SPC AC 231221
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0721 AM CDT Mon Jun 23 2025
Valid 231300Z - 241200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
PLAINS INTO THE UPPER MS VALLEY AND UPPER GREAT LAKES...
...SUMMARY...
Storms with isolated severe wind gusts and hail will be possible
today from the southern and central Plains northeastward into the
Great Lakes.
...Central Plains into the Upper MS Valley and Upper Great Lakes...
Early-morning satellite imagery shows a shortwave trough progressing
through ND and southern SK/MB. Surface analysis places the low
associated with this shortwave over far northwestern ON, with an
attendant cold front arcing from this low through the MN arrowhead
and back through south-central MN, northwest IA,
eastern/south-central NE to another low in northwest KS. Showers and
thunderstorms are ongoing along this frontal zone from northeast NE
into southern MN.
Expectation is for the shortwave trough to continue northeastward
through far northwest ON throughout the day, with the primary
surface low also tracking northeastward just ahead of its parent
shortwave. Gradual eastward/southeastward progress of the cold front
is anticipated, although its forward progression will slow with
time, particularly from the Mid MO Valley southwestward into the
southern High Plains. A warm and moist airmass exists ahead of this
front, with temperatures expected to reach the mid 80s to low 90s
amid dewpoints in the upper 60s to low 70s. These conditions will
result in strong buoyancy and little to no convective inhibition
along much of the front by 21Z.
Large-scale forcing for ascent will be negligible, but persist
low-level convergence should be enough to initiate deep convection,
with numerous to widespread thunderstorms anticipated. The stronger
deep-layer vertical shear will lag behind the front across much of
the region, but steep low-level lapse rates and ample moisture
should still result in sporadic damaging gusts. There will be better
overlap between the shear and buoyancy from WI into MI, and there is
some chance for one or more forward-propagating line segments in
this area. Some isolated hail is possible within the more robust
early-stage storms. Storm mergers could also result in updrafts
briefly becoming strong enough to produce hail.
...Southern and Central High Plains...
Numerous thunderstorms are expected to develop during the afternoon
amid persistent low-level convergence within the warm, moist, and
weakly sheared airmass over the region. The lack of stronger shear
will result in largely outflow-dominant storm structures. Given the
high cloud bases and steep low-level lapse rates, damaging gusts are
possible with the stronger storms.
...Northern ME...
A convectively augmented vorticity maximum currently over
northeastern ON is forecast progress eastward through southern QC
and into the Canadian Maritimes during the period. Showers and
thunderstorms will accompany this vorticity max, with a few stronger
storms potentially glancing northern ME this evening. Moderately low
to mid-level westerly flow will support the threat for some damaging
gusts as these storms move through the region.
...Southeast...
Scattered to numerous diurnally driven thunderstorm are expected
across the region today. Shear will be weak, with a multicellular
pulse mode anticipated. Given the ample moisture and likelihood of
storm interactions, a few strong, water-loaded downbursts are
possible. Limited coverage precludes the need for any severe
probabilities.
..Mosier/Leitman.. 06/23/2025
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
SPC AC 230600
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Mon Jun 23 2025
Valid 241200Z - 251200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR EASTERN
WY...NORTHEAST CO...AND PARTS OF WESTERN NE/SD...
...SUMMARY...
Severe storms are possible Tuesday from eastern Wyoming into
southwest South Dakota, the Nebraska Panhandle, and northeast
Colorado. Isolated strong to severe storms will also be possible
from parts of the central Plains and Midwest into the Northeast.
...Synopsis...
A mid/upper-level shortwave trough is forecast to move from the
Southwest into the northern Rockies on Tuesday. Downstream, a strong
mid/upper-level trough will move across parts of Ontario and Quebec,
resulting in some dampening of the persistent upper ridge over the
East.
At the surface, a warm front will move northward across parts of the
central Plains, while the eastern portion of the front will be
draped somewhere from the Midwest into the southern Great Lakes
vicinity. A cold front will move southward across parts of the
northern Great Lakes and Northeast/New England.
...WY/CO into western NE/SD...
Increasing low-level moisture beneath generally steep midlevel lapse
rates will support moderate destabilization across parts of eastern
WY into northeast CO. Veering wind profiles will support organized
storms, and isolated to widely scattered supercells may develop from
late afternoon into the evening. Large to very large hail, localized
severe gusts, and perhaps a tornado are all possible. Some upscale
growth will be possible through the evening, which could spread at
least an isolated severe threat into parts of western NE/SD. The
longevity of the severe threat into Tuesday night is uncertain, due
to increasing low-level stability.
...Lower MO River Valley into the Midwest and Great Lakes...
In the wake of morning convection, strong heating/destabilization
will support development of strong to potentially severe storms from
parts of eastern KS/southeast NE into the Midwest and Great Lakes,
along the periphery of the upper ridge. Development will likely be
focused near an outflow-influenced front, and potentially near any
remnant MCVs. Deep-layer shear is expected to be relatively weak
along/ahead of the front, but unidirectional southwesterly flow will
support potential for outflow-driven clusters capable of locally
damaging wind.
