FOUS30 KWBC 092006
QPFERD
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
406 PM EDT Tue Jun 9 2026
Day 1
Valid 16Z Tue Jun 09 2026 - 12Z Wed Jun 10 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
NORTHERN PLAINS, OHIO AND TENNESSEE VALLEYS, AND SOUTHERN
APPALACHIANS...
.Northern Plains...
16Z Update: The trends in guidance maintain a signal for locally
heavy rainfall over portions of North Dakota into northern MN later
this evening. Progressive nature of the convection may limit the
expanse of significant flash flood potential, however anomalous
deep moist environment coupled with the energetic nature of the
disturbance and a very buoyant environment will likely enhance
convective cores, providing capability for rates to exceed 2"/hr in
the strongest cells. CAMs have been generous with local amounts
between 3-5" in the areas hardest hit with the bullseye focused
over northeastern ND, so it's very plausible to see at least a few
flash flood warnings arise in this setup. The previous SLGT risk
was general maintained with some trimming of the southwestern flank
to account for trends in the 12z CAMs indicating a local min just
to the northeast of Bismarck.
Kleebauer
..Previous Discussion..
A potent upper level trough will push across the northern Rockies
into the Plains today and spur cyclogenesis over the northern
Plains. Low pressure will strengthen over the region with a cold
front extending to the southwest and a warm front extending to the
east. Southerly winds ahead of the trough will direct warm, moist,
unstable air into the northern Plains, with PWAT values expected to
exceed 1.5 inches and MUCAPE expected to rise above 3000 J/kg.
Increasing mid/low level winds on the leading edge of the trough
will create a highly sheared environment that is conducive for
supercell development this afternoon. By this evening, an
intensifying low level jet oriented parallel to the surface cold
front will support upscale convective growth into a linear MCS.
Deep convection within supercells and eventually the more organized
MCS will be able to tap into the atmospheric moisture to produce
very intense rainfall rates in excess of 2 inches per hour.
Relatively fast storm motion will be a limiting factor to the flash
flood risk, but rainfall rates will be enough to overwhelm FFGs
and cause flash flooding, especially if heavy rain occurs in urban environments. A Slight Risk of excessive rainfall remains in effect
for the heaviest convective activity expected over central and
eastern North Dakota and northwestern Minnesota. A broader Marginal
Risk area extends into the Midwest where convection may focus
along a surface boundary extending from the northern Plains cyclone
tonight.
.Ohio and Tennessee Valleys and Southern Appalachians...
16Z Update: First of two shortwaves are currently impacting the
southern Ohio Valley this morning with the most notable zone of
impact focused between the Ohio River basin near and west of
Louisville into west-central KY between the I-65/75 corridors. 12z
HREF was very aggressive in a signature of a pronounced 1-2 punch
during the period with neighborhood probabilities for >3" showing a
broad axis of 80+% across much of western KY and even some moderate
probs for >5" (40-60%) located near and along the I-65 corridor.
Very buoyant environment will be situated over the region for the
entirety of the forecast with SBCAPE indices between 2000-3000 J/kg
likely to encompass the area of interest. Heavy precip chances will
expand away from the above areas, as well, with the prospects for
rainfall rates between 1-3"/hr expanding north and northwest across
southern IN/IL, as far south as north-central TN, and as far east
as southern WV as enhanced theta_E advection on the western and
northern flank of the ridge over the Southeast will control the
overall pattern and subsequent mean flow of any activity that
materializes. The SLGT risk remains over a broad area of the
southern Ohio Valley and neighboring Tennessee Valley with a high-
end SLGT threshold pin-pointed across the western two-thirds of KY
with emphasis on that zone between the I-65 and I-75 corridors
down to the TN state line.
Other area of interest in the period will lie across eastern GA up
through the SC and western NC Piedmont where persistent south to
southeasterly flow around the ridge will maintain a narrow tongue
of elevated instability and deep moist advection that has
maintained a round of heavy convection this morning. This threat
will last for another 2-4 hours before dissipating, but maintained
the SLGT to account for what is already occurring.
Kleebauer
..Previous Discussion..
An upper level trough will lift northeast across the Midwest and
Great Lakes region today accompanied by a surface low over the
Great Lakes and a slow-moving warm front extending south into the
Ohio and Tennessee Valleys. The air mass in place across these
regions will be anomalously moist with PWAT values around 2 inches,
2-2.5 standard deviations above normal for this time of year.
