WW 545 SEVERE TSTM MN SD 090455Z - 091200Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 545
NWS Storm Prediction Center Norman OK
1155 PM CDT Sat Aug 8 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Far West-Central Minnesota
Northeast South Dakota
* Effective this Saturday night and Sunday morning from 1155 PM
until 700 AM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Scattered damaging wind gusts to 70 mph possible
SUMMARY...Elevated thunderstorms have developed near the central
North Dakota/South Dakota border over the past hour. A very unstable
and strongly sheared environment exists in this area and
southeastward across northeast SD. These conditions support the
potential for large to isolated very large hail and damaging gusts
across northeast South Dakota and into far west-central Minnesota
tonight.
The severe thunderstorm watch area is approximately along and 50
statute miles north and south of a line from 20 miles south of
Mobridge SD to 30 miles east northeast of Watertown SD. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU5).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
29035.
...Mosier
WW 0545 Status Updates
STATUS REPORT ON WW 545
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..KERR..08/09/26
ATTN...WFO...ABR...FSD...
STATUS REPORT FOR WS 545
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
MNC011-155-090840-
MN
. MINNESOTA COUNTIES INCLUDED ARE
BIG STONE TRAVERSE
SDC005-011-013-021-025-029-037-039-045-049-051-057-059-065-069-
077-089-091-107-109-115-119-129-090840-
SD
. SOUTH DAKOTA COUNTIES INCLUDED ARE
BEADLE BROOKINGS BROWN
CAMPBELL CLARK CODINGTON
DAY DEUEL EDMUNDS
FAULK GRANT HAMLIN
HAND HUGHES HYDE
KINGSBURY MCPHERSON MARSHALL
POTTER ROBERTS SPINK
SULLY WALWORTH
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
MD 1875 CONCERNING SEVERE THUNDERSTORM WATCH 545... FOR NORTHEASTERN SOUTH DAKOTA AND ADJACENT PORTIONS OF MINNESOTA
Mesoscale Discussion 1875
NWS Storm Prediction Center Norman OK
0227 AM CDT Sun Aug 09 2026
Areas affected...northeastern South Dakota and adjacent portions of
Minnesota
Concerning...Severe Thunderstorm Watch 545...
Valid 090727Z - 090930Z
The severe weather threat for Severe Thunderstorm Watch 545
continues.
SUMMARY...Storms could gradually evolve into an organizing cluster,
with some continuing risk for severe hail and, perhaps, increasing
potential to produce strong to severe wind gusts through 3-5 AM CDT.
DISCUSSION...Strong thunderstorm development has been focused within
a narrow corridor east of Mobridge, aided by lift associated with
low-level warm advection/frontogenesis, to the north/northeast of a
weak surface low over central South Dakota. Forcing associated with
a subtle short wave impulse digging within seasonably strong
west-northwesterly mid/upper flow may also be providing support. As
this perturbation progresses southeastward during the next few
hours, the surface low is forecast to weaken with a gradual
southward advancement of the near-surface frontal zone.
Although storms are likely elevated above at least a shallow stable
surface-based layer, they have been maintained by inflow of
seasonably high moisture content supportive of large CAPE, beneath
steep mid-level lapse rates associated with a plume of warm elevated
mixed-layer air. This moisture, still largely concentrated over
central/eastern South Dakota and Nebraska, is forecast to advect
eastward in an evolving plume along the frontal zone across southern
Minnesota/northern Iowa through 9-11Z.
As it does, as least some convection allowing-guidance suggests
potential for continuing upscale growth into an organizing cluster,
which may eventually pose increasing potential to produce strong to
severe surface gusts.
..Kerr.. 08/09/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MPX...FSD...ABR...
LAT...LON 45709909 45509774 44779624 44039656 43909765 44649925
45150006 45590027 45709909
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1215 AM CDT Sun Aug 09 2026
Valid 091200Z - 101200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MIDWEST...AND PORTIONS OF THE DAKOTAS...
...SUMMARY...
Scattered damaging winds may occur today into this evening from
southern Minnesota and eastern Iowa eastward across parts of
northern Illinois, southern Wisconsin, southern Lower Michigan,
northwest Ohio, and northern Indiana. Damaging wind and hail is also
expected across portions of the Dakotas.