Corridors of greater severe threat may eventually evolve within the
broad Marginal Risk across this region, but confidence in the
placement of the front and any MCVs or other vorticity maxima
precludes higher probabilities at this time.
...Parts of the Northeast/New England...
Midlevel lapse rates will be weak, but relatively strong heating
will support moderate buoyancy by afternoon across parts of the
Northeast, along and ahead of the cold front. Stronger ascent and
deep-layer flow will remain north of the front, but sufficient flow
and steepening of low-level lapse rates will support a threat of
damaging gusts with any strong storms across the region. Storm
coverage is uncertain, but greater severe probabilities may
eventually be needed if trends support more than isolated storm
development during the afternoon and evening.
...Southeast into the Carolinas and Mid Atlantic...
A remnant EML will gradually move southwestward along the periphery
of the upper ridge across parts of the Carolinas, Mid Atlantic, and
Southeast on Tuesday. While this will support strong buoyancy, there
is a considerable amount of spread regarding storm coverage across
this region Tuesday. At this time, the highest confidence in storm
development is over the southern Appalachians, where deep-layer
shear will be negligible underneath the upper ridge. If confidence
in storm coverage increases where slightly stronger flow aloft will
be present, severe probabilities may eventually be needed.
..Dean.. 06/23/2025
WUUS02 PTSDY2
SPC AC 230742
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0242 AM CDT Mon Jun 23 2025
Valid 251200Z - 261200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN A CORRIDOR
FROM THE NORTHERN HIGH PLAINS INTO THE MIDWEST AND NORTHEAST...AND
ALSO ACROSS PARTS OF THE SOUTHEAST...
...SUMMARY...
Strong to potentially severe storms are possible Wednesday in a
corridor from the northern High Plains into the Midwest and
Northeast, and also across parts of the Southeast.
...Synopsis...
An upper ridge is forecast to persist across parts of the Ohio
Valley and Southeast on Wednesday, with some gradual weakening of
the ridge expected through the forecast period. Multiple
low-amplitude midlevel shortwave troughs will move along the western
and northern periphery of the ridge, from the central/northern
Plains into the Upper Midwest and Great Lakes. Along the southern
periphery of the ridge, a slow-moving mid/upper-level low will is
forecast to approach Florida from the Bahamas.
...Parts of the central/northern Plains into the Upper Midwest...
A remnant MCS may be ongoing somewhere from the north-central Plains
into parts of southern MN/northern IA Wednesday morning. This system
is currently expected to gradually diminish with time as the
nocturnal low-level jet weakens. A localized severe could accompany
this remnant MCS through part of the morning.
In the wake of this MCS, diurnal heating of a richly moist
environment will support strong destabilization near an
outflow-reinforced front. Storm development will be possible along
this front/outflow by late afternoon, with MLCAPE potentially in
excess of 3000 J/kg supporting vigorous updrafts. Deep-layer flow
will be relatively modest, though locally backed winds near the
boundary could support initial supercell development, before storm
clustering becomes more prominent with time. Damaging winds,
isolated hail, and possibly a tornado could accompany the strongest
afternoon/evening storms. A corridor of greater severe probabilities
may eventually be needed, if confidence increases regarding the
evolution of morning convection and placement of remnant surface
boundaries.
Farther west, a relatively moist post-frontal regime could again
support strong to potentially severe storms across parts of the
central/northern High Plains. There is some potential for this
region to be in the wake of a departing midlevel shortwave trough
during the afternoon and evening, making diurnal storm coverage
uncertain. Deep-layer shear will be sufficient for at least an
isolated severe threat in the region during the afternoon and
evening.
...Lower Great Lakes into the Mid Atlantic/Northeast...
Scattered storm development will be possible Wednesday afternoon
across parts of the lower Great Lakes into the Mid Atlantic and
Northeast, along/south of a cold front. While temperatures aloft
will be rather warm, diurnal heating will support moderate to
locally strong buoyancy. Deep-layer flow/shear is forecast to be
relatively weak, but unidirectional west-northwesterly flow could
support outflow-dominant clusters capable of at least isolated wind
damage.
...Parts of the Southeast/Carolinas...
A pocket of steep midlevel lapse rates will be in place across parts
of the Southeast and Carolinas on Wednesday. The favorable lapse
rates combined with strong diurnal heating of a very moist airmass
will result in development of strong to extreme instability by
afternoon. With some further weakening of the upper ridge, storm
coverage may increase compared to previous days.
20-30 kt of northeasterly flow aloft will also develop across parts
of the region, to the northwest of the offshore upper low. This
modestly enhanced flow could support at least transient storm
organization within the very unstable environment. Damaging winds
and isolated hail will be possible within this regime. Any loosely
organized clustering could result in localized corridors of more
concentrated wind damage.
..Dean.. 06/23/2025
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1930Z
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