Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
643 PM EDT Sun Apr 6 2025

Day 1
Valid 2221Z Mon Apr 07 2025 - 12Z Mon Apr 07 2025

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHEASTERN UNITED STATES...

Training convection is currently ongoing across portions of the
central Gulf Coast producing areas of flash flooding. With plenty
of upstream instability and persistent, slow moving,
convergence...this axis of training convection should continue
through the evening hours. The axis of convection will slowly make
eastward progress, while also likely expanding off to the
northeast with time. This convection will be capable of hourly
rainfall as high as 2-3"...and recent HRRR runs show a swatch of
total rainfall amounts of 3-5", locally as high as 5-8". This swath
will likely stretch from southern AL into portions of the far
western FL Panhandle and possibly west central GA. Rainfall rates
and magnitudes will likely be high enough for scattered to numerous
instances of flash flooding along this training corridor...some of
which could be locally considerable in nature. The ongoing MDT
risk area was expanded to the south to account for this threat.

Across portions of the Carolinas into Virginia showers and
embedded heavier convective elements are expected to expand in
coverage overnight. Additional rainfall of 1-3" is expected, which
should not result in widespread impacts...however localized
instances of flash flooding can not be ruled out.

Chenard


Day 2
Valid 12Z Mon Apr 07 2025 - 12Z Tue Apr 08 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE SOUTHEAST US ON MONDAY...

19Z Update: Upon examination of the 12Z model and CAM guidance
suite, the inherited Marginal Risk area was expanded a little to
the north to include the greater Richmond, VA metro area and all of
Hampton Roads, and a modest extension to the west to include the
foothills of the southern Appalachians. The ARW has a slower exit
of some of the heavier rainfall through midday Monday, with the
potential for some 1-2 inch totals along and just northwest of the
Interstate 85 corridor. There may also be a second area of enhanced
rainfall across the coastal plain of North Carolina and extending
into southeast Virginia where higher PWs and instability will exist
ahead of the cold front, mainly south of Interstate 64. Depending
on how much convective training occurs, some instances of 2-3+ inch
totals will be possible on Monday before things taper off Monday
evening, with some lingering lighter rains after sunset and ending
overnight. One of the mitigating factors here is recent dry weather
and higher flash flood guidance, so the threshold of flooding is
higher and therefore this precludes the need for any Slight Risk
areas at this time.

Hamrick

...Previous Discussion...

Overall...the ongoing forecast remained on track and only some
minor adjustments were needed to account for a few pieces of
guidance which still favored a slower solution and, consequently,
higher rainfall amounts over a somewhat larger territory than in
the previous outlook. Still think that any lingering moderate to
heavy rainfall will continue to shift eastward on Monday as the
large scale flow pattern remains progressive. Current model QPF
generally remained in the 1.5 inch to 2.5 inch range with isolated
higher totals possible from far northern Florida northward into
the eastern portions of the Carolinas. The plume of 1.75+ inch
precipitable water values slowly decreases with time before being
shunted entirely off the Carolina coast Monday evening (and across
the central Florida peninsula late Monday night/early Tuesday
morning. Until that happens...moisture transport of deeper moisture
remains favorable to support a low- end risk of excessive rainfall
(especially in regions of poor drainage),

Bann

Day 3
Valid 12Z Tue Apr 08 2025 - 12Z Wed Apr 09 2025

A much needed return to drier weather comes by Tuesday morning and
the cold front will be offshore, except for the Florida Peninsula,
where it should exit by Tuesday evening. There may be a few
heavier showers and storms that develop over South Florida, and any
localized slow moving cells may result in some ponding of water in
poor drainage areas, but not enough of a concern to merit any risk
areas at this time. Most rainfall amounts should be under an inch.

Hamrick


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