SPC Aug 27, 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 Thu Aug 27 2026

Valid 271630Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID-ATLANTIC/NORTHEAST...THE CENTRAL PLAINS...AND CENTRAL
MONTANA...

...SUMMARY...
Scattered strong to severe thunderstorms are possible across parts
of the Northeast and Mid-Atlantic today. Damaging winds, severe
hail, and a tornado or two may accompany these thunderstorms. Large
to very large hail and severe gusts are also possible across parts
of northern High Plains and central Plains.

...Mid-Atlantic/Northeast...
Recent surface analysis places a low over western Quebec, with a
cold front arcing from this low southwestward through the middle OH
Valley, western TN Valley and then westward across central AR and
central OK. Satellite imagery reveals a shortwave trough extending
from northeastern Ontario through western PA, just west of the
analyzed surface low. There also appears to be a more subtle
shortwave trough farther south moving through WV towards VA.

Expectation is for the primary shortwave trough and cold front to
continue eastward, interacting with the very moist airmass across
the Northeast to support thunderstorm development this afternoon.
12Z ILN and PIT soundings sampled the moderate westerly flow aloft,
supporting the potential for strong multicells along both the cold
front and pre-frontal troughing. A few supercells are possible if
warm sector development can mature without too much interaction with
other convection. Primary risk will be damaging gusts, although the
modestly cool temperatures aloft (i.e. -10 to -12 deg C at 500-mb)
suggest some hail is possible as well.

A somewhat displaced area of earlier thunderstorm development is
manifesting across the northern Mid-Atlantic. As mentioned in MCD
#2145, a broken band of thunderstorms is ongoing as of mid-morning
from the New York City vicinity southwest toward Baltimore, with
that activity potentially being aided by forcing for ascent
associated with the subtle shortwave trough moving into VA. Airmass
across this region is very moist, and instability is steadily
building under modest diurnal heating. Most guidance suggests this
activity gradually increases in coverage and intensity over the next
few hours. The presence of a vertically veering wind profile
with around 30 to 35 kt of effective bulk shear would support a
conditional risk for embedded supercell structures capable of
locally damaging winds, marginally severe hail, and perhaps a brief
tornado.

...Northern Rockies/High Plains...
Recent satellite imagery depicts a shortwave trough progressing
across eastern OR towards ID and western MT. Moderate mid-level
moisture and forcing for ascent associated with this wave are
forecast to initiate thunderstorms across the northern Rockies this
afternoon. This activity is then forecast to progress northeastward
off the higher terrain into central MT, where a deeply mixed airmass
is forecast to be in place. Despite this deep mixing and somewhat
limited low-level moisture, the mid-level moisture associated with
the shortwave will allow for at least modest buoyancy (i.e. MLCAPE
over 500 J/kg). This should support storm maintenance off the
terrain, with a trend towards outflow-dominant bowing segments with
time. Primary severe risk is damaging gusts, including the potential
for gusts from 65 to 75 mph.

...Central Plains...
Moist southerly flow will help maintain moderate low-level moisture
through the NE Panhandle and into southwest SD amid the strong
heating and boundary-layer mixing expected this afternoon.
Additionally, this modest, but persistent, warm-air advection is
likely to force convective initiation this afternoon over the
western NE/SD border vicinity. Low-level southerly flow veering to
moderate northwesterlies aloft will support deep-layer shear of 40
to 50 kt, more than adequate for supercell development with any
mature convective. Any sustained supercells will be capable of
producing large hail (some 2+ inches) as they track
south-southeastward through the late afternoon into the evening.
Upscale growth into one or more bowing segments appears likely this
evening, with strong to severe gusts (65 to 75 mph) possible.

An isolated threat for severe hail/gusts may also exist
farther west/south across the CO Front Range to Raton Mesa vicinity.
Weaker buoyancy and deep-layer shear should keep any more organized
updrafts confined to the higher terrain and Foothills.

