Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
349 PM EDT Mon Jun 8 2026
Day 1
Valid 16Z Mon Jun 08 2026 - 12Z Tue Jun 09 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE OZARKS...
16Z Update...
The inherited Moderate Risk area was dropped due to the MCS now
exiting the region. A section of a new Slight Risk area was left
over southwest MO as new thunderstorm activity flares up over
southwest MO and far northwest AR. In collaboration with several
Kansas WFOs, a Slight Risk was introduced for much of northern KS
to account for the highly anticipated MCS that will traverse the
Central Plains. Model soundings show anomalous PWs above 1.7" and
soils from northern KS to eastern KS are more sensitive given
recent rainfall (especially eastern KS). Progressive storm motions
should limit the areal extent of the flash flood threat, however an
acceleration in the low-level jet will intersect the southern flank
of the MCS and could lead to back-building convection late tonight
and into Tuesday AM. Latest 12Z HREF probabilities do show moderate
chances (40-50%) for QPF totals >3" tonight and 30-50% chances for
3-hr QPF totals exceeding 3-hr FFGs. For these reasons, the Slight
Risk was introduced in northern KS.
In the Mid-South 12Z CAMS, HREF, and REFS guidance have all
increased probabilities for >3" rainfall totals farther south into
central AL and central GA. The air-mass is essentially a tropical
air-mass, highlighted by the 12Z BMX sounding which measured a
2.18" PW, little-to-no capping inversion, and RAP forecasts
depicting >1,000 MLCAPE. Weak synoptic-scale forcing will keep
storms more hit-or-miss in nature, but persistent SWrly flow will
provide some lift as it intersects the higher terrain in northern
AL/GA. Soils are incredibly saturated with soil moisture topping
the 95th percentile on NASA SPoRT-LIS in the 0-10cm and 0-40cm
layers. Expanded the Slight Risk farther south, although the
greatest concern for flash flooding is in northeast AL and
northwest GA where soils are the most sensitive.
Lastly, expanded the Slight Risk farther south into central WI.
the potent and compact 850mb low in the Upper MS Valley will have
PWs above the 99.5 climatological percentile at its disposal this
afternoon and tonight. There is concern for organized clusters of
storms to form and train over southwest WI that could contain max
rainfall rates around 2"/hr. There is greater concern in this area
given the 12Z HREF probabilities show moderate-to-high chances
(50-70%) for rainfall totals >3". The areal coverage of the flash
flood threat is not high enough to consider a Moderate Risk, but
the setup still could support scattered instances of flash flooding
this evening.
Mullinax
---Previous Discussion---
Convection will be ongoing at the start of the period across the
Ozarks where a low level jet ahead of a mid-level vortex/wave will
create favorable convective conditions that will likely lead to
impactful flash flooding, especially near steep terrain. During the
early morning hours, hi-res CAMs are showing rainfall totals as
high as 5-8 inches for portions of southeastern Kansas,
northeastern Oklahoma, southwestern Missouri, and northwestern
Arkansas where slow, back-building thunderstorms are expected. An
anomalously moist and unstable air mass is already in place across
the central U.S., which will support deep convection with highly
efficient rainfall rates (rates of 2-3 inches per hour are already
being observed). This region was incorporated in a special update
Moderate Risk area overnight, and the Moderate Risk will continue
into the beginning of the Day 1 period this morning. Convection
should wane and shift southeast later this morning into this
afternoon as the system becomes dominated by the outflow.
The broader Slight Risk area includes much of the Middle
Mississippi and Tennessee Valleys where widespread showers and
thunderstorms are expected in the warm sector of a northern stream
cyclone today. Much of the convective activity will be driven by
mesoscale boundaries and remnant MCV activity continuing from the
overnight period, which will result in variability of the QPE
across the warm sector. Some convection may be more focused along a
quasi-stationary frontal boundary draped over the Tennessee Valley
and southern Appalachians. Convection will be enhanced by a
leading upper level shortwave with embedded MCV activity that will
push east across these regions, and the environment will be
extremely supportive of heavy rainfall with high moisture (PWAT
values around 2 inches) and high instability (MUCAPE greater than
3000 J/kg). Storms are expected to be slow moving due to a lack of
steering flow, which will allow for locally high rainfall totals.
Latest CAM guidance suggests rainfall rates up to 2-3 inches per
hour and totals up to 5-8 inches will be possible over portions of
the Middle Mississippi and Tennessee Valleys. HREF neighborhood
probabilities show the highest chances of exceeding 5 inches of
rainfall in 24 hours (25-45%) will be over an area from southern
Illinois and Indiana through western Kentucky and Tennessee. These
areas can expect impacts on the higher end of the Slight Risk
category. Some of the areas within the Slight Risk received heavy
rainfall on Sunday, which may increase the risk of flash flooding
if areas are impacted by additional storms with heavy rainfall
today. The Slight Risk areas has also been extended north into
central Wisconsin and eastern Iowa where slow-moving storms are
expected to be enhanced by a mid-level low this afternoon.
