SPC Aug 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
1124 AM CDT Fri Aug 21 2026

Valid 211630Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS...MIDWEST...LOWER MS VALLEY...AND CAROLINAS...

...SUMMARY...
Scattered severe thunderstorms capable of producing large hail (some
2+ inches) and severe winds may occur over parts of the central
Plains into the Midwest this afternoon and evening. Damaging winds
will also be possible with scattered to numerous thunderstorms
across portions of the Carolinas and northern Gulf Coast states.

...Central Plains into the Midwest...
A northwest flow regime will result in a weakly forced and in a
limited confidence severe setup across the central Plains. Ongoing
widely scattered storm activity may persist and reinvigorate during
the afternoon, or new development occurs along residual outflow as
the airmass becomes moderately to strongly unstable. Forecast
sounding profiles show moist low levels beneath steep 700-500 mb
lapse rates amid veering and strengthening flow with height. Large
hail (some 2+ inches) would be a threat with any sustained
supercells along with severe gusts (60-75 mph). If a small cluster
can eventually develop, the severe-wind hazard would likely focus
with these potential storms.

A small west to east oriented band of storms is moving south across
southern WI to the east of a weak surface low and immediately
downstream of an associated mid-level perturbation. While effective
bulk shear is forecast to remain fairly modest (around 20-30 kt), a
mix of multicells and marginal supercells is expected to develop
later this afternoon across parts of southern WI into
northern/central IL along and ahead of a weak front. Severe hail
may occur with any persistent cells, while the threat for damaging
winds should increase as small clusters form and spread
east-southeastward through the early evening. While low-level
flow is not forecast to become overly strong, sufficient veering
with height through low/mid levels should exist to support modest
low-level hodograph curvature and some risk for a brief tornado.

...Carolinas...
Weakened shower/thunderstorm activity associated with an MCV over
the western Carolinas will likely dissipate during the early
afternoon. However, renewed storm development is forecast in
proximity to this upper disturbance, as well as near residual
outflow from the earlier convection and a surface cool front draped
from the GA/SC Piedmont northeastward into the coastal plain of
eastern NC. Strong heating of a seasonably moist boundary layer
will result in strong instability by mid afternoon. Sufficient
deep-layer shear for some organized multicell potential will be
greatest near the upper-level feature. Farther southeast near the
SC Low Country, weaker flow will result in a pulse thunderstorm
mode. Scattered damaging gusts are possible with the stronger
thunderstorms through the early evening before nocturnal stability
weakens storms and ends the severe threat.

...North TX east into northern Gulf Coast states...
Antecedent outflow from overnight storm clusters over the lower MS
Valley and AL will serve as a focus for storm development this
afternoon. Farther west, a more pronounced decaying MCS and
associated southward-moving MCV over east-central OK will also focus
storm activity across east TX into western LA. The 12 UTC Little
Rock raob showed a belt of enhanced flow around the 4-5 km layer
(35-40 kt). Other than a localized corridor where moderate
northerly flow will overspread a strongly destabilizing boundary
layer, slightly weaker northerly to northeasterly flow will
encompass this larger region from north TX to Mobile Bay.
Nonetheless, the development of very steep 0-3 km lapse rates (9 deg
C/km) by early to mid afternoon and high PW (1.75-2.0 inches) will
support scattered wind damage with the more intense downdrafts (most
likely and concentrated from east TX through southern MS).

...Northern Great Basin into the Snake Valley...
A mid-level vorticity max rotating northward around the western
periphery of the Four Corners upper high, will move into northern
NV/UT by late afternoon. Deep inverted-V profiles will develop by
mid afternoon with a dry sub-cloud layer featuring large surface
temperature-dewpoint spreads. A linear cluster of storms is
expected to evolve and move north across the NV/UT/ID vicinity
during the late afternoon and early evening. Evaporatively cooled
downdrafts will be potentially capable of severe gusts 60-75 mph.

..Smith/Chalmers.. 08/21/2026


Read more CHECK UPDATE ZOOM GRAPHIC


http://dlvr.it/TV6nk9

SPC Aug 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
1256 AM CDT Fri Aug 21 2026

Valid 211200Z - 221200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CENTRAL PLAINS...THE MIDWEST AND THE CAROLINAS...

