ACUS01 KWNS 071246
SWODY1
SPC AC 071244

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0744 AM CDT Mon Aug 07 2023

Valid 071300Z - 081200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FAR EASTERN
KY/NORTHEAST TN/NORTHWEST NC...WESTERN AND NORTHERN VA...SOUTHERN
AND EASTERN WV...CENTRAL MD...AND FAR SOUTH-CENTRAL PA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SEPARATELY OVER
THE CENTRAL HIGH PLAINS...

...SUMMARY...
A severe weather outbreak is possible across parts of the eastern
U.S. today with widespread damaging winds, locally destructive, and
isolated tornadoes as the greatest threats from the southern and
central Appalachians to the Mid-Atlantic States.

...Southeast to the Upper OH Valley to the Mid-Atlantic States...
A shortwave trough over the Lower OH Valley will advance across the
northern Appalachians by this evening. A pair of 500-mb speed maxima
from 55-65 kts are expected to be centered by late afternoon across
eastern KY/TN and southern WV into western VA/NC, and separately
over the Mid-South. Peak flow within an expansive 700-mb jet should
be centered between the 500-mb maxima across the TN Valley. A plume
of large potential buoyancy supported by high PW and steep mid-level
lapse rates, and centered over the Mid-South/TN Valley will expand east-northeast towards the central/southern Appalachians with an
expansive swath of MLCAPE from 2000-3500 J/kg expected by peak
heating. The 12Z BNA sounding well-sampled this potentially volatile environment.

To the north of the steeper mid-level lapse rate plume, minimal
inhibition will result in scattered thunderstorms forming by midday
centered on far southern OH across eastern KY ahead of the
aforementioned trough. This activity will progress into an
increasingly favorable thermodynamic and kinematic environment
downstream, yielding many supercells capable of producing large
hail, damaging winds, and tornadoes. Upscale growth into several
linear clusters with embedded supercells is anticipated during the
afternoon as convective coverage becomes widespread from PA/MD
south-southwest across the southern Appalachian states. Forecast
soundings suggest the greatest tornado threat will probably exist
across eastern KY/TN northeast across southern/eastern WV, western
VA, central MD and into southeast PA. Given the supercell wind
profiles, significant severe wind gusts will also be possible on a
localized basis.

Across the Southeast, the separate mid-level speed max approaching
the Mid-South, aiding in the low-level warm-advection regime of
elevated thunderstorms over OK/AR this morning, will likely support
scattered surface-based thunderstorms forming across the TN Valley