Weather Prediction Center

National Oceanic and Atmospheric Administration

Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 PM EDT Sat Aug 08 2026

Valid 00Z Sun Aug 09 2026 - 00Z Tue Aug 11 2026

...Heat to persist across much of the CONUS, with record highs
possible across portions of the West and central Rockies/ Plains...

...Multiple rounds of strong to severe thunderstorms expected from
the Plains to the Great Lakes, Northeast, and Mid-Atlantic...

...Heavy rainfall and flash flooding possible across portions of
the southern Great Lakes and upper Ohio Valley...

A broad upper ridge will extend across much of the southern CONUS
through early next week, with a break in the ridge near the lower
Mississippi Valley. This pattern will support above-normal
temperatures across much of the CONUS, with the greatest
temperature anomalies extending from California and the northern
Intermountain West eastward to the mid Mississippi Valley.
Record-breaking highs and very warm overnight lows are expected
across portions of the Southwest, central Rockies, and High
Plains. Meanwhile, a series of disturbances lifting out of the
western Gulf and across the eastern portion of the ridge will
support periods of showers and thunderstorms from parts of the
southern Plains and western Gulf Coast into the Southeast.
Monsoonal convection will also provide some localized relief from
the heat across the Southwest and Great Basin, but these storms
will pose a threat for heavy rainfall and flash flooding. Farther
north, drier conditions will persist from parts of the Cascades
eastward to the northern High Plains, supporting continued
elevated fire weather concerns.

Meanwhile, farther north, a series of upper-level disturbances
will generate additional periods of showers and thunderstorms from
the northern Plains through the Great Lakes, Northeast, and
Mid-Atlantic. Some of these storms are expected to become strong
to severe. On Sunday, a concentrated area of damaging winds and
hail is expected across much of South Dakota, while scattered
damaging wind gusts will also be possible from eastern Iowa across
northern Illinois and Indiana. On Monday, thunderstorms capable of
producing severe wind gusts will be possible from parts of
northern Illinois eastward into western Pennsylvania, with
isolated severe gusts also possible from portions of the central
and northern Plains into the Midwest.

In addition to damaging winds and hail, some of these
thunderstorms will produce locally heavy rainfall and flash
flooding. The greatest potential for heavy rainfall and flash
flooding will be focused across the southern Great Lakes and upper
Ohio Valley, where multiple rounds of convection could produce
locally heavy rainfall and exacerbate flash flood concerns.
Showers and thunderstorms will remain possible into early Tuesday,
particularly across the Northeast and Mid-Atlantic.

Pereira

Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
319 PM EDT Sat Aug 8 2026

Valid 12Z Tue Aug 11 2026 - 12Z Sat Aug 15 2026


...Multi-day heavy rainfall threat extending from parts of the
Mid- Mississippi Valley to Ohio Valley next week...

...Hazardous heat builds across much of the South-Central and
Southeast U.S. through the end of next week...


...Overview...

Upper ridge over the Four Corners shifts east midweek and remains
stretched out across much of the Southeast and south-central U.S.
through Friday. Meanwhile, shortwave disturbances and troughing
across the Northern Tier (particularly Northeast and Pacific
Northwest) brings shower and thunderstorm chances. Multiple days
of heavy rainfall may lead to flooding concerns across parts of the
Mid-Mississippi and Ohio valleys. Troughing extending along the
West Coast and Great Basin by midweek will also increase southerly
flow and monsoonal moisture into the region, increasing the
coverage of shower and thunderstorm chances throughout Southwest,
Intermountain West, and Interior/Southern California.


...Guidance/Predictability Assessment...

Latest deterministic and ensemble guidance generally agrees on the
large-scale evolution, although uncertainty remains regarding the
amplitude and timing of individual shortwave impulses embedded
within the northern-stream flow. Model spread increases towards the
latter portion of the period, especially with the latitudinal
placement of the central Plains frontal boundary. This will impact
the confidence in the location for the greatest heavy rainfall
threat between the High Plains and Midwest/Ohio Valley. The 06Z GFS
was a southern outlier with respect to this feature, but trended
favorably towards consensus with the 12Z run. The broader signal
for precipitation potential across parts of the Upper Midwest into
the Great Lakes and Northeast is reasonably well supported. General
model weights were used in the forecast through day 6 before
trending away from the 06Z GFS and towards ensemble means.


