RSS Mesoscale Discussions from Storm Prediction Center
WW 501 TORNADO MI WI LM LS 202050Z - 210400Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 501
NWS Storm Prediction Center Norman OK
350 PM CDT Mon Jul 20 2026
The NWS Storm Prediction Center has issued a
* Tornado Watch for portions of
The Upper Peninsula of Michigan
Northeast Wisconsin
Lake Michigan
Lake Superior
* Effective this Monday afternoon and evening from 350 PM until
1100 PM CDT.
* Primary threats include...
A few tornadoes likely with a couple intense tornadoes possible
Scattered damaging winds and isolated significant gusts to 75
mph likely
Scattered large hail and isolated very large hail events to 2.5
inches in diameter possible
SUMMARY...Scattered supercell development is expected late this
afternoon into early tonight across north central/northeast
Wisconsin and the Upper Peninsula of Michigan. The storm
environment favors the potential for a few tornadoes, including a
couple of strong (EF2+) tornadoes, as well as isolated very large
hail of 2-2.5 inches in diameter. As storms cluster by late
evening, the threat for wind damage will increase, with a few
significant (75+ mph) gusts possible.
The tornado watch area is approximately along and 75 statute miles
east and west of a line from 35 miles west northwest of Marquette MI
to 45 miles west southwest of Green Bay WI. For a complete depiction
of the watch see the associated watch outline update (WOUS64 KWNS
WOU1).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and 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.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 500...
AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 2.5 inches. Extreme turbulence and surface wind
gusts to 65 knots. A few cumulonimbi with maximum tops to 550. Mean
storm motion vector 30035.
...Thompson
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WW 500 TORNADO IA WI 202005Z - 210300Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Tornado Watch Number 500
NWS Storm Prediction Center Norman OK
305 PM CDT Mon Jul 20 2026
The NWS Storm Prediction Center has issued a
* Tornado Watch for portions of
Northeast and central Iowa
Extreme southwest Wisconsin
* Effective this Monday afternoon and evening from 305 PM until
1000 PM CDT.
* Primary threats include...
A few tornadoes likely with a couple intense tornadoes possible
Scattered damaging winds likely with isolated significant gusts
to 75 mph possible
Scattered large hail and isolated very large hail events to 2.5
inches in diameter possible
SUMMARY...Supercell development is underway across northern Iowa and
these storms will spread southeastward through this evening. The
storm environment favors a few strong-intense tornadoes (EF2+), very
large hail (up to 2.5 inches in diameter) and isolated significant
severe gusts (75+ mph), especially where the supercells interact
with a modifying outflow boundary.
The tornado watch area is approximately along and 85 statute miles
east and west of a line from 10 miles west of Knoxville IA to 70
miles north northeast of Waterloo IA. For a complete depiction of
the watch see the associated watch outline update (WOUS64 KWNS
WOU0).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Tornado Watch means conditions are favorable for
tornadoes and 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.
&&
AVIATION...Tornadoes and a few severe thunderstorms with hail
surface and aloft to 2.5 inches. Extreme turbulence and surface wind
gusts to 65 knots. A few cumulonimbi with maximum tops to 600. Mean
storm motion vector 33030.
...Thompson
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WW 0501 Status Updates
STATUS FOR WATCH 0501 HAS NOT BEEN ISSUED YET
Read more
WW 0500 Status Updates
STATUS FOR WATCH 0500 HAS NOT BEEN ISSUED YET
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MD 1675 CONCERNING SEVERE POTENTIAL...TORNADO WATCH LIKELY FOR PORTIONS OF CENTRAL IOWA
Mesoscale Discussion 1675
NWS Storm Prediction Center Norman OK
0248 PM CDT Mon Jul 20 2026
Areas affected...Portions of central Iowa
Concerning...Severe potential...Tornado Watch likely
Valid 201948Z - 202145Z
Probability of Watch Issuance...95 percent
SUMMARY...Storms in north-central Iowa are becoming surface based.