There will also be sufficient synoptic forcing and instability to
support scattered to potentially widespread convection from the
Great Lakes to the Interior Southeast. Convection will be ongoing
at the start of the period and should translate east throughout the
day as the system progresses. High moisture content in the
atmosphere will support chances for locally heavy rainfall, and
more intense rainfall may be possible over the Ohio and Tennessee
Valleys where convection will be enhanced by a couple quick-moving
mid-level waves rounding the top of the ridge positioned over the
Gulf. The first wave will pass over the region early in the period,
resulting in a burst of more intense convection this morning. The
second wave will pass over this area tonight into early Wednesday
morning and will have the potential for back-building storms along
a surface boundary extending into the lower Ohio Valley from the
northern Plains cyclone. Hi-res guidance suggests rainfall rates of
2-3 inches will be possible in stronger cells, and most hi-res
CAMs are showing a swath of rainfall totals of 3-5 inches, with
locally higher amounts, across portions of Kentucky and maybe
southern Indiana as well. The HREF and RRFS are both showing
relatively high probabilities (50-70% and 40-50% respectively) of
24 hr totals exceeding 5 inches in this area. Enhanced convection
will also be possible, but to a lesser extent, under the upper
waves over Tennessee and in upslope areas of the southern
Appalachians. Some areas may be more susceptible to heavy rain
today after recent heavy rains over the past few days. A Slight
Risk of excessive rainfall covers the area of enhanced convection
over the Ohio and Tennessee Valleys and southern Appalachians and a
Marginal Risk area extends north through the Great Lakes.
Dolan
=20
Day 2
Valid 12Z Wed Jun 10 2026 - 12Z Thu Jun 11 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
CENTRAL PLAINS UP THROUGH THE MIDWEST...
.Midwest and Central Plains...
20Z Update: A larger change was implemented for the D2 period, but
much of the synoptic scale evolution described in the previous
forecast was maintained. 12z CAMs were finally able to depict the
full D2 window with a broader scope of heavy rainfall potential
within the budding warm sector across the Midwest. Strengthening
theta_E ridge across the Central U.S. east of I-35 will be one of
the more important aspects of the forecast as the meridional push
of unstable air ahead of the maturing front will aid in a
moderately buoyant environment with increasing large scale ascent
aligned from southwest to northeast from KS up through WI. Shear
levels will be highest further north into IA/IL/WI leading to more
organized cell clusters propagating east/southeast through the
region. Models are struggling with specific convective placements,
so we have a few camps on positioning of the heavier rainfall for
the period. Recent ML output aligns the heaviest precip over
southeast NE up through the Mississippi River Valley between IA/IL
with a northern expanse into WI. HREF neighborhood prob fields for
2" is highest across north-central WI between Eau Claire to Green
Bay with several other "bullseyes" situated between northern MO
through eastern IA, northern IL, and southern WI. Rates between
2-3"/hr are forecast in the strongest cell cores with the highest
rates correlated over the area where CAPE can breach 3000 J/kg.
This leads to a southern tail in heavier precip potential arcing
back towards southeast NE to eastern KS where greatest instability
is forecast. Considering the more widespread modest neighborhood
probs and expected environment across a very large area ahead of
the maturing synoptic pattern, a SLGT risk was expanded northeast
to include much of the Midwest situated east of the Mississippi
River, tailing back through portions of IA/NE/KS/MO.
Kleebauer
..Previous Discussion..
On Wednesday, the northern Plains cyclone will move into south-
central Canada and push a trailing cold front across the Midwest.
Showers and storms will be ongoing Wednesday morning ahead of the
system over northern Minnesota, then another round of convection is
expected across the Midwest and Central Plains Wednesday afternoon
and evening ahead of and along the cold front. Deep southerly flow
ahead of the system will increase PWAT values to 1.5-2 inches,
with the higher values focused between northern Missouri and
southern Wisconsin. Instability should increase through the
afternoon as daytime heating kicks in, but the best instability
(3000-4000 J/kg) looks like it will focus from eastern Kansas and
southeastern Nebraska into northern Missouri and southern Iowa,
where there is a Slight Risk of excessive rainfall. This area will
likely experience a period of enhanced convection Wednesday night
as a frontal wave develops at the intersection of the cold front
and a dryline. A secondary wave of moisture and instability will
surge into the central Plains as a low level jet strengthens
Wednesday night, which should support efficient rainfall rates,
potentially exceeding 2 inches per hour, that could lead to
scattered instances of flash flooding.
Dolan
.Tennessee Valley and Southern Appalachians...