-- No other changes needed to the outlook with the text for the
additional areas appended from the 13Z Outlook below --

...Great Basin...
High-based thunderstorms should also develop this afternoon across
portions of northeast NV into northwest UT and southeast ID. While
low/mid-level winds and related thunderstorm organization will
likely be somewhat weaker/limited compared to areas farther north,
steep lapse rates and large DCAPE will support potential for strong
to severe outflow gusts as this convection spreads northeastward
into the early evening.

...South-Central/Coastal Texas into Southern Louisiana...
Ongoing thunderstorms across southern LA may pose a threat for gusty
winds this morning before they move offshore. Additional
thunderstorms may develop this afternoon from parts of south-central
TX towards the upper TX Coast, with isolated severe/damaging
downburst winds possible given ample moisture/instability forecast.
Weak deep-layer shear should limit the overall severe threat.

..Mosier/Chalmers.. 08/27/2026


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SPC Aug 27, 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
1255 AM CDT Thu Aug 27 2026

Valid 271200Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID-ATLANTIC AND NORTHEAST...AND ALSO ACROSS PARTS OF
WESTERN/CENTRAL NE INTO NORTHWEST KS...

...SUMMARY...
Scattered strong to severe thunderstorms are possible across parts
of the Northeast today. Damaging wind, hail and a tornado or two may
accompany these storms. Large to very large hail and severe gusts
are also possible across parts of western Nebraska and northwest
Kansas.

...Mid-Atlantic/Northeast into parts of the central/southern
Appalachians...
An upper trough will remain in place over much of the eastern CONUS
today. Moderate destabilization will be possible along/ahead of a
weak surface trough/front extending from central NY/PA into the
central/southern Appalachians. Scattered thunderstorm development is
expected by mid/late afternoon, with sufficient deep-layer
flow/shear for some storm organization (especially from the northern
Mid-Atlantic into the Northeast). The strongest cells/clusters will
be capable of producing scattered damaging winds and at least
isolated hail. Modestly enlarged low-level hodographs may also
support some brief-tornado potential. Some severe threat may persist
into the evening before storms weaken and/or move offshore.

Father south, deep-layer flow/shear will be weaker into parts of the
central/southern Appalachians, but scattered storm development
within a relatively warm and well-mixed environment will support
potential for localized strong/damaging gusts.

...Central Plains...
Moderate to locally strong destabilization is expected across parts
of the central High Plains this afternoon, beneath modest
northwesterly mid/upper-level flow. While large-scale ascent will
generally remain rather modest, a subtle midlevel vorticity maximum
may aid in isolated to widely scattered storm development from far
southwest SD into western/central NE. Deep-layer shear will be
sufficient for supercells, with steep lapse rates and relatively
elongated hodographs supporting potential for large to very large
hail, in addition to a threat for localized severe gusts. 00Z CAM
guidance shows some uptick in storm coverage within this favorable
environment, and a 15% hail area has been added for parts of
west-central NE into northwest KS. Some guidance (notably the 00Z
HRRR) also shows upscale growth and an attendant swath of
severe-wind potential, though this scenario remains more uncertain.
Greater wind probabilities may eventually be needed if confidence
increases in the MCS scenario.

Surrounding the Level-2/Slight Risk, a more isolated threat of
severe hail and wind may accompany the strongest cells from parts of
the Raton Mesa and CO Front Range vicinity into eastern WY.

...Western/central Montana...
Despite rather limited low-level moisture, widely scattered storm
development is expected this afternoon across parts of
western/central MT, aided by strong heating and the influence of a
midlevel shortwave trough and jet maximum that are forecast to crest
the amplified upper ridge that is covering much of the interior
West. Steep lapse rates will support potential for localized
downbursts and strong to severe outflow gusts as storms spread
east-northeastward across MT.

...Northeast NV/northwest UT/southeast ID...
High-based storm development is also expected from parts of
northeast NV into northwest UT and southeast ID. While deep-layer
flow and storm organization will likely be somewhat weaker compared
to areas farther north, steep lapse rates and large DCAPE will
support potential for strong to severe outflow gusts from this
afternoon into the early evening.

