SPC Aug 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
0100 AM CDT Thu Aug 20 2026

Valid 201200Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE MID ATLANTIC...THE MIDWEST AND CENTRAL PLAINS....

...SUMMARY...
Scattered severe storms are possible today and tonight across parts
of the Mid Atlantic, posing a risk for damaging wind gusts. Large
hail and isolated wind damage will be possible with severe storms
from Nebraska into northwest Wisconsin.

...Mid Atlantic and central Appalachians...
A shortwave trough embedded within broader northwesterly flow aloft
is forecast to move eastward from the OH valley into the Mid
Atlantic through today. Embedded within a broader upper trough over
the eastern Great Lakes, this shortwave perturbation will serve as a
focus for convective development across the Mid Atlantic and central
Appalachians this afternoon. As ascent overspreads the area, a warm
front is forecast to lift northward across southern PA, northern MD
into NJ and southern NY.

South of the front, a very moist air mass (dewpoints in the 70s F)
will lift northward. Despite poor low and mid-level lapse rates,
moderate buoyancy is expected south of the front and ahead of a
trailing lee trough into southern VA. Ongoing storms from a remnant
morning cluster may reintensify as they cross the Appalachians late
morning and early afternoon. Additional, possibly discrete,
development may occur east of the Blue Ridge and across the higher
terrain of southern PA and northern MD near the front by late
morning. 40-50 kt of deep-layer shear ahead of the front is forecast
to support a mix of supercells and line segments. Damaging winds and
isolated severe gusts appear probable. Enlarged low-level hodographs
near the front may also support a couple of tornadoes and marginally
severe hail with any more robust QLCS segments or supercells.

...Central Plains...
Strong northwesterly flow aloft will overspread a cold front moving
southward from the western Great Lakes into the central Plains.
Ahead of the front, warm temperatures and dewpoints in the mid to
upper 60s F will support moderate to large buoyancy by mid
afternoon. A shortwave impulse within the broader trough should
overspread the destabilizing air mass and aide in convective
development along the front across MN and SD, and farther south near
the front and surface trough intersection in central NE.

Forecast soundings show supercell wind profiles, with
elongated/straight hodographs aloft. Isolated to widely scattered
storms will develop by late afternoon/early evening, posing a risk
for large hail, severe wind gusts and perhaps a tornado. Some
significant hail (greater than 2 inch diameter) is possible across
the southern risk area given steeper mid-level lapse rates/cool
temperatures aloft and somewhat deeper low-level moisture. Some risk
for isolated damaging gusts may persist into the early overnight
across southern NE and northern KS if clustering can occur.

...Southeast...
South of the primary upper wave over parts of the Western Carolinas
and TN Valley, a surface trough in the lee of the Appalachians may
focus convective development during the afternoon. A few stronger
clusters with damaging gusts are possible, though weaker flow aloft
suggests more limited storm organization.

Additional scattered thunderstorms are expected again this afternoon
within a seasonably hot and humid air mass across the southeast and
lower MS Valley. Convective coverage is likely to focus along a
weakening cold front sagging southward across parts of AR/LA and
western MS and near a weak MCV across the central Gulf Coast. With
PWATs upwards of 2 inches, some potential for wet microbursts are
possible with the stronger storm clusters through early evening.

...AZ...
Strong heating beneath a prominent upper ridge will support another
round of scattered thunderstorms this afternoon and evening.
Seasonably rich monsoon moisture (dewpoints in the upper 50s to 60s
F) will support moderate destabilization amid modest easterly
mid-level flow. A few high-based clusters are possible, initially
over the higher terrain, before expanding west and south into the
lower elevations. This could support a few severe gusts given steep
lapse rates.

..Lyons/Thornton.. 08/20/2026


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SPC Aug 19, 2026 2000 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0257 PM CDT Wed Aug 19 2026

Valid 192000Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE LOWER MISSOURI VALLEY...THE MID MISSISSIPPI VALLEY...AND
SOUTHERN ARIZONA...

