Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Oct 28 2023 07:24:55

FOUS30 KWBC 280724
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
324 AM EDT Sat Oct 28 2023

Day 1
Valid 12Z Sat Oct 28 2023 - 12Z Sun Oct 29 2023

....THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF NORTHEAST TEXAS...=20=20
=20
....Northeast TX into the Lower Ohio Valley...=20=20
Precipitable water values of 1.5-2.2" are expected near a
slow-moving front draped across the region ahead of a
strengthening positively tilted upper level trough.  The degree of
low-level inflow and effective bulk shear available should
continue to organize what should be ongoing convection Saturday
morning into training bands as the flow is fairly uniformly out of
the west-southwest with height.  MU CAPE of 500+ J/kg should be
sufficient to achieve hourly rain totals to 2.5" at times, which
would be a problem across area terrain, which should slowly lower
with time as instability slowly lessens.  Local amounts in the
3-5" range are indicated by the available guidance overall.  The
Slight Risk area from continuity looked within reason which was
shifted minimally based upon the most recent model guidance,
though extension farther back into northeast TX to accommodate the
new Moderate Risk area -- where spots have picked up 8"+ of rain
overnight -- appeared wise given ongoing rainfall and the threat
for additional heavy rains early on.=20
=20=20
Roth


Day 2
Valid 12Z Sun Oct 29 2023 - 12Z Mon Oct 30 2023

....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM NORTHEAST
TEXAS INTO THE MID-SOUTH...=20
=20
Southern Plains into the Ohio Valley...=20
Precipitable water values will be in slow decline this period,
maximizing above 1.75" early on before falling into the
1.25-1.5"range by Monday morning.  A positively-tilted upper level
trough will be approaching the region from the west and north
causing some forward progression to the front across Texas and the
Lower Mississippi Valley with time.  The degree of low-level
inflow and effective bulk shear available could organize
convection into training bands during the day Sunday, assuming
sufficient instability, as the flow is fairly uniformly out of the
west-southwest with height, but should be fading somewhat Sunday
night into Monday morning.  MU CAPE of 250-500 J/kg should be
sufficient to achieve hourly rain totals of 1-2" at times early
on, which would be a problem across area terrain and places that
rained heavily on preceding days, but the 00z NAM indicates the
instability fades with time on Sunday and Sunday night.  Local
amounts in the 2-4" range are indicated by the available guidance
overall.  The biggest change to continuity was to extend the
Slight Risk area farther southwest, which has as much to do with
current soil saturation and ongoing heavy rainfall as it does with
the possibility of additional heavy rainfall.  There was some
temptation to raising the threat level to a Moderate Risk,
particularly early in the period when the parameters for heavy
rainfall look best which would account equally for heavy rainfall
continuing into Sunday morning and how much rain fell the
preceding day in and near AR, but the minimal instability forecast
was the biggest drawback.
=20
Roth


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!_Fq4KbuP5tRDfLpEbw_naon-uk9-cA-4MgTMFvKL8uH_=
QfY4IeZsd7IcU2eAtWFHGDUSTiaidZXt1uk-TOrEXxF3YrA$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!_Fq4KbuP5tRDfLpEbw_naon-uk9-cA-4MgTMFvKL8uH_=
QfY4IeZsd7IcU2eAtWFHGDUSTiaidZXt1uk-TOrE3Xz5HnI$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!_Fq4KbuP5tRDfLpEbw_naon-uk9-cA-4MgTMFvKL8uH_=
QfY4IeZsd7IcU2eAtWFHGDUSTiaidZXt1uk-TOrE9ds6auk$=20


$$



=3D =3D =3D
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