...South-central TX into the LA Gulf Coast region...
Uncertainty remains regarding how far south an ongoing storm cluster
and its attendant outflow will move across parts of LA/MS early this
morning. If this cluster persists to the beginning of the forecast
period (as forecast by the 00Z HRRR), then a localized wind-damage
threat will be possible near the immediate LA/MS Gulf Coast before
storms move offshore. If the cluster weakens and more substantial
recovery and diurnal destabilization occurs later today (as forecast
by more recent HRRR runs and some other HREF members), then storm
redevelopment will be possible by afternoon, potentially aided by a
remnant MCV. This scenario could also result in a localized
wind-damage threat.

Farther west, scattered storm development is forecast across
south-central TX this afternoon, near a weak southward-moving cold
front. Deep-layer shear will likely remain quite weak, but moderate
buoyancy, large PW, and steep low-level lapse rates will support
potential for localized downbursts. Despite the weak shear, the
northerly flow regime may result in one or more outflow-driven
clusters that will move southward into the early evening before
weakening.

..Dean/Weinman.. 08/27/2026


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SPC Aug 26, 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
0259 PM CDT Wed Aug 26 2026

Valid 262000Z - 271200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN GREAT LAKES/MIDWEST...CENTRAL HIGH PLAINS...AND
OZARKS/MID SOUTH INTO THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Isolated to widely scattered severe thunderstorms are forecast today
across parts of the southern Great Lakes into the Midwest,
central/southern High Plains, and the Ozarks into the Mid-South and
Lower Mississippi Valley. Severe/damaging winds should be the main
threat across these regions, though large hail is also possible,
particularly across the central High Plains.

...20z Update...

...Central Great Plains...
Visible satellite imagery depicts an area of agitated cumulus
developing in close proximity to a weak surface boundary across
eastern Colorado. Recent HRRR/RRFS runs are split on the evolution
of this convection, with the HRRR suggesting minimal thunderstorm
development and the RRFS depicting the development of a
southeastward-propagating cluster. This scenario remains uncertain;
however, the 5% wind probabilities have been expanded southeastward
to account for the potential for a cluster of thunderstorms to
evolve from this region. See MCD 2139 for additional short-term
information.

...Mid-South and Lower Great Lakes...
Severe probabilities were trimmed slightly across portions of
northeastern IL, northwestern IN, and southwestern MI in the wake of
ongoing convection and the passage of a surface cold front. Severe
probabilities were also trimmed across portions of the Mid South
where increased low-level static stability owing to outflow from
prior convection casts uncertainty on additional convective
development this afternoon/evening.

Elsewhere, the forecast remains largely on track with only minor
changes made to the existing outlook. See the text below for
additional information.

..Chalmers/Thornton.. 08/26/2026

.PREV DISCUSSION... /ISSUED 1127 AM CDT Wed Aug 26 2026/

...Mid-South/TN Valley...
An MCS continues to push gradually southward/southeastward across
western and middle TN. The downstream airmass is heating and
destabilizing, but vertical shear remains weak and the overall
system has not strengthened notably in the past hour.
Destabilization across the region is strongest from the Mid-South
into the Lower MS Valley, where dewpoints are largely in the mid
70s. Less low-level moisture is noted from middle TN into northern
AL, but airmass destabilization is still anticipated amid modest
heating. The general expectation is for the MCS to continue, but
with new and/or stronger updrafts likely trending towards the
western flank where the buoyancy is greatest. Even then, the lack of
stronger vertical shear suggests an outflow-dominant mode with
minimal organization. As such, sporadic damaging gusts are possible,
particularly via updraft augmentation via storm interactions, but
the current magnitude and orientation of the wind probability seems
sufficient.

