SPC Jul 20, 2026 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... 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


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SPC Jul 20, 2026 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0718 AM CDT Mon Jul 20 2026

Valid 201300Z - 211200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE UPPER MIDWEST AND GREAT LAKES...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTH
CAROLINA AND FAR SOUTHERN VIRGINIA...

...SUMMARY...
Severe thunderstorms are expected across portions of the Upper
Midwest and Great Lakes vicinity, especially late this afternoon and
tonight. Swaths of damaging winds, large hail, and a few tornadoes
will all be possible. Isolated damaging wind gusts may also occur
over parts of the Carolinas and southern Virginia.

...Upper Midwest/Great Lakes...
Radar/IR satellite composite this morning shows a decaying MCS over
far northern IA into west-central WI with warm-advection-related
storms moving east-southeast atop the MCS cold pool. This
convective activity is occurring downstream of a seasonably potent
mid-level shortwave trough and associated jet streak.

Surface analysis this morning places a front over the mid MS Valley
extending north-northwest and intersecting an outflow boundary over
southwest MN. A surface low over western ON is forecast to develop
east across north-central ON as an attendant cold front pushes
southeast across the Upper Midwest. The front over the mid- to
upper MS Valley will advance northeast as a warm front and the warm
sector will become increasingly narrow with northward extent in the
northern WI vicinity.

A warm and seasonably moist airmass will advect northeast into WI in
wake of the morning showers/thunderstorms, while a plume of elevated
mixed-layer air overspreads the region from the west. Models
generally show upper 60s to lower/middle 70s F surface dewpoints
contributing to a very unstable boundary layer by mid-late
afternoon. However, considerable uncertainty remains regarding
details with this forecast update due in part to the morning
convection and downstream destabilization/hazard specifics for later
this afternoon/evening.

It is plausible the initial storms that develop later this afternoon
will quickly organize into supercells given strong deep-layer shear
and ample buoyancy ahead of the cold front. In agreement with prior
forecast thinking, a corridor of large hail and tornado risk will
extend from Iowa across Wisconsin into Upper MI. Forecast soundings
show elongated hodographs with 35-50 kt 700 mb flow, which will act
to enlarge hodographs and perhaps support a couple of strong
tornadoes. However, will defer any potential severe changes to
later outlook updates if greater confidence and morning convective
details are resolved. Eventually, a few clusters will probably
evolve this evening, with a continued damaging wind and some tornado
risk persisting southeastward before eventually waning overnight.

...Carolinas and southern Virginia...
Strong heating to the south of a west-east oriented stalled front
will contribute to moderate buoyancy by early to mid afternoon.
Rich low-level moisture (surface dewpoints in the 70s F) and moist
tropospheric profiles will yield high PW and the potential for
water-loaded downdrafts with the more intense thunderstorm cores.
Scattered thunderstorms with an isolated to scattered wind-damage
threat will probably focus during the 18-00 UTC period.

...Florida...
Tropical Depression Two is forecast to slowly intensify across the
northeast Gulf of America today and tonight (refer to NHC's latest
forecast details). Model guidance shows some gradual strengthening
of 2-3km AGL flow, especially across the western Florida Peninsula.
Yet, forecast soundings imply the possibility for transient
supercell structures will likely be limited/low due to substantially
weaker flow in the midlevels---precluding a low-severe highlight at
this time.

..Smith/Broyles.. 07/20/2026


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SPC Jul 20, 2026 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0102 AM CDT Mon Jul 20 2026

Valid 201200Z - 211200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE UPPER MIDWEST AND GREAT LAKES...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTH
CAROLINA AND FAR SOUTHERN VIRGINIA...

...SUMMARY...
Severe thunderstorms are expected across portions of the Upper
Midwest and Great Lakes vicinity, especially late this afternoon and
tonight. Swaths of damaging winds, large hail, and a few tornadoes
will all be possible. Isolated damaging wind gusts may also occur
over parts of the Carolinas and southern Virginia.

