SPC Aug 18, 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 Mon Aug 17 2026

Valid 180100Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL AND NORTHERN PLAINS...AND FROM NORTHEASTERN ALABAMA INTO
WESTERN NORTH CAROLINA...

...SUMMARY...
Thunderstorms with severe wind gusts and large hail are expected
this evening across parts of the central and northern Plains.
Isolated severe gusts will also be possible from parts of the
northern Gulf Coast States into the southern Appalachians and
Carolinas.

...Central and Northern Plains...
The latest water vapor imagery shows west-northwesterly flow over
much of the northern U.S., with a low-amplitude shortwave trough
moving through the flow in the northern Plains. At the surface, a
cold front is advancing southeastward through the Dakotas. Ahead of
the front, surface dewpoints are in the 60s F. The RAP has an axis
of moderate to strong instability located from central Nebraska
northeastward into eastern South Dakota, along which MLCAPE is
estimated in the 2500 to 3500 J/kg range. Isolated thunderstorms are
ongoing near the instability axis with scattered storms ongoing to
the west of the instability max in western Nebraska and southwestern
South Dakota.

These storms are located along the eastern edge of an elevated mixed
layer extending eastward from the central Rockies. Near the storms,
the RAP is estimating 700-500 mb lapse rates in the 7.5 to 8.5 C/km
range. In addition, the North Platte WSR-88D VWP has 0-6 km shear
near 50 knots with significant directional shear evident in the
lowest 3 km above ground level. This environment will support
supercells with large hail and severe wind gusts this evening. The
more intense storms could produce hailstones exceeding 2 inches in
diameter. Short-term model forecast suggest that the storms will
continue to move east-southeastward toward the instability axis this
evening, remaining relatively discrete. However, a transition to a
broken line segment should eventually occur, which would result in a
greater wind-damage threat. A few severe gusts above 75 mph will be
possible. The severe threat should persist into the mid to late
evening...See MCD 2019.

...Northern Gulf Coast States/Southern Appalachians/Carolinas...
The latest surface analysis shows a distinct outflow boundary from
northern Alabama eastward into the western Carolinas. Strong to
severe thunderstorms are ongoing near the outflow boundary. To the
south of the boundary, surface dewpoints are in the 70s F and the
RAP is estimating MLCAPE in the 2000 to 3500 J/kg range. Within the
most unstable air, RAP forecast soundings early this evening have
0-3 km lapse rate in the 7.5 to 8 C/km range, with precipitation
water above 2 inches. In addition, the WSR-88D VWP in northeast
Alabama has 0-6 km shear in the 20 to 25 knot range. This
environment will support a potential for severe wet downbursts for a
couple more hours this evening.

..Broyles.. 08/18/2026


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SPC Aug 17, 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
1152 AM CDT Mon Aug 17 2026

Valid 171630Z - 181200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTH-CENTRAL PLAINS/UPPER MIDWEST AND SOUTHERN APPALACHIANS...

...SUMMARY...
Thunderstorms with severe wind gusts and large hail are expected
this afternoon and evening across parts of the central and northern
Plains. Damaging gusts will also be possible in parts of the
southern Appalachians to the North Carolina Piedmont, and possibly
across portions of the Mid-South and southern Plains.

...Northern/Central Plains...
Weak height falls are expected regionally with a seasonally
prominent strengthening of northwesterly flow aloft. A surface low
will shift eastward and an attendant cold front will push
southward/southeastward across eastern Montana, North Dakota and
toward west/northwest Minnesota. The airmass preceding this front
will be moist and strongly unstable, with dewpoints in the upper 60s
and MLCAPE over 2500 J/kg. Multiple areas of initial development are
expected, including along the front from eastern Dakotas into
western Minnesota, and in the vicinity of the pre-frontal trough
and/or front over the NE Panhandle vicinity, southern South Dakota,
and southeast Montana/far eastern Wyoming.

Mid/Late-afternoon storm development in each of these areas will
progress into zones of greater buoyancy by evening. Some initial
supercells capable of large hail are expected, especially given the
strength of the deep-layer wind profiles, while steep low-level
lapse rates and high cloud bases will support strong wind gust
potential, especially with the possibility that storms may
cluster/organize this evening across Nebraska/southern South Dakota,
and possibly across Siouxland and western Minnesota.

...Central/Southern Appalachians into the Piedmont...
Within a very moist airmass, renewed thunderstorm development is
expected along the southern flank of a remnant thunderstorm cluster
and in vicinity of the higher terrain/mountains this afternoon.
Vertical shear will not be overly strong, but moderate/strong
buoyancy and steep low-level lapse rates will still support the
potential for damaging wind gusts. These strong outflows could
promote the development of several
forward-propagating/southeast-moving line segments with a persistent
potential for wind damage, at least through early evening.

...Oklahoma/Arkansas to Mid-South...
Aided by an MCV, a small cluster of storms with a morning history of
occasional severe-caliber winds continues at midday across northwest
Arkansas. For additional short-term details, see Mesoscale
Discussion 2010. While not certain or perhaps likely, a general
eastward-persistence of this cluster could occur. Additional
isolated storm development may occur regionally later this afternoon
along the remnant outflow and/or front, with steep low-level lapse
rates and ample buoyancy supportive of damaging downburst potential
through around sunset.

..Guyer/Chalmers.. 08/17/2026


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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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