MESOSCALE PRECIPITATION DISCUSSION 0486
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1000 PM EDT THU JUL 19 2018

AREAS AFFECTED...NEAR THE MO/IL BORDER

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

VALID 200159Z - 200559Z

SUMMARY...THUNDERSTORMS ARE BACKBUILDING ACROSS NORTHEAST MO WHICH
COULD CONTINUE FOR ANOTHER COUPLE HOURS BEFORE DROPPING SOUTH NEAR
THE IL/MO BORDER.  HOURLY RAIN TOTALS TO 1.75" WITH LOCAL AMOUNTS
TO 3" ARE EXPECTED.

DISCUSSION...THUNDERSTORMS HAVE BEGUN TO BACKBUILD WITHIN A SHORT
WARM CONVEYOR BELT TO THE SOUTHEAST OF A DEEP LAYER LOW OVER
SOUTHERN MN.  AT THE TOP OF THE BACKBUILDING CONVECTION IS AN
INSTABILITY POOL WITH 3000-3500 J/KG OF ML CAPE.  PRECIPITABLE
WATER VALUES ARE ~1.6" PER GPS DATA.  INFLOW AT 850 HPA IS ROUGHLY
35 KTS PER VAD WIND PROFILES.  EFFECTIVE BULK SHEAR OF 40-50 KTS
LIES ACROSS THE REGION.

THE EXPECTATION IS FOR THE CURRENT NORTHWEST-SOUTHEAST ORIENTED
CONVECTION TO REARRANGE MORE NORTH-SOUTH ORIENTED WITH TIME
PARALLEL TO THE INSTABILITY GRADIENT.  BACKBUILDING SHOULD END IN
THE NEXT HOUR OR TWO AS A LOW-LEVEL BOUNDARY/FRONT MOVES SOUTHEAST
ERODING THE INSTABILITY POOL FROM THE NORTHWEST WITH TIME.  THIS
BAND COULD TRAIN FOR A FEW HOURS BEFORE EVENTUALLY SHORTENING FROM
NORTH TO SOUTH AS THE TRAINING CEASES.  HOURLY RAIN TOTALS TO
1.75" WITH LOCAL AMOUNTS TO 3" ARE EXPECTED.  A NORTHEAST ADJUSTED
18Z NAM CONEST SOLUTION APPEARS THE MOST PLAUSIBLE HERE
CONSIDERING THE CURRENT CONVECTIVE PATTERN AND EXPECTATIONS.

ROTH

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

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

LAT...LON   40609224 40269081 38398978 38509131 39799234