20Z Update: Only minor changes were necessary across the Tennessee
Valley to Southern Appalachian front with the changes more
reflected in the change in CAMs QPF output and positioning of
convection on Wednesday morning. The MRGL risk remains with best
potential over eastern KY/TN over into southwest VA and down
through the western Carolina's.
Kleebauer
..Previous Discussion..
Convection should be ongoing across portions of the Tennessee
Valley and southern Appalachians at the start of the period. A
quick-moving upper level wave will round the top of the ridge
positioned over the Gulf and support a period of enhanced
convection late Tuesday night into Wednesday morning. Anomalous
moisture and sufficient instability will be in place to support
efficient rainfall rates, and slow storm motions will contribute to
high rainfall totals. There will also be some potential for back-
building storms along a surface boundary extending from the
northern Plains/southern Canada cyclone into the Tennessee Valley,
mainly focusing over Kentucky. Showers and storms will also be
enhanced by upslope flow along the southern Appalachians.
Convection should start to weaken Wednesday morning and wane by
Wednesday afternoon, but there will at least be enough rainfall
over saturated soils to continue a Marginal Risk of excessive
rainfall into Wednesday morning.
Dolan
.Northeast U.S...
20Z Update: The MRGL risk remains for portions of the Northeastern
U.S. with the primary area of interest likely across Upstate NY
down through eastern PA. The main change was an expansion of the
risk down through much of eastern PA, northwest of the metro
corridors as recent CAMs have been highlighting a secondary area of
focus within an expected developing surface trough bisecting the
central Mid Atlantic up towards the Pocono's. Increased convergence
signature within a maturing instability axis across the Mid
Atlantic will lead to a period of heavy rainfall prospects within
the confines of the boundary as it evolves during the afternoon
Wednesday. 12z HREF probs are quite bullish over the Lower
Susquehanna Valley between US15 to US422 in PA with modest probs
for >3" locally in that region of southeastern PA. This area was
highlighted in various CAMs which typically is a signal for at
least a low-end threat given the overlap. Will be something to
monitor over the next 24 hours for the potential.
Kleebauer
..Previous Discussion..
A Marginal Risk of excessive rainfall was introduced for portions
of the Interior Northeast. An upper level trough will cross over
the Great Lakes into southeastern Canada accompanied by a surface
low pressure system that will bring precipitation chances to much
of the Northeast. The warm sector of this system will be
characterized by an anomalously moist air mass with PWAT values up
to 2 inches. There should be enough moisture and synoptic forcing
to support locally heavy rainfall in stronger convection near the
low pressure center over southeastern Canada and the Interior
Northeast. Rainfall totals and flash flood potential may also be
increased by terrain and upslope flow Wednesday afternoon.
Dolan
.Southwest Florida...
Sea breeze pattern with convergent winds around the southern
periphery of high pressure to the north will create a period of
heavy convective potential across southwest FL by Wednesday
afternoon. HREF probs for >3" along the coast between Port
Charlotte to Naples are between 60-90%, but do fall back to lower
probs between 15-30% for the >5" threshold meaning forecasts
consistently show a range between 3-5" in the hardest hit
locations. Area FFG's remain high, however the urban zones along
I-75 will be the most susceptible to localized flash flood chances.
This setup is likely to materialize between 18z Wed and 02z Thu
before dissipating. A MRGL risk was added to the aforementioned
area to cover for the low-end threat.
Kleebauer
=20
Day 3
Valid 12Z Thu Jun 11 2026 - 12Z Fri Jun 12 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM NORTHEASTERN
MISSOURI THROUGH EASTERN IOWA AND NORTHERN ILLINOIS TO SOUTHERN
WISCONSIN...
20Z Update: Little change was necessary for the D3 time frame as
the multi-model consensus continued to depict quite the widespread
heavy rain prospect over the Midwest. The scenario is a classic
frontal ascent pattern capable of a swath of heavy rainfall over
several states as the front marches eastward. Highly anomalous
PWATs and large scale low to mid-level ascent will be the primary
drivers for the setup, favoring areas from northern MO up through
the Central Midwest, including the metro areas like the Quad
Cities, Chicago, and Milwaukee. Widespread 1-3" of rainfall with
isolated totals upwards of 5" will be plausible in the setup, so
the previous SLGT risk was sufficient for the period.
Kleebauer
..Previous Discussion..
