FOUS30 KWBC 300034
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
834 PM EDT Tue Oct 29 2024

Day 1
Valid 01Z Wed Oct 30 2024 - 12Z Wed Oct 30 2024

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.

Chenard


Day 2
Valid 12Z Wed Oct 30 2024 - 12Z Thu Oct 31 2024

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM THE
SOUTHERN PLAINS TO THE UPPER MISSISSIPPI VALLEY/UPPER MIDWEST...

A deep layered trough is expected to eject into the Plains by
Wednesday morning, which in turn results in surface troughing that
draws Gulf moisture northward ahead of an approaching cold front.
Cooler air filtering in from the west/north will encounter the warm
air advection associated with the low- level jet. Convection over
the region is expected to increase in both coverage and intensity
with the set up becoming more favorable for isolated heavy
rainfall amounts/rates and localized flooding concern.

The 12Z global and ensemble guidance continues to show two
distinct areas swaths of higher QPF. The first remains focused near
the juncture of Oklahoma, Texas and Arkansas state borders amid
areas of higher instability...on the order of 1500 to 2500 J per kg
of surface based CAPE. The second area from northeast Kansas to
northern and central Wisconsin still inched westward in this model
cycle close the the greatest mid- and upper-level height falls
which was roughly co-located near a region of sloped frontogenesis
in the 800 mb to 600 mb layer late in the period. At the same
time...the 29/12Z NAM accelerates low level flow to the 45 kt to 65
kt range acting to enhance moisture transport into the area as
early as 31/03Z in a few spots. The Marginal Risk area needed only
a minor nudge after the shape was altered more noticeably in the
previous outlook.

Antecedent conditions are quite dry...as reflected by the very high
flash flood guidance. That should mitigate any widespread threat
of excessive rainfall as well as progressive cells. Even so...the
Marginal Risk area still seemed appropriate based on what the
magnitude of the instability and mesoscale forcing from the coarser
numerical guidance with room to adjust with future guidance
(including the CAM guidance).

Campbell/Bann


Day 3
Valid 12Z Thu Oct 31 2024 - 12Z Fri Nov 01 2024

...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE LOWER MISSISSIPPI VALLEY...

2030Z Excessive Rainfall Update...
Instability remains the highest in portions of the Lower
Mississippi Valley while the flow pattern/mesoscale forcing weakens
farther north. The previous outlook had that pretty well handled
so no change was made.

Bann

083-Z Excessive Rainfall Discussion...

The upper level trough will continue to advance through the Upper
Midwest which will send the cold front through the eastern portions
of the Southern Plains and mid-Mississippi Valley. Strong to
severe thunderstorms will persist for areas along and ahead of the
advancing frontal boundary per SPC (Marginal Risk); which will
shift the heavy rain potential to the central Gulf Coast to
western Kentucky where there is a Marginal Risk area for excessive
rainfall. Areal averages will be in the 1 to 2 inch range with
locally higher amounts possible.

Campbell

Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!5zUUpMJMmY3cwM7DwJELR6ixr6zq4_Un6UL7XGSJUb-a=
Y6dKZwJHKn2-r44uzST69VM4XAcaKcLUtpnVGcRDUmXyCSY$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!5zUUpMJMmY3cwM7DwJELR6ixr6zq4_Un6UL7XGSJUb-a=
Y6dKZwJHKn2-r44uzST69VM4XAcaKcLUtpnVGcRDY7kkGbg$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!5zUUpMJMmY3cwM7DwJELR6ixr6zq4_Un6UL7XGSJUb-a=
Y6dKZwJHKn2-r44uzST69VM4XAcaKcLUtpnVGcRD1yGZ6g0$=20

=3D =3D =3D
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