SPC Sep 13, 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
1139 AM CDT Sun Sep 13 2026

Valid 131630Z - 141200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE
NORTHEAST...

...SUMMARY...
Isolated to widely scattered severe thunderstorms will be possible
across parts of the upper Ohio Valley into the Northeast this
afternoon and evening. Isolated strong to severe thunderstorms may
also occur across parts of the central and northern High Plains.

...Northeast and upper/middle Ohio Valley...
Have upgraded portions of the region to a categorical Slight Risk
with expectations of a semi-focused regional corridor of wind damage
later this afternoon through early evening. Within large-scale upper
troughing over eastern Canada, a strong west-southwesterly mid-level
jet will overspread the Great Lakes into the Ohio Valley and
Northeast later today into tonight. A surface cold front will
likewise track eastward across these regions through tonight. A
seasonably moist low-level airmass will be in place ahead of the
cold front, but poor lapse rates aloft (around 6-6.5 C/km) and cloud
cover should limit the degree of destabilization that can occur this
afternoon, although cloud cover has tended to thin/abate since early
this morning across the upper Ohio Valley. While the main influence
of the upstream upper-level trough will not arrive until this
evening, strengthening mid-level flow through the day will support
35-45 kt of deep-layer shear and the potential for organized bands
of convection.

At least widely scattered thunderstorms are expected to develop
along/ahead of the front by mid afternoon (around 19-22Z) from parts
of Ohio into western New York, and then spread quickly eastward
across the upper Ohio Valley into the Northeast. The deep-layer
shear will be strong enough for some supercells initially, with
perhaps a marginal/isolated hail threat even with the poor lapse
rates present aloft. But, clusters/bowing segments with an isolated
damaging wind threat should quickly develop given the linear forcing
of the front. This convection is forecast to weaken with eastward
extent this evening with the onset of nocturnal cooling, and as it
encounters a less unstable airmass.

...Wyoming and central/northern High Plains to Missouri Valley...
A closed mid/upper-level low over the Pacific Northwest this morning
will move eastward to the northern Rockies/High Plains through the
period. Diurnal destabilization will generally be limited ahead of
this low, though a narrow zone of weak instability may develop by
late afternoon across southern Wyoming, and across northeast
Colorado into the Nebraska Panhandle in a modest low-level upslope
flow regime. Isolated thunderstorm development is expected with
sufficient wind profiles for isolated severe hail/wind potential.

Elevated thunderstorms should again increase in coverage across
western/central South Dakota towards the mid Missouri Valley late
tonight into early Monday morning. Moderate MUCAPE and sufficient
cloud-layer shear could support an isolated hail threat with the
initial development across western/southern South Dakota, though
mergers/interactions and weakening buoyancy will likely limit the
longevity and eastward extent of this threat into the mid Missouri
Valley.

..Guyer/Weinman.. 09/13/2026


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SPC Sep 13, 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
0744 AM CDT Sun Sep 13 2026

Valid 131300Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE OHIO VALLEY INTO THE NORTHEAST...AND THE CENTRAL/NORTHERN HIGH
PLAINS...

...SUMMARY...
Strong to locally severe thunderstorms will be possible across parts
of the upper Ohio Valley into the Northeast this afternoon and
evening. Isolated strong to severe thunderstorms may also occur
across parts of the central and northern High Plains.

...Ohio Valley into the Northeast...
Within large-scale upper troughing over eastern Canada, a strong
west-southwesterly mid-level jet will overspread the Great Lakes
into the OH Valley and Northeast by this evening. A surface cold
front will likewise track eastward across these regions through the
period. While a seasonably moist low-level airmass will be in place
ahead of the cold front, poor lapse rates aloft (around 6-6.5 C/km)
and cloud cover should limit the degree of destabilization that can
occur this afternoon. Still, even with the thermodynamic environment
remaining marginal, strengthening mid-level flow through the day
will support 35-45 kt of deep-layer shear and the potential for
organized convection.

Current expectations are for isolated to scattered thunderstorms to
develop along/ahead of the front by mid afternoon (around 19-22Z)
from parts of OH into western NY, and then spread quickly eastward
across the upper OH Valley into the Northeast. The deep-layer shear
will be strong enough for supercells initially, with perhaps a
marginal/isolated hail threat even with the poor lapse rates present
aloft. But, clusters/bowing segments with an isolated damaging wind
threat should quickly develop given the linear forcing of the front.
This convection is forecast to weaken with eastward extent this
evening with the onset of nocturnal cooling, and as it encounters a
less unstable airmass. Confidence in a corridor of greater damaging
wind potential remains too low for higher severe wind probabilities
at this time.

...Central/Northern High Plains into the Mid Missouri Valley...
A closed mid/upper-level low over the Pacific Northwest this morning
will move eastward to the northern Rockies/High Plains through the
period. Diurnal destabilization will generally be limited ahead of
this low, though a narrow zone of weak instability may develop by
late afternoon from northeast CO into southeast WY and the NE
Panhandle in a modest low-level upslope flow regime. Isolated
thunderstorm development appears possible across this area, with
sufficient deep-layer shear for transient updraft organization and
isolated severe hail/wind potential.