...IA/MN into the Midwest...
Convection is expected to be ongoing this morning across parts of
southern MN into eastern IA. This early day activity could pose a
risk for damaging gusts. This activity is likely to continue to
spread eastward across the Lake Michigan vicinity through the
afternoon on the nose a of modest low-level jet and along a surface
front oriented across southern WI and Lower MI. This activity could
intensify as is moves into a destabilizing airmass by midday.
Additional development is possible within the moisture rich warm
sector across northern IL/IN along the southern flank of ongoing
convection and/or outflow. Strong to extreme instability is
forecast, while vertically veering wind profiles support 30+ kt
effective shear magnitudes. Low-level SRH also will be enhanced
along the surface boundary. While damaging winds are expected to be
the primary hazard with convection, some risk for hail and a tornado
or two also will exist through evening. Depending on the evolution
of morning convection, it is possible higher probabilities will be
needed in subsequent outlooks.
...Dakotas and western NE...
A surface front is expected to develop southward across the central
Plains, becoming oriented across northern KS by tonight. Low-level
warm advection atop the boundary, and surface winds becoming
south/southeasterly with time will maintain 60s dewpoints across the
region. Within this post-frontal upslope regime, moderate
northwesterly flow aloft will persist. A modest south/southwesterly
low-level jet is also forecast to develop during the evening hours.
Low-level convergence within the warm advection regime and
increasing low-level jet may be sufficient for isolated to scattered
thunderstorm development. Supercell wind profiles and steep
low-level lapse rates will support initial storms capable of large
hail and damaging winds. If sufficient clusters/outflow
consolidation can occur, upscale growth during the late evening into
overnight hours is possible, with an increasing risk for swaths of
severe/damaging gusts.
...Southern Appalachians...
Scattered thunderstorm development is expected over higher terrain
within a seasonally moist and unstable airmass. Steepening low-level
lapse rates and high PW values may support locally strong gusts with
wet microbursts through early evening.
...AZ...
Modest easterly mid/upper flow will persist across the region on the
southern periphery of an upper high over the Four Corners. Another
day of hot conditions will promote steep lapse rates and modest
destabilization. As convection develops over higher terrain and
spread westward, strong outflow gusts may occur.
..Leitman/Moore.. 08/09/2026
SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1242 AM CDT Sun Aug 09 2026
Valid 101200Z - 111200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN GREAT LAKES...
...SUMMARY...
Thunderstorms with severe wind gusts will be possible Monday
afternoon and evening from northern Illinois eastward into western
Pennsylvania. Isolated severe gusts and hail will also be possible
from parts of the central and northern Plains into the Midwest.
...Southern Great Lakes...
At mid-levels, west-northwesterly flow will be in place on Monday
from the northern Plains into the Great Lakes. A subtle mid-level
shortwave trough and an associated jet streak will move through the
Great Lakes. To the south of the jet streak, a cold front is
forecast to advance southward into northern Illinois, northern
Indiana and northern Ohio by mid afternoon. Low-level convergence
along the front will be a focus for convective development. To the
south of the front, surface dewpoints in the 70s F will contribute
to moderate to strong destabilization by afternoon, with MLCAPE
likely peaking in the 2000 to 3500 J/kg range. Thunderstorms are
expected to develop near the front and move east-southeastward into
the stronger instability during the afternoon and evening.
Along the instability axis in the late afternoon from Lincoln,
Illinois to Pittsburgh, Pennsylvania, the ECMWF has 0-6 km shear
around 30 knots. This should support a mixed mode, with short
intense line segments and embedded rotating storms possible. The
primary threat will damaging wind gusts, with the maximum threat
located ahead of any cold pool that can organize. The severe threat
could persist into the early to mid evening, especially if MCS
development takes place, maintained by increasing low-level flow.
...Central and Northern Plains/Midwest...
West-northwesterly mid-level flow will be in place over the
north-central U.S. on Monday. A subtle shortwave trough is forecast
to move east-southeastward across the northern Plains. At the
surface, a cold front is forecast to advance southward across
western South Dakota during the day, with a dryline extending
southward into western Nebraska. To the east of the dryline, surface
dewpoints in the 60s and 70s F will contribute to moderate to strong
instability by afternoon. Isolated thunderstorms appear likely to
develop near the dryline during the mid to late afternoon.