...Weather/Hazards Highlights...

The increasing troughing over northern/eastern U.S. will bring
thunderstorm and showers development, especially over areas where
deep moisture, instability, and slow- moving boundaries overlap.
Additionally, the shortwave crossing the northern Rockies/High
Plains will move towards the Great Lakes/Upper Midwest on Tuesday.
A surface low and trailing frontal boundary will accompany this
feature as it interacts with moist and unstable airmass, leading to
thunderstorm development along the front within west-northwest flow
aloft. With the slow- moving, organized convection, locally heavy
rainfall will be possible across the Great Lakes/Midwest into the
Ohio Valley and portions of the Mid- Atlantic. The 00Z run of the
ECMWF EFI highlights parts of the Upper Ohio Valley for potentially
extreme rainfall through Wednesday. By the middle to later part of
next week across portions of the High Plains and central U.S., a
decent moisture connection from the eastern subtropical Pacific in
connection to troughing over the West will allow for moisture to
overrun a frontal boundary draped across the central U.S., this
will lead to a stripe of additional heavy rain and flash flooding
potential extending from the central High Plains to the Ohio
Valley, with daily thunderstorm chances occurring along this axis
through Saturday. The Day 4 and 5 Excessive Rainfall Outlooks
maintain broad Marginal Risks with embedded Slight Risks centered
around the Upper Ohio Valley.

Over into southwestern U.S., the persistent ridging will start to
move eastward, but monsoonal moisture will continue to generate
thunderstorms over the Southwest and increase in coverage
throughout the week. Multiple days of showers and thunderstorms
may lead to locally heavy rainfall and flash flooding across the
Southwest, central Great Basin, Rockies, and parts of
Interior/Southern CA, particularly over burn scars and steep
terrain.

The ridge will support hazardous heat over the southern Plains,
Southeast and Gulf Coast throughout much of the week. Widespread
Major HeatRisk is forecast to extend into parts of the central
Plains and Lower Ohio Valley on Tuesday before the area shrinks
southward with the approaching frontal boundary and
shower/thunderstorm chances. Longest duration of above average and
potentially dangerous levels of heat are expected through Saturday
across parts of the Southern Plains to Southeast. This is depicted
on the WPC Day 3-7 Hazards Chart. Highs are forecast in the mid-
upper 90s (triple digits across parts of OK and TX), with lows only
dropping into upper 70s. Heat- related impacts could become
significant where the combination of high temperatures and humidity
persist for several consecutive days.


Oudit/Snell



Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
are at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
854 PM EDT Sat Aug 8 2026
Day 1
Valid 01Z Sun Aug 09 2026 - 12Z Sun Aug 09 2026

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE OHIO VALLEY AND NORTHEAST, THE UPPER MIDWEST, AND THE
SOUTHWEST...

...OH Valley to Northeast...
One shortwave currently moving across NH and ME will continue to
produce localized areas of heavy rainfall as it pushes east this
evening. A cold front from OH into NY should also be a focus for
isolated to scattered thunderstorms tonight. Enough forcing is
present to sustain some development into the overnight hours, but
generally quick cell motions and limited organization/coverage
should keep any flash flood risk very isolated.

..SD into MN and IA...
Still seeing a good signal for overnight upscale convective growth
across portions of SD/MN. A strengthening low level jet and
moisture convergence axis will combine with subtle mid level energy
and an upper jet to the north to produce an expanding area of
convection. Most signs point towards a forward propagating MCS,
which should limit the extent of any flash flood risk. However,
there is a strong enough axis of moisture transport and enough CAPE
to support heavy rainfall rates. Thus a localized flash flood risk
is possible both in the MCS formation phase where cell mergers are
more likely (eastern SD), and also downstream over MN and IA if a
leading band of convection ahead of the MCS results in local
training. Overall not anticipating widespread flash flooding, but a
few areas of impacts are possible overnight into Sunday morning.

...Southwest...
Convection over portions of central AZ into southeast NV and
southwest UT, and over the central Sierra, will continue to pose a
localized flash flood risk for a few more hours. These areas
should see decreasing convective coverage and intensity after 03z.

