Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
408 AM EDT Thu Mar 23 2023

Day 1
Valid 12Z Thu Mar 23 2023 - 12Z Fri Mar 24 2023

...THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL OVER A PORTION
OF THE MID/SOUTHERN MISSISSIPPI VALLEY..

An abundant, steady stream of Gulf moisture as a deep-layer trough
ejects from the Southern Rockies and results in strengthening low
level flow.  At about the same time, upper level divergence from
an upper level jet aids in surface low pressure forming along a
quasi-stationary front extending from Oklahoma northeastward into
the Ohio/Tennessee Valley. Precipitable water values at or
slightly greater than 1.25 inches reaches eastern Oklahoma by
23/18Z before becoming more expansive by 24 00Z, from Texas to
Kentucky. Strong moisture convergence along the boundary along
with support from the upper level jet will aid in the production
of moderate to locally heavy rainfall, especially from eastern
Oklahoma to the southern Indiana. There still  potential for 1 to
2 inch/hour rain rates during the afternoon, but especially
by/after 00Z. While this area is not as saturated as it was a
couple of weeks ago...there is local concern given that ground
conditions are still fairly moist. The Moderate and Slight Risk
areas were expanded to the southwest across Oklahoma to reflect
the latest trends in the guidance and WPC QPF.

Campbell


Day 2
Valid 12Z Thu Mar 23 2023 - 12Z Fri Mar 24 2023

...THERE IS A MODERATE RISK FOR EXCESSIVE RAINFALL FROM THE OZARKS
TO THE OHIO VALLEY...

Showers and thunderstorms will continue from the day 1 period in
proximity to the sprawling frontal boundary with moisture flux
convergence increasing across parts of the Mississippi Valley and
into the Ohio Valley as a surface low pressure with trailing cold
front moves east across the Southern Plains. By 25/00Z a PW fetch
of 1.5 inches will span from the Gulf Coast to the MO boot heel,
feeding right into the frontal boundary, which is some (+2 to +2.5
standard deviations greater than climatology for late March. 
Repeating storms will track across areas soaked from recent rains
and will likely surpass local FFGs early into the Day 2 period.
The latest model runs have been persistent with areal averages of
2 to 4+ inches with above average confidence. This part of the
nation will be sensitive to additional rainfall, let alone a large
area with several inches of new accumulations. The Moderate Risk
area was adjusted a little to the southwest.The Slight Risk was
expanded a smidgen toward the Oklahoma/Arkansas border while
trimmed northward across northern Mississippi and Alabama. The
Marginal Risk area was also trimmed northward across the Lower
Mississippi Valley.

Campbell

Day 3

The Day 3 outlook will be updated by 0830Z.


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