SPC Aug 29, 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
1129 AM CDT Sat Aug 29 2026

Valid 291630Z - 301200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN
NEVADA ACROSS NORTHERN UTAH INTO FAR SOUTHWEST WYOMING...

...SUMMARY...
Widely scattered strong to severe storms are expected across parts
of the northern Great Basin, northern/central Rockies, and northern
Plains. Severe wind gusts are the main threat.

...Great Basin through the central Rockies...
Enhanced mid-level southwesterly flow aloft exists between the upper
ridging centered over the southern High Plains and a shortwave
trough moving through the Pacific Northwest. 12Z SLC sounding
sampled this enhanced flow well, reporting a belt of 50-55 kt wind
around 600 to 500 mb. This sounding also sampled the increased
mid-level moisture within this belt of stronger flow, resulting
precipitable water over 1.1".

Modest heating of this airmass is expected to foster moderate
buoyancy, although the widespread cloudiness could keep the airmass
from fully destabilizing. Most RAP soundings across the region
maintain lingering convective inhibition from UT into southern WY.
Even so, the combination of modest buoyancy, mid-level moisture, and
ascent attendant to a low-amplitude shortwave trough progressing
through the region will support scattered to numerous thunderstorms
from eastern NV across UT into northwest CO/southern WY. Some
isolated hail is possible with the strongest cores (which could
briefly acquire supercellular characteristics), but the primary
severe risk is strong to severe wind gusts. Highest severe coverage
is still expected from east-central NV into northern UT where the
greatest afternoon buoyancy is forecast.

...Northeast CO/eastern WY/NE Panhandle into the western/central
Dakotas...
High-based showers and thunderstorms along the leading edge of the
strongest ascent attendant to the shortwave trough moving through
the Great Basin and central Rockies should emerge into a diurnally
destabilized and moderately buoyant airmass from northeast CO into
eastern WY and the NE Panhandle during the late afternoon/early
evening. This could result in reintensification, and a risk for both
large hail and damaging gusts across the region throughout the
evening. Most of the guidance was overly aggressive with
destabilization and buoyancy across this region yesterday, and there
is some concern that cloud cover could again limit heating. That
being said, there is a pocket of greater low-level moisture across
SD and the region is currently under widely scattered cloud cover.
Enhanced westerly flow atop low-level easterlies will support at
least moderate deep-layer shear, so any updrafts that can mature
should be able to organize, with an attendant risk for large hail
and damaging gusts.

...AZ...
12Z PHX sounding sampled moderate mid-level moisture atop warm and
dry low levels. Scattered thunderstorm development is anticipated
across much of the region. Vertical shear is weak and a largely
disorganized storm mode is anticipated. Still, given the high storm
bases and steep low-level lapse rates, isolated strong to severe
gusts are possible this afternoon and evening.

..Mosier/Moore.. 08/29/2026


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SPC Aug 29, 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
0758 PM CDT Fri Aug 28 2026

Valid 290100Z - 291200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE GREAT
BASIN...TO THE CENTRAL ROCKIES AND NORTHERN PLAINS...

...SUMMARY...
Isolated strong to severe storms are possible across the northern
Plains, and from parts of the Great Basin and Desert Southwest into
the Rockies.

...Great Basin/Rockies...
Evening water vapor imagery showed an expansive area of high
pressure centered over the Four Corners with broad southwesterly
flow aloft ongoing over much of the Great Basin and Rockies. To the
west of the ridge, an upper low and broad trough were moving onshore
across the Pacific Northwest and CA respectively. Ahead of these
features, several weaker perturbations and a plume of mid-level
moisture were contributing to widely scattered thunderstorms over
the Great Basin and central Rockies this evening.

Despite limited buoyancy owing to expansive cloud cover, plentiful
monsoon moisture should continue to support widely scattered
high-based thunderstorms this evening and into the overnight hours.
At least isolated strong to severe gusts are possible owing to dry
low-levels suitable for strong downdrafts with the established
storms/clusters. This appears most likely from far eastern NV,
across northern UT, and into central WY where the air mass remains
the warmest.

...Northern Plains...
The first of the mid-level shortwave troughs embedded within the
broader southwest flow are expected to eject eastward over the
northern Plains tonight. As ascent from the wave overspreads a warm
front, the low-level jet is forecast to strengthen (40-50 kt),
supporting a broad area of low-level warm air advection across the
eastern Dakotas into MN/IA. Elevated storms should develop near the
front with moderate buoyancy and deep-layer shear supportive of
supercells. Some hail risk is possible with these storms overnight.
Given the increasing forcing for ascent, upscale growth into a
cluster or MCS is possible, which could result in a low-probability
risk for damaging gusts over southwest MN and adjacent northwest IA
through 12z Saturday.