The environment is favorable for all severe hazards, including some
significant. A tornado watch is likely this afternoon for portions
of central Iowa.
DISCUSSION...Visible satellite imagery over the last half hour
suggest storms are becoming surface based in north-central Iowa.
Given the very unstable and strongly sheared environment to the
south of these storms, storms will likely become severe this
afternoon. The presence of a modifying outflow boundary will provide
enhancement to low-level shear. Tornadoes, some potentially strong,
will be possible. Large to very-large hail will also be a concern
given the strong buoyancy and steep mid-level lapse rates. Severe
wind gusts could remain isolated in the short term with a
supercellular mode, but could become more prevalent with time as
clustering occurs. A tornado watch is likely this afternoon.
..Wendt/Thompson.. 07/20/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DVN...ARX...DMX...
LAT...LON 41609368 42419442 42999451 43339437 43499384 43429320
42589229 42079212 41479223 41399268 41529331 41609368
MOST PROBABLE PEAK TORNADO INTENSITY...120-145 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
Read more
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1130 AM CDT Mon Jul 20 2026
Valid 201630Z - 211200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
INTO EARLY TONIGHT FROM EASTERN IOWA AND NORTHWESTERN ILLINOIS
ACROSS WISCONSIN INTO WESTERN UPPER MICHIGAN...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
ACROSS CENTRAL NORTH CAROLINA...
...SUMMARY...
Severe thunderstorms are expected across portions of the Upper
Midwest and Great Lakes vicinity, especially late this afternoon
into late evening. A few strong-intense tornadoes, swaths of
damaging winds, and isolated very large hail will all be possible.
Isolated damaging gusts may also occur over parts North Carolina
this afternoon.
...Upper Midwest through tonight...
A midlevel shortwave trough is cresting the ridge and will turn
southeastward today while moving over the upper MS Valley, as an
associated cold front likewise moves southeastward into Upper MI, WI
and IA. Earlier storms in Upper MI have weakened, while a cluster
is ongoing in eastern IA. Destabilization will occur in the wake of
the eastern IA storms as a reservoir of low-mid 70s boundary-layer
dewpoints spreads northeastward from IA/southern MN into WI and
western Upper MI. The low-level moistening will occur beneath a
plume of midlevel lapse rates greater than 8 C/km and in tandem with
surface heating in cloud breaks, all of which will drive MLCAPE in
excess of 3000 J/kg. As is typical with lingering morning
convection, there is some uncertainty regarding the specific
locations of afternoon storm development in its wake. Wind profiles
will favor supercells as the initial storm mode this afternoon along
and just ahead of the cold front, given very long hodographs
oriented largely orthogonal to the front. Low-level shear/hodograph
curvature will also be substantial, which combined with the moist
boundary layer, steep lapse rates and large buoyancy will support
the potential for a few strong-intense tornadoes. Very large hail
will be possible with the more discrete supercells, while
significant severe outflow gusts will be possible with any
clustering of storms later this afternoon/evening.
Initial supercells will likely evolve into a cluster or two by early
tonight while spreading southeastward across eastern IA, northern
IL, northwest IN and Lower MI with a continued threat for occasional
wind damage and isolated large hail.
...Central NC area this afternoon/evening...
Thunderstorm development is expected again this afternoon along a
stalled front/differential heating zone across NC, to the west of
the more persistent cloud cover in far eastern NC. NC remains near
the south edge of the midlevel westerlies, with mid 70s
boundary-layer dewpoints coincident with temperatures at or above 90
F contributing to MLCAPE in excess of 2000 J/kg. A few damaging
downbursts will be possible with precipitation-loaded downdrafts in
an environment with steepening low-level lapse rates.
...FL Big Bend today...
Tropical Depression #2 is forecast to drift slowly westward across
the northeast Gulf through tomorrow and become a tropical storm.
