SPC Aug 17, 2026 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook


Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0754 AM CDT Mon Aug 17 2026

Valid 171300Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN AND CENTRAL PLAINS...AND THE SOUTHERN APPALACHIANS INTO
THE NORTH CAROLINA PIEDMONT...

...SUMMARY...
Thunderstorms with severe wind gusts and hail will be possible this
afternoon and evening across parts of the central and northern
Plains. Damaging gusts will also be possible in parts of the
southern Appalachians into the North Carolina Piedmont, Oklahoma and
Arkansas.

...Northern/Central Plains...
Modest height falls are expected across the northern Plains as
troughing over central Canada deepens. As it does, an associated
surface low will shift eastward and an attendant cold front will
push southward/southeastward across eastern MT, ND, and northwest
MN. The airmass preceding this front will be moist and strongly
unstable, with dewpoints likely in the upper 60s and MLCAPE over
2500 J/kg. Several different areas of initial development appear
possible, including along the front from eastern ND into
northwestern MN, in the vicinity of the pre-frontal trough over the
NE Panhandle vicinity, and south of the front across eastern MT.

Development across eastern ND/northwestern MN and the NE Panhandle
should progress southeastward into the corridor of greater buoyancy.
Even so, weak ascent and relatively warm mid-levels could limit both
overall storm coverage and updraft longevity. That being said,
vertical shear will be strong enough to support updraft organization
and supercell structures with any deep updrafts. Steep low-level
lapse rates and high cloud bases suggest strong gusts are the
primary severe risk, but some isolated large hail is also possible.
Widely scattered nature of the storms casts doubt regarding upscale
growth into a coherent MCS, but several separate bowing clusters
appear probable.

Thunderstorm coverage is expected to remain isolated from central
into eastern MT as well, with modest ascent attendant to a shortwave
trough progressing through the northern periphery of the western
CONUS ridging acting as the primary impetus for initiation.
Predominantly outflow-dominant storm structures are anticipated,
with strong gusts as the primary severe risk through the evening.
Convective evolution is uncertain, but these storms could continue
eastward through SD and NE overnight, reintensifying as they
interact with the stronger buoyancy expected to be in place. In
addition to strong gusts, large hail would be possible with these
storms if reintensification occurs.

...Central/Southern Appalachians into the Piedmont...
Early-morning satellite and regional radar imagery show a decaying
MCS progressing across central KY, well ahead of weak cold front
that extends from far northwest OH southwestward through far
southeast MO and northern AR. This MCS is forecast to continue
eastward throughout the day, moving through the central Appalachians
and eventually central VA. The airmass over this region is very
moist, with recent surface analysis sampling upper 60s dewpoints
over the higher terrain and low to mid 70s farther east from central
VA into the Carolina Piedmont.

General expectation is for renewed thunderstorm development along
the southern flank of the MCS, likely from far southeast KY into
Middle TN. Some reintensification is also possible farther north
over WV and downstream in northern/central VA, but buoyancy will be
lower than farther south, suggesting predominantly muted/transient
updrafts. Currently, the highest storm coverage appears most likely
across far western WV, eastern TN, and western NC. Vertical shear
will be weak, but moderate/strong buoyancy and steep low-level lapse
rates will still support the potential for damaging gusts. These
strong outflows could promote the development of several
forward-propagating line segments, where updrafts/downdrafts along
the outflows could result in additional damaging gusts.

...Oklahoma/Arkansas...
An MCS continues to progress eastward into northeast OK this
morning, with a well-defined MCV noted in radar imagery back across
far northwest OK. An associated outflow boundary currently arcs from
the leading edge of the MCS in Osage County back southwestward
through southwest OK. This MCS is forecast to weaken as it
progresses eastward this morning, with weakening outflow also moving
southeastward. A composite outflow/cold front will likely extend
from southern OK into central AR this afternoon. Low-level
convergence near this boundary will likely result in widely
scattered thunderstorms by the late afternoon. Vertical shear will
be weak, limiting storm organization. However, moderate instability,
high cloud bases, and steep low-level lapse rates will still support
the potential for isolated severe downbursts.

..Mosier/Dean.. 08/17/2026


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SPC Aug 17, 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
0102 AM CDT Mon Aug 17 2026

Valid 171200Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND NORTHERN PLAINS...AND IN THE SOUTHERN
APPALACHIANS...

...SUMMARY...
Thunderstorms with severe wind gusts and hail will be possible this
afternoon and evening across parts of the central and northern
Plains. Severe gusts will also be possible in parts of the southern
Appalachians. Isolated severe gusts may occur in parts of Oklahoma
and Montana.

