Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
317 AM EST Fri Dec 6 2024

Day 1
Valid 12Z Fri Dec 06 2024 - 12Z Sat Dec 07 2024

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

Churchill


Day 2
Valid 12Z Sat Dec 07 2024 - 12Z Sun Dec 08 2024

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
EASTERN TEXAS AND WESTERN LOUISIANA...

A low-level jet streaming Gulf moisture northward across eastern
Texas will interact with a strong shortwave trough which will move
northeastward out of New Mexico and into the central Plains. PWATs
along the Upper Texas coast are expected to increase to 1.5"+ and
instability should remain minimal (and mostly confined to the
coast). The heaviest rain is forecast to be on Saturday night due
to the typical nocturnal strengthening of the low-level jet. Soils
have become a bit more saturated in this region due to the recent
rainfall, and some rainfall is expected on Friday. Isolated flash
flooding is possible, especially in areas of more saturated soils,
urban areas, and flood prone/low lying areas.

Churchill/Roth


Day 3
Valid 12Z Sun Dec 08 2024 - 12Z Mon Dec 09 2024

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
LOWER MISSISSIPPI VALLEY AND CENTRAL GULF COAST...

Continued moisture flux transport via a moderately strong low-
level jet is expected to result in increasing coverage of flash
flooding on Sunday, as the bulk of the forcing and jet dynamics
via the aforementioned strong shortwave trough will not arrive
until midday (along with maximized instability). Localized training
is expected to result in 2-4" totals, suggesting a lower-end
Slight Risk based on the probability spectrum (which ranges from
15-40%). Given that most of the region is experiencing very dry
antecedent soil conditions (10th percentile or lower for much of
MS/AR/LA, per NASA SPoRT-LIS 0-100 cm soil moisture), any flooding
should be relegated to flood-prone areas (with the greatest risk
for any localized significant flash flooding over west-central LA,
where antecedent soil conditions and streamflows are locally higher).


Churchill


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt