Mesoscale Precipitation Discussion 0869
NWS Weather Prediction Center College Park MD
602 AM EDT Sat Aug 05 2023

Areas affected...Central illinois

Concerning...Heavy rainfall...Flash flooding likely

Valid 050959Z - 051500Z

SUMMARY...Heavy rain and flash flooding from a potent low 
continues drifting east over central Illinois rest of this
morning. Rainfall rates of 2 to 3 inches per hour and up to 5
inches in two hours should overcome the dry antecedent conditions,
so flash flooding is considered likely.

DISCUSSION...Regional NEXRAD denotes a well defined MCV north of a
surface low over western IL is slowly drifting east. Maintenance
of a convergent swath east and around the north side of the low
will continue across central IL as southerly low level inflow
brings unstable air from southern IL on top of high moisture under
the MCV and south through southwestern IL with PW of 2 to 2.2".

The deeper moisture intersection near the surface low and
northward should continue to have ample narrow skinny CAPE for
strong updrafts and moisture flux for 2-3"/hr rates through the
rest of the morning. Slow, nearly due eastward progression of the
MCV/surface wave should keep orientation of some cells to align
favorably for longer duration and support a swath of highest two
hour rainfall totals of 3 to 5" possible.

Central IL has been generally dry over the past several days, with
FFG generally around 3"/3hr. However, given the slow motion and
highly efficient rainfall of longer than an hour duration, flash
flooding is considered likely through 15Z. One wildcard is the
presence of the stationary front just to the east. Whether the
southerly flow can maintain enough instability to allow further
heavy rain is a bit of a question.


Jackson

ATTN...WFO...DVN...ILX...LOT...LSX...

ATTN...RFC...NCRFC...NWC...

LAT...LON   41228973 41128902 40728848 39728868 39498943
            39629034 40269062 40749096 41059063 41169021