...SUMMARY...
Thunderstorms capable of severe wind gusts and hail will be possible
this afternoon across the lower Missouri Valley, the mid Mississippi
Valley, and southern Arizona.

...20z Update...
A compact, but severe, MCS has begun tracking eastward along a
residual/diffuse frontal zone into southeast NE. Based on the recent
18 UTC OAX RAOB, the MCS is beginning to orient more orthogonal to
the deep-layer bulk shear vector, which should continue to promote
storm organization and intensity. The potential for severe winds,
including winds near 75 mph, should continue through late afternoon
and early evening hours before moving into more stable air mass
across north-central MO. See MCD #2041 for additional short-term
details.

...Mid-Mississippi Valley/lower Ohio Valley...
Recent GOES visible imagery and surface observations show
temperatures rebounding into the low to mid 80s as skies clear ahead
of an approaching mid-level wave. This destabilization appears to be
on track with recent guidance, which suggests that initially
discrete/semi-discrete storm development should begin by around
22-00 UTC across south-central MO on the western fringe of the
residual cold pool. Forecast soundings from this region depict
elongated hodographs conducive for large hail, including the
potential for hail up to 2 inches in diameter (based on sounding
analogs and hodograph structure). Given a favorable kinematic
environment, adequate buoyancy, and a signal in recent high-res
ensemble guidance for strong convection, a CIG 1 hail contour has
been introduced to portions of southern Missouri.

Elsewhere, only minor modifications were made based on recent
convective trends. See the discussion below and MCD #2040 for
additional details.

..Moore.. 08/19/2026

.PREV DISCUSSION... /ISSUED 1134 AM CDT Wed Aug 19 2026/

...Mid MO Valley...
Radar/visible satellite mosaic imagery depicts a small cluster of
severe thunderstorms immediately ahead of a migratory shortwave
trough moving southeast over the mid MO Valley. Some heating
downstream of this activity will result in temperatures warming and
the airmass gradually destabilizing amid filtered sunshine. Gradual
upscale growth is underway and should continue into the early
afternoon. Large hail and severe gusts 60-70 mph will be the
primary severe hazards as this cluster moves into adjacent portions
of NE/MO/IA later this afternoon.

...Ozarks into the Mid MS Valley...
Residual showers/thunderstorms from an overnight MCS over the
southeast MO into western KY vicinity will slowly dissipate this
afternoon with greater heating ensuing in the wake of these storms.
Models continue to show moderate destabilization by late this
afternoon ahead of the MO Valley upper vort. Weak low-level
convergence along an upstream cold front will support thunderstorm
development within this destabilized airmass this evening.
Strengthening mid-level flow will result in moderate to strong
deep-layer vertical shear supportive of supercells. Models vary
regarding the propensity for cellular mode to be maintained beyond
the initial storm development phase, casting doubt on supercell
longevity and tornado potential. Nonetheless, some strengthening of
850-mb flow during the evening may enable some mesocyclone potential
to persist, and an accompanying isolated risk for a tornado or two.
Otherwise, storms will tend to cluster with eastward extent, with
the threat for damaging gusts persisting within these bowing line
segments.

...Ohio Valley...
A somewhat secondary area of late afternoon/early evening
thunderstorm development is anticipated from central IL into central
IN and central OH. Moderate buoyancy and strong westerly flow aloft
supports the potential for isolated supercells capable of large hail
and isolated damaging gusts.

...Central/Southern High Plains...
A seasonably moist airmass will undergo strong heating/mixing and
result in moderate buoyancy by mid-late afternoon. Thunderstorm
development is expected across the higher terrain before then
progressing eastward into the lower elevations. Moderate
northwesterly flow aloft will support organized storms
structures, and large hail is possible along the Foothills.
Steep lapse rates and large temperature-dewpoint depressions will
lead to outflow-dominant storms capable of severe gusts with the
more intense cores/outflow.