...Mid Atlantic to the Southeast...
Several clusters of scattered thunderstorms remain ongoing ahead of
a weak front from VA to the northern Gulf Coast. These storms have
slowly weakened through the evening and should continue to do so
with the loss of diurnal heating. Ahead of the front, high PWAT
content (2-2.5 inches) may still support a sporadic downbursts with
the stronger clusters this evening. However, weak shear and waning
diurnal buoyancy suggest an organized or expansive severe threat is
unlikely.

..Lyons.. 08/29/2026


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SPC Aug 28, 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
0242 PM CDT Fri Aug 28 2026

Valid 282000Z - 291200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
CENTRAL/NORTHERN PLAINS...GREAT BASIN AND DESERT SOUTHWEST INTO THE
NORTHERN ROCKIES...NORTH GEORGIA INTO THE CAROLINAS AND
MID-ATLANTIC...AND PARTS OF CENTRAL/EASTERN MAINE...

...SUMMARY...
Isolated strong to severe storms are possible across the central and
northern Plains, northern Georgia into the Carolinas and
Mid-Atlantic, central and eastern Maine, and from parts of the Great
Basin and Desert Southwest into the northern Rockies.

...20z Update...
The previous forecast largely remains on track with only minor edits
required - primarily to the general thunder line to reflect recent
convective trends. Weak/poorly organized convection ongoing across
the Mid-Atlantic and portions of Maine should continue to pose a
localized severe threat (mainly damaging wind) through late
afternoon. See MCDs #2162 and #2163 for additional short-term
details. Transient downbursts have been noted across the greater
Houston, TX area over the past 1-2 hours as thunderstorms develop
along the sea breeze. While small swaths of damaging wind may occur
with the more intense downbursts, this threat is expected to remain
fairly transient given poor deep-layer wind shear across the region
(wind speeds are generally 15 knots or less through the column per
regional VWPs).

Across the Great Basin, slight expansions of the 5% wind
probabilities were made to better reflect trends in recent
time-lagged CAM guidance. Some of the more aggressive solutions -
notably recent runs of the RRFS - hint at one or more corridors of
higher severe wind potential across eastern WY into SD as high-based
convection encounters richer low-level moisture/buoyancy over the
Plains. However, these solutions are exhibiting a considerable warm
bias compared to current observations and suggest that any residual
inhibition should be mixed out by this point in the day. Latest GOES
imagery and regional 18z soundings both depict lingering inhibition,
which casts considerable uncertainty onto the accuracy of the more
aggressive solutions.

..Moore.. 08/28/2026

.PREV DISCUSSION... /ISSUED 1130 AM CDT Fri Aug 28 2026/

...Maine...
Morning surface analysis places a low over eastern Quebec, with a
cold front extending southward from this low through northern NY
before arcing more southwestward and becoming increasingly diffuse
across the Upper OH Valley. A shortwave trough is forecast to
progress through southern Quebec towards the St. Lawrence Valley
today. The surface low is forecast to eject northeastward in
response, with its attendant cold front sweeping eastward across ME.
A moist airmass precedes this front, with current observations
sampling mid to upper 60s dewpoints. This airmass should destabilize
amid filtered daytime heating ahead of the front, although poor
mid-level lapse will limit the overall buoyancy. Scattered
thunderstorm development is anticipated as the cold front interacts
with this modestly buoyant airmass. A few strong to severe storms
are possible, but deep-layer shear largely parallel to the frontal
boundary will contribute to a predominantly linear mode and a likely
trend toward undercutting of new updrafts. Even so, any updrafts
that can mature could organize, potentially becoming supercell
storms capable of locally wind gusts and hail.

...Mid-Atlantic into Georgia...
Morning surface analysis places a low off the southern New England
coast and another over southern NJ (near the ongoing thunderstorms).
A weak front extends through these two lows, continuing
southwestward across the Carolina Piedmont into northern GA. Widely
scattered thunderstorms are expected to form along
the front this afternoon, with slow-moving but strong storms
possible. The stronger (but still modest) deep-layer shear will
occur across VA and NC, with the stronger buoyancy displaced farther
south across SC and GA. Even so, the expectation is that a
combination of moderate CAPE, high PWAT values, and limited
deep-layer shear will promote isolated strong storms capable of
water-loaded downbursts.

...Great Basin through Wyoming..
A belt of stronger mid-level flow currently extends from central CA
through the northern Rockies between the upper troughing over
western Canada and the upper ridging centered over the Four Corners.
Low-amplitude shortwave troughs embedded within this enhanced flow,
and associated ascent and mid-level moisture, will contribute to
thunderstorm development this afternoon. A deeply mixed boundary
layer is anticipated throughout much of this region, suggesting any
of the stronger, more persistent storms could produce damaging
gusts. Highest storm coverage is expected from eastern NV into
central/northern UT, resulting in a relatively greater threat for
damaging gusts within this corridor.