...SUMMARY...
Scattered damaging hail (some greater than 2 inch diameter) and
severe wind gusts may occur over parts of the central Plains this
afternoon and evening. Scattered storms, some with severe wind gusts
and hail, also are possible across parts of the Midwest. Scattered
to numerous storms with damaging wind guts are possible over the
Carolinas and Southeast.

...Central Plains...
Mid-level ridging over the western US is forecast to intensify,
strengthening northwesterly flow aloft over much of the central US.
Several embedded disturbances will pass overhead with the enhanced
northwesterlies through the day. A surface low will move
southeastward through the Great Lakes as a weak trailing cold front
moves southward through the central Plains and Midwest.

Ahead of the front, a plume of steep mid-level lapse rates will
shift eastward across the central Plains toward the Mid-MO Valley
atop a corridor of rich low-level moisture. Diurnal destabilization
should result in 3000-4000 J/kg of MLCAPE from SD to NE. Isolated to
widely scattered thunderstorm development is expected from the Black
Hills southeastward along the cold front. Elongated/straight
hodographs and 45+ kt effective shear will favor initial supercells.
Large to very large hail (some greater than 2 inches diameter) will
be possible. With time, a forward propagating cluster or two may
develop and move southeast across parts of NE and KS with the
potential for severe gusts (a few near 70-80 mph). It is unclear
exactly how far southeast any storms will persist overnight, but any
more substantial clustering could allow at least an isolated severe
threat to continue into early Saturday.

A much drier and hotter environment over the High Plains to the west
could also support isolated to widely scattered high-based storms
from eastern CO into western KS. Very steep lapse rates in the
lowest 2-3 km with modest buoyancy aloft could allow a few severe
gusts.

...Midwest...
Beneath the upper trough over the western Great Lakes, cool
mid-level temperatures and robust surface moisture should result in
moderate destabilization from WI into eastern IA and northwest IL.
Scattered thunderstorms by mid afternoon ahead of the cold front
spreading southeastward. Enhanced northwesterly flow with deep-layer
shear of 30-40 kt will promote a mix of organized clusters and
supercells. The large buoyancy will support a risk for damaging
gusts and some hail.

...Southeast and Gulf Coast...
A broad upper trough will move across the central US into parts of
the southern Appalachians while a weak cold front moves southward
from the mid Atlantic today and tonight. Weak ascent from the upper
trough and near the front should focus diurnal thunderstorm activity
across the Carolians and southern Appalachians. Warm surface
temperatures and plentiful boundary-layer moisture will support
large buoyancy (3000+ J/kg MLCAPE) through the afternoon and evening
despite modest mid-level lapse rates. With scattered to numerous
storms expected, a few organized clusters may emerge with a risk
primarily for damaging wind gusts. Slight enhancement of the
westerly flow aloft could also support some isolated hail with the
stronger updrafts.

Farther south and west, a very humid and warm air mass is forecast
to become strongly unstable by early afternoon across the lower MS
Valley and Gulf Coast. Scattered to numerous thunderstorms are
expected along prior outflows and a weak, southward moving cold
front from East TX into LA/MS. The very strong buoyancy and high
PWAT content will support clustering and strong downdrafts with
sporadic damaging gust potential. Otherwise, weak vertical shear
will limit overall organization.

..Lyons/Weinman.. 08/21/2026


Read more CHECK UPDATE ZOOM GRAPHIC


http://dlvr.it/TV6H92

SPC Aug 20, 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
0255 PM CDT Thu Aug 20 2026

Valid 202000Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE MID-ATLANTIC...PARTS OF THE SOUTHEAST...AND FROM THE CENTRAL
PLAINS INTO THE UPPER MISSISSIPPI VALLEY...

...SUMMARY...
Scattered severe storms are possible this afternoon into this
evening across parts of the Mid Atlantic, posing a risk for a couple
of tornadoes and damaging wind gusts. Large hail and isolated wind
damage will be possible late today into tonight with severe storms
from Nebraska into northwest Wisconsin. Scattered damaging gusts
are possible over parts of the Deep South this afternoon into the
early evening.

