FOUS30 KWBC 070816
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
416 AM EDT Sun Jun 7 2026

Day 1
Valid 12Z Sun Jun 07 2026 - 12Z Mon Jun 08 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
MID-MISSISSIPPI VALLEY, OZARKS, AND WESTERN TENNESSEE VALLEY...

Numerous thunderstorms are expected to form this afternoon into 
tonight over a broad area spanning across the Great Plains and 
Mississippi, Ohio, and Tennessee Valleys. Three primary forcings 
will trigger storms: an upper level shortwave moving north across 
the central Plains, Mid-Mississippi Valley, and Upper Midwest, a 
strengthening cyclone emerging in the northern/central Plains, and 
a quasi-stationary frontal boundary draped across the Mid-
Mississippi and Ohio Valleys. These features will interact with a 
moist, unstable air mass that will support efficient rainfall 
processes that could lead to heavy rainfall. Deep, moist southerly 
flow has primed the atmosphere across the Plains and Mississippi 
Valley, increasing PWAT values to around 2 inches (2-2.5 standard 
deviations above normal for this time of year). Hi-res CAM guidance
suggests rainfall rates of 2-4 inches per hour will be possible in
thunderstorm cells across the Mid-Mississippi Valley and portions 
of the Ozarks and western Tennessee Valley, which would exceed 
current flash flood guidance and result in scattered instances of 
flash flooding within the Slight Risk area. Areas from eastern 
Oklahoma into western Arkansas and east-central Illinois into west-
central Indiana may be more susceptible to flash flooding after 
rainfall yesterday left soils thoroughly saturated. Heavy rain will
likely result in locally high rainfall totals, potentially 
reaching 5-7 inches for some locations within the Slight Risk area.

Locally heavy rainfall will also extend along the quasi-stationary
frontal boundary into Ohio Valley. Storms forming along the
boundary will have the potential to produce rainfall rates over 2
inches per hour, and storm motion will be fairly slow. However,
convection should be more isolated over the Ohio Valley portion of
the front, resulting in only a Marginal Risk. Stronger convection
will also be possible in the vicinity of the low pressure system
over the northern Plains, but storms will be much more progressive
in this region, which will limit heavy rainfall potential and the
risk of flash flooding. The Marginal Risk area extends across the
northern Plains to account for isolated flash flood potential with
stronger thunderstorms that may form. 

Dolan


Day 2
Valid 12Z Mon Jun 08 2026 - 12Z Tue Jun 09 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
MID-MISSISSIPPI, LOWER OHIO, AND TENNESSEE VALLEYS...

On Monday, the northern stream cyclone will move north into 
Canada, which will lift the previously stationary frontal boundary 
north across the Upper Midwest and Great Lakes as a warm front and
push the tail end of the front south into the Carolinas. Heavy 
rainfall potential will be focused in the warm sector of the system
over the Mid-Mississippi, lower Ohio, and Tennessee Valleys where 
a very moist and unstable air mass will still be in place. A 
splitting upper level shortwave will push some energy across these 
regions, which will support a broad area of widespread/numerous 
thunderstorms. With weakening steering flow, storm motions are 
expected to become very slow, which will heighten the threat of 
flash flooding. The RRFS shows modest probabilities (20-40%) of 
hourly rainfall rates exceeding 2 inches per hour for several hours
across the Slight Risk area. Some of these areas will also receive
heavy rainfall during the day 1 period, which may increase the 
risk of flash flooding if areas are impacted by additional storms 
with heavy rainfall on Monday.

Outside of the Slight Risk area, a broad Marginal Risk area extends
into the Upper Midwest and central Plains. Anomalous moisture will
surge north behind the lifting warm front, which will support
locally heavy rainfall that may lead to isolated instances of flash
flooding for the western Great Lakes states. Models have also
started consistently showing a potential MCS forming underneath a
potent upper level shortwave moving quickly east across the central
Plains on Monday evening. Though this feature would likely be
progressive, it could have the potential to produce heavy rainfall
and isolated flash flooding. There is still some uncertainty
regarding the location of this feature, resulting in a broad
Marginal Risk area that will likely be narrowed down over the next
few forecast cycles.

Dolan


Day 3
Valid 12Z Tue Jun 09 2026 - 12Z Wed Jun 10 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE UPPER MIDWEST AND OHIO AND TENNESSEE VALLEYS...

On Tuesday, an upper level trough will move across the 
northwestern U.S. and support cyclogenesis over the northern 
Plains. A wave of convection is expected to form ahead of the 
developing cyclone, bringing thunderstorms to much of the Upper 
Midwest. A moist and unstable air mass will be in place across the 
Upper Midwest after a warm front lifts north on Monday, which will 
support heavy rainfall in thunderstorms. Flash flood potential 
should be limited by the progressive nature of this system, but 
locally heavy rainfall could still lead to isolated instances of 
flash flooding, especially where soils will be moistened from 
rainfall expected on Sunday and Monday. A Marginal Risk area seems 
sufficient to cover the flash flood threat at this time. 

Another Marginal Risk area is in place for much of the Ohio and
Tennessee Valleys and portions of Michigan where a slow moving
frontal boundary will linger through Tuesday. This frontal boundary
will provide modest lift/support for scattered convection across
these regions. An anomalously moist air mass will still be in
place, which should be enough to support locally heavy rain in some
stronger storms and may lead to isolated instances of flash
flooding. The flash flood threat will be significantly lower for
these regions than on Monday with much weaker synoptic support.

Dolan
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