Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1210 PM EDT Fri Jul 10 2026

Day 1
Valid 16Z Fri Jul 10 2026 - 12Z Sat Jul 11 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE MID MISSISSIPPI VALLEY...

...Mid MS Valley to the Central Appalachians...

16Z Update...
Guidance still in general agreement that heavy rainfall will
overspread much of the Mid-Mississippi Valley into the Tennessee
Valley and parts of the Ohio Valley/Central Appalachians today.
Evaluation of 12Z guidance suggests that the potential remains for
locally very heavy rainfall (HREF 24-hr probabilities for 5"
over 20%) which is depicted via most high- res CAMs. However, the
placement remains quite uncertain as there is virtually no overlap
in the footprint between the available high-res models. After
coordination with the local WFOs, a targeted MDT risk was added
basically to overlap the area that had significant rainfall
overnight leading to extremely vulnerable soils with 3-hr FFG less
than 1".

Elevated PWs above +1.5 sigma combined with 1000-3000 J/kg will
support heavy rain producing convection anywhere across this region
today, with the wavering front and any weak mid-level impulses
providing the locally enhanced ascent for stronger convection. This
will likely cause at least scattered instances of flash flooding
due to compromised FFG from recent rainfall. The focus for the
heaviest rainfall (and accompanying flash flooding) should be
downstream of a potent (especially for July) shortwave dropping
across MO which will additionally interact with the stationary
front and the relatively higher moisture along and to its south. A
potent LLJ progged to reach 30-35 kts will draw impressive
thermodynamics into the boundary as well, supporting a situation
with impressive training (weak and anti-parallel Corfidi vectors)
with rainfall rates of 2-3"/hr thanks to more than 4000m of warm
cloud depth. Training of these intense rain rates will likely
produce stripes of heavy rainfall for which nearly all high-res
CAMs indicate will reach 5-7+" in localized areas. Despite that,
the probabilities are only marginally supportive of a higher ERO
category, but at least locally significant impacts are becoming
more likely from near southeast MO through western KY and central
TN where the 0-10cm RSM from NASA SPoRT is above 70% due to recent
heavy rainfall, creating enhanced vulnerability across the region.

Previous Discussion:
The Slight risk has been expanded northward across portions of MO,
IL, IN and OH to account for multiple evolving convective threats.
Otherwise the broad Slight risk remains similar to the previous
forecast.

Convection will be ongoing at 12z this morning across southern MO
into portions of KY and TN, with areas of flash flooding already
underway across portions of this region. While the activity across
KY and TN today is forecast to become primarily forward
propagating, which should limit the overall magnitude of the flash
flood risk, strong low level westerly moisture transport will help
maintain weak Corfidi vectors. Thus, upwind propagation and periods
of backbuilding/training are possible as the convection tracks
across KY and TN today. This introduces the potential that
localized rainfall totals will exceed high res model guidance, a
trend that will be monitored closely.

A Slight risk area also covers slow moving convection that should
develop near a frontal boundary across portions of IN/OH and
southwest PA. PWs are slightly lower here than past days events,
but still remain well above climatological averages. When combined
with upwards of 2000 J/kg of CAPE, this environment supports
intense rainfall rates locally around 2" per hour. Slow cell
motions and periodic mergers should result in isolated to scattered
instances of flash flooding. The 00z HREF FFG exceedance
probabilities exceed 25%, with REFS values over 40% (noting a
typical high bias for the REFS in this type of regime).

The northward expansion of the Slight risk across portions of
MO/IL/IN covers the convective threat associated with a
shortwave/MCV ejecting eastward from the ongoing Plains
convection. Thunderstorms should become increasingly organized by
this afternoon and evening across this region. While the storm
mode may lean forward propagating, some cell mergers appear likely
and should drive a flash flood threat. Both the 00z HREF and REFS
highlight this corridor with FFG exceedance probabilities of 15-30%
and depict a 10-30% chance of hourly rainfall exceeding 3".