...AZ...
The presence of monsoon moisture will support moderate buoyancy
across the lower elevations of south-central AZ during the late
afternoon. Scattered storms are expected to eventually develop
towards the early evening. Trends in model guidance showing a
cluster potentially evolving within an adequately moist/inverted-V
environment lend confidence in introducing a level 1 intensity
highlight for peak gusts in the 70-80 mph range.

...Southeast into northern FL...
A very moist airmass analyzed late this morning (mid to upper 70s F
surface dewpoints) will remain in place along the Gulf Coast. Strong
heating is anticipated, with high temperatures in the upper 90s
across much of the region. As surface temperatures warm, moderate
instability will develop, with scattered thunderstorms expected amid
modest low-level convergence from MS into western/southern AL and
across the FL Panhandle into northern FL. The deep low-level
moisture combined with steep low-level lapse rates will support an
isolated wind-damage threat during the mid to late afternoon.


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SPC Aug 19, 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
1134 AM CDT Wed Aug 19 2026

Valid 191630Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE MID AND LOWER MISSOURI VALLEY...THE MID MISSISSIPPI VALLEY...AND
SOUTHERN ARIZONA...

...SUMMARY...
Thunderstorms capable of severe wind gusts and hail will be possible
this afternoon across the lower to mid Missouri Valley, the mid
Mississippi Valley, and southern Arizona.

...Mid MO Valley...
Radar/visible satellite mosaic imagery depicts a small cluster of
severe thunderstorms immediately ahead of a migratory shortwave
trough moving southeast over the mid MO Valley. Some heating
downstream of this activity will result in temperatures warming and
the airmass gradually destabilizing amid filtered sunshine. Gradual
upscale growth is underway and should continue into the early
afternoon. Large hail and severe gusts 60-70 mph will be the
primary severe hazards as this cluster moves into adjacent portions
of NE/MO/IA later this afternoon.

...Ozarks into the Mid MS Valley...
Residual showers/thunderstorms from an overnight MCS over the
southeast MO into western KY vicinity will slowly dissipate this
afternoon with greater heating ensuing in the wake of these storms.
Models continue to show moderate destabilization by late this
afternoon ahead of the MO Valley upper vort. Weak low-level
convergence along an upstream cold front will support thunderstorm
development within this destabilized airmass this evening.
Strengthening mid-level flow will result in moderate to strong
deep-layer vertical shear supportive of supercells. Models vary
regarding the propensity for cellular mode to be maintained beyond
the initial storm development phase, casting doubt on supercell
longevity and tornado potential. Nonetheless, some strengthening of
850-mb flow during the evening may enable some mesocyclone potential
to persist, and an accompanying isolated risk for a tornado or two.
Otherwise, storms will tend to cluster with eastward extent, with
the threat for damaging gusts persisting within these bowing line
segments.

...Ohio Valley...
A somewhat secondary area of late afternoon/early evening
thunderstorm development is anticipated from central IL into central
IN and central OH. Moderate buoyancy and strong westerly flow aloft
supports the potential for isolated supercells capable of large hail
and isolated damaging gusts.

...Central/Southern High Plains...
A seasonably moist airmass will undergo strong heating/mixing and
result in moderate buoyancy by mid-late afternoon. Thunderstorm
development is expected across the higher terrain before then
progressing eastward into the lower elevations. Moderate
northwesterly flow aloft will support organized storms
structures, and large hail is possible along the Foothills.
Steep lapse rates and large temperature-dewpoint depressions will
lead to outflow-dominant storms capable of severe gusts with the
more intense cores/outflow.

...AZ...
The presence of monsoon moisture will support moderate buoyancy
across the lower elevations of south-central AZ during the late
afternoon. Scattered storms are expected to eventually develop
towards the early evening. Trends in model guidance showing a
cluster potentially evolving within an adequately moist/inverted-V
environment lend confidence in introducing a level 1 intensity
highlight for peak gusts in the 70-80 mph range.