Additional isolated storms are expected to develop further east
along the moist axis from eastern Nebraska into Iowa.
Forecast sounding along the moist axis in the late afternoon have
MLCAPE peaking in the 3000 to 4000 J/kg range with 0-6 km shear
around 30 knots. This environment, combined with steep low to
mid-level lapse rates, will support isolated potential for severe
wind gusts and hail.
..Broyles.. 08/09/2026
SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0224 AM CDT Sun Aug 09 2026
Valid 111200Z - 121200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE OHIO VALLEY AND CENTRAL APPALACHIANS...
...SUMMARY...
Thunderstorms with severe wind gusts will be possible on Tuesday
over parts of the Ohio Valley and central Appalachians. Isolated
severe gusts and hail will also be possible from parts of the
central and northern Plains into the Midwest.
...Ohio Valley/Central Appalachians....
At mid-levels, west-northwesterly flow will be in place on Tuesday
from the northern Plains to the central and northern Appalachians.
Along the southern edge of the stronger mid-level flow, a
west-northwest to east-southeast corridor of moderate to strong
instability is forecast to develop by afternoon. It appears that an
outflow boundary from the previous day's storms will be located from
approximately north-central Illinois east-southeastward into
southern Ohio. Low-level convergence along this boundary will be a
focus for convective initiation. In the afternoon, thunderstorms are
expected to develop near the boundary and move east-southeastward
into the stronger instability over the Ohio Valley. A cluster of
strong to severe storms is expected, and MCS development will be
possible across the region.
Instability is forecast to be similar to the previous day, with
MLCAPE peaking in the 2000 to 3500 J/kg range. According to the
ECMWF, deep-layer shear may be a bit stronger with 0-6 km shear in
the 30 to 40 knot range. This would support supercells and short
intense line segments capable of severe wind gusts. The wind-damage
threat would become maximized if a cold pool can develop during the
late afternoon and early evening. The current thinking is that the
ECMWF has a better handle on where the outflow boundary will be than
other solutions, and the Slight Risk area has been placed favoring
the ECMWF scenario.
...Central and Northern Plains/Midwest...
West-northwesterly mid-level flow will remain over the north-central
U.S. on Tuesday. At the surface, dewpoints in the 60s and 70s F from
South Dakota and Nebraska eastward into Iowa will contribute to
strong destabilization by afternoon. MLCAPE is forecast to peak
above 4000 J/kg along parts of the moist axis by late afternoon. In
spite of the instability, large-scale ascent is forecast to remain
relatively weak. Isolated to scattered storms could still develop
along zones of low-level convergence. The strong instability along
with moderate deep-layer shear should support an isolated severe
threat from mid afternoon to mid evening. Severe wind gusts and hail
will be the primary threats. Due to the weak forcing, there is some
uncertainty as to where the greatest convective coverage will be.
..Broyles.. 08/09/2026
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0114 AM CDT Sun Aug 09 2026
Valid 091200Z - 101200Z
...Synopsis...
Elevated fire weather conditions are expected across a broad swath
of the western CONUS for today, stretching from northern California
into the northern Great Basin and central Rockies. Additionally,
isolated dry thunderstorms are possible across portions of the Great
Basin and into the southern High Plains.
...California into the Great Basin and Wyoming...
Early morning water-vapor imagery continues to depict a broad upper
ridge over the Southwest. This feature is expected to linger over
the region for the next several days, and will act to modulate any
low-level mass response associated with weak perturbations embedded
within northern stream of the ridge axis. Consequently, surface
winds today will mainly be driven by orographic influences through
terrain-favored locations. Most high-res guidance depicts sustained
winds generally around 15 mph for most locations from northern CA
into the northern Great Basin and portions of WY. However, deep
mixing within a very dry environment will facilitate downward
transport of stronger flow near the top of the boundary layer, which
should manifest as 15-25 mph gusts at the surface. Given the
antecedent dry air mass (which should yield afternoon RH minimums in
the teens to single digits) and very limited rainfall over the past
1-2 weeks, areas of elevated fire weather conditions appear likely.
Sustained elevated conditions appear most likely across northwest NV
and eastern WY where more focused corridors of downslope flow will
promote sustained 15-20 mph winds.
