIONS OF IA AND IL.  TO THE SOUTHWEST, AN INSTABILITY POOL OF
1000-5000 J/KG IS ACTING AS THE FOCUS FOR CLOUDINESS ACROSS
NORTHERN MO, WHICH IS BEGINNING TO SHOW SIGNS OF CUMULUS
DEVELOPMENT WITHIN A CAPPED ENVIRONMENT ALOFT.  INFLOW AT 850 HPA
IS CONVERGENT AT 20-30 KTS. BULK SHEAR OF 30-50 KTS EXISTS HERE,
WHICH SHOULD ORGANIZE CONVECTION.  PRECIPITABLE WATER VALUES ARE
NEAR 1.4" PER THE 18Z SOUNDINGS FROM QUAD CITIES IA AND LINCOLN IL.

THE 12Z GFS, 12Z SPC WRF, RECENT RAP MASS FIELDS AND 12Z NSSL WRF
APPEAR TO HAVE A GOOD HANDLE ON THE EXPECTATIONS OVER THE NEXT SIX
HOURS, WITH HRRR RUNS STRUGGLING TO CATCH UP.  WITH A BROADLY
DIVERGENT THICKNESS PATTERN IN THE REGION, A CONVECTIVE COMPLEX IS
LIKELY TO FORM.  A SURFACE WAVE ALONG THE FRONT IS EXPECTED TO
SHIFT SOUTHWEST, WITH CONVECTION FOCUSING WITHIN ITS WARM
ADVECTION PATTERN.  WINDS AT 850 HPA INCREASE FROM THE SOUTHWEST
AFTER 22Z, WHICH MAY LEAD TO BACKBUILDING CONVECTION LATER THIS
AFTERNOON.  CONVECTION IS BEGINNING TO INITIATE FIRST IN SOUTHEAST
IA AND NORTHERN IL, WHICH SHOULD SHIFT SOUTHWARD WITH THE
BOUNDARY.  FORWARD PROPAGATION APPROXIMATELY TO THE EAST-SOUTHEAST
AT 30 KTS IS EXPECTED.  CELL TRAINING AND MESOCYCLONES ARE
EXPECTED TO BE THE MAIN HEAVY RAIN RISK IN THIS ENVIRONMENT. 
HOURLY RAIN RATES TO 2", WITH LOCAL AMOUNTS TO 4" ARE EXPECTED. 
THE SOILS IN SOME OF THIS AREA HAVE BEEN PARTIALLY SATURATED BY
RECENT RAINS.  FLASH FLOODING IS A CONCERN, PARTICULARLY WITHIN
URBAN ENVIRONMENTS.

ROTH

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

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

LAT...LON   41829035 41778770 40948783 40478812 39818860
            39548905 39139024 39149116 39559226 40649294
            41769126


Last Updated: 251 PM EDT SAT JUN 17 2017