SPC Jul 21, 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
1118 AM CDT Tue Jul 21 2026

Valid 211630Z - 221200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE OHIO VALLEY TO MID-ATLANTIC STATES...

...SUMMARY...
Numerous severe thunderstorms are expected across a broad region
from the Tennessee and Ohio Valleys to the Mid-Atlantic and
Northeast States today into tonight. Swaths of damaging wind gusts
are expected to be the most common impact, but some tornadoes are
possible as well.

...Tennessee/Ohio Valley into the Mid-Atlantic and Northeast...
Recent satellite imagery reveals a shortwave trough moving quickly
southeastward across the Upper Great Lakes region, embedded within
the upper troughing that covers much of eastern Canada and extends
down into the Ohio Valley. Moderate mid-level flow accompanies this
shortwave, with wind speeds greater than 50 kt sampled around 500 mb
on the 12Z ILX, DTX, ILN, and PIT soundings. The strongest flow was
sampled at ILX and DTX, and the expectation is for this stronger
flow to spread eastward today, moving in tandem with the progressive
shortwave.

Showers and thunderstorms are already ongoing downstream of this
shortwave, with the highest coverage along and near the pre-frontal
trough in Ohio. Recent surface analysis reveals a somewhat complex
boundary structure, with a wavy warm front, a diffuse pre-frontal
trough, and a cold front. Primary warm front appears to extend
west-to-east from southeast Ohio across southern Pennsylvania and
into northern New Jersey, far southern New York, and extreme
southwest Connecticut. The cold front arcs southwestward from
northern Lower Michigan through central Illinois and central
Michigan.

Highest overall coverage is anticipated along and ahead of the cold
front this afternoon through this evening, with additional
development expected farther east (from central Pennsylvania into
central Virginia) along the lee trough as well. Highest buoyancy is
expected along the western periphery of the cold front from central
into western Kentucky, where mid to upper 70s dewpoints are
anticipated amid temperatures in the upper 80s/low 90s. Strong
buoyancy is still anticipated across Ohio as well. Robust
thunderstorm development is expected along the front. Vertical shear
is robust enough for supercells, but linear forcing along the front
and strong downdraft production will likely lead to quick upscale
growth. In either convective mode, damaging gusts (with speeds from
55 to 70 mph) will be the primary risk, with brief tornadoes as a
secondary threat, and large hail tertiary.

Farther east, a similar convective environment exists, although with
slightly less buoyancy and deep-layer vertical shear. A more
outflow-dominant multicell mode is anticipated across the central
Virginia vicinity, with a trend towards a more organized mode
possible with northern extent. Primary risk will be damaging gusts,
including a few around 65 to 70 mph. A somewhat confined corridor of
greater tornado potential exists from the Hudson Valley vicinity
into western Massachusetts/Connecticut as the warm front lifts
northward. Here, enhanced vorticity along the boundary coupled with
stronger low-level southerly flow could support a few brief
tornadoes.

...Great Basin...
Scattered to numerous thunderstorms are expected across the Great
Basin today, supported by strong diurnal heating/mixing and moderate
mid-level moisture along the western periphery of the upper ridging
centered over the central Rockies. A few strong updrafts/downdrafts
are possible, with an attendant risk for strong to severe (i.e. 50
to 65 mph) wind gusts.

...Gulf Coast...
Tropical Storm Bertha is expected to continue to drift
west-northwestward over the northern Gulf tonight from off the coast
of the Florida Panhandle toward the southern Mississippi/southern
Alabama coast. Reference the National Hurricane Center for the
latest details.

A strong low-level wind field will approach these coastal areas
later today and tonight. However, as is typical for a westward
moving tropical cyclone, forecast SRH should remain relatively
modest inland. Given the marginal thermodynamic profiles (aside from
the rich boundary layer moisture) and limited SRH over land, any
Bertha-related mini-supercell potential is expected remain offshore.

..Mosier/Chalmers.. 07/21/2026


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SPC Jul 21, 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
1259 AM CDT Tue Jul 21 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 today. All
severe hazards are possible, but swaths of damaging wind gusts
should be the primary severe risk during the afternoon and early
evening hours.