Heading into tonight, convection from the aforementioned
shortwave/MCV is forecast to dive southeastward from IL/IN into KY
and TN. High res model simulated reflectivity suggest a forward
propagating convective line. However, persistent low level
westerly moisture transport will keep Corfidi vectors weak,
offering further opportunities for upwind propagation and
backbuilding into the westerly flow. Should this occur, rainfall
totals and the flash flood risk could end up higher than currently
forecast by the models. Thus while FFG exceedance probabilities
from both the HREF and REFS are generally under 15% across this
area, the Slight risk remains fully warranted due to the potential
for multiple convective rounds and backbuilding. However, we will
hold off any any MDT risk upgrade due to the modest model QPF
blends and lower confidence on the exact convective mode.

...Arizona...
A similar mesoscale setup to Thursday is expected, though
potentially with slightly higher instability. Convection is
forecast to develop over the higher terrain during the afternoon
before propagating southwest into the desert valleys. Just like
yesterday, localized cell mergers could enhance rainfall and
result in a localized flash flood risk. While models suggest
overall storm coverage may be slightly greater today, the threat
remains isolated enough to maintain a Marginal risk, and the risk
area was cosmetically adjusted slightly to account for new
probabilities and the plume of highest instability.

...High Plains...
Additional shortwave energy ejecting out of the Rockies will lead
to convective development this afternoon from CO into KS and south
to the TX Panhandle. This activity is expected to be less robust
than yesterday due to generally weaker low level inflow, lower
instability, and weaker large scale forcing. Nonetheless, one or
two organized convective clusters should develop and push
eastward, posing a localized flash flood threat.

Chenard/Weiss


Day 2
Valid 12Z Sat Jul 11 2026 - 12Z Sun Jul 12 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF
THE MS VALLEY TO THE CENTRAL APPALACHIANS...

...MS/OH/TN Valleys...
A shortwave trough is progged to extend from MO to OH by 12z
Saturday, likely featuring one or more embedded MCVs. Uncertainty
remains with the exact rack and strength of these mesoscale
features, which will play a large role in where the flash flood
threat is maximized.

Some high res guidance indicates an MCV moving towards WV Saturday,
which could interact with a southward dropping frontal boundary
and produce an area of enhanced convective coverage. Slow moving
convection near these features could maintain a flash flood threat
for portions of WV/OH/PA/MD/VA. Confidence is highest over WV,
where the Slight risk remains, with a Marginal risk maintained
further north and east.

Model consensus is trending towards a stronger shortwave/MCV
hanging back over IL/IN/KY, although guidance diverges on how
convection evolves around this feature. This evolution is
dependent on Friday's convective outcomes and the ultimate
strength/position of the shortwave. The RRFS/REFS/FV3/Gem reg
focus heavy convection over central/eastern TN and KY to the
southeast of the shortwave, a solution also generally supported by
the AIFS and AIGFS. Conversely, the GFS and ECMWF are displaced
further southwest, placing maximum rainfall over AR, MS and western
TN and showing lower values to the northeast.

At the moment, higher confidence is placed in the high res/AI
consensus favoring a maximum over central/eastern TN and KY. Given
that portions of this region will have seen heavy rainfall on day
1, a higher end Slight risk remains warranted due to the
possibility of increased hydrologic sensitivity. If models
converge on a repeatable heavy rainfall footprint over these areas,
a MDT risk upgrade may eventually be needed. Additionally, heavy
rainfall is also expected to extend westward across western TN, AR
and portions of MS and AL. The Slight risk has been expanded
westward into more of AR with this update, where the
RRFS/REFS/FV3/3km NAM all support heavier convection...with
northern AR potentially favored for training and backbuilding along
the southwestern flank of the broader convective regime.

...Southwest...
The terrain driven convective pattern continues as storms roll off
the higher elevations of AZ and into a pooling instability axis
across the southern portion of the state. Instability and PW
values are forecast to be higher than on day 1. The 00z REFS
neighborhood probabilities show a 40-60% chance of locally
exceeding 3" of rain, with the 3km NAM and FV3 also depicting
locally high totals. Given the favorable environmental ingredients
and a growing model QPF signal, southern AZ has been upgraded to a
Slight risk with this update.

Chenard


Day 3
Valid 12Z Sun Jul 12 2026 - 12Z Mon Jul 13 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF ARIZONA AND FROM TEXAS INTO THE SOUTHEAST...

