Mesoscale Precipitation Discussion 0693
NWS Weather Prediction Center College Park MD
718 PM EDT Sun Aug 19 2018

Areas affected...Southwest MN

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

Valid 192317Z - 200317Z

Summary...Gathering thunderstorms across southwest MN could be
difficult to dislodge over the next several hours.  Hourly rain
totals to 2" and local amounts to 4" are expected.

Discussion...A surface wave across southwest MN and a stationary
front to its northeast is focusing a growing area of showers and
thunderstorms across western MN.  A deep layer low in the central
Plains is sponsoring divergence aloft.  Inflow at 850 hPa is
backing, becoming south-southeast at 10-15 kts per VAD wind
profiles.  ML CAPE values upstream are 2000+ J/kg.  Precipitable
water values of 1.5-1.75" lie in the area per GPS data.  Effective
bulk shear of ~20 kts appears to be trying to organize the
activity.

Convection should be increasingly difficult to propagate eastward
as the 850 hPa flow increases somewhat out of the southeast to
east.  Cell training is expected as forward propagating convective
vectors favor a southwest to northeast trajectory along the axis
of the line.  Occasional cell mergers also appear to be possible
over the next hour or two as storms to the southeast merge in.  It
appears an outflow boundary from earlier convection in southeast
SD could be what ends convection from southwest to northeast with
time.  Until the outflow boundary overtakes the current convective
activity, hourly rain totals to 2" with local amounts to 4" are
expected.

Roth

ATTN...WFO...ABR...FGF...FSD...MPX...

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

LAT...LON   46419534 46059433 44459544 44089599 44459674