...Upper Midwest/Great Lakes...
A potentially active severe-weather scenario is expected later today
into tonight, although some key uncertainties persist related to the
potential impacts of early day convection and associated cloud
debris.

A substantial shortwave trough over southern Manitoba will continue
to gradually amplify and spread southeastward to the Lake Superior
vicinity through tonight, with a strengthening belt of
mid/high-level west-northwesterly flow overspreading the Upper
Midwest toward the Lake Michigan vicinity, highlighted by 50-70 kt
mid-level winds and 100 kt winds in the upper levels across
Minnesota/Wisconsin. An east/southeastward-advecting plume of steep
mid-level lapse rates will overspread a warm sector with upper 60s
to lower/middle 70s F dewpoints.

Initially, a few early day storms could produce hail and perhaps
some strong wind gusts across east/southeast Minnesota into western
Wisconsin and eastern Iowa, amidst ample elevated instability and
effective shear over 50 kt. This activity may continue to spread
southeastward this morning but tend to wane during the day, leading
to a potential regional break prior to additional/more vigorous
development by late afternoon along the cold front as it progresses
east-southeastward toward Wisconsin/Upper Michigan and
northern/eastern Iowa.

The initial storms should primarily be supercells given such strong
deep-layer shear. A corridor of large hail and tornado risk is
evident east of the instability axis from Iowa across Wisconsin into
Upper MI. Even while near-surface winds may tend to veer with time,
effective SRH may exceed 300 m2/s2, especially across Wisconsin
toward Upper Michigan as supported by the seasonally very-strong 2-3
km AGL winds (700 mb winds in excess of 50 kt). The degree of SRH
could support a couple strong tornadoes (EF2+), and somewhat higher
tornado probabilities could be warranted in subsequent outlooks as
early day convection details are resolved. While supercells will
persist for a time, several storm clusters will evolve this evening,
with a continued damaging wind and some tornado risk persisting
southeastward this evening prior to storm intensity eventually
waning overnight.

...Carolinas and southern Virginia...
Convection and related cloud debris may persist early today, but a
moist air mass will again diurnally destabilize this afternoon along
and south of a roughly west/east-oriented front. Daytime heating,
70s F dewpoints and surface convergence will aid storm formation and
intensification this afternoon. MLCAPE in excess of 2000 J/kg, PWAT
over 2.00", and mid-level westerly flow aloft of 15-20 kt will lead
to multicellular storm mode with isolated damaging wind gusts during
the afternoon until around sunset.

...Florida...
Tropical Depression Two may gradually strengthen across the
northeast Gulf of America today and tonight. Reference the National
Hurricane Center for the latest development/forecast details. While
various global models support the notion of a strengthening of
southerly winds in the lowest 2-3km AGL, especially across the
western Florida Peninsula, it currently appears that
supercell-related tornado potential should remain low, largely
attributable to the overall weakness of the Depression and weak wind
aloft.

..Guyer/Weinman.. 07/20/2026


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SPC Jul 20, 2026 0100 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0100Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0805 PM CDT Sun Jul 19 2026

Valid 200100Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE DAKOTAS/UPPER MIDWEST...

...SUMMARY...
Scattered severe thunderstorms capable of large hail and wind gusts
will remain possible mainly across the Dakotas into Minnesota.

...Northern Plains/Upper Midwest...
Severe thunderstorms including some supercells will continue to
focus this evening across the Dakotas, primarily across
south-central/eastern North Dakota as well as north-central/eastern
South Dakota, while also expanding into parts of Minnesota tonight.
Bouts of large hail will remain possible along with severe-caliber
wind gusts. This will be as storms progress east-southeastward with
the primary moisture/instability axis, supported by an amplifying
shortwave trough over Saskatchewan toward Manitoba, and the
development of a modest-strength southwesterly low-level jet across
the Upper Midwest tonight.

...Carolinas/Mid-Atlantic States...
A few strong/locally severe storms could still occur this evening,
but overall storm intensifies are expected to continue to wane with
the loss of daytime heating.

..Guyer.. 07/20/2026


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