Further west into central CA, an onshore flow regime should promote
downslope off the coastal terrain and into the Central Valley.
Sustained winds near 15 mph coupled with 15-20% RH minimums should
support areas of elevated fire weather conditions, especially in
close proximity to terrain features.
...Southern High Plains...
Hot and dry conditions will prevail across the Southern Plains this
afternoon where high temperatures will likely exceed 100 F. Weak lee
troughing juxtaposed with high pressure over the mid/lower MS Valley
will yield a swath of 15-20 mph gradient winds from the TX Panhandle
into southwest KS. The combination of hot/dry conditions and breezy
winds will support a swath of elevated fire weather conditions.
While the primary fire weather concern will be focused across the
OK/TX Panhandles, fire weather conditions may extend well into
central KS; however, recent rainfall over the past 72 hours should
modulate fuel status to some degree with east/northeastward extent.
...Dry Thunderstorms...
00 UTC RAOBs from the Southwest/Great Basin sampled very steep
mid-level lapse rates with sufficient mid-level monsoonal moisture
for 250-500 J/kg MUCAPE. Additionally, soundings from the Great
Basin sampled very dry boundary-layer conditions, which is reflected
in surface observations by poor overnight RH recoveries. MRMS QPE
and lightning activity over the past 24 hours suggests dry
thunderstorms occurred across portions of the Great Basin/Four
Corners yesterday afternoon, and similar thermodynamic conditions
should prevail today. However, the dry thunderstorm risk will be
displaced further north compared to yesterday due to continued
northward advection of monsoonal moisture on the western edge of the
ridge. Regardless, the potential for dry lightning over dry fuels
will pose a risk for additional lightning ignitions this
afternoon/evening.
..Moore.. 08/09/2026
...Please see www.spc.noaa.gov/fire for graphic product...
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0143 AM CDT Sun Aug 09 2026
Valid 101200Z - 111200Z
...Synopsis...
Another day of elevated fire weather conditions is expected across
the northern Great Basin into the central/northern Rockies as well
as portions of the southern High Plains. Isolated dry thunderstorms
will also pose a fire weather concern for parts of the Great Basin.
...Northern Great Basin...
As with today, a persistent upper-level ridge will modulate any
low-level mass response across the western CONUS, resulting in weak
gradient winds for most locations Monday afternoon. However, deep
mixing and localized orographic enhancements will promote areas of
15-20 mph winds (gusting to 20-25 mph at times). Little moisture
recovery is expected across the central to northern Great Basin,
which will promote another day of single digit to low teen RH
minimums by mid-afternoon. Widespread areas of elevated fire weather
conditions are expected, but hot, dry, and windy conditions may be
more prolonged/widespread in the lee of the northern Sierra Nevada
in northwest/western NV, through the Snake River Valley, and across
east-central WY in proximity to a weak surface low.
...CA Central Valley...
An onshore flow regime is expected to persist into Monday. Downslope
westerly flow off the coastal terrain should promote 15-20 mph winds
into western portions of the Central Valley. Dry conditions (RH
values in the teens to low 20s) coupled with preceding days of
dry/windy conditions should support some fire weather concern.
...Southern High Plains...
A modest deepening of the lee trough along the central to northern
High Plains will maintain modest pressure gradient winds across the
southern and central Plains on Monday. Another day of afternoon high
temperatures in the 100s will promote very dry conditions across
western OK into the Panhandles and southwest KS. A combination of
15-20 mph gradient winds (gusting to 20-25 mph) and RH minimums in
the teens should support a swath of elevated fire weather
conditions.
...Dry Thunderstorms...
A plume of monsoonal moisture will continue to shift northward over
the next 24-48 hours. Weak ascent - largely driven by orographic
lift - will promote isolated thunderstorms across much of the Great
Basin and Southwest/Four Corners. However, drier conditions on the
northern fringe of the returning moisture (characterized by PWAT
values of 0.45 to 0.75 inches), coupled with antecedent dry
low-level conditions, should support favorable thermodynamic
profiles for dry thunderstorms. With dry fuels already in place
across much of the region, lightning ignitions will be possible.
..Moore.. 08/09/2026
...Please see www.spc.noaa.gov/fire for graphic product...
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