Mesoscale Precipitation Discussion 0562
NWS Weather Prediction Center College Park MD
849 PM EDT Mon Jun 30 2025

Areas affected...Southeast MO...Southern IL...Southwest IND...Far
Western KY...

Concerning...Heavy rainfall...Flash flooding possible

Valid 010050Z - 010630Z

SUMMARY...Slow moving, efficient thunderstorms to increase in
coverage with cell mergers, potential repeat tracks resulting in
localized 2-4" totals resulting in scattered possible flash
flooding tonight.

DISCUSSION...GOES-E WV suite shows a southern stream shortwave
sliding out of SE MO into S IL south of the digging synoptic
northern stream trough across WI to NE KS with an associated cold
front.  This front continues to dig south across the middle Great
Lakes but due to the shortwave, a weak surface wave has developed
in the buckling mid-level flow near Quincy, IL; before the cold
front digs across central MO.   The mid-level binary interaction
between the shortwave and northern stream will further slow deep
layer flow and help with boundary layer cyclogenesis
near/southeast of the St.Louis Metro. 

Low level winds are already backing and deep layer moisture is
increasing across S IL with solid convergence breaking out
numerous updrafts.   MLCAPEs of 2000+ J/kg and PWats over 2" will
allow for strong moisture flux convergence into stronger updrafts
and will support rates of of 2-2.25"/hr.  These cells should
remain along the southeast and eastern quadrants of the shortwave
with perhaps a flanking line along the effective cold
front/trailing convergence trof back into the Bootheel of MO. 
Cell motions will continue to be eastward to east-northeastward
with some solid potential for mergers/training.  Spots of 2-4"
will become scattered acoss S IL into SW IND/W KY over the next
4-6hrs with possible localized flash flooding.

A bit more uncertainty with respect to flash flooding will occur
with ongoing cells along the synoptic cold front.  Most should
remain progressive, but near the pivot; deeper confluence and
chaotic cells motions as the cyclone tries to vertically
stack/pivot may allow for some widely scattered cells that could
pivot or potentially remain stationary as well.  Cells may
initially be close to Metro St. Louis to further make evolution of
potential flash flooding more concerning, as broader impermeable
surfaces would result in greater runoff IF cells do end up
lingering in that vicinity further increasing potential for flash
flooding.

Gallina

ATTN...WFO...ILX...IND...LSX...MEG...PAH...

ATTN...RFC...KRF...MSR...ORN...TIR...NWC...

LAT...LON   39938840 39818771 39178716 38418712 37948730
            37568743 36628879 36378987 36499049 37299055
            37889064 38559137 38949136 39299103 39528961