...Arklatex across much of AR into the Mid-South/Lower MS Valley...
A somewhat separate area of thunderstorm development is anticipated
this afternoon west of what was discussed in the previous paragraph,
although some interaction between these two regimes may occur over
the Mid-South vicinity. Recent surface observations depict a surface
low along the central TX/OK border (in the GYI/DUA vicinity). This
low is forecast to progress gradually eastward into a moist and
diurnally destabilized airmass from the Arklatex across much of AR
and northern LA. A weak MCV, noted in visible satellite imagery,
lags behind this surface low, and could augment ascent as it too
moves eastward. Low-level convergence on a stalled frontal boundary
that extends across central AR as well as along a front approaching
northern AR this evening could act as additional mechanisms for
thunderstorm initiation. All of these factors will likely result in
scattered to numerous thunderstorms across the region.

Modest deep-layer shear should support some updraft organization,
with multicell clusters likely the dominant mode. High total
precipitable water values and large buoyancy will support robust
downbursts capable of damaging wind gusts. Strong buoyancy could
support occasional hail as well. Clustering may eventually result in
several bowing segments this evening. As such, there is potential
for at least isolated damaging winds to persist across parts of
southern LA/MS.

...Southern Great Lakes into the Midwest...
Satellite imagery continues to show a well-defined shortwave trough
moving across the Upper Great Lakes. Primary surface low associated
with this system is occluded over northwest Ontario, but a secondary
triple point low is moving across Upper MI. This system is forecast
to move eastward today, with the attendant cold front progressing
southeastward. Modest low-level moisture advection and heating ahead
of this front will result in a corridor of moderate to strong
buoyancy from central IL northeastward into southern Lower MI.
Thunderstorm development is anticipated within this corridor this
afternoon.

Low/mid-level winds will tend to remain fairly modest and veered,
but 25-35 kt of deep-layer shear should foster some updraft
organization. A mix of multicell clusters and marginal supercells
should pose a threat for both hail and damaging winds, with the wind
threat potentially becoming the primary risk with eastward extent
into the Midwest as thunderstorms grow upscale. Veered low-level
flow should keep the tornado potential low. The overall severe
threat will likely diminish quickly this evening as convection
outpaces the low-level moisture/instability, and nocturnal cooling
stabilizes the boundary layer.

...Central High Plains...
Low levels across the central High Plains are currently
characterized by dewpoints in the upper 50s and low 60s. Modest
low-level upslope flow will help maintain this low-level moisture
through the afternoon. This moisture combined with diurnal heating
and steep mid-level lapse rates will result in airmass
destabilization and moderate buoyancy by the late afternoon.
Additionally, southern periphery of the enhanced northwesterly flow
extending from the northern Plains into the Mid MS Valley will be
over the central High Plains, resulting in 25 to 35 kt of effective
bulk shear. Late afternoon thunderstorm development is anticipated
within this environment, with some isolated supercells possible.
Hail will be the primary risk initially, particularly across the CO
Foothills. A trend towards clustering and more damaging wind
potential is expected as this activity spreads east-southeastward
through the evening.

...Southern High Plains...
Mid-level flow and related deep-layer shear should be somewhat
weaker than areas farther north. Still, convection that develops
across central into eastern NM may become loosely organized while
posing an isolated threat for severe gusts given the presence of a
very well-mixed boundary layer. This threat may continue into parts
of the OK/TX Panhandles and west TX through the evening before
eventually weakening.


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SPC Aug 26, 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
1127 AM CDT Wed Aug 26 2026

Valid 261630Z - 271200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN GREAT LAKES/MIDWEST...CENTRAL HIGH PLAINS...AND
OZARKS/MID-SOUTH INTO THE LOWER MISSISSIPPI VALLEY...

...SUMMARY...
Isolated to widely scattered severe thunderstorms are forecast today
across parts of the southern Great Lakes into the Midwest,
central/southern High Plains, and the Ozarks into the Mid-South and
Lower Mississippi Valley. Severe/damaging winds should be the main
threat across these regions, though large hail is also possible,
particularly across the central High Plains.