...Dakotas into western Minnesota and northern Iowa...
There could potentially be two rounds of convection across the
northern Plains today. The first will be with any of the high-based
convection from WY as it spreads eastward into western
Dakotas, where greater low-level moisture and buoyancy will be in
place. The greater buoyancy could result in reintensification and a
few bowing structures capable of producing locally damaging wind
gusts and hail.

Additional warm-air advection associated development is then
possible later this evening as the low-level jet strengthens over
the Plains. These elevated storms should develop within an
environment characterized by moderate buoyancy and deep-layer shear,
suggesting a few supercells capable of large hail are possible
initially. Over time, some upscale growth is possible, which could
result in a low-probability risk for damaging gusts over southwest
MN and adjacent northwest IA early tomorrow morning.


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SPC Aug 28, 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
1130 AM CDT Fri Aug 28 2026

Valid 281630Z - 291200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
CENTRAL/NORTHERN PLAINS...GREAT BASIN AND DESERT SOUTHWEST INTO THE
NORTHERN ROCKIES...NORTH GA INTO THE CAROLINAS AND
MID-ATLANTIC...AND PARTS OF CENTRAL/EASTERN ME......

...SUMMARY...
Isolated strong to severe storms are possible across the central and
northern Plains, northern Georgia into the Carolinas and
Mid-Atlantic, central and eastern Maine, and from parts of the Great
Basin and Desert Southwest into the northern Rockies.

...Maine...
Morning surface analysis places a low over eastern Quebec, with a
cold front extending southward from this low through northern NY
before arcing more southwestward and becoming increasingly diffuse
across the Upper OH Valley. A shortwave trough is forecast to
progress through southern Quebec towards the St. Lawrence Valley
today. The surface low is forecast to eject northeastward in
response, with its attendant cold front sweeping eastward across ME.
A moist airmass precedes this front, with current observations
sampling mid to upper 60s dewpoints. This airmass should destabilize
amid filtered daytime heating ahead of the front, although poor
mid-level lapse will limit the overall buoyancy. Scattered
thunderstorm development is anticipated as the cold front interacts
with this modestly buoyant airmass. A few strong to severe storms
are possible, but deep-layer shear largely parallel to the frontal
boundary will contribute to a predominantly linear mode and a likely
trend toward undercutting of new updrafts. Even so, any updrafts
that can mature could organize, potentially becoming supercell
storms capable of locally wind gusts and hail.

...Mid-Atlantic into Georgia...
Morning surface analysis places a low off the southern New England
coast and another over southern NJ (near the ongoing thunderstorms).
A weak front extends through these two lows, continuing
southwestward across the Carolina Piedmont into northern GA. Widely
scattered thunderstorms are expected to form along
the front this afternoon, with slow-moving but strong storms
possible. The stronger (but still modest) deep-layer shear will
occur across VA and NC, with the stronger buoyancy displaced farther
south across SC and GA. Even so, the expectation is that a
combination of moderate CAPE, high PWAT values, and limited
deep-layer shear will promote isolated strong storms capable of
water-loaded downbursts.

...Great Basin through Wyoming..
A belt of stronger mid-level flow currently extends from central CA
through the northern Rockies between the upper troughing over
western Canada and the upper ridging centered over the Four Corners.
Low-amplitude shortwave troughs embedded within this enhanced flow,
and associated ascent and mid-level moisture, will contribute to
thunderstorm development this afternoon. A deeply mixed boundary
layer is anticipated throughout much of this region, suggesting any
of the stronger, more persistent storms could produce damaging
gusts. Highest storm coverage is expected from eastern NV into
central/northern UT, resulting in a relatively greater threat for
damaging gusts within this corridor.

...Dakotas into western Minnesota and northern Iowa...
There could potentially be two rounds of convection across the
northern Plains today. The first will be with any of the high-based
convection from WY as it spreads eastward into western
Dakotas, where greater low-level moisture and buoyancy will be in
place. The greater buoyancy could result in reintensification and a
few bowing structures capable of producing locally damaging wind
gusts and hail.

Additional warm-air advection associated development is then
possible later this evening as the low-level jet strengthens over
the Plains. These elevated storms should develop within an
environment characterized by moderate buoyancy and deep-layer shear,
suggesting a few supercells capable of large hail are possible
initially. Over time, some upscale growth is possible, which could
result in a low-probability risk for damaging gusts over southwest
MN and adjacent northwest IA early tomorrow morning.

..Mosier/Moore.. 08/28/2026


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