SPC AC 090600
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Wed Jul 09 2025
Valid 091200Z - 101200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CAROLINAS INTO THE MID-ATLANTIC...AND PORTIONS OF THE
NORTHERN/CENTRAL PLAINS...
...SUMMARY...
Scattered damaging winds are possible this afternoon to early
evening from parts of the Carolinas to the Mid-Atlantic. Large hail
and severe gusts are also possible across parts of the
northern/central Plains beginning late this afternoon and continuing
into the evening.
...Southeast into the Mid-Atlantic...
A weak mid-level trough will move slowly eastward today across the
Great Lakes/OH Valley. A belt of modestly enhanced southwesterly
mid-level flow will remain over the Mid-Atlantic through this
evening, diminishing with southward extent in the Southeast.
Scattered to numerous thunderstorms are once again expected to
develop this afternoon over the southern Appalachians and Blue Ridge
Mountains, and then spread eastward towards the coast. The presence
of rich low-level moisture will compensate for poor lapse rates
aloft to support MLCAPE generally around 1500-3000 J/kg across lower
elevations. A few loosely organized clusters may eventually develop
from parts of VA towards the DelMarVa Peninsula and vicinity owing
to somewhat more favorable deep-layer shear across these regions.
Isolated hail may occur initially with the more cellular/discrete
convection, before scattered severe/damaging winds becomes the
primary risk with eastward extent as multiple clusters potentially
develop. Generally minor adjustments have been made to the ongoing
Marginal/Slight Risk areas to account for latest guidance trends.
...Northern/Central Plains...
Downstream of a low-amplitude mid-level ridge emanating from an
upper-level anticyclone over the Southwest, most guidance continues
to suggest that isolated to scattered thunderstorms should form by
late this afternoon along a weak surface trough. Ample low-level
moisture ahead of this trough will gradually build beneath a stout
EML. A corridor of strong to very strong instability will likely
exist by late afternoon/early evening from parts of western/central
ND into NE, aided by daytime heating and steep lapse rates aloft.
Despite modest mid-level west-northwesterlies owing to the proximity
of the upper ridge, stronger upper-level westerlies will support
adequate deep-layer shear for a few supercells initially, with
associated threat for large to isolated very large hail.
Outflow-dominated downdrafts should foster clustering
east-southeastward across the Dakotas and perhaps parts of NE, with
a risk for scattered severe gusts, some of which could be 75+ mph on
an isolated basis given the rather favorable thermodynamic
environment forecast.
While confidence is somewhat lower regarding convective coverage
with southward extent across the central Plains (into KS and
vicinity), a conditionally favorable environment for at least
isolated severe convection will be in place. Have therefore expanded
the Marginal Risk southward to account for this potential.
...Interior Northwest/Northern Rockies...
Downstream of a shortwave trough moving eastward across northern CA
into the northwest Great Basin, an elongated belt of enhanced
southwesterly mid-level flow will exist across the northern Great
Basin/Rockies. Within this favorable flow regime amid steepened
low-level lapse rates through daytime heating, scattered
thunderstorms should foster strong to isolated severe gusts from
parts of eastern OR into MT.
...Lower Michigan into Northwest Ohio...
Isolated/marginally severe hail and locally damaging winds appear
possible this afternoon across parts of Lower Michigan and northwest
OH as scattered thunderstorms develop beneath a weak upper trough,
supported by a modest combination of instability and deep-layer
shear.
..Gleason/Weinman.. 07/09/2025
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
SPC AC 090558
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Wed Jul 09 2025
Valid 101200Z - 111200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE
CENTRAL AND NORTHERN GREAT PLAINS AS WELL AS PORTIONS OF THE
SOUTHEAST...
...SUMMARY...
Scattered severe thunderstorms are possible over parts of the
central and northern Great Plains, mainly during the late afternoon
and evening on Thursday. Additional severe thunderstorms will be
possible during the afternoon across portions of the Southeast.
... Synopsis ...
A complex evolution of the mid-to-upper level pattern is expected to
unfold on Thursday across the central United States. A de-amplifying
short-wave trough will move from northern Utah into the central
Great Plains. At the same time, a larger-scale, positive-tilt trough
will amplify during the period across southern Canada as it pushes
east. This will result in an effective split-flow pattern across the
north-central US.
... Central and Northern Great Plains ...
