Mesoscale Precipitation Discussion 0798
NWS Weather Prediction Center College Park MD
1015 PM EDT Fri Sep 07 2018

Areas affected...Southern MO...Southern IL...Southern
IND...Northern/Western KY...Ext Northern AR/TN...

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

Valid 080215Z - 080815Z

SUMMARY...Outer bands of remnants of Gordon intersecting with
frontal zone enhancing convergence/convection and threat for
continued likely flash flooding.

DISCUSSION...Remote sensors and observations show the remnant low
center of Gordon in far north central Arkansas lifting into MO. 
At least 3 maybe 4 convergence outer bands within the northeast
quadrant act as a focus for convective development/moisture
pooling within the warm sector.  Low level southerly/southeasterly
flow along these bands are also starting to intersect with a
slowly southward sagging stationary front that extends from near
CVG to LWV to BLV to VIH, before draping over the center of Gordon
and angling south into far NW AR.  Mid-level baroclinic trof is
also starting to dig with left exit region to the jet broadly over
the entire length of the frontal zone providing excellent
ascent/outflow evacuation for convective development.   Warm
sector can be denoted by mid-70s temps and Tds in the low 70s and
with mild mid-level cooling lapse rates, supporting MLCAPEs to
1500 J/kg even as the solar isolation is gone.  Moisture flux with
saturated profiles over 5H per surrounding 00z RAOBs and RAP
soundings, have led to total PWATs in the range of 2.25-2.4" near
the core of Gordon and to the northeast. 

Freezing/melting layer well above 14kt feet with a bulk of updraft
in the collision/coalescence warm cloud process zone, allowing for
highly efficient rainfall generation and rates of 2"/hr.   It is
at the intersections of the bands and the front though that
flux/mergers will increase rates to 2.5-3"/hr and pose the
greatest risk areas for likely flash flooding, particularly the
inner most band where winds are increased slightly nearly near
SAR/FAM/BLV vicinity.  Eventually, the inner most band of Gordon
will rotate and merge/parallel the front from SGF to FAM and with
that moisture flux convergence should pose a likely flash flooding
setup with 3-5" totals likely with higher amounts possible in the
next 6hrs.

Further east across SW IND/SE IL/N central KY...cells are a bit
more scattered with a bit less wind convergence (departure from
best height falls further west) and deeper moisture.  Still, the
rainfall efficiency and cell mergers will also pose a threat for
flash flooding, though RADAR presentation is a bit less
impressive. 

Gallina

ATTN...WFO...ILX...IND...LMK...LSX...LZK...MEG...PAH...SGF...

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

LAT...LON   39548755 39368661 38838553 37888549 37628613
            37618652 37708701 37628762 37148822 36478865
            36258910 36498989 36529016 36369101 36359244
            36689322 37299344 37899313 38449229 39388909