...20z Update...
The previous forecast largely remains on track with only minor
adjustments made based on recent convective trends and recent
guidance. Regional radar mosaics show the development of discrete
and semi-discrete supercells across the northern MD into southern PA
ahead of a mid-level perturbation and weak cold front. The recent 18
UTC IAD sounding sampled modest buoyancy (around 1000 J/kg MLCAPE),
which seems to be more marginal compared to recent RAP mesoanalysis
MLCAPE depictions. Nonetheless, strong shear was sampled by this
RAOB, including just under 200 m2/s2 effective SRH. This environment
likely exists downstream into far southeast PA and western NJ and
warranted a slight northward expansion of the CIG1 tornado contour.
Confidence in convective coverage with southwestward extent into
southern VA and NC remains limited based on trends in
radar/satellite trends and latest high-res guidance. Other forecast
thoughts outlined in the previous discussion below remain on track.

...Northern MS/AL...
Convection is developing along/ahead of a weak surface front and
mid-level wave across southeast AR into northern MS. This aligns
well with recent guidance, especially RRFS solutions, which depict
increasing thunderstorm coverage through early evening. Wind and
hail probabilities have been adjusted slightly across northern
AL/southern TN to reflect these solutions and capture areas where
air mass recovery continues.

...Northern MN...
A surface low is becoming apparent in surface observations and GOES
visible imagery across northern MN with early stages of convection
noted over the past 45 minutes. With 64-66 F dewpoints spreading
north towards north-central MN, some potential exists for more
robust convection than previously depicted by guidance. Recent
RRFS/HRRR time-lagged ensembles have also trended slightly north
with the strongest UH signals, which matches these recent
observations and warranted a northward expansion of probabilities.

Elsewhere, the forecast outlined below remains on track. See MCD
#2053 for additional short-term details regarding the near-term
severe threat across north-central NE.

..Moore.. 08/20/2026

.PREV DISCUSSION... /ISSUED 1133 AM CDT Thu Aug 20 2026/

...Central Appalachians into the Mid-Atlantic...
Radar mosaic late this morning showed a couple of weak convectively
related vorticity maxima moving east across the central and southern
Appalachians (i.e., southwest PA, eastern KY). One of these lead
disturbances was sampled by the WSR-88D VAD at Jackson, KY, with an
upstream shortwave trough over the OH Valley moving towards the
Mid-Atlantic states.

The airmass across the Mid-Atlantic into the Carolinas will continue
to heat amid patchy but thinning cloud cover. Model guidance shows
moderate buoyancy developing by early to mid afternoon from the
southern Appalachians northward into the northern Mid-Atlantic
region. A belt of stronger 700-500 mb westerly flow (30-45 kt) will
overspread the northern half of VA northward into PA/NJ. Beneath
this stronger flow, southerly low-level flow veering and
strengthening with height will support hodographs favorable for
organized severe storms, including supercells and organized line
segments. The latest model guidance shows a few simulated
supercells developing in the area centered over MD and the upper
Chesapeake Bay vicinity during the 20-00z timeframe. This scenario
seems plausible given some low-level enlargement to the hodograph
and effective shear around 40 kt. A tendency for upscale growth
into a line segment is expected as this activity moves east towards
the coast during the evening. A couple of supercell tornadoes are
possible with this activity, in addition to a line-embedded
mesovortex and scattered damaging gusts.

...Carolinas into the TN Valley and lower MS Valley...
Ample low-level moisture and strong heating will result in an
unstable airmass from the Carolinas into much of the Southeast.
Low-level convergence along a cold front that will extend from the
western Carolinas into AR this afternoon will result in scattered
thunderstorm coverage as 2500-4000 J/kg MLCAPE develops by mid
afternoon. High PW (in excess of 2 inches) and steep 0-3 km lapse
rates and modest westerly to west-northwesterly flow will favor
damaging downbursts with the stronger southeast-moving clusters.

...Central Plains into the Upper MS Valley...
A tongue of relatively rich low-level moisture (mainly 60s F surface
dewpoints) will extend from the central Great Plains northward ahead
of a cold front, which is forecast to be draped from western MN into
western NE this afternoon. Thunderstorm initiation is anticipated
first across the Upper MS Valley before expanding southwestward.

Moderate northwesterly flow aloft will support supercell wind
profiles, with elongated/straight hodographs, and the threat for all
severe hazards. Large to very large hail (i.e. greater than 2 inch
diameter) will be the primary severe hazard, particularly during the
early evening as the storms move into greater instability. Isolated
strong to severe gusts (i.e. 55 to 75 mph) are possible as well.
Given the supercellular storm mode and low-level southerly flow, a
low-probability tornado risk also exists. Some risk for isolated
damaging gusts may persist into the early overnight across southern
NE and northern KS if clustering can
occur.

