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
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/TTct00