Chenard


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
854 PM EDT Sat Aug 8 2026
Day 2
Valid 12Z Sun Aug 09 2026 - 12Z Mon Aug 10 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
UPPER GREAT LAKES AND UPPER MISSISSIPPI VALLEY...

...Upper Great Lakes & Mississippi Valley...

20Z Update: The overall pattern remains favorable for a multi-
round convective episode during the D2 period with the area of
greatest focus likely to materialize over northern IL and southern
WI and points east with the Chicago area the most notable area of
potential impacts. There's a growing concern for a more locally
significant flash flood prospect for the Chicago metro, including
adjacent suburbs with the nocturnal convective maturation that's
expected on Sunday night into early Monday morning. Warm front
positioning and a strengthening 850mb LLJ will be key components in
the threat over the area, one that is more susceptible to flash
flooding thanks to the broad urban sprawl that extends from
southern Lake Michigan and encompasses the entire area spanning
northeast IL through northwestern IN. 12z HREF neighborhood
probabilities for >3" are upwards of 60-80% currently for the above
region, including the center of Chicago proper where high run off
capabilities are notorious for local flooding hazards. There are
even some notable >5" probs of 40-60% within the area spanning the
western and northern Chicago suburbs down through the center of
Chicago proper, a testament to the potential in this setup, and a
general agreement from the CAMs on the positioning of the heavier
rainfall.

Ensemble mean QPF is greater than 2" over much of the
Chicago metro, a signal that typically favors at least scattered
flash flooding with perhaps widespread flash flood concerns if
everything comes together perfectly. The back-building scenario
with the setup is the reason for such a strong mean QPF signature,
correlating well with the strong low-level convergence regime and
locally backed flow between sfc-700mb positioned near the warm
front. Ultimately, that frontal positioning will be pivotal in
where the heaviest rainfall will materialize, and current
indications is it will be within that zone bisecting northern IL
into northern IN by the second half of the period. In this case,
there is enough of a signal and general consensus on a high-end
SLGT risk forecast for that zone with emphasis on northeast IL and
northwest IN given the elevated probabilities for >3" of rainfall.

Kleebauer

..Previous Discussion..

A series of disturbances moving eastward along the southern
periphery of a large upper low well into Canada will result in
multiple rounds of storms on Sunday across the Slight Risk area.
The first will be the remnants of an MCS that will start the day in
far southeastern Minnesota, and will then track south and east
along the Wisconsin/Illinois border. The storms in general should
be pretty fast moving, so it's unlikely too many flooding impacts
will be seen from this feature alone. However, what it will do is
prime the soils by moistening them up for the later round.

The second round will form at the nose of a developing low level
jet Sunday night. The storms will follow the greatest instability,
which will mean the storms will track southward. The should be
significantly slower moving, and much more widespread compared to
the first round earlier in the day. The widely scattered instances
of flash flooding associated with the Slight will be mostly
confined to this Sunday night period. Urban and small stream
impacts in and around Chicago and possibly Milwaukee are the most
likely impacts.

Wegman

...Marginals Elsewhere...

20Z Update: Only minor adjustments made to the remaining MRGL risks
across both the Eastern and Southwestern U.S. Primary change was a
narrow expansion of the MRGL to include the VA Tidewater and
southern VA as guidance insists on another round of convection with
rates between 1-2"/hr impacting these areas by Sunday afternoon and
early evening before dwindling with the loss of diurnal
instability after sunset. Southwestern U.S. remains on track for
prevalent monsoonal moisture making its presence known across AZ,
extending northward through the Great Basin.

Kleebauer

..Previous Discussion..

As on previous days, deep tropical moisture across the Southeast
will favor another round of afternoon showers and storms from
northern Mississippi into the southern Appalachians. Flash flooding
will likely be confined to areas where the storms are most
persistent (northern Mississippi), or where terrain helps funnel
the rainwater (southern Appalachians). Generally the storms, while
scattered, should be disorganized, so a Marginal was maintained for
now, though targeted Slights are certainly possible in the coming
days.

The monsoon will continue across the 4 Corners region on Sunday.
While a bit more widespread over the Southwest, most organized
convection will be very limited, so few changes to the inherited
Marginal Risk were needed.