Though deep-layer wind profiles are not particularly favorable in
the northeast quadrant of the cyclone, where winds aloft are from
the northeast, there is just enough low-level shear to support
weakly rotating storms in the outer convective bands. An isolated
tornado/waterspout or two may occur today in coastal areas of the FL
Big Bend.
..Thompson/Chalmers.. 07/20/2026
Read more
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Mon Jul 20 2026
Valid 202000Z - 211200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE UPPER MIDWEST...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS CENTRAL
NORTH CAROLINA...
...SUMMARY...
Severe thunderstorms are expected across portions of the Upper
Midwest and Great Lakes vicinity, especially late this afternoon
into late evening. A few strong-intense tornadoes, swaths of
damaging winds, and isolated very large hail will all be possible.
Isolated damaging gusts may also occur over parts of North Carolina
this afternoon.
...20z Update...
The previous forecast largely remains on track with only minor
adjustments made. Recent GOES imagery and surface observations show
gradually building cumulus across eastern MN into northwest WI along
a diffuse surface cold front. Latest high-res guidance suggests this
will be the primary initiation zone over the next few hours, which
increases confidence in the downstream severe threat and implies the
severe threat is diminishing for areas further west. Risk
probabilities were trimmed across northeast MN to reflect this
trend. Elevated convection migrating across southeast MN/WI are
indicative of steeper mid-level lapse rates (observed in upstream 18
UTC soundings) spreading east in the wake of this morning's weak
MCS. This, coupled with steady warming/moistening of the low-level
air mass and 50-60 knot mid-level flow observed by the KMPX and KDVN
VWPs, lends confidence in the ongoing forecast for much of the
region. See the previous discussion (below) and MCD #1674 for
additional forecast details.
...North Carolina...
Ongoing thunderstorms have exhibited pulse-like behavior over the
past few hours across NC and adjacent areas. While much of this
activity has been sub-severe, low-level thermodynamic conditions
will remain favorable through early evening for strong to severe
downburst winds. Given the ongoing coverage of convection across
north-central NC, 15% risk probabilities were maintained.
Elsewhere, more isolated strong/severe winds appear possible across
northeast ND/northwest MN as a pocket of colder mid-level
temperatures coincident with 30-40 knot low-level winds overspreads
the region in tandem with the primary mid/upper-level trough.
Similarly, very sporadic severe gusts associated with downbursts
within a deeply-mixed environment are possible across
central/southern AZ, as well as northern FL/far southern GA where
local velocity data shows embedded swaths of strong winds associated
with the outer convective bands of Tropical Depression 2. However,
all of these regions, the kinematic/thermodynamic environments
appear fairly marginal and/or convective signals in recent ensemble
guidance are too weak to warrant severe wind highlights.
..Moore.. 07/20/2026
.PREV DISCUSSION... /ISSUED 1130 AM CDT Mon Jul 20 2026/
...Upper Midwest through tonight...
A midlevel shortwave trough is cresting the ridge and will turn
southeastward today while moving over the upper MS Valley, as an
associated cold front likewise moves southeastward into Upper MI, WI
and IA. Earlier storms in Upper MI have weakened, while a cluster
is ongoing in eastern IA. Destabilization will occur in the wake of
the eastern IA storms as a reservoir of low-mid 70s boundary-layer
dewpoints spreads northeastward from IA/southern MN into WI and
western Upper MI. The low-level moistening will occur beneath a
plume of midlevel lapse rates greater than 8 C/km and in tandem with
surface heating in cloud breaks, all of which will drive MLCAPE in
excess of 3000 J/kg. As is typical with lingering morning
convection, there is some uncertainty regarding the specific
locations of afternoon storm development in its wake. Wind profiles
will favor supercells as the initial storm mode this afternoon along
and just ahead of the cold front, given very long hodographs
oriented largely orthogonal to the front. Low-level shear/hodograph
curvature will also be substantial, which combined with the moist
boundary layer, steep lapse rates and large buoyancy will support
the potential for a few strong-intense tornadoes. Very large hail
will be possible with the more discrete supercells, while
significant severe outflow gusts will be possible with any
clustering of storms later this afternoon/evening.