...Ohio Valley into the Mid-Atlantic...
A broad area of 40-50-kt midlevel west-southwesterly flow will
overspread the OH Valley into the Mid-Atlantic as a large-scale
trough shifts across the northeastern CONUS. Scattered to numerous
thunderstorms are expected to develop ahead of an eastward-moving
cold front across the OH Valley and along a pre-frontal trough over
the Mid-Atlantic. In the base of the trough, a convectively
augmented midlevel impulse moving from the lower OH Valley into the
Mid-Atlantic may also serve as a focus for convective development.

Diurnal heating within cloud breaks, combined with upper 60s to
lower 70s dewpoints, will support moderate surface-based instability
across the broad pre-frontal warm sector. The most favorable overlap
of this instability and 40-50 kt of effective shear is expected from
the lower OH Valley into the Mid-Atlantic, where a mix of organized
clusters and supercells should evolve and spread eastward through
the day. Swaths of damaging wind gusts will be the primary severe
hazard, though severe hail will also be possible with any sustained
supercells. Additionally, a gradually strengthening and expanding
30-kt low-level jet will contribute to clockwise-curved low-level
hodographs, and a few tornadoes may occur.

...Mid-South into the Tennessee Valley...
Greater instability is expected southwestward into portions of the
Mid-South and TN Valley, although somewhat weaker deep-layer shear
(around 30-40 kt of effective shear) may temper storm organization
compared to ares farther northeast. Nevertheless, widely scattered
thunderstorms capable of organizing into multicell clusters and
occasional supercell structures will pose a risk of damaging wind
gusts and isolated severe hail ahead of the cold front during the
afternoon and early evening hours.

...Northeast...
Increasing midlevel height falls/forcing for ascent preceding the
upper trough will support scattered thunderstorm development near an
effective warm front moving northward across portions of the
Northeast. While poor midlevel lapse rates and weaker instability
should limit the overall severe risk compared to areas farther
south, around 40 kt of effective shear will still support organized
storm structures. Damaging wind gusts will be the primary concern,
though isolated severe hail and a tornado or two will also be
possible.

..Weinman/Jirak.. 07/21/2026


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SPC Jul 21, 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
0800 PM CDT Mon Jul 20 2026

Valid 210100Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE UPPER GREAT LAKES INTO THE LOWER MISSOURI VALLEY...

...SUMMARY...
Severe thunderstorms capable of producing damaging wind gusts,
severe hail, and a couple of tornadoes will continue across portions
of the Upper Great Lakes and Lower Missouri Valley through late
tonight.

...01Z Update...
Water-vapor imagery and VWP data indicate a robust midlevel wave and
accompanying belt of 50-60-kt west-northwesterly flow overspreading
the Upper Midwest, and this feature will continue east-southeastward
across the Great Lakes region tonight. In the low-levels, an
attendant cold front will continue east-southeastward across this
region as well. In the Upper Great Lakes and Midwest, 50-60 kt of
deep-layer shear (sampled by regional VWPs) oriented perpendicular
to the cold front and a relatively narrow corridor of strong
pre-frontal buoyancy (around 3000 J/kg MLCAPE) will continue to
promote semi-discrete supercell structures. Locally damaging wind
gusts, severe hail, and a couple of tornadoes will be possible with
this activity, given ample low-level hodograph curvature (around 250
m2/s2 effective SRH) beneath the core of a 40-kt LLJ. This activity
will generally spread east-southeastward across parts of Lower MI
tonight, where a continued risk of damaging wind gusts, severe hail,
and a tornado or two will continue ahead of the cold front before
encountering increasingly stable air.

Farther south, a couple organized clusters are tracking southward
across parts of southern IA and western IL. Given strong cold pools
with this activity, the primary concern will be severe wind gusts
and isolated/sporadic hail. These storms will continue tracking
south-southeastward along a surface-based buoyancy gradient before
gradually weakening overnight.

..Weinman.. 07/21/2026


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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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