Mesoscale Precipitation Discussion 0869
NWS Weather Prediction Center College Park MD
735 AM EDT Thu Sep 20 2018

Areas affected...Southeast SD into northern IA

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

Valid 201134Z - 201704Z

Summary...An additional 1-2" of rain over saturating soil may
result in continued flooding concerns into the morning hours.

Discussion...Areas of flooding are ongoing this morning across
portions of southeast SD into northern IA...where MRMS and
observations show a swath of 3-6" of rainfall over the past 24
hours. Rain rates this morning do not appear to be that
impressive. Recent satellite images show a lack of colder
convective cloud tops...likely indicative of weak and shallow CAPE
profiles. A shortwave lifting north across SD this morning is
helping increase an axis of surface convergence from southeast SD
east near the MN/IA border. This increased synoptic ascent from
the wave and low level convergence may help locally increase
rainfall rates this morning. Although weak CAPE profiles should
persist through the morning...likely keeping most rainfall rates
below a half inch an hour.

Thus, overall not anticipating significant additional rainfall
amounts in the next 6 hours through 17z. Current expectations are
for an additional 1-2" across the MPD area (southeast SD east near
the MN/IA border) through 17z. This rain in itself will probably
not be heavy enough to result in additional significant flash
flood concerns. However, given the heavy antecedent rainfall
mentioned above and ongoing flooding concerns across the
area...this additional rainfall may at least help to maintain some
flooding issues over the next several hours. Recent runs of the
HRRR appear too far north with their QPF axis...with the ARW and
ARW2 at least a little better with the axis of convective rains.

Chenard

ATTN...WFO...ARX...DMX...FSD...MPX...

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

LAT...LON   43839697 43839652 43639603 43609502 43669443
            43519349 43519235 43529201 43439139 43199099
            42949088 42729097 42759170 42789247 42749337
            42699405 42649504 42659592 42729669 42839714
            43339841 43679776