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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