...Southeast Quarter of the Country...
A broad Marginal risk extends from eastern TX stretching
northeastward into portions of the TN/OH Valley, the southern Mid-
Atlantic and much of the Southeast.

An embedded shortwave/MCV is forecast to become blocked downstream
of an expanding upper level ridge centered over the Rockies. This
feature will interact with a southward dropping front and an upper
level jet streak, providing ample synoptic forcing to focus
convective development. Across much of the region, PW values will
exceed 2" alongside CAPE values of 2000-3000 J/kg where daytime
heating is maximized. While this environment is favorable for high
rainfall rates and some organized convective clusters, significant
uncertainty exists regarding the finer details, including the
strength/position of the shortwave and exact positioning of the
frontal boundary.

Given the high PW and instability profiles, an embedded Slight
risk or two will almost certainly be needed on future updates.
However, because FFG is climatologically higher across this
portion of the country (particularly from the lower MS Valley into
the Southeast), avoided placing a large Slight risk with this
update. Current model guidance hints at two potential heavy
rainfall maxima...one over the carolinas where an MCV may interact
with a backdoor front, and another in the vicinity of AR to the
central Gulf Coast. Not confident enough at the moment for a Slight
risk across either area...but will continue to closely monitor
trends.

...Southwest...
Moisture and instability will continue to expand northwestward on
Sunday, warranting a larger Marginal risk across AZ. While an
embedded Slight risk may eventually be required, lingering
questions regarding the overall coverage and organizational
structure of convection justify keeping the risk at Marginal for
this update.

Chenard


Day 4 and Day 5

Valid 12Z Mon Jul 13 2026 - 12Z Wed Jul 15 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ALONG PARTS OF THE
CENTRAL GULF COAST ON MONDAY...

...Southeast U.S. into Texas...

A generally stable upper pattern will lead to relative persistence
in the convective setup across the CONUS as we move into early
next week. Broad ridging over the center of the country will
maintain prevalence on Mon/Tue with a prevailing easterly flow
situated around the southern periphery of the ridge. At the
surface, a cold front will eventually hit a road block along the
Gulf coast, extending westward into TX leading to a transition to
a quasi-stationary front situated from the Southeastern U.S. back
into central TX. Deep moisture layer will be present within the
southern confines of the ridge with a well-defined theta_E
alignment positioned within proximity of the front. Diurnal
destabilization on Monday will allow for enhanced convective
potential with cell motions liable to anchor and/or train over the
same areas as they become fixated to the stationary front. This is
a generally classic pattern for heavy rainfall across the Southern
U.S. this time of year as high CAPE, low shear environments provide
conditionally favorable patterns for multi-day heavy rainfall
potential. This setup is no different with the multi-model
consensus and global ensemble means indicating heavy convective
episodes possible from the SC/GA area, on west through the
Southeast, eventually making headway back into the Southern Plains
of TX. The area of greatest focus currently is over the Central
Gulf coast extending into east TX where the adage of a organized
mid-level disturbance rotating out of the Tennessee Valley will
enter the picture allowing for enhanced forcing and perhaps a
surface wave component that would provide targeted low-level
convergence where the disturbance moves nearby. A SLGT risk was
maintained from the previous forecast across the Central Gulf coast
area for the D4 period with a broad MRGL encompassing on D4,
followed by a general MRGL D5 over similar areas on the southern
periphery of the ridge.

...Southwest U.S...

Further west, the Southwestern U.S. will lie within the western
flank of the broad ridge pattern over the Central and Eastern U.S
which will provide a dominant southerly flow over the region
allowing for continued moisture advection and enhanced surface
troughing over AZ up through the Great Basin. This pattern is a
continuation of the Monsoonal presence out west with a potential
for increasing flash flood prospects as multi-day impacts could
spur targeted opportunities for repetition of areas getting hit by
convection in consecutive periods. For now, maintained a MRGL risk
throughout the Southwestern CONUS for both the D4 and D5 time
frames, however will need to monitor the periods closely as move
forward in time for possible upgrades with the greatest potential
likely over southeastern AZ up through the Mogollon Rim where
several days of consecutive impacts are forecast beginning this
weekend, carrying forward into next week as the pattern remains
stable.

Kleebauer


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