FOUS30 KWBC 120841
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
441 AM EDT Sun Jul 12 2026

Day 1  Valid 12Z Sun Jul 12 2026 - 12Z Mon Jul 13 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
KENTUCKY AND TENNESSEE INTO THE CAROLINAS..

...Southeast Quarter of the Country...
The Slight risk remains in place from portions of KY/TN into
southern VA and the Carolinas. The mid level shortwave feature has
evolved into a deeper closed low, with slow moving convection
expected in the vicinity of that low across portions of KY and TN.
While widespread convective organization is not expected, the slow
storm motions combined with PW values between 1.75" and 2" will
support locally heavy rainfall rates. FFG is lowered across this
region due to antecedent rainfall, making isolated to scattered
exceedance likely today.

Further east from VA into the Carolinas, there is greater
uncertainty regarding convective evolution within a messy mesoscale
environment. Large scale forcing ahead of the mid level trough will
interact with a slow moving backdoor front to trigger scattered
convection. Stable air is filtering into southwest VA and central
NC, while easterly flow off the Atlantic is pulling more
instability into eastern VA/NC. Stronger instability exists over
SC south of the front. So overall a messy setup and tough to pin
down where stronger convection may focus long enough for flash flooding.

The primary convective focus will probably be from far southern NC
into SC where the instability is maximized near and south of the
front. A secondary local max could materialize from portions of
eastern/southeast VA into eastern NC where easterly flow enhances
convergence. While instability should largely wane tonight
persistent easterly upslope flow into the central and southern
Appalachians overlapping with at least some weak instability could
spark low topped convective development overnight somewhere across
southwest VA or central/western NC.

Overall the broad environmental setup within the Slight risk
remains conducive to heavy rainfall given PWs over 2" and multiple
low level convergence axes. While exact mesoscale boundaries
remain to be pinned down, isolated flash flooding is likely, and a
corridor or two of more concentrate impacts could emerge.

Surrounding the Slight risk, a broad Marginal encompasses eastern
NM, TX and much of the Southeast. A southward advancing cold front,
the aforementioned mid level shortwave/low, and upper jet support
will provide the necessary synoptic forcing for scattered
convection. PWs over 2" and CAPE of 2000-3000 J/kg where daytime
heating is maximized, will support heavy rainfall rates. While
conditions are close to Slight risk thresholds across this
corridor, regional FFG values are higher, and the latest HREF/REFS
EAS probabilities do not highlight a well defined axis of higher
convective concentration. Pockets of over 3" of rain are likely
within this Marginal risk area, but overall coverage is expected
to stay just below Slight risk thresholds.

Consideration was given to a Slight risk upgrade for portions of
north TX today, where a shortwave dropping south into the region
should help focus convection. Localized flash flooding is likely
here, particularly as an urban threat. However due to generally
high FFG and spatial discrepancies with the current model
guidance, we will hold at Marginal.

...Southwest...
Monsoonal moisture and instability will expand northwestward on
Sunday, necessitating a broader Marginal risk across AZ. While an
embedded Slight risk may eventually be needed, lingering questions
regarding storm coverage and organization keep the risk at
Marginal for now. Current indications suggest that while robust
convection will initiate over the terrain, it will propagate
westward quickly, potentially limiting the threat to isolate
instances of flash flooding.

Chenard
 

Day 2  Valid 12Z Mon Jul 13 2026 - 12Z Tue Jul 14 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
TEXAS INTO THE CENTRAL GULF COAST...

...Texas and Central Gulf Coast...
The Slight risk has been expanded deeper into TX with this update.
Embedded shortwave energy is forecast to migrate westward
underneath a sprawling upper level ridge centered over the Northern
Plains. In the low levels we will see increasing southerly flow
and moisture transport. However, with northerly flow prevailing
aloft, cloud layer mean winds will become weak. Corfidi vectors
will also be oriented north to south, opposite the lower cloud
layer flow...which supports some backbuilding and training threat.
PW values are forecast to exceed 2" over much of central and
eastern TX, with values potentially topping 2.25" over east TX.
Some instances of flash flooding appear likely in this setup.

A favorable synoptic and mesoscale setup for training and
backbuilding is forecast to align along the central Gulf Coast.
Enhanced west to northwesterly low level flow south of the
persistent shortwave/low over the TN/GA vicinity will converge with
west-southwesterly inflow off the Gulf. This configuration is
conducive for upwind propagation and some training convection.
Based on latest model guidance, this threat may remain confined
pretty close to the coast. A very moist airmass with PWs around
2.25" will support heavy rainfall rates.

...Southeast and Southern Mid-Atlantic...
A broad Marginal risk remains from TN into the Southeast and
southern Mid-Atlantic. Similar to day 1, a lingering shortwave and
closed low will continue to interact with a a backdoor front. Model
guidance show some spread regarding the exact positioning of these
features and where the primary axis of instability will reside. An
embedded Slight risk upgrade may eventually be needed as these
mesoscale details clarify. At a minimum, localized flash flooding
will occur, but the potential exists for a more concentrated flash
flood threat to materialize. North GA into SC currently appear most
at risk, but will see how todays convection evolves and what the
new high res model show.

...Southwest...
A Marginal risk is maintained from southern NM into AZ, southeast
CA and southern NV. Deep monsoonal moisture will continue to push
northwestward with isolated to scattered convection expected to
result in at least a localized flash food threat.

Chenard
$$
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