Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
306 PM EST Tue Mar 3 2026

Day 1
Valid 16Z Tue Mar 03 2026 - 12Z Wed Mar 04 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE MIDWEST AND OHIO VALLEY...

16Z Update...

The 12Z HREF guidance has trended just a tad wetter across
especially the OH Valley for the period ending 12Z/Wednesday.
Ongoing moderate to locally heavy rains this morning are very
gradually moistening up the soils across areas of central/southern
IL through the southern half of IN, however, much of the rainfall
continues to be stratiform in nature. A new surge of stronger warm
air advection associated with a southwest low-level jet of 30 to 40
kts interacting with a frontal zone should favor additional rounds
of heavy rainfall potential this evening and overnight. MUCAPE
values are forecast to rise to near or slightly above 500 J/kg.
This will help support some elevated convection near and poleward
of the front that should remain draped across the OH Valley going
through tonight. Some rainfall rates may reach a 0.50" to 1"/hour
with the stronger cells, and these rates are supported by the 12Z
HREF guidance. Multiple CAMs do suggest some localized cell-
training concerns that may yield some additional 1 to 2+ inch
totals. However, the antecedent conditions for most areas (minus
areas closer to the central Appalachians/WV) are rather dry. This
coupled with the relatively modest rates suggest any runoff
concerns would tend to be more urbanized in nature and certainly
isolated. The threat farther east into the central Appalachians
(notably central and northern WV) could end up being a bit higher
given the wetter antecedent conditions here, but the guidance
overall generally pegs the heaviest totals occurring farther west
across areas of central IL eastward through southwest OH. As such,
the Marginal Risk is maintained for this update.

Orrison

Previous discussion...

Models have solidified their agreement in an axis of 1-2 inch
rainfall totals generally from northeastern Missouri eastward
through southern Ohio. These totals will coincide with an east-west
oriented front across the region, with point forecast soundings
suggesting fairly fast cellular motions and minimal surface-based
instability. The main contributor for flash flood potential with
this axis is repeating/training rainfall, though dry antecedent
conditions remain a mitigating factor for a larger-scale flash
flood risk. One exception to this is West Virginia - soil
moistures are relatively wet there compared to points west.
Rainfall totals may be somewhat lighter there too though (0.5-1.5
inches), also keeping any flash flood potential isolated.

Cook

Day 2
Valid 12Z Wed Mar 04 2026 - 12Z Thu Mar 05 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM NORTH TEXAS
NORTHEASTWARD INTO THE OHIO VALLEY...

20z Update: Minimal changes made to the inherited risk. The threat
across eastern OK, northwest AR and southern MO is right on the
border of a higher end Marginal or lower end Slight risk, with
localized rainfall over 3" likely. Given max hourly rain currently
forecast to only peak ~1.5" and the dry antecedent conditions, we
will continue to hold this at a Marginal, with primarily localized
flash flooding expected.

Chenard

...Previous Discussion...

Minimal changes are made to the inherited outlook. At the mid-
levels, an approaching trough will reach the central Plains during
the forecast period. As this occurs, strengthening, confluent low-
level flow from north Texas into the Missouri Ozarks will aid in
moisture transport and eventually deep convective development
especially during the afternoon/evening hours. That convective
development will migrate from southwest to northeast within the
aforementioned warm conveyor, with areas of training/repeating
possible along with local rainfall totals exceeding 3 inches
through 12Z Thursday. The collocation of these rainfall totals with
varied/sensitive terrain over southwest Missouri/northwest Arkansas
suggests that higher probabilities and a Slight Risk may need to be
introduced at some point. Lingering concerns regarding antecedent
conditions (very dry soils) and eventual convective evolution
(models exhibiting a slight westward trend over the past 24 hours)
gives pause on introducing an upgrade at this time, however.
Current trends suggest that the greatest risk of flash flooding
will exist along an axis from Fayetteville, AR to Rolla, MO,
though this axis may change between now and Wednesday
afternoon/evening.

Farther northeast, areas of rain (approaching 1-1.5 inch total in
spots) will develop from southern Illinois eastward through West
Virginia in similar locations that are expected to receive 1-2
inches of rain during the D1 forecast period (Tuesday into Tuesday
night). Soils should continue to moisten during this period, with
isolated instances of flash flooding remaining possible.

Cook

Day 3
Valid 12Z Thu Mar 05 2026 - 12Z Fri Mar 06 2026

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

20z Update: Additional convection is probable across portions of
the OH valley. The current QPF is generally 1" or less, and this
amount of rain would typically not produce a flood risk. However,
heavier totals are possible, and hydrologic conditions will be more
sensitive from the previous two days of rainfall. Thus we may
eventually need to carry a Marginal risk here, but will hold off
for now and continue to monitor both the forecast rainfall for this
day, and how the previous rainfall impacts soil and streamflow
conditions.

Chenard

...Previous Discussion...

Models are in general agreement that longwave trough will deepen
across the Intermountain West, spreading southwesterly flow aloft
over a large part of the Great Plains. Meanwhile, low-level
moisture advection will aid in an airmass characterized by 1.25-1.5
inch PW values along and just east of a dryline generally extending
from near Goodland to near Amarillo. Models depict scattered
convection developing amid supercellular wind fields Thursday
afternoon, with a mix of cells and linear segments possible along
parts of the dryline. Local cell mergers may result in a couple
spots of 2-3 inch rainfall totals in this regime, though the
overall footprint of heavier rainfall should be too small to even
delineate a Marginal Risk area at this timeframe. Antecedent dry
conditions/drought are also mitigating factors for flash flood
potential. This scenario will need to be monitored for any
potential increase in convective coverage that might necessitate a
Marginal in later outlooks.

Cook


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