Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun May 07 2023 08:26:44

FOUS30 KWBC 070826
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
426 AM EDT Sun May 07 2023

Day 1
Valid 12Z Sun May 07 2023 - 12Z Mon May 08 2023

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE MIDWEST...

Consensus of 1 to 3 inches across this part of the country
persists from the previous run and WPC forecast, with the NAM and
UKMET continuing to hint at isolated maxima of 4 to 6 inches.  The
operational global runs and some of the higher resolution
guidance...including the HREF...have started showing about 10
percent probabilities of 1 hour rainfall accumulation in an hour
exceeding 1-hour Flash Flood Guidance between 08/03Z and
08/06Z...with and 20+ percent probability of 3-hour rainfall
accumulation exceeding the 3-hour Flash Flood Guidance during
roughly the same time frame from portions of eastern Iowa into
northern Illinois.  This corresponds to the when the southwesterly
flow at 850 mb ramps up to between 20 and 30 kts.  Sided more with
the 07/00Z GFS/NAM/UKMET rather than the ECMWF/CMC which sped a
QPF max eastward closer to the OH River.  Even though the EC/CMC
idea can not be ruled out....the latest spaghetti plot of 2 inch
contours from the SREF (from both the NMM and ARW) lends more
support to solution over Iowa. To cover the possibility that the
EC/CMC is right...a broad Marginal risk was maintained to signal
the uncertainty rather than telegraphing the idea that the entire
area is about to be drenched.

Bann



Day 2

The Day 2 outlook will be updated by 0830Z.


Day 3

The Day 3 outlook will be updated by 0830Z.


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!7XB7I4gtyIyGOMxfO_6PO1Ts575fJtbrfq9jxUYQy3Nx=
8wwsms6pVZZ9kUpXnMu4ZS_acf1fNIPPPWqDPGJ6hS_DNy0$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!7XB7I4gtyIyGOMxfO_6PO1Ts575fJtbrfq9jxUYQy3Nx=
8wwsms6pVZZ9kUpXnMu4ZS_acf1fNIPPPWqDPGJ6O8JoX-Y$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!7XB7I4gtyIyGOMxfO_6PO1Ts575fJtbrfq9jxUYQy3Nx=
8wwsms6pVZZ9kUpXnMu4ZS_acf1fNIPPPWqDPGJ68kW_JbY$=20


$$



=3D =3D =3D
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