...Southeast into northern FL...
A very moist airmass analyzed late this morning (mid to upper 70s F
surface dewpoints) will remain in place along the Gulf Coast. Strong
heating is anticipated, with high temperatures in the upper 90s
across much of the region. As surface temperatures warm, moderate
instability will develop, with scattered thunderstorms expected amid
modest low-level convergence from MS into western/southern AL and
across the FL Panhandle into northern FL. The deep low-level
moisture combined with steep low-level lapse rates will support an
isolated wind-damage threat during the mid to late afternoon.

..Smith/Wendt.. 08/19/2026


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SPC Aug 19, 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
1257 AM CDT Wed Aug 19 2026

Valid 191200Z - 201200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID MISSISSIPPI VALLEY...

...SUMMARY...
Thunderstorms with severe wind gusts and hail will be possible this
afternoon across the mid Mississippi Valley. Isolated severe gusts
and hail will also be possible from the lower to mid Missouri Valley
westward into the Great Plains. A few severe gusts could also occur
in southern Arizona and in the Southeast.

...Mid Mississippi Valley...
At mid-levels, a shortwave trough and an associated speed max will
move southeastward into the mid Mississippi Valley today. At the
surface, an outflow boundary associated with morning convection will
move southward into southern Missouri by midday. To the north of the
boundary, surface dewpoints will be in the 70s F. Moderate
instability is expected to develop in areas that are not impacted by
morning outflow. As low-level convergence becomes focused near the
boundary during the late afternoon and early evening, isolated to
scattered convective initiation is expected. From this convection,
thunderstorms will likely develop and move eastward across the mid
Mississippi. One or two organized line segments will be possible
during the evening.

Early evening RAP forecast soundings in south-central Missouri,
where the strongest instability is expected, have 0-6 km shear
around 40 knots with precipitable water near 2 inches. MLCAPE is
expected to peak in the 2500 to 3000 J/kg range with 0-3 km lapse
rates around 7.5 C/km. This environment will support a severe threat
with supercells and multicell line segments. Severe wind gusts and
hail will be the primary hazards. The severe threat could persist
into the mid to late evening, with storms that are maintained by a
low-level jet that is forecast to strengthen in southeast Missouri.

...Great Plains...
Mid-level northwesterly flow will be in place across the Great
Plains today. At the surface, dewpoints in the 60s and 70s F will
contribute to moderate destabilization over much of the region.
During the afternoon, isolated storm development will be possible
within the unstable airmass from the lower to mid Missouri Valley
southwestward into the central Plains. A few severe gusts and hail
will be possible but the storms will remain isolated due to limited
large-scale ascent. The greater convective coverage is expected
further south in the higher terrain of eastern Colorado and
northeast New Mexico. Thunderstorms will likely form due to
topographic forcing during the mid to late afternoon and move
east-southeastward into the lower elevations. Ahead of these storms,
RAP forecast soundings at 00Z in the northern Texas Panhandle and
southwest Kansas have 0-6 km shear around 40 knots with 0-3 km lapse
rates near 8 C/km, and surface-temperature dewpoint spreads
exceeding 30 degrees. This environment will support an isolated
potential for severe gusts.

...Southern Arizona...
Low-level moisture will be in place today across southern Arizona,
where surface dewpoints will be mostly in the 50s F. As surface
temperature warm, isolated to scattered convective initiation will
occur in the higher terrain of southeastern Arizona. These storms
will move west-southwestward toward an axis of instability. Steep
low to mid-level lapse rates and large temperature-dewpoint spreads
will support and isolated potential for severe gusts late this
afternoon into early evening.

...Southeast...
A very moist airmass will be in place today across the Southeast,
where surface dewpoints will be in the 70s F. As surface
temperatures warm, moderate instability will develop over much of
the region. Scattered thunderstorms are expected to develop and move
southward across parts of Mississippi and western Alabama. The deep
low-level moisture combined with steep low-level lapse rates will
support an isolated wind-damage threat during the mid to late
afternoon.

..Broyles/Thornton.. 08/19/2026


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