Wegman


Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
854 PM EDT Sat Aug 8 2026
Day 3
Valid 12Z Mon Aug 10 2026 - 12Z Tue Aug 11 2026

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE GREAT LAKES AND SOUTHEASTERN ARIZONA...

...Great Lakes...

20Z Update: The setup for D3 remains pretty consistent in run-to-
run continuity with the highlight of heavy rainfall extending over
the southern Great Lakes and northern Ohio Valley into western PA
and the adjacent WV Highlands. A lot of the setup is contingent on
the behavior of any complexes that materialize upstream over the
Midwest and migrate east through the forecast. Looks like activity
will be prone to producing rates upwards of 2"/hr, locally higher
given a robust moist and unstable airmass present on the northern
periphery of a broad ridge to the south, and the southern
inflection of a sprawling ULL over Canada. In any case, the setup
is textbook for an area of above normal convective chances that
will take advantage of both a favorable thermodynamic and kinematic
environment as the positioning of the jet will favor large scale
ascent across much of the Great Lakes and Ohio Valley into the
Appalachian front. As of now, the only change from the previous
forecast was to expand the SLGT a bit further south into WV and
east to bank up against the western slopes of the Appalachians in
PA. Will be monitoring this setup closely as a high-end SLGT is not
out of the realm of possibility considering all of the above
factors, as well as the addition of terrain influences on the
eastern extent of the current SLGT.

Kleebauer

..Previous Discussion..

A large upper level low well over Canada will spin a strong
shortwave across the Great Lakes on Monday. Deep tropical moisture
will be drawn northward from the reservoir of moisture over the
Southeast, allowing for widespread showers and thunderstorms,
generally from Chicago east to portions of the Central
Appalachians. The inherited Slight was expanded to the east, to
includes much of eastern Ohio, western Pennsylvania, including
Pittsburgh, and far western New York, including Buffalo with this
update.

Wegman

...Southeastern Arizona...

20Z Update: A favorable setup for heavy rainfall across
southeastern AZ exists within a majority of guidance with ensemble
mean QPF pushing >1" over much of the terrain focused within
eastern Pima, Santa Cruz, and Cochise counties along and south of
I-10. The previous high-end SLGT forecast continues to have merit
with some of the deterministic outputs pushing local totals up near
3", a threshold that would undoubtedly cause locally significant
flash flood concerns within the aforementioned areas. Areas like
the Huachuca mountains over to I-19 are the most likely areas to
see significant rainfall in the setup. As we move closer to CAMs
range, it will be an area to monitor for potential further upgrades
if the signal becomes more pronounced in the general magnitude of
the rainfall forecast. For now, the SLGT remains with the
highlighted area across the southern tier the noted high-end SLGT
risk.

Kleebauer

..Previous Discussion..

Deep tropical moisture moving up the Gulf of California will
intrude into southeastern Arizona on Monday, with PWATs exceeding
1.5 inches in many areas. A thermal low due to the strong high
aloft will support widespread shower and thunderstorm activity,
particularly along the Mexican border and up I-19 from Nogales
through Tucson. This corridor is both highly flood prone, has seen
numerous days of widely scattered flash flooding in recent days,
and is right in line for additional widespread convection Monday
afternoon. There is considerable uncertainty moving west up I-10
beyond Tucson, so the introduced Slight is primarily for this most
vulnerable corridor, where a higher-end Slight in in place.

Wegman

Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
154 PM EDT Wed May 6 2026

Valid 00Z Thu May 07 2026 - 00Z Sun May 10 2026

...WPC Winter Weather Desk no longer routinely staffed until
late September, 2026...

Pending any significant winter weather, the WPC Winter Weather Desk
will not be staffed through the summer. The desk will resume
continuous staffing starting in the fall.

The WPC winter products will continue to be produced, however, and
all products except the heavy snow discussion (HSD) will be
available. This includes the Winter Storm Outlook (WSO), Winter
Storm Severity Index (WSSI), and Probabilistic Winter Precipitation
Forecasts (PWPF).


