Flash Flood Guidance

AWUS01 KWNH 210943

Mesoscale Precipitation Discussion 0773
NWS Weather Prediction Center College Park MD
541 AM EDT Wed Aug 21 2019

Areas affected...Central to Southeast NE...Northeast
KS...Northwest MO...Far Southwest IA

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

Valid 210935Z - 211400Z

SUMMARY...Very heavy showers and thunderstorms continue to impact
a large area of central to southeast NE, northeast KS and
northwest MO. Flash flooding is ongoing across many areas, and
additional flash flooding can be expected going through the early
to mid morning hours.

DISCUSSION...The latest radar imagery is shows a progressive MCS
and associated mid-level shortwave/vort center continuing to
advance east across western NE. The MCS itself has likely peaked
in intensity, but it is advancing downstream and beginning to
merge in with an elongated axis of very slow-moving and locally
training convection across central to southeast NE. This same axis
of convection extends down across northeast KS and northwest MO as
increasing warm-air advection north of a quasi-stationary frontal
zone over KS and strong elevated instability parameters promote
deeper layer forcing and sustainable convective potential.

The 06Z HREF suite of guidance is notably under-performing with
respect to the overall coverage of convection and the rainfall
amounts that have been verifying, although the last few runs of
the HRRR have been gradually doing better. The convection given
from central to southeast NE will likely peak soon if not already,
but the upstream MCS will likely maintain the overall convective
threat going past 12Z across these areas.

Meanwhile, one area of more notable concern is across northeast KS
and northwest MO where convection has been very slow-moving
continuing to expand in coverage with very cold convective tops.
The latest HRRR does favor additional rainfall totals of as much
as 3 to 5 inches across these areas going through the early to
mid-morning hours.

Gradually the convection should begin to weaken area-wide after
12Z, but additional areas of flash flooding are likely in the
meantime, and especially over areas that have already seen heavy
rainfall overnight and over the last week.


...Please see www.wpc.ncep.noaa.gov for graphic product...



LAT...LON   42219996 42089887 41829759 41279610 40469442
            39799344 39089336 38809388 38869468 39069550
            39279647 39519708 39829792 40189921 40459996
            40860063 41330077 41950069