While any diurnally developing convection will likely weaken through
the evening with the loss of daytime heating, elevated thunderstorms
should increase in coverage across western/central SD towards the
mid MO Valley late tonight into early Monday morning. Moderate
MUCAPE and sufficient cloud-layer shear could support an isolated
hail threat with the initial development across western SD, though
mergers/interactions and weakening buoyancy will likely limit the
longevity and eastward extent of this threat into the mid MO Valley.

...Long Island/Southern New England...
Bands of precipitation with embedded thunderstorms are ongoing this
morning across NJ into southern NY/New England. This activity is
being aided by ascent associated with a low-amplitude mid-level
shortwave trough. As this feature develops northeastward through the
early afternoon, continued low-level warm/moist advection will occur
across Long Island into southern New England. Most guidance
continues to show minimal surface-based instability over land, with
generally elevated thunderstorms expected. Still, given the modestly
enhanced low-level flow/shear forecast, trends will be monitored for
signs of surface-based instability/thunderstorm potential.

..Gleason/Lyons.. 09/13/2026


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SPC Sep 13, 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
1258 AM CDT Sun Sep 13 2026

Valid 131200Z - 141200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
OHIO VALLEY INTO THE NORTHEAST...AND ALSO ACROSS PARTS OF THE
CENTRAL/NORTHERN HIGH PLAINS...

...SUMMARY...
Strong to locally severe storms are possible across parts of upper
Ohio Valley and Northeast this afternoon and evening. Isolated
strong to severe storms are also possible across parts of the
central and northern High Plains.

...Parts of the Ohio Valley to the Northeast...
A mid/upper-level trough is forecast to amplify as it moves across
the Great Lakes region toward the Northeast through tonight. A
surface low will move across Quebec, as a trailing cold front moves
through the eastern Great Lakes and Northeast this afternoon and
evening. The strongest deep-layer flow and large-scale ascent will
tend to lag the cold front, but some strengthening of flow in the
700-500 mb layer is expected across the warm sector this afternoon,
resulting in favorable wind profiles for organized convection.

Moderate buoyancy is expected to develop by late afternoon as CINH
weakens, and widely scattered storm development is eventually
expected along/ahead of the front. Despite the favorable wind
profiles, weak midlevel lapse rates and modest ascent may tend to
limit updraft intensity. Guidance continues to vary regarding the
magnitude of severe potential, with the 00Z HRRR/RRFS more
aggressive in developing organized convection (and possible
supercells), while other HREF guidance depicts generally weak
convection.

Localized damaging wind and isolated hail may accompany the
strongest storms. If later observational and guidance trends support
the more aggressive scenario, then greater severe probabilities may
eventually be needed.

...Central/northern High Plains...
A mid/upper-level low/trough initially over the Pacific Northwest
will move toward the northern Rockies and High Plains through the
period. Diurnal destabilization will generally be limited ahead of
this trough, though a narrow zone of moderate buoyancy may develop
by late afternoon from northeast CO into southeast WY and the NE
Panhandle. Isolated storm development will be possible, with
sufficient deep-layer shear for at least transient storm
organization and isolated severe hail/wind potential.

While any diurnal storms may tend to weaken through the evening,
elevated convection is expected to increase in coverage across
western/central SD tonight. Moderate elevated buoyancy and
sufficient effective shear could support an isolated severe threat
with the initial elevated storm development across western SD,
though storm interference and weakening buoyancy may tend to limit
the longevity and eastward extent of the threat.

...Parts of MT into northwest ND...
Increasing ascent associated with the approaching mid/upper-level
low/trough will result in elevated storm development this evening
across MT, which will spread into northwest ND overnight. Generally
weak buoyancy is currently expected to limit organized severe
potential, though small hail and locally gusty winds could accompany
the strongest storms.

..Dean/Halbert.. 09/13/2026


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SPC Sep 13, 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
0745 PM CDT Sat Sep 12 2026

Valid 130100Z - 131200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTH-CENTRAL PLAINS...

...SUMMARY...
Strong to severe storms capable of severe wind gusts and isolated
hail remain possible tonight across parts of the south-central
Plains.

...South-central Plains and vicinity...
Isolated strong to severe storms are ongoing this evening from
southwest KS into northwest OK and the TX Panhandle, with another
persistent storm cluster across eastern KS. Earlier storm
development across central/northwest OK was driven by very strong
heating in the vicinity of an outflow boundary, within a regime of
generally weak deep-layer flow/shear. This activity is expected to
generally weaken through late evening, due to the onset of nocturnal
cooling/stabilization. However, isolated hail and strong to severe
gusts will remain possible with any remaining storms through
mid/late evening.

Another surface boundary is located across southern KS, with moist
low-level easterly flow in place between this boundary and the
outflow boundary across OK. Short-term CAM guidance continues to
depict persistence of strong to locally severe storms through late
evening within this regime from southern KS into far northern OK and
perhaps southwest MO, potentially aided by a modest strengthening of
the nocturnal low-level jet. While this convection may tend to
become increasingly elevated with time, favorable lapse rates and
buoyancy and sufficient deep-layer shear (as depicted on the 00Z DDC
sounding) will support vigorous cells and perhaps a loosely
organized cluster, with potential for strong to severe gusts and
isolated hail.

See MCDs 2290 and 2291 for more information regarding the short-term
threats in this region.

..Dean.. 09/13/2026


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