Thunderstorms are expected at the start of the period across eastern
portions of the central and northern Great Plains, driven primarily
by warm, moist low-level advection. In the wake of this convection,
the airmass is expected to quickly recover yielding moderate to
extreme instability.
By late afternoon, thunderstorms are expected to develop across the
terrain of northeast Colorado and eastern Wyoming. As the
aforementioned low-amplitude short-wave trough begins to eject into
the central Great Plains, these thunderstorms should quickly move
off the terrain and into the Plains. Damaging winds will be possible
with these storms as the quickly grow upscale in response to the
increasing large-scale ascent. The overall degree of instability
will also support the potential for sporadic large hail.
To the north across North Dakota, convective evolution is more
uncertain. The atmosphere will be extremely unstable in the presence
of a surface boundary and approaching large-scale ascent. Despite
the absence of a more robust signal in the convective allowing
guidance for afternoon convection, coarser-scale guidance suggests
at least scattered thunderstorm development will occur during the
evening and overnight hours. These thunderstorms will be capable of
damaging thunderstorm winds with at least some potential for large
hail.
... Portions of the Southeast ...
Thunderstorms will once again develop within a warm, moist, and
weakly capped environment. High precipitable water value (locally in
excess of 2 inches) will support water loaded downdrafts giving way
to wet downbursts capable of wind damage. A Level 2/Slight Risk was
added to highlight the area of highest coverage of potential wet
downbursts.
... Portions of the Northeast ...
Diurnal heating of a moist boundary layer will result in scattered
thunderstorm development across the region. Most-unstable CAPE
values greater than 1000 J/kg and modest effective-layer shear
should support the potential for scattered wind damage. Should
coverage of thunderstorms be greater than currently anticipated an
upgrade to Level 2/Slight Risk may be warranted in subsequent
forecasts.
..Marsh.. 07/09/2025
WUUS02 PTSDY2
SPC AC 090729
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CDT Wed Jul 09 2025
Valid 111200Z - 121200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE HIGH
PLAINS OF THE SOUTHERN AND CENTRAL ROCKIES NORTHEAST TO THE UPPER
GREAT LAKES AND FROM THE CAROLINAS TO CENTRAL PENNSYLVANIA...
...SUMMARY...
A few strong to severe thunderstorms capable of producing large hail
and damaging winds will be possible across portions of the central
Great Plains. Additional strong storms capable of producing sporadic
wind damage will be possible from the Carolinas to central
Pennsylvania.
... Central Plains ...
A low-amplitude short-wave trough across the central Great Plains
will begin to phase with / be absorbed by a larger scale trough
moving across the northern Great Plains. At the surface, a cold
front will slowly push southeast through much of Iowa during the
day.
At the start of the forecast period, convection from the previous
day should still be ongoing across portions of the area. The overall
pattern would suggest that one or more mesoscale convective vortices
(MCVs) may accompany this ongoing convection. Guidance consensus and
the overall pattern would support this convection persisting through
much of the day.
To the south of this convection, diurnal heating of a moist airmass
below steep mid-level lapse rates will result in a strongly unstable
atmosphere by mid afternoon. Additional thunderstorms should develop
within this strongly unstable atmosphere and be capable of producing
large hail and damaging winds.
At present, the combination of a weakening mid-level wind field and
uncertainty associated with the location of any ongoing/persistent
convection prevents the inclusion of higher probabilities with this
forecast. However, locally enhanced effective-layer shear associated
with any remnant MCVs should support some organization of a severe
threat such that an upgrade to Level 2/Slight Risk may be warranted
as the details of such features become clear.
... Carolinas to central Pennsylvania ...
Diurnal heating of a moist and weakly capped boundary layer will
result in afternoon thunderstorms. Precipitable water values look to
be less on Friday than previous days, but still should be sufficient
for widely scattered to scattered wet downbursts. Wind damage will
be possible with the stronger downbursts.
... Eastern Colorado into the southern Great Plains ...
Thunderstorms are expected to develop across northeast Colorado
during the afternoon. Large-scale flow should result in these storms
moving southeast through the evening and overnight hours as they
grow upscale into a large MCS. The overall pattern would suggest the
potential for at least a couple of severe wind reports associated
with this southeastward moving MCS.
..Marsh.. 07/09/2025
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 1930Z
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