Initial supercells will likely evolve into a cluster or two by early
tonight while spreading southeastward across eastern IA, northern
IL, northwest IN and Lower MI with a continued threat for occasional
wind damage and isolated large hail.
...Central NC area this afternoon/evening...
Thunderstorm development is expected again this afternoon along a
stalled front/differential heating zone across NC, to the west of
the more persistent cloud cover in far eastern NC. NC remains near
the south edge of the midlevel westerlies, with mid 70s
boundary-layer dewpoints coincident with temperatures at or above 90
F contributing to MLCAPE in excess of 2000 J/kg. A few damaging
downbursts will be possible with precipitation-loaded downdrafts in
an environment with steepening low-level lapse rates.
...FL Big Bend today...
Tropical Depression #2 is forecast to drift slowly westward across
the northeast Gulf through tomorrow and become a tropical storm.
Though deep-layer wind profiles are not particularly favorable in
the northeast quadrant of the cyclone, where winds aloft are from
the northeast, there is just enough low-level shear to support
weakly rotating storms in the outer convective bands. An isolated
tornado/waterspout or two may occur today in coastal areas of the FL
Big Bend.
Read more
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Mon Jul 20 2026
Valid 211200Z - 221200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE UPPER OHIO VALLEY INTO THE MID-ATLANTIC...
...SUMMARY...
Numerous severe thunderstorms are expected across a broad region
from the Ohio Valley into the Mid-Atlantic and Northeast on Tuesday.
All severe hazards are possible, but swaths of damaging wind gusts
should be the primary severe risk Tuesday afternoon into the
nighttime hours.
...Synopsis...
High amplitude ridging will build across the western US with
continued progressive troughing across the east on Tuesday. Multiple
short-wave impulses will rotate through the eastern US trough, with
a belt of enhanced northwesterly flow traversing the Midwest into
the Ohio Valley. At the surface, a cold front will shift south and
east through the period, with a surface low across southern
Ontario/Quebec. A pre-frontal surface trough will also be in place
across western/central NY into the Mid-Atlantic vicinity. Widely
scattered thunderstorm activity is expected through the period.
...Mid-Atlantic and Northeast...
Thunderstorm activity is expected to increase along the pre-frontal
trough from western/central New York into the Northeast/Mid-Atlantic
late Tuesday morning into the afternoon. Though there may be
potential for early morning cloud cover, it does appear that
sufficient heating/moistening will occur for at least moderate
instability to develop across the region through the afternoon.
Mid-level flow will increase through the day along with forcing for
ascent. It appears widely scattered thunderstorm activity with
several clusters/embedded supercells will be ongoing by the
afternoon. Highest confidence in transient embedded supercell modes
would be closer to the surface low and near the front across western
NY into eastern PA. Here, there may be potential for both damaging
wind, large hail, and perhaps a couple of tornadoes. Guidance
suggests the best signal for damaging wind will be across the
Mid-Atlantic, where several damaging clusters could occur. As such,
the Enhanced was expanded eastward into portions of the
Mid-Atlantic.
...Ohio Valley...
Evolution of overnight convection will play a large role in
development/maintenance of thunderstorm activity across the Ohio
Valley Tuesday. It appears that remnant convection will be ongoing
at the start of the period near/just ahead of the surface front
across northern Kentucky/southern Indiana/Ohio. This will likely
re-intensify and continue to expand south and east during the
morning as daytime heating begins. Strong daytime heating and moist
profiles should support moderate to strong instability developing
though the afternoon. Storm mode appears to be generally linear,
with the greatest threat being for damaging wind given more linear
forcing/initially boundary parallel shear along residual southward
moving outflow. As such, the primary hazard will be damaging wind.