...AZ...
Not much change from prior forecast thinking in that isolated to
widely scattered storms are forecast but a generally lower risk for
severe gusts is anticipated later today into this evening. Steep
lapse rates and inverted-V profiles will support an isolated risk
for severe gusts with the more intense downdrafts.


Read more CHECK UPDATE ZOOM GRAPHIC


http://dlvr.it/TV6863

SPC Aug 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
1133 AM CDT Thu Aug 20 2026

Valid 201630Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE MID-ATLANTIC...PARTS OF THE SOUTHEAST...AND FROM THE CENTRAL
PLAINS INTO THE UPPER MISSISSIPPI VALLEY...

...SUMMARY...
Scattered severe storms are possible this afternoon into this
evening across parts of the Mid Atlantic, posing a risk for a couple
of tornadoes and damaging wind gusts. Large hail and isolated wind
damage will be possible late today into tonight with severe storms
from Nebraska into northwest Wisconsin. Scattered damaging gusts
are possible over parts of the Deep South this afternoon into the
early evening.

...Central Appalachians into the Mid-Atlantic...
Radar mosaic late this morning showed a couple of weak convectively
related vorticity maxima moving east across the central and southern
Appalachians (i.e., southwest PA, eastern KY). One of these lead
disturbances was sampled by the WSR-88D VAD at Jackson, KY, with an
upstream shortwave trough over the OH Valley moving towards the
Mid-Atlantic states.

The airmass across the Mid-Atlantic into the Carolinas will continue
to heat amid patchy but thinning cloud cover. Model guidance shows
moderate buoyancy developing by early to mid afternoon from the
southern Appalachians northward into the northern Mid-Atlantic
region. A belt of stronger 700-500 mb westerly flow (30-45 kt) will
overspread the northern half of VA northward into PA/NJ. Beneath
this stronger flow, southerly low-level flow veering and
strengthening with height will support hodographs favorable for
organized severe storms, including supercells and organized line
segments. The latest model guidance shows a few simulated
supercells developing in the area centered over MD and the upper
Chesapeake Bay vicinity during the 20-00z timeframe. This scenario
seems plausible given some low-level enlargement to the hodograph
and effective shear around 40 kt. A tendency for upscale growth
into a line segment is expected as this activity moves east towards
the coast during the evening. A couple of supercell tornadoes are
possible with this activity, in addition to a line-embedded
mesovortex and scattered damaging gusts.

...Carolinas into the TN Valley and lower MS Valley...
Ample low-level moisture and strong heating will result in an
unstable airmass from the Carolinas into much of the Southeast.
Low-level convergence along a cold front that will extend from the
western Carolinas into AR this afternoon will result in scattered
thunderstorm coverage as 2500-4000 J/kg MLCAPE develops by mid
afternoon. High PW (in excess of 2 inches) and steep 0-3 km lapse
rates and modest westerly to west-northwesterly flow will favor
damaging downbursts with the stronger southeast-moving clusters.

...Central Plains into the Upper MS Valley...
A tongue of relatively rich low-level moisture (mainly 60s F surface
dewpoints) will extend from the central Great Plains northward ahead
of a cold front, which is forecast to be draped from western MN into
western NE this afternoon. Thunderstorm initiation is anticipated
first across the Upper MS Valley before expanding southwestward.

Moderate northwesterly flow aloft will support supercell wind
profiles, with elongated/straight hodographs, and the threat for all
severe hazards. Large to very large hail (i.e. greater than 2 inch
diameter) will be the primary severe hazard, particularly during the
early evening as the storms move into greater instability. Isolated
strong to severe gusts (i.e. 55 to 75 mph) are possible as well.
Given the supercellular storm mode and low-level southerly flow, a
low-probability tornado risk also exists. Some risk for isolated
damaging gusts may persist into the early overnight across southern
NE and northern KS if clustering can
occur.

...AZ...
Not much change from prior forecast thinking in that isolated to
widely scattered storms are forecast but a generally lower risk for
severe gusts is anticipated later today into this evening. Steep
lapse rates and inverted-V profiles will support an isolated risk
for severe gusts with the more intense downdrafts.

..Smith/Wendt.. 08/20/2026


Read more CHECK UPDATE ZOOM GRAPHIC


http://dlvr.it/TV5zDc