FOUS30 KWBC 110851
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
451 AM EDT Sat Jul 11 2026

Day 1 Valid 12Z Sat Jul 11 2026 - 12Z Sun Jul 12 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
ARIZONA AND THE SOUTHERN PLAINS TO THE CENTRAL APPALACHIANS...

...OK into the OH and TN valleys...
An active convective regime is anticipated ahead of a
southeastward moving shortwave trough axis extending from MO to OH.
At 12z this morning, an initial round of convection will be
ongoing from southern IL into portions of KY and TN. Model
guidance supports a transition toward a primarily forward
propagating convective mode this morning, which should place the
overall flash flood risk on a declining trend, though localized
upwind propagation may keep an isolated threat going.

By this afternoon, the primary MCV/shortwave will shift over IL
and IN, interacting with a southward moving frontal boundary to
trigger scattered redevelopment across portions of IL, IN and WV.
Within this zone, PW values near or just under 2" will overlap with
CAPE of 1000-2000 J/kg. While widespread convective organization
is not anticipated, slow cell motions and localized mergers near
the frontal zone will support heavy rainfall rates capable of
producing localized pockets of 2-3" of rain. This is supported by
the 00z HREF and REFS, which both show FFG exceedance
probabilities of 15-40%.

A more organized, and potentially higher end, flash flood threat
is expected to evolve later this afternoon into tonight across
portions of KY and TN. Convection should develop to the south-
southeast of the main shortwave/MCV, likely focusing along remnant
outflow boundaries and instability gradients left behind by the
morning activity. Global deterministic and AI models favor a heavy
rainfall axis focused primarily from KY into northeast TN,
whereas high res models (including the RRFS/REFS) suggest the core
threat may track further south into TN. Given the strong westerly
low level moisture transport south of the MCV, the environment
will be favorable for backbuilding and training convective clusters
tonight. This environment, combined with PWs hovering around 2",
suggests that many HREF members may be underdoing the
afternoon/nocturnal threat. Do expect to see a swath of heavy
rainfall materialize somewhere across the KY/TN corridor, where an
axis of locally higher end flash flood impacts is possible. A
higher end Slight risk is maintained, with a MDT risk upgrade not
out of the question if we gain spatial model convergence and more
confidence on exact convective mode.

Further west, isolated to scattered flash flooding is also expected
across portions of central OK into AR. Low level flow will become
convergent on the southwestern flank of the broader convective
regime. Slow cell motions near a boundary will pose a threat over
OK, while enhanced northerly flow on the western periphery of the
MCV/shortwave will converge with the broad south-southwesterly
inflow to promote some backbuilding/training threat over parts AR.

...Mid-Atlantic...
A localized flash flood threat is forecast across portions of the
Mid-Atlantic. While low level flow will be northerly, one or two
low level convergence axes are projected to setup across the
region, potentially acting as a focus for convection. Despite the
northerly flow, ample moisture and instability will remain in
place. Convective cells will generally track from north to south,
but localized repeating cells will be possible along the trough
axis. The strongest signal for localized 3" totals with the HREF
resides along the coastal plain from NJ southward into southeast
VA where convergence is enhanced. Because FFG values are generally
higher here compared to inland locations, think the overall flash
flood risk should stay isolated, though localized urban and low
lying flood impacts are expected.

...AZ and NM...
The persistent terrain driven pattern continues across the
Southwest, with convection developing over the higher elevations
before propagating southwestward into a pooling instability axis
over the lower deserts of southern AZ. Instability and moisture
profiles should be a bit higher today relative to the past few
days, leading to a corresponding increase in the overall flash
flood risk. Both the 00z HREF and REFS depict greater convective
coverage and higher localized rainfall totals. While fast
southwestward storm propagation and cell speeds may act as a
limiting factor, the moisture/instability footprint should be
sufficient to promote some cell mergers and localized 1-2"/hr
rainfall, justifying the maintenance of the Slight risk.

A Marginal risk has been added to portions of eastern NM. This area
received locally heavy rain yesterday, and the model QPF signal is
a bit stronger today within an environment characterized by
slightly higher moisture and instability. Convection should remain
isolated to scattered, with the primary flash flood threat focused
over recent burn scars, particularly across the Sacramento Mountains.

...TX...
A Marginal risk was added to portions of the TX Hill Country, where
PWs are forecast to climb above 2". Isolated to scattered
convection is expected within a broad southerly low level flow
regime. While most cells will remain transient and produce only
brief downpours, any cells that establish mesoscale organization
could briefly train or backbuild into the low level inflow.
Guidance suggests a weak MCV currently south of the Rio Grande
that may track northward towards the region later today, which
could provide an additional focus for ascent. The risk area aligns
closely with the HREF and REFS 1" EAS probabilities of 10-20%
(signaling organization potential), and 3" neighborhood
probabilities exceeding 40%. Global deterministic and AI suites
also show a distinct convective focus over this corridor.

Chenard


Day 2 Valid 12Z Sun Jul 12 2026 - 12Z Mon Jul 13 2026

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

...Southeast Quarter of the Country...
A Slight risk has been introduced stretching from KY and TN
eastward into southern VA and the Carolinas. A well defined
shortwave/low over the KY/TN vicinity will interact with a slow
moving backdoor front to focus organized convection. High res
guidance, including the RRFS, FV3 and 3km NAM, indicates a
concentrated axis of convection capable of producing localized
totals exceeding 3". While the global GFS and ECMWF are less
pronounced with their QPF swaths the GEM regional and UKMET are
more in line with the high res guidance. The AIFS and AIGFS also
depict a corridor of enhanced QPF that generally matches the Slight
risk placement. Beneath the closed low over KY and TN, convection
may be less organized, but slow moving. Given PWs near 2" and the
possibility of saturated soils from day 1 rainfall, a flash flood
risk should continue. Across the central and eastern Carolinas PWs
over 2" combined with low level southerly moisture transport and
backdoor frontal convergence should create an environment for high
rainfall rate driven flash flood potential.

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. Some
mesoscale uncertainty exists with the track and strength of the
shortwave and frontal positions. An embedded Slight risk or two
may be needed on future updates as confidence increases. Increasing
low level westerly flow along the central Gulf Coast provides a
signature for backbuilding and training, but model divergence on
the exact axis remains. Given the higher regional FFG, did not
want to go with an overly large Slight risk at this time.

...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
$$
--- MultiMail/DOS
* Origin: capitolcityonline.net * KY, USA (618:250/10)

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
$$
--- MultiMail/DOS
* Origin: capitolcityonline.net * KY, USA (618:250/10)