Mesoscale Precipitation Discussion 0912
NWS Weather Prediction Center College Park MD
450 PM EDT Mon Oct 01 2018

Areas affected...eastern IA into southern WI/northern IL

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

Valid 012050Z - 020245Z

Summary...Rainfall of 1-3 inches is expected through 02Z from
eastern IA into southern WI and possibly northern IL. Given wet
antecedent conditions, flash flooding will be possible.

Discussion...Regional radar and cooling trends in IR satellite
imagery through 2030Z showed an increase in thunderstorm intensity
over northeastern IA. The heaviest rainfall over the region was
occurring in Buchanan and Delaware counties (northeast IA) with
KARX estimates of 0.5 to 1.0+ in/hr. This increase was likely tied
to increased low level moisture transport ahead of a 700 mb trough
axis atop a slow moving warm front which stretched west to east
across eastern IA into northern IL and southern Lower Michigan.

VAD wind plots at 700 mb showed the low level trough axis well
with west winds at OAX and southwest at ARX, with an estimated
850-700 mb maximum of 30-40 kt across central IA and atop the
surface warm front. Unidirectional flow above the RAP-sounding
estimated LFC of 800 mb just north of the warm front will support
training and repeating cell motions. The SPC mesoanalysis
estimates MUCAPE ranged between 250-750 J/kg across southern WI
which may limit rainfall rates to 0.5 to 1.5 in/hr given GPS
observed precipitable water values of 1.2 to 1.6 inches across IA
into far southwest WI. However, given 1-3 inches of rainfall over
the past 24 hours which fell in a narrow stripe from northeastern
IA into southern WI and recent reports of ongoing flooding across
these areas, flash flooding may occur with an additional 1-3
inches of rain through 02Z.

Otto

ATTN...WFO...ARX...DMX...DVN...GRB...LOT...MKX...

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

LAT...LON   43988806 43518731 42728754 42168778 41998847
            42049131 42389231 42999221 43529094