Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Jan 30 2023 20:11:25

FOUS30 KWBC 302011
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
310 PM EST Mon Jan 30 2023

Day 1
Valid 16Z Mon Jan 30 2023 - 12Z Tue Jan 31 2023

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

Mullinax


Day 2
Valid 12Z Tue Jan 31 2023 - 12Z Wed Feb 01 2023

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

Mullinax

Day 3
Valid 12Z Wed Feb 01 2023 - 12Z Thu Feb 02 2023

....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
EASTERN TX, NORTHWEST LA, & FAR SOUTHERN AR...

While parts of the South-Central U.S. are set to see periods of
rain today and Tuesday, it is Wednesday that has the better odds
of seeing excessive rainfall rates. A disturbance ejecting out of
the base of a positively tilted trough over the Southwest will
provide additional vertical ascent over Texas and into the Lower
Mississippi Valley. Meanwhile, a frontal boundary around 850mb
overhead will act as a trigger for showers and thunderstorms.
Temperatures at low-levels will be much cooler, but the strong
S-SW flow aloft will lead to a deep warm nose at mid-levels,
giving rise to some modest values of elevated instability. What
does favor potential excessive rainfall is a combination of mean
layer winds (850-300mb) will be oriented parallel to the 850mb
front, which could support possible training of elevated
convection. The other factor is moisture content as PWs will reach
as high as 1.25" over southeast TX and into central LA, which are
above the 90th climatological percentile for Feb 1.

Some soil moisture percentiles remain above the 90th
climatological percentile across eastern TX, northern LA, and far
southern AR according to NASA SPoRT-LIS. The biggest question mark
for this setup will be instability. MUCAPE will be limited to <750
J/kg and seeing temperatures mired in the 30s and 40s does not
usually support notable flash flooding potential. That said, the
combination of anomalous moisture content, possible training of
cells, and some areas featuring overly saturated soils suggests
flash flooding is possible from south-central TX to the Lower MS
Valley. Southeast TX on northeast to northern LA features the best
mixture of these ingredients for excessive rainfall, which is why
the Slight Risk remains in place for these areas. These risk areas
could be adjusted further in future updates depending upon where
the best instability sets up. Locations most prone to flash
flooding are atop the aforementioned overly saturated soils, in
more heavily urbanized communities that contains a greater
concentration of hydrophobic surfaces, and poor drainage areas.

Mullinax


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!_-VrG085OXyNJXhcEGe0EwMDKm_VcMoS93CUd6z_dth0=
Z5xceUlvOCO-jqRj7KhHkPbNGtLeo05QxctuDCq_8c0rTfs$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!_-VrG085OXyNJXhcEGe0EwMDKm_VcMoS93CUd6z_dth0=
Z5xceUlvOCO-jqRj7KhHkPbNGtLeo05QxctuDCq_Fl_Gqf4$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!_-VrG085OXyNJXhcEGe0EwMDKm_VcMoS93CUd6z_dth0=
Z5xceUlvOCO-jqRj7KhHkPbNGtLeo05QxctuDCq_Ix7LbLw$=20


$$



=3D =3D =3D
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