...Mid-South/TN Valley...
An MCS continues to push gradually southward/southeastward across
western and middle TN. The downstream airmass is heating and
destabilizing, but vertical shear remains weak and the overall
system has not strengthened notably in the past hour.
Destabilization across the region is strongest from the Mid-South
into the Lower MS Valley, where dewpoints are largely in the mid
70s. Less low-level moisture is noted from middle TN into northern
AL, but airmass destabilization is still anticipated amid modest
heating. The general expectation is for the MCS to continue, but
with new and/or stronger updrafts likely trending towards the
western flank where the buoyancy is greatest. Even then, the lack of
stronger vertical shear suggests an outflow-dominant mode with
minimal organization. As such, sporadic damaging gusts are possible,
particularly via updraft augmentation via storm interactions, but
the current magnitude and orientation of the wind probability seems
sufficient.

...Arklatex across much of AR into the Mid-South/Lower MS Valley...
A somewhat separate area of thunderstorm development is anticipated
this afternoon west of what was discussed in the previous paragraph,
although some interaction between these two regimes may occur over
the Mid-South vicinity. Recent surface observations depict a surface
low along the central TX/OK border (in the GYI/DUA vicinity). This
low is forecast to progress gradually eastward into a moist and
diurnally destabilized airmass from the Arklatex across much of AR
and northern LA. A weak MCV, noted in visible satellite imagery,
lags behind this surface low, and could augment ascent as it too
moves eastward. Low-level convergence on a stalled frontal boundary
that extends across central AR as well as along a front approaching
northern AR this evening could act as additional mechanisms for
thunderstorm initiation. All of these factors will likely result in
scattered to numerous thunderstorms across the region.

Modest deep-layer shear should support some updraft organization,
with multicell clusters likely the dominant mode. High total
precipitable water values and large buoyancy will support robust
downbursts capable of damaging wind gusts. Strong buoyancy could
support occasional hail as well. Clustering may eventually result in
several bowing segments this evening. As such, there is potential
for at least isolated damaging winds to persist across parts of
southern LA/MS.

...Southern Great Lakes into the Midwest...
Satellite imagery continues to show a well-defined shortwave trough
moving across the Upper Great Lakes. Primary surface low associated
with this system is occluded over northwest Ontario, but a secondary
triple point low is moving across Upper MI. This system is forecast
to move eastward today, with the attendant cold front progressing
southeastward. Modest low-level moisture advection and heating ahead
of this front will result in a corridor of moderate to strong
buoyancy from central IL northeastward into southern Lower MI.
Thunderstorm development is anticipated within this corridor this
afternoon.

Low/mid-level winds will tend to remain fairly modest and veered,
but 25-35 kt of deep-layer shear should foster some updraft
organization. A mix of multicell clusters and marginal supercells
should pose a threat for both hail and damaging winds, with the wind
threat potentially becoming the primary risk with eastward extent
into the Midwest as thunderstorms grow upscale. Veered low-level
flow should keep the tornado potential low. The overall severe
threat will likely diminish quickly this evening as convection
outpaces the low-level moisture/instability, and nocturnal cooling
stabilizes the boundary layer.

...Central High Plains...
Low levels across the central High Plains are currently
characterized by dewpoints in the upper 50s and low 60s. Modest
low-level upslope flow will help maintain this low-level moisture
through the afternoon. This moisture combined with diurnal heating
and steep mid-level lapse rates will result in airmass
destabilization and moderate buoyancy by the late afternoon.
Additionally, southern periphery of the enhanced northwesterly flow
extending from the northern Plains into the Mid MS Valley will be
over the central High Plains, resulting in 25 to 35 kt of effective
bulk shear. Late afternoon thunderstorm development is anticipated
within this environment, with some isolated supercells possible.
Hail will be the primary risk initially, particularly across the CO
Foothills. A trend towards clustering and more damaging wind
potential is expected as this activity spreads east-southeastward
through the evening.

...Southern High Plains...
Mid-level flow and related deep-layer shear should be somewhat
weaker than areas farther north. Still, convection that develops
across central into eastern NM may become loosely organized while
posing an isolated threat for severe gusts given the presence of a
very well-mixed boundary layer. This threat may continue into parts
of the OK/TX Panhandles and west TX through the evening before
eventually weakening.

..Mosier/Chalmers.. 08/26/2026


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