Additional thunderstorm development is likely along and ahead of the
front through the afternoon with increasing forcing for ascent with
approaching shortwaves. Strong deep layer shear may become more
boundary perpendicular supporting a supercell or two as the front
sags south, with potential for large hail and perhaps a tornado.
Confidence in this scenario is on the lower end and the primary
hazard is expected to be a secondary wave of damaging wind
potential. Should storms be able to cluster and establish a more
organized cold pool, potential for some corridor of significant wind
may be possible. Overall, no significant wind areas were included
given low confidence in exact morning storm evolution and concerns
over generally poor lapse rates.
..Thornton.. 07/20/2026
Read more
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0220 PM CDT Mon Jul 20 2026
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF NORTH
CAROLINA INTO SOUTHEAST VIRGINIA...
...SUMMARY...
Isolated strong to severe thunderstorms will pose a risk for
damaging wind gusts across parts of southeast Virginia and North
Carolina.
...Discussion...
Upper-level troughing will remain in place across the eastern US on
D3/Wednesday, with several shortwave impulses rotating through. A
cold front will be located roughly from the Mid-Atlantic south into
the Carolinas and western Tennessee. Moisture will be largely
scoured out behind this front, with the more favorable plume of
moist air remaining east of the Appalachians and Blue Ridge
Mountains across southern New England into the
Mid-Atlantic/Carolinas. Daytime heating will be maximized from the
Mid-Atlantic southward to the Carolinas, where moderate instability
will be realized by the afternoon. Instability will be more marginal
with north extent into New England, though strong deep layer shear
may still support a few organized storms. Widely scattered
thunderstorm development is expected near and ahead of the cold
front by the afternoon, with the main hazard being damaging wind,
with the greatest risk across parts of VA/NC and vicinity.
Outer bands of Tropical Depression Two will bring thunderstorms
potential inland across the Gulf States by D3/Wednesday. The tornado
threat appears to be too marginal for an outlook area at this time.
See advisories from the National Hurricane Center for more
information on this potential (nhc.noaa.gov).
..Thornton.. 07/20/2026
Read more
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0213 PM CDT Mon Jul 20 2026
Valid 211200Z - 221200Z
Minor modifications were made to the IsoDryT area based on the
latest observations and high-resolution forecast guidance.
Southern/central Oregon remain the mostly likely area for mixed
wet/dry thunderstorm development. Cloud cover, smoke, and warmer
temperatures aloft will help limit thunderstorm development/coverage
across the IsoDryT area, but isolated thunderstorms remain possible
if not likely. Additionally, if the upper low off the coast shifts
farther east in the next 24-36 hours, this will help increase
thunderstorm probabilities and coverage, including overnight.
Locally elevated conditions are likely in portions of South Carolina
as south-southwest sustained winds of 10-15 mph overlap minimum RH
of 30-40%. ERCs generally range from the 80th-95th percentile across
this area.
..Nauslar.. 07/20/2026
.PREV DISCUSSION... /ISSUED 0149 AM CDT Mon Jul 20 2026/
...Synopsis...
Along the northwestern periphery of a large-scale ridge encompassing
much of the central and western CONUS, ample midlevel moisture will
be in place atop a warm and dry air mass across parts of northern CA
into OR. This will yield inverted-V profiles with weak (albeit
sufficient) buoyancy for isolated high-based thunderstorms across
the area during the afternoon and evening hours. Given relatively
weak large-scale forcing for ascent, the greatest confidence in
thunderstorm development is over the Cascades in southern/central
OR. While 0.8 to 1.2 inch PW may promote a mix of wet/dry storms,
relatively fast storm motions and the dry boundary layer should
limit rainfall. As a result, isolated lightning-induced ignitions
will be possible. Elsewhere across the CONUS, minimal fire-weather
concerns are expected.
...Please see www.spc.noaa.gov/fire for graphic product...
Read more
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