Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1210 PM EDT Sat Jun 13 2026

Day 1
Valid 16Z Sat Jun 13 2026 - 12Z Sun Jun 14 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR SOUTHWESTERN
MISSOURI...

...Southern Plains, Mid-Mississippi Valley, western Ohio Valley...

Maintained the Moderate Risk area for southwestern Missouri and
adjoining areas with a continued signal for heavy rain this
afternoon/evening and early overnight hours. A broader Slight Risk
outline extends from the eastern half of Oklahoma northeastward to
the far western Ohio Valley.

At 15Z, a cold front extended from the Upper Midwest back to the
central Plains and will continue to push southeastward today. In
addition, a warm front extended from southeastern Nebraska across
southern Missouri into the Tennessee Valley. Southerly flow from
Texas and the Gulf will continue to supply warm/moist air to the
region as dew points in the 60s/low 70s are common across the warm
sector along with precipitable water values of 1.75-2.00 inches.
Morning convection over central/southern MO (near and east of the
warm front) will continue eastward this afternoon, allowing for
some clearing to the west. By 00Z, cold front from the northeast
will push into southeastern KS with an increase in the LLJ and an
expected convective expansion into the Moderate Risk area. 40+kt
850mb southwesterly flow along/ahead of the surface cold front
should favor sufficient growth with heavy rain rates of 2-3 inches
per hour, especially where any training occurs if the cold front
slows. 12Z CAMs still show potential for a fairly widespread 1-3"
of rain and embedded 6+" totals over southwestern MO and far
northeastern OK per some members. HREF mean signal has been
consistent since 00Z and little change to the outlook area was
made. The topography of the Ozarks across southern Missouri
supports a heightened flash flooding threat as the mountains
quickly funnel the heaviest rains into narrow valleys, worsening
the impacts of any flooding that develops there. Will note the
AI guidance from the ECMWF and GFS (though lower res at 0.25 deg)
showed a QPF max over either eastern KS or northeastern OK rather
than into MO, but their D1 skill is generally not as good as the
traditional CAM guidance.

A much larger Marginal Risk area exists from the southern Rockies
all the way to the southwestern Great Lakes in the broad warm
sector ahead of the front, with expected coverage isolated.

...Central/Eastern Florida...

Trimmed the Marginal Risk area to remove the western portion of
the peninsula. Westerly flow, though light, should favor
convergence inland and over eastern areas. Moisture levels remain
higher than climo -- near 2" -- and coupled with slow-moving cells
may favor local flash flooding especially in urban areas. 12Z HREF
neighborhood probabilities for at least 3 inches per hour are
10-40% (a little higher in the 06Z REFS) and 1-h FFG values are
generally 3-4 inches per hour. Farther north into
eastern/southeastern SC/NC inland from the coast, combination of
sea breezes and incoming front to the north could support isolated
heavier rain and very localized flash flooding should any
convection remain slow-moving, though the coverage is likely less
than the 5% threshold for a Marginal Risk outline.

Fracasso/Wegman


Day 2
Valid 12Z Sun Jun 14 2026 - 12Z Mon Jun 15 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR AREAS FROM
SOUTHERN NEW MEXICO THROUGH WESTERN MISSISSIPPI...

A slow-moving but potent cold front will approach portions of north
Texas through into Arkansas on Sunday. The MCS that caused the
Moderate Risk flooding in Missouri Saturday night will be
responsible for the heavy rains that elevate northeast Texas
through the lower Mississippi Valley into the Slight Risk
category. Associated heavy rain will be ongoing at the start of the
period Sunday morning, and will weaken and dissipate by midday.
Since the forward/southward progression of the heavies rains will
slow after daybreak Sunday, some areas may see several hours of
weakening but still heavy rains. Abundant moisture will remain in
place south of the front, as PWATs rise as high as 2.25 inches.
Thus, any cells producing rains will have no trouble doing so
efficiently. During the afternoon and evening, this area may see
additional widely scattered storms with the strong front stalled
out in the area, but coverage will be somewhat in question as the
stalled out front alone will not be enough forcing due to flow on
either side of the front weakening to light and variable winds.

Further west into west Texas and New Mexico, a shortwave trough
running into some of the same Gulf moisture as further east should
allow for scattered showers and thunderstorms to develop in
clusters from the afternoon well into the evening. Topographic
assistance by the Sacramento Mountains and other ranges may locally
produce heavy rains, where any burn scars may take over at raising
the flash flooding risk. The same front extends into the
Appalachians and interior Northeast. While the storms will be
racing in these areas, the abundance of moisture advecting north
into the front will support the storms in their capability of
producing heavy rainfall. The Marginal Risk for these areas was
expanded along the Canadian border through northern Maine.

