RSS Mesoscale Discussions from Storm Prediction Center
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1245 AM CDT Sat Jul 12 2025
Valid 121200Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS IN THE CENTRAL
GREAT LAKES TO THE LOWER OH VALLEY...
...SUMMARY...
Scattered damaging winds are most probable across eastern Lower
Michigan to the Lower Ohio Valley, mainly from mid-afternoon through
dusk.
...Great Lakes...
A shortwave trough centered on the MB/ON to Dakotas/MN borders will
take on an increasingly negative tilt as it ejects across northwest
ON and the Upper Great Lakes. Ahead of this feature, a convectively
aided shortwave impulse should dampen as it accelerates
north-northeast through the central Great Lakes into northeast ON by
early afternoon. Belts of enhanced mid-level southwesterlies will be
confined to WI/MI.
Ongoing convection from Lake MI to MO is expected to largely decay
this morning. Some guidance suggests reinvigoration may occur in the
late morning across northern Lower into eastern Upper MI as the lead
shortwave impulse passes. Primary storm development along an initial
composite cold front/outflow is anticipated by mid to late afternoon
from parts of eastern Lower MI towards the Wabash/Lower OH Valleys.
Ample buoyancy will be prevalent ahead of this boundary despite warm
mid-level temperatures. Unidirectional southwesterlies and nearly
uniform wind speeds through much of the kinematic profile will limit
deep-layer shear and the degree of organized clustering. Still, the
setup will be adequate for mainly a scattered damaging wind threat
that will subside after dusk in parts of OH/KY.
Isolated severe hail/damaging winds may also develop along the
secondary cold front pushing east across northern/eastern WI and
upper MI. Cooling mid-level temperatures will aid in weak MLCAPE of
500-1000 J/kg this afternoon. Westerly low-level wind profiles will
modulate the degree of deep-layer shear and help to marginalize the
overall threat.
...OK/TX/NM/CO...
Multiple areas of ongoing thunderstorms from southern NE to the TX
Panhandle are expected to persist and shift south-southeastward this
morning. Differential diabatic heating in vicinity of remnant
MCVs/outflows and orographic forcing for ascent will be the primary
drivers of storm development today. Convection across OK/TX will
probably persist and gradually intensify in tandem with downstream
boundary-layer heating. Within predominately weak deep-layer shear,
slow-moving and mainly disorganized updrafts will dominate. Sporadic
strong to marginal severe gusts along with small to marginally
severe hail will be possible in a mix of cells/clusters.
Modestly enhanced mid/upper-level north-northwesterlies over the
higher terrain of NM/CO should aid in weak/transient updraft
rotation as numerous cells develop during the afternoon. Isolated
severe hail will be possible regionwide, with isolated severe gusts
mainly across interior to southern NM.
...Mid-South/TN Valley to the southern Piedmont...
A pulse storm environment characterized by weak effective bulk shear
but moderate buoyancy will support a threat for erratic wet
microbursts from mid-afternoon to early evening.
..Grams/Thornton.. 07/12/2025
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SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1216 AM CDT Sat Jul 12 2025
Valid 131200Z - 141200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM VIRGINIA
INTO NEW YORK...AND EASTERN OKLAHOMA INTO SOUTHERN MISSOURI...
...SUMMARY...
Marginally severe thunderstorms producing strong wind gusts will be
possible across the eastern U.S. from the mid-Atlantic region
northward into upstate New York. Additional isolated strong storms
may occur from eastern Oklahoma into southern Missouri.
...Discussion...
Broad cyclonic flow aloft will envelop the northern Plains to the
Northeast as an upper shortwave trough meanders east while
de-amplifying on Sunday. Over the southern Plains, a weak upper low
may stall over the region.
A seasonally very moist boundary layer will extend across much of
the southern Plains to the Midwest and into the Eastern Seaboard,
providing areas of moderate instability. However, stronger vertical
shear will remain displaced to the north, near the international
border, limiting overlap of instability with wind profiles
sufficient of organized severe convection. Furthermore, heavy rain
across parts of the southern Plains is forecast for Saturday/Day 1.
This may dampen stronger heating and result in poor lapse rates,
limiting overall severe potential. While some gusty winds are
possible across the broad moist warm sector from the southern
Rockies into the Mid-MS/Lower OH Valley vicinity, weak deep-layer
flow and a lack of any discernible mechanisms to focus/organize
thunderstorm activity should limit overall severe potential and the
Marginal risk (level 1 of 5) has been removed for much of the
region. The exception is across portions of OK into southern MO on
the eastern periphery of the weak upper low and a possible MCV from
convection in the Day 1/Saturday period. This feature may provide
some local focus/enhancement to shear and a couple of strong to
severe storms producing gusty winds will be possible.
Some greater potential for strong wind gusts still appears possible
across parts of the VA into NY. Stronger heating will support
steepened low-level lapse rates within the very moist and unstable
airmass, and sporadic wet microbursts may occur. Some modestly
enhanced westerly flow across PA/NY may aid in development of
propagating clusters/outflows as well, and the Marginal risk (level
1 of 5) remains largely unchanged from the prior Day 3 outlook.
..Leitman.. 07/12/2025
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SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0139 AM CDT Sat Jul 12 2025
Valid 141200Z - 151200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE NORTHERN PLAINS...
...SUMMARY...
Isolated strong to severe thunderstorms are possible across portions
of the northern Plains Monday evening.
...Discussion...
Generally low-amplitude west/northwest flow will spread across the
northern tier of the U.S. on Monday, confining any enhanced
deep-layer flow to the north-central states. Elsewhere, a weak
deep-layer flow regime will prevail within modest upper ridging
across the Southeast and West. A weak upper low may persist over the
southern Plains/Ozark Plateau vicinity.
A seasonally moist airmass with pockets of moderate instability will
support scattered convection from the Plains to the Eastern
Seaboard. However, lack of forcing and weak deep-layer flow will
limit severe potential across much of the country. The exception may
be across parts of the northern Plains.
A surface low is forecast to develop across the northern High Plains
in response to weak height falls during the evening/overnight. A
cold front will develop south across parts of the Dakotas while a
surface trough extends south across the northern High Plains. These
boundaries could become a focus for isolated thunderstorm
development during the late afternoon/evening. Steep lapse rates,
moderate instability and sufficient shear should support a few
organized cells capable of producing strong/severe wind gusts and
perhaps isolated hail.
..Leitman.. 07/12/2025
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Day 4-8 Outlook
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 AM CDT Sat Jul 12 2025
Valid 151200Z - 201200Z
...DISCUSSION...
Several shortwave impulses are forecast to move through
low-amplitude upper troughing over the northern tier of the U.S.
during the Day 4-8 period. At the surface, a cold front is expected
to develop south/southeast across portions of the northern/central
Plains and Upper Midwest on Days 4-5/Tue-Wed. Given a moist and
unstable airmass ahead of this feature, some severe potential is
possible from the central Plains to the Upper Midwest. However,
medium range guidance shows large spread in the location and timing
of the front and any associated convection, resulting in low
predictability.
Later in the period, strong upper ridging will develop over the
Southeast. Some severe potential could continue eastward across the
Great Lakes to the Mid-Atlantic around Days 5-6/Wed-Thu as the
aforementioned cold front stalls in response to the building
Southeast ridge. However, large-scale ascent and deep-layer flow
will remain modest, and any severe potential would likely be driven
by mesoscale processes not well resolved at this time scale.
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