...Central and Northern Plains...
At mid-levels, a subtle shortwave trough will move across the
northern Plains today, within west-northwesterly flow. Ahead of this
feature, a broad corridor of low-level moisture will be in place
over the central and northern Plains. A moist axis, with surface
dewpoints in the upper 60s and lower 70s F, will setup from
northwest Kansas north-northeastward into central Nebraska and
eastern South Dakota. Along and near the moist axis, moderate to
strong instability will develop by midday with MLCAPE likely
increasing into the 2000 to 3000 J/kg range. At the surface, a cold
front will move southeastward across the Dakotas during the day.
Low-level convergence will become maximized ahead of the front
across central Nebraska and southeast South Dakota. This will lead
to scattered convective initiation, with thunderstorms forming and
moving southeastward into the stronger instability during the late
afternoon and early evening.

RAP forecast soundings near the instability axis at 00Z from
northeastern Nebraska into eastern South Dakota have 0-6 km shear
near 40 knots with low to mid-level lapse rates in the 7 to 7.5 C/km
range. This will support supercell development and isolated large
hail production in areas that have the best overall environment.
However, a mixed mode is expected. Supercells and multicells will be
capable of severe wind gusts. The severe threat will likely continue
into the mid evening, as a somewhat large convective cluster moves
southeastward into the mid Missouri and upper Mississippi Valleys.

...Southern Appalachians...
A mid-level shortwave trough will move east-southeastward across the
Ohio and Tennessee Valleys today, reaching the southern Appalachians
by early evening. Ahead of this feature, a moist and unstable
airmass will be in place. Surface dewpoints in the 70s F will lead
to the development of moderate to strong instability by midday. At
the surface, a cold front will advance southeastward into the
southern Appalachians. Low-level convergence along the front, along
with topographic forcing, will result in scattered thunderstorm
development in the afternoon. These storms are expected to move
east-southeastward across the higher terrain of the southern
Appalachians and into the lower elevations by early evening. The
very moist and unstable air, along with 0-6 km shear in the 20 to 30
knot range will support a wind-damage threat. Severe gusts will be
most likely with short organized line segments. The severe threat
could persist into the early evening.

...Southern Plains...
At the surface, a quasi-stationary front will remain in place across
southern and western Oklahoma today. Within the post-frontal air,
surface dewpoints will be from the mid 60s to the mid 70s F. As
surface temperatures warm, moderate to strong instability will
develop along and near the most axis. The instability, combined with
sufficient deep-layer shear and 0-3 km lapse exceeding 8 C/km will
be favorable for isolated severe wet downbursts.

...Northern High Plains...
West-northwest mid-level flow will be in place in the northern High
Plains over the top of a post-frontal airmass. Surface dewpoints in
parts of central and eastern Montana will be around 50 F. MLCAPE
will increase into the 500 to 1000 J/kg range over parts of the
northern High Plains. As temperatures warm during the day,
thunderstorms are expected to form in the higher terrain of central
Montana, with isolated cells moving eastward across the upper
Missouri Valley. Very steep low to mid-level lapse rates could
support an isolated potential for severe wind gusts during the late
afternoon and early evening.

..Broyles/Thornton.. 08/17/2026


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SPC Aug 17, 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
0759 PM CDT Sun Aug 16 2026

Valid 170100Z - 171200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE
OHIO VALLEY INTO THE MID-ATLANTIC...AND ACROSS THE CENTRAL HIGH
PLAINS...

...SUMMARY...
Thunderstorms with severe wind gusts will be possible this evening
from parts of the Ohio Valley into the Mid-Atlantic. Thunderstorms
with isolated severe gusts and hail will be possible in parts of the
High Plains.

...Ohio Valley/Central Appalachians/Mid-Atlantic...
On water vapor imagery, a mid-level shortwave trough is evident in
the Ohio Valley within west-northwest flow. This feature is moving
into the central Appalachians where surface dewpoints are mostly in
the upper 60s and lower 70s F. Moderate instability is analyzed by
the RAP across much of the region. Low-level convergence is
maximized along a pre-frontal trough in the Mid-Atlantic where
isolated strong thunderstorms are ongoing. A secondary max of
convergence is located from central Kentucky into western West
Virginia, along which an organized line segment is ongoing. These
storm clusters are expected to persist for a few more hours.

Ahead of the ongoing storms, the WSR-88D VWPs at Jackson, Kentucky
and Blacksburg, Virginia have 0-6 km shear of about 30 knots with
nearly unidirectional west to northwesterly winds in the low to
mid-levels. The 00Z sounding at Roanoke, Virginia has MLCAPE around
2200 J/kg, with 0-3 km lapse rates near 7.5 C/km. This environment
will support a potential for severe wind gusts with the stronger
cells this evening.