The Marginal for portions of the Mid-Atlantic was split into 2
areas with this update. One for the I-95 corridor from DC to
Philly, and a second for the Hampton Roads area. Abundant
Gulf/Atlantic moisture in these areas will support fast-moving but
training storms capable of producing heavy downpours. Due to
ongoing drought, the threat really is focused on the urban areas
where FFGs are lower. The intermediate rural areas were removed
with this update as any training storms that occur over most of the
Delmarva will be over rural and flood-resistant/flat areas.

Wegman


Day 3
Valid 12Z Mon Jun 15 2026 - 12Z Tue Jun 16 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
LOWER MISSISSIPPI VALLEY TO EASTERN TEXAS...

A large, half-continent sized upper level low over northern Ontario
will spin numerous shortwaves around its periphery over the eastern
2/3 of the country. The jet stream will coincide with a strong but
stalled out cold front over north Texas and southern Arkansas. To
the south of that front, Gulf moisture will pool to well-above
normal levels, with PWATs to 2.25 inches over east Texas and
northern Louisiana. When the shortwaves track over that cold front,
it will both allow it to continue drifting southward, but also
provide sufficient upper level forcing to trigger numerous and
persistent thunderstorms along the east-west oriented front and
south. This will support an extended duration of training storms,
especially from east Texas through southwest Mississippi. A
higher-end Slight remains in effect for this area. The inherited
Slight was trimmed out of south-central Texas and central Alabama
on the west and east ends, but expanded north-south over Louisiana
through the Houston Metro. Rainfall totals in some areas could
easily exceed 6 inches, with totals to 10 inches in localized areas
possible due to the extended duration of heavy rain, especially
along the Texas/Louisiana border. The area remains in a higher end
Slight for now primarily due to very high FFGs and dry soils in the
area, but further increases in rainfall, especially as this period
moves into the CAMs range, could allow for a Moderate Risk upgrade
due to the very high rainfall amounts forecast for some areas.

Wegman


Day 4 and Day 5

Valid 12Z Tue Jun 16 2026 - 12Z Thu Jun 18 2026

...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF THE
SOUTHERN PLAINS, LOWER MISSISSIPPI VALLEY, AND THE SOUTHEAST...

The first half of the medium range will see two particular threats
for flash flooding. First, along the Gulf Coast, a stationary
front will work in tandem with with tropical moisture to develop
thunderstorms capable of torrential downpours both on Day 4
(Tuesday) and Day 5 (Wednesday). There is greater confidence in
Tuesday's flash flood threat given better model agreement in
placement of QPF and the nearby frontal boundary remaining strong
enough to help trigger numerous showers and thunderstorms. PWs
will remain above 2.0" in many cases as well, allowing developing
thunderstorms to contain highly efficient rainfall rates. Soils
will be more saturated in wake of Monday's thunderstorms as well,
making the region more susceptible to flash flooding. The forecast
remains largely on track for Tuesday (Day 4) with only some minor
tweaks to the inherited Marginal and Slight Risks to more closely
resemble the latest WPC QPF. By Wednesday (Day 5) the frontal
boundary will undergo frontolysis and the source of lift at the
surface will weaken. However, ensemble guidance continues to show
ample tropical moisture along the Central Gulf Coast, which at by
Wednesday will have dealt with multiple rounds of Excessive
Rainfall. A Marginal Risk was introduced along the I-10 corridor
from the Houston metro on east to the FL Panhandle to account for
the flash flood potential around the more urbanized communities
along the central Gulf Coast.

Farther north, Wednesday looks like an active day from the Midwest
on east into the OH Valley. A 500mb shortwave trough racing east
towards the Great Lakes late Wednesday will provide healthy upper-
level ascent aloft to foster the development of low pressure.
Meanwhile, a strengthening LLJ will direct anomalous moisture
located over the South northward into the region. NAEFS shows an
impressive IVT for mid-June that surpasses 750 kg/m/s over the
eastern Corn Belt that will provide copious amounts of moisture.
Guidance is not in agreement yet as to which locations are most
favored to witness the heaviest thunderstorm activity. Fast storm
motions should also help to limit residency times of developing
storms. That said, PWs ranging between 1.75-2.0" will be the norm
late Wednesday with storms likely containing efficient rainfall
rates. A Marginal Risk was introduced to account for the localized
flash flood potential on Wednesday from the Middle MS River on east
into the OH Valley.

Mullinax


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