WPC

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
319 PM EDT Sat Aug 8 2026

Valid 12Z Tue Aug 11 2026 - 12Z Sat Aug 15 2026


...Multi-day heavy rainfall threat extending from parts of the
Mid- Mississippi Valley to Ohio Valley next week...

...Hazardous heat builds across much of the South-Central and
Southeast U.S. through the end of next week...


...Overview...

Upper ridge over the Four Corners shifts east midweek and remains
stretched out across much of the Southeast and south-central U.S.
through Friday. Meanwhile, shortwave disturbances and troughing
across the Northern Tier (particularly Northeast and Pacific
Northwest) brings shower and thunderstorm chances. Multiple days
of heavy rainfall may lead to flooding concerns across parts of the
Mid-Mississippi and Ohio valleys. Troughing extending along the
West Coast and Great Basin by midweek will also increase southerly
flow and monsoonal moisture into the region, increasing the
coverage of shower and thunderstorm chances throughout Southwest,
Intermountain West, and Interior/Southern California.


...Guidance/Predictability Assessment...

Latest deterministic and ensemble guidance generally agrees on the
large-scale evolution, although uncertainty remains regarding the
amplitude and timing of individual shortwave impulses embedded
within the northern-stream flow. Model spread increases towards the
latter portion of the period, especially with the latitudinal
placement of the central Plains frontal boundary. This will impact
the confidence in the location for the greatest heavy rainfall
threat between the High Plains and Midwest/Ohio Valley. The 06Z GFS
was a southern outlier with respect to this feature, but trended
favorably towards consensus with the 12Z run. The broader signal
for precipitation potential across parts of the Upper Midwest into
the Great Lakes and Northeast is reasonably well supported. General
model weights were used in the forecast through day 6 before
trending away from the 06Z GFS and towards ensemble means.


...Weather/Hazards Highlights...

The increasing troughing over northern/eastern U.S. will bring
thunderstorm and showers development, especially over areas where
deep moisture, instability, and slow- moving boundaries overlap.
Additionally, the shortwave crossing the northern Rockies/High
Plains will move towards the Great Lakes/Upper Midwest on Tuesday.
A surface low and trailing frontal boundary will accompany this
feature as it interacts with moist and unstable airmass, leading to
thunderstorm development along the front within west-northwest flow
aloft. With the slow- moving, organized convection, locally heavy
rainfall will be possible across the Great Lakes/Midwest into the
Ohio Valley and portions of the Mid- Atlantic. The 00Z run of the
ECMWF EFI highlights parts of the Upper Ohio Valley for potentially
extreme rainfall through Wednesday. By the middle to later part of
next week across portions of the High Plains and central U.S., a
decent moisture connection from the eastern subtropical Pacific in
connection to troughing over the West will allow for moisture to
overrun a frontal boundary draped across the central U.S., this
will lead to a stripe of additional heavy rain and flash flooding
potential extending from the central High Plains to the Ohio
Valley, with daily thunderstorm chances occurring along this axis
through Saturday. The Day 4 and 5 Excessive Rainfall Outlooks
maintain broad Marginal Risks with embedded Slight Risks centered
around the Upper Ohio Valley.

Over into southwestern U.S., the persistent ridging will start to
move eastward, but monsoonal moisture will continue to generate
thunderstorms over the Southwest and increase in coverage
throughout the week. Multiple days of showers and thunderstorms
may lead to locally heavy rainfall and flash flooding across the
Southwest, central Great Basin, Rockies, and parts of
Interior/Southern CA, particularly over burn scars and steep
terrain.

The ridge will support hazardous heat over the southern Plains,
Southeast and Gulf Coast throughout much of the week. Widespread
Major HeatRisk is forecast to extend into parts of the central
Plains and Lower Ohio Valley on Tuesday before the area shrinks
southward with the approaching frontal boundary and
shower/thunderstorm chances. Longest duration of above average and
potentially dangerous levels of heat are expected through Saturday
across parts of the Southern Plains to Southeast. This is depicted
on the WPC Day 3-7 Hazards Chart. Highs are forecast in the mid-
upper 90s (triple digits across parts of OK and TX), with lows only
dropping into upper 70s. Heat- related impacts could become
significant where the combination of high temperatures and humidity
persist for several consecutive days.


Oudit/Snell



Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
are at:

https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw