Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Oct 26 2023 07:17:55

FOUS30 KWBC 260717
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
317 AM EDT Thu Oct 26 2023

Day 1
Valid 12Z Thu Oct 26 2023 - 12Z Fri Oct 27 2023

....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
WISCONSIN TO MICHIGAN & CENTRAL TO EASTERN TEXAS...=20
=20
Our potent shortwave over TX will eject northeast into the Central
Plains, eventually crossing into the Midwest Thursday night into
Early Friday. Convective development is expected along and south
of a front where the theta-E gradient will be present. Scattered
showers and thunderstorms over IA/MN will advance northeastward
through the period, but an enhancement in the afternoon and
evening hours is anticipated due to the increasing ascent provided
by the shortwave presence.  Heavy rainfall is expected downwind of
the pool of 500+ J/kg MU CAPE.  The Marginal Risk concern in
eastern IA and northwest IL would be if 1.5"+ totals seen on some
of the guidance near the IA/IL border materialized within an hour,
which could become an urban problem.  HREF probabilities for
3"/12-hrs are modest, running between 20-30% within an area that
has seen a fair amount of rainfall very recently. The combination
of long duration locally heavy rainfall will provide an
opportunity for flash flooding concerns, especially within the
zone extending from central WI eastward into northwest MI where
the lower FFGs exist from the previous convective event.  Risk
areas saw some rearrangement, but not major changes from
continuity.
=20
Across central and eastern TX, very anomalous moisture presence
will persist due to prevailing southerly flow ahead of the mean
trough to the west and the western flank of our mid-level ridge
east of the Mississippi.  MU CAPE of 1000+ J/kg should exist in
this area.  PWAT indices between 2-2.3" will be common along and
east of I-35 and south of I-20. Weak mid-level forcing advecting
up from MX and the adjacent Gulf will meet a convergence point
created from the area convection that will be decaying to the
west.  This environment should support hourly rain totals to 2.5",
which would be more overwhelming in urban environments, given
recent dryness.  The guidance shows some variance, but enough
agreement that the Slight Risk area was nudged south.
=20
Roth


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!5dC55mk9ui0iQtbmQ3N1unTRoOlvCqAji14qGELVNhJg=
oGMJe7m3Zyon6GSYfAdRp6QDXGJBxhBNaLD1yXtScHs6H2w$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!5dC55mk9ui0iQtbmQ3N1unTRoOlvCqAji14qGELVNhJg=
oGMJe7m3Zyon6GSYfAdRp6QDXGJBxhBNaLD1yXtSuhbceCE$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!5dC55mk9ui0iQtbmQ3N1unTRoOlvCqAji14qGELVNhJg=
oGMJe7m3Zyon6GSYfAdRp6QDXGJBxhBNaLD1yXtSjuHpL40$=20


$$



=3D =3D =3D
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