Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
429 AM EDT Sun Apr 20 2025

Day 1
Valid 12Z Sun Apr 20 2025 - 12Z Mon Apr 21 2025

..THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS THE CENTRAL
US TODAY INTO TONIGHT...

Introduced a Slight Risk area for the potential of excessive
rainfall from parts of Texas into the Upper Midwest/Northern
Plains. It is really a composite of multiple reasons to warrant a
Slight Risk area in different geographical areas. The northern
portion of the Slight Risk area covers the growing model signal for
2-3+ inches of rain due to a combination of deformation
zone/surface low and good divergence aloft from the highly curved
anticyclonic upper level jet all becoming more or less collocated.
Rainfall amounts in the central part of the US are forecast to be
less than areas to the north...but the Slight Risk area was more
targeted for overlap between future rainfall on top of what MRMS
has shown for the past 24-36 hrs in anticipation of how the FFG
values will change. Lastly...kept some parts of the Southern Plains
in an outlook area based on short term radar/satellite trends.
While rates have come down as the plume of highest equivalent
potential temperature has narrowed overnight...suspect that the
potential for at least some excessive rainfall will persist beyond
the start of Day 1 period at 20/12Z. Those areas can be removed in
the mid- morning Day 1 ERO assuming that trends continue downward.

Bann

Day 2
Valid 12Z Mon Apr 21 2025 - 12Z Tue Apr 22 2025

The probability of rainfall exceeding Flash Flood Guidance is less
than 5 percent.

Bann

Day 3
Valid 12Z Tue Apr 22 2025 - 12Z Wed Apr 23 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF TEXAS AND/OR THE ADJACENT SOUTHERN PLAINS...

Largely maintained a Marginal Risk area over portions of the
Southern Plains from Tuesday into early Wednesday morning due to
the suite of 00Z numerical guidance continuing to show the
potential for repeat/training of cells during the day and with
overnight activity within an emerging moist and unstable return
flow into and over several frontal boundaries. With the models
struggling to latch onto a coherent signal...as shown by some
guidance focusing heaviest QPF near the Gulf coast in proximity to
a weakening cold front and other guidance developing the threat
closer to the Red River in response to the approach of a mid-level
wave...have opted to highlight concern for excessive rainfall in
broad and rather unfocused Marginal Risk area close to a consensus
placement of the precipitable water axis. With PW values generally
being 1.25 inches or less...would not be expected numerous
torrential downpours. The cumulative effect of what has already
fallen from this weekends event and what falls on Tuesday/early
Wednesday needs to be watched.

Bann

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