Outside of the Slight Risk area, a broad Marginal Risk area extends
into the Upper Midwest and central Plains where locally heavy
rainfall may lead to isolated instances of flash flooding. Storms
across much of the Upper Midwest should be fairly progressive,
which will limit flash flood potential, but isolated flooding
concerns will be possible if heavy rainfall impacts any urban
areas. Models continue to also show a potential MCS forming
underneath a potent upper level shortwave moving quickly east
across the central Plains this evening. Though this feature would
be very progressive, deep convection will have the potential to
produce heavy rainfall and isolated flash flooding. This shortwave
may also enhance convection again over the Middle Mississippi
Valley tonight, and there could be a scenario where a targeted
Moderate Risk area is needed.
Dolan
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
349 PM EDT Mon Jun 8 2026
Day 2
Valid 12Z Tue Jun 09 2026 - 12Z Wed Jun 10 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
NORTHERN PLAINS AND WESTERN KENTUCKY AND TENNESSEE...
20Z Update...
The inherited threat areas in the Northern Plains and Upper
Mississippi Valley were adjusted based on latest WPC QPF and 12Z
HREF probabilistic guidance. The primary change this forecast cycle
was to expand the Slight Risk in the Mid-South farther south and
east into the TN Valley and southern Appalachians. Latest 12Z
guidance has shown a gradual southward expansion in the QPF field,
which aligns well with where the highest PWs (around 2.0" PWs) and
instability will be located. A sheared 500mb trough tracking
towards the Southeast will also promote healthy upscale ascent over
an area with very sensitive soils. The 12Z HREF/REFS probabilistic
guidance shows moderate-to-high chances (50-70%) for rainfall
totals >3" in northern GA and parts of the western Carolinas.
In addition, farther north, the same 12Z HREF/REFS guidance shows
low chance probabilities (20-40%) in central KY and northern TN.
These areas under what would be considered the "high-end Slight"
section within the larger Slight Risk area in the Mid-South. CAMs
guidance is more on the southern envelope of QPF rather than global
models which are farther north. Still, some CAMs members show some
locally significant rainfall totals where back-building and
training storms occur.
The northern Plains and Upper Mississippi Valley threat areas had
minor adjustments based on latest guidance, but otherwise no
additional threat areas were proposed this cycle.
Mullinax
---Previous Discussion---
On Tuesday, a potent upper level trough will move across the
northern Rockies and emerge into the northern Plains. This trough
will spur cyclogenesis over the northern Plains while a low level
jet increases moisture and instability ahead of the system. The
environment will be ideal for supercell development Tuesday
afternoon, and increasing shear over the region will allow storms
to evolve into an MCS Tuesday evening into Tuesday night. Deep
convection within these severe storms will be able to tap into
moisture in the atmosphere (PWAT values 1.5-2 inches) and create
very heavy rainfall. The quick nature of the MCS should somewhat
limit the risk of flash flooding, but intense rainfall rates in
excess of 2 inches per hour will exceed FFGs and could lead to
impactful flash flooding, especially in urban areas. A Slight Risk
area has been introduced for much of central and eastern North
Dakota and northwestern Minnesota.
Scattered showers and storms are forecast from the southern
Appalachians and Tennessee Valley through the Ohio Valley and Great
Lakes region, which will be supported by an upper level shortwave
lifting northeast across the Ohio Valley and Great Lakes and a slow
moving warm front extending south into the Tennessee Valley and
southern Appalachians. The air mass in place will be anomalously
moist (PWATs around 2 inches) and sufficiently unstable to support
locally heavy rainfall. Available hi-res guidance suggests higher
rainfall totals will be possible across western Kentucky and
Tennessee where convection will continue from the Day 1 period into
Tuesday morning. A mid-level shortwave will be enhancing this
convection and should allow for efficient rainfall rates over 2
inches per hour. A Slight Risk area has been introduced to cover
the elevated flash flood threat over western Kentucky and
Tennessee. Global models have also been showing locally enhanced
rainfall totals over portions of the Ohio Valley, but there is
still a significant amount of uncertainty in the location of these
higher totals. It is possible the Slight Risk area may need to be
expanded to the northeast as convective details become more clear
with additional hi-res guidance available later today.
Dolan
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
349 PM EDT Mon Jun 8 2026
Day 3
Valid 12Z Wed Jun 10 2026 - 12Z Thu Jun 11 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN KANSAS
INTO NORTHERN MISSOURI AND SOUTHERN IOWA...
20Z Update...
The inherited risk areas remain in good shape and the rationale
provided from the previous shift remains on track. Did adjust the
Slight Risk a little farther south and west to account for typical
QPF biases in global guidance that tend to be too far north. But
otherwise, no significant changes were made this forecast cycle.
