SPC - No watches are valid as of Mon Jul 20 13:40:02 UTC 2026

No watches are valid as of Mon Jul 20 13:40:02 UTC 2026.

SPC MD 1671

MD 1671 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR WESTERN UPPER PENINSULA OF MICHIGAN AND ADJACENT WISCONSIN

Mesoscale Discussion 1671
NWS Storm Prediction Center Norman OK
0837 AM CDT Mon Jul 20 2026

Areas affected...Western Upper Peninsula of Michigan and adjacent
Wisconsin

Concerning...Severe potential...Watch unlikely 

Valid 201337Z - 201530Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated damaging winds and marginally severe hail are
possible this morning. A gradual weakening trend is anticipated and
a watch is not expected. Trends will continue to be monitored.

DISCUSSION...A small elevated linear segment has moved into the
western Upper Peninsula of Michigan. The observed soundings from INL
and APX this morning show around 7 C/km mid-level lapse rates. This
activity is currently being driven by moderate low-level warm
advection. With time, however, the low-level jet will weaken and
veer. Elevated buoyancy will be able to sustain robust convection
for another hour or two as it moves southeastward at around 35 kt.
The overall expectation is for this linear segment to outpace
favorable buoyancy before low-level moistening increases later
today. Isolated damaging winds will be the main threat this morning,
though steep mid-level lapse rates could support marginally severe
hail as well.

..Wendt/Thompson.. 07/20/2026

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MQT...GRB...

LAT...LON   46548988 47188889 46428704 45818661 45508680 45478777
            46548988 

MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN

SPC MD 1670

MD 1670 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR FAR SOUTHEAST MINNESOTA...EASTERN IOWA

Mesoscale Discussion 1670
NWS Storm Prediction Center Norman OK
0755 AM CDT Mon Jul 20 2026

Areas affected...Far Southeast Minnesota...Eastern Iowa

Concerning...Severe potential...Watch unlikely 

Valid 201255Z - 201500Z

Probability of Watch Issuance...20 percent

SUMMARY...An isolated wind-damage threat will likely continue with a
short line of strong to severe storms near the Iowa-Minnesota state
line. This line will move south-southeastward across eastern Iowa
over the next couple of hours. The threat is expected to be marginal
and weather watch issuance appears unlikely.

DISCUSSION...The latest surface analysis shows a north-to-south
corridor of low-level moisture from far western Missouri northward
into western Iowa, along which dewpoints are in the mid 70s F.
Slightly further east, the RAP has an axis of moderate instability
with MLCAPE in the 1000 to 2000 J/kg range analyzed over central
Iowa. Scattered thunderstorms are ongoing along the instability
gradient to the east of this axis. The storms are being supported by
a subtle mid-level shortwave trough evident on water vapor imagery
moving southeastward across the upper Mississippi Valley. Although
forecast soundings across eastern Iowa this morning have a
near-surface inversion in place, effective shear is estimated to be
near 40 knots. This could support an isolated and marginal threat
for severe wind gusts over the next couple of hours, especially as
surface temperatures ahead of the storms begin to increase.

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

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...DVN...ARX...MPX...DMX...

LAT...LON   43549372 43049385 41999340 41419293 41159252 41039199
            41089155 41329112 41759080 42189082 42839106 43439143
            43809184 43999228 43979296 43799344 43549372 

MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN

SPC Jul 20, 2026 1300 UTC Day 1 Convective Outlook

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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