Further west into the mid Mississippi Valley, strong thunderstorms
are currently ongoing along a gradient of moderate to strong
instability, analyzed by the RAP in eastern Missouri. The unstable
thermodynamic environment along with sufficient deep-layer shear
will support an isolated wind-damage threat for a few more hours
this evening.

...High Plains...
Mid-level flow is west-northwesterly over the High Plains this
evening. According to water vapor imagery, a shortwave trough is
located over eastern Colorado. Ahead of this feature, a moist
airmass is present over much of the central Plains, where surface
dewpoints are mostly in the 60s F. An axis of moderate instability
is analyzed by the RAP from the northern Texas Panhandle northward
into northwestern Nebraska. Along and near this axis, multiple small
clusters of strong to severe storms are ongoing. The strongest
deep-layer shear is analyzed by the RAP from east-central Colorado
northward into western Nebraska, where 0-6 km shear is estimated to
be in the 30 to 40 knot range. Within this zone, low to mid-level
lapse rates are estimated to be around 7 C/km. This environment will
be sufficient for an isolated severe threat this evening. Severe
wind gusts and hail will be the primary threats.

..Broyles.. 08/17/2026


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SPC Aug 16, 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
1144 AM CDT Sun Aug 16 2026

Valid 161630Z - 171200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE FRONT
RANGE AND CENTRAL/NORTHERN HIGH PLAINS AND OHIO
VALLEY/MID-ATLANTIC...

...SUMMARY...
Thunderstorms with damaging wind gusts will be possible this
afternoon and early evening over parts of the Ohio Valley and
Mid-Atlantic. Large hail and isolated severe wind gusts will also be
possible across the Front Range and central/northern High Plains.

...Upper Ohio Valley to Appalachians and Mid-Atlantic/Carolinas...
An MCV persists at midday across far southeast Michigan and northern
Ohio, with some recent uptick in convection ahead of it across
northern Ohio. Reference Mesoscale Discussion 1195 for short-term
details regarding a further increase in severe potential through
early/mid-afternoon within this regional corridor.

While storms have weakened, showers/cloud cover remain prevalent
near/east of the Appalachians at midday across the Mid-Atlantic
region. This will tend to limit/delay destabilization in many areas
(especially with north-northeastward extent). That said, air mass
recovery/advection is expected from the west, with ample upstream
clearing per visible satellite imagery across the Cumberland Plateau
into parts of the Allegheny Plateau. Pending the timing/location of
destabilization, some terrain/lee trough-related development may
diurnally occur, although the most prevalent/more certain scenario
may be for potentially severe storms to spread into the region this
evening. Damaging winds will be the most common hazard regionally,
although a tornado could occur, attributable to MCV-enhanced flow
and/or with any storms interacting with the effective warm front
across the Mid-Atlantic region.

...Middle Mississippi Valley including Missouri/Illinois...
An MCV over the Nebraska/Kansas/Iowa/Missouri border vicinity late
this morning will likely continue generally eastward, while probably
largely maintaining its related belt of enhanced mid-level flow as
observed from regional WSR-88D VWP data. A key downstream
uncertainty is the midday persistence of weak convection across
eastern Missouri into west/southwest Illinois, and that mid-level
lapse rates are rather poor to its north aside from some lingering
cloud cover.

More certain/greater destabilization may occur to the west across
Missouri, with the southeastward-advancing front being a focus for
renewed thunderstorm development later this afternoon and evening
amidst moderate/locally strong buoyancy. Deep-layer shear will tend
to be limited to around 30 kt in most areas, although somewhat
stronger MCV-related winds aloft may support upwards of 35-40 kt
effective shear for any storms across northern Missouri into
west-central/southwest Illinois. Bouts of damaging winds are the
most likely hazard regionally.

...Front Range/Raton Mesa and northern/central High Plains...
A relatively similar pattern/scenario as prior few days will
continue regionally, except a somewhat more northward-extent of the
severe risk (such as Black Hills vicinity) and a trend toward a more
northerly component to the flow aloft across the north-central High
Plains. At least widely scattered thunderstorm development is
expected into mid/late afternoon spanning the Front Range/Raton Mesa
vicinity northward across eastern Wyoming/southeast Montana and the
Black Hills vicinity. In the presence of upwards of 1500-2000 J/kg
MLCAPE, moderate vertical shear (30-40 kt) could support a few
supercells capable of severe hail. Isolated damaging winds will be
possible. This includes the most probable zone for gradual
upscale-growing linear cluster(s) across the south-central High
Plains/Raton Mesa vicinity including southeast Colorado/northeast
New Mexico toward the Oklahoma/Texas Panhandles and far southwest
Kansas. A couple of southeastward-moving thunderstorm clusters
capable of wind/damage may also emerge this evening out of the Black
Hills vicinity/western Nebraska.

..Guyer/Chalmers.. 08/16/2026


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