The frontal wave that developed over the central Plains Wednesday
night will progress northeast and intensify as a strong upper
trough swings into the northern and central Plains Thursday
morning. A strong low level jet will increase moisture and
instability across the central Plains Wednesday night, and this air
mass will expand towards the Upper Midwest as southerly winds surge
ahead of the surface frontal boundary. A large swath of high PWAT
values above 2 inches will stretch from the southern Plains to the
Midwest, which will support a broad area of convection capable of
producing locally heavy rainfall. A wave of deeper convection will
accompany the strong frontal wave as it progresses, resulting in
high rainfall totals over an area from northeastern Missouri
through eastern Iowa, northern Illinois, and southern Wisconsin.
These areas are highlighted by a Slight Risk of excessive rainfall
to account for enhanced convection capable of producing scattered
instances of flash flooding. A broader Marginal Risk of excessive
rainfall surrounds the Slight and includes much of the Midwest and
portions of the central and southern Plains.
Dolan
=20
Day 4 and Day 5
Valid 12Z Fri Jun 12 2026 - 12Z Sun Jun 14 2026
...THERE IS A DAY 4 MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE
SOUTHERN PLAINS TO THE NORTHERN MID-ATLANTIC...
Widespread showers and thunderstorms will develop along and out
ahead of a strong and expansive cold front that races into the
eastern U.S. and becomes quasi-stationary over the South on Friday.
PWs are likely to surpass the 90th climatological percentile ahead
of the cold front from the TN and OH Valleys into the Northeast.
Storms will be progressive and help to limit the footprint of
potential flash flooding from the OH Valley on north into the
northern Mid-Atlantic. However, the 00Z ECMWF-EFI does depict a
minor signal (0.6-0.7) for unusually high CAPE-Shear for early-
to-mid June over the OH Valley and Northeast. This environment is
likely to support organized thunderstorms that contain heavy
downpours and may cause localized flash flooding. Farther south,
PWs will more commonly remain over 1.5" and in some instances
approach 2.0" from the ArkLaTex to the Lower MS Valley. Storms
could contain Excessive Rainfall rates as far west as the Guadalupe
and Sacramento Mountains where SErly flow ushers in much above
normal PWs. Burn scars in New Mexico could be at risk for flash
flooding as a result.
Mullinax
...THERE IS A DAY 5 SLIGHT RISK OF EXCESSIVE RAINFALL IN THE
SOUTH CENTRAL U.S....
850mb high pressure located over the eastern Gulf will work in
tandem with lower pressure to the north and west to produce a deep
fetch of rich moisture originating from the Bay of Campeche. The
ECMWF ENS and NAEFS show IVTs >500 kg/m/s in the western Gulf
aimed at south Texas, which is serving as the firehose that is
introducing the anomalous moisture into the South Central U.S.. PWs
above the 90th climatological percentile will be common from
southern New Mexico and West Texas on east across the Southern
Plains and into the Ozarks. At the same time, a cold front diving
south from the Central Plains will collide with the hot/humid air-
mass in the south to trigger numerous showers and thunderstorms.
Storms are likely to persist into the overnight hours not just due
to the persistent low-level jet, but due to the Central Plains and
Ozarks ideal location beneath the diffluent right-entrance region
of a 250mb jet streak. The 00Z ECMWF EFI does show a 0.6-0.8 area
(indicating the potential for unusually heavy rainfall for this
time of year) within the 00Z Sun - 00Z Mon time frame from eastern
OK and southeast KS on east into the Ozarks, starting as early as
Saturday night.
After a couple days worth of rainfall across the region, there is
added concern that soils will be more sensitive to Excessive
Rainfall rates on Saturday. Where exactly the heaviest rainfall
occurs will be determined upon the position of the frontal boundary
located over the Central Plains. For these reasons, the Slight
Risk remains in place for this forecast update. The localized flash
flood threat is possible as far east as the Middle MS River Valley
and as far west as eastern NM and western TX.
Mullinax
=20
Day 1 threat area:
https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-WvgigEF-g9kXoi64_OV8tKXvDYLN9dtv6KcX9IxTpPp= kRuuW61lxhP4Oe38urWr9wsqcNVo7eiv50wZGEXHIBXqFJo$=20
Day 2 threat area:
https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-WvgigEF-g9kXoi64_OV8tKXvDYLN9dtv6KcX9IxTpPp= kRuuW61lxhP4Oe38urWr9wsqcNVo7eiv50wZGEXHneu8C-A$=20
Day 3 threat area:
https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-WvgigEF-g9kXoi64_OV8tKXvDYLN9dtv6KcX9IxTpPp= kRuuW61lxhP4Oe38urWr9wsqcNVo7eiv50wZGEXHbEUaFVY$=20
$$
=3D =3D =3D
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