Subj : MESO: Heavy rain - floodi
To   : All
From : Mike Powell
Date : Wed Jul 12 2023 07:37:00

AWUS01 KWNH 121209
FFGMPD
IAZ000-121658-

Mesoscale Precipitation Discussion 0706
NWS Weather Prediction Center College Park MD
809 AM EDT Wed Jul 12 2023

Areas affected...Iowa

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

Valid 121158Z - 121658Z

Summary...Intense rain rates up to 2"/hr will be possible this
morning with multiple rounds of thunderstorms. Localized totals
between 2-4" and flash flooding will be possible.

Discussion...Thunderstorms this morning continue to move west to
east along/north of a well defined stationary boundary that is
draped across central/southern Iowa into Illinois. Ahead of a fast
moving squall line now entering western Iowa, isolated to
scattered slower moving thunderstorms have developed across
central Iowa where IR imagery cloud tops continue to cool and area
radar imagery shows instantaneous rain rates exceeding
1.5-2.0"/hr. The latest mesoanalysis showed an axis of elevated
instability reaching 3000 J/kg across the outlook area with the
latest blended precipitable water product indicating upwards of
1.25" of available PW.

Multiple, repeating rounds of heavy rainfall appear most likely
this morning across portions of central Iowa where initial/leading
convection will remain slower than the advancing squall line.
Merging lines and clusters are also likely. The most recent runs
of the HRRR seem to be handling the current activity fairly well,
indicating streaks of 2-4" likely where those line mergers and
overlap occur. While the squall line is expected to be
increasingly progressive, helping to limit the duration, intense
rain rates near 2"/hr will be possible for a few more hours this
morning.

Antecedent conditions have been drier than normal over the last 7
days per the AHPS precipitation analysis, which may limit the
overall flash flood threat to the more sensitive and vulnerable
locations including urban areas.

Taylor

ATTN...WFO...ARX...DMX...DVN...FSD...OAX...

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

LAT...LON   43259319 43169270 42749153 42179100 41049129 
            40729237 40749333 40759435 40859480 41249527 
            41569539 42519519 43159455 

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