Mullinax
---Previous Discussion---
On Wednesday, the northern Plains cyclone will be moving swiftly
east and pushing a cold front across the Midwest. Showers and
thunderstorms are expected ahead of and along the frontal boundary
from the Midwest to the central Plains, which are encompassed by a
Marginal Risk of excessive rainfall. The tail end of the front will
likely hang up on the Rockies and flatten out over the central
Plains, and low pressure is expected to develop over Kansas where a
dryline will intersect the boundary. Models are showing impressive
moisture transport ahead of the frontal boundary Wednesday morning
and a secondary surge Wednesday night as a strong low level jet
brings increasing moisture and instability into the central Plains.
This set up will be conducive for heavy rainfall, and global models
are showing potential for heightened rainfall totals of 2-4 inches
within the Slight Risk area, which may be underdone given the
convective limitations of the models. Locally heavy rainfall may
also be possible over central Wisconsin and could impact areas
highlighted with a Slight Risk on Day 2, which could warrant an
additional Slight Risk upgrade. However, there is much more
uncertainty regarding rainfall totals in Wisconsin, which may be
limited by the progressive nature of the cold front.
Dolan
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
400 PM EDT Mon Jun 8 2026
A cold front is forecast to push across the Midwest on Thursday
and provide a focus for thunderstorms in a moist and unstable
environment. Flash flooding is a possibility with potentially
repeating rounds of convection, and a Slight Risk is in place
across portions of the Midwest in the Day 4/Thursday ERO. The
Storm Prediction Center is calling for a risk of severe weather in
a similar area as well. The front will push eastward into Friday
and could produce locally heavy rain in parts of the Appalachians
Friday, and a Marginal Risk is indicated there for the Day 5/Friday
ERO. Meanwhile, the front will start to extend from west to east
across the central U.S. and meander near south-central parts of the
Plains and Mississippi Valley to the Tennessee/Ohio Valleys,
allowing for the Marginal to stretch across those regions. The
generally west to east oriented front is forecast to meander in the
central U.S. for multiple days. Thus thunderstorms will be common
in that region into the weekend, with heavy rain potential and
additional flood risks especially if rounds of rain repeat over
similar areas. Scattered thunderstorms that tend to be diurnally
driven are likely in the Southeast (including Florida) and
potentially expanding into the Mid-Atlantic for multiple days.
Elsewhere, the northern Rockies and High Plains may see some
precipitation, dependent on the evolution of shortwave energy.
The mean upper-level ridge over the eastern U.S. is expected to
bring the first significant heat of the summer into late week, as
temperatures reach 10-15 degrees above average. The heat looks to
reach its peak across the Mid-Atlantic and Northeast on Friday, and
several record highs and record warm minimum temperatures could be
set, before gradually moderating by the weekend. See WPC's Key
Messages for more. Subtropical ridging across the southern tier
will yield hot conditions there as well, generally a few degrees
above already warm averages. The Desert Southwest can expect
temperatures well into the 100s, while heat indices should be over
100 in the southern Plains to Lower Mississippi Valley. Into early
next week, upper ridging possibly reaching the West Coast could
bring well above average temperatures particularly to the Pacific
Northwest.
Kong/Tate
Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
400 PM EDT Mon Jun 8 2026
A cold front is forecast to push across the Midwest on Thursday
and provide a focus for thunderstorms in a moist and unstable
environment. Flash flooding is a possibility with potentially
repeating rounds of convection, and a Slight Risk is in place
across portions of the Midwest in the Day 4/Thursday ERO. The
Storm Prediction Center is calling for a risk of severe weather in
a similar area as well. The front will push eastward into Friday
and could produce locally heavy rain in parts of the Appalachians
Friday, and a Marginal Risk is indicated there for the Day 5/Friday
ERO. Meanwhile, the front will start to extend from west to east
across the central U.S. and meander near south-central parts of the
Plains and Mississippi Valley to the Tennessee/Ohio Valleys,
allowing for the Marginal to stretch across those regions. The
generally west to east oriented front is forecast to meander in the
central U.S. for multiple days. Thus thunderstorms will be common
in that region into the weekend, with heavy rain potential and
additional flood risks especially if rounds of rain repeat over
similar areas. Scattered thunderstorms that tend to be diurnally
driven are likely in the Southeast (including Florida) and
potentially expanding into the Mid-Atlantic for multiple days.
Elsewhere, the northern Rockies and High Plains may see some
precipitation, dependent on the evolution of shortwave energy.
The mean upper-level ridge over the eastern U.S. is expected to
bring the first significant heat of the summer into late week, as
temperatures reach 10-15 degrees above average. The heat looks to
reach its peak across the Mid-Atlantic and Northeast on Friday, and
several record highs and record warm minimum temperatures could be
set, before gradually moderating by the weekend. See WPC's Key
Messages for more. Subtropical ridging across the southern tier
will yield hot conditions there as well, generally a few degrees
above already warm averages. The Desert Southwest can expect
temperatures well into the 100s, while heat indices should be over
100 in the southern Plains to Lower Mississippi Valley. Into early
next week, upper ridging possibly reaching the West Coast could
bring well above average temperatures particularly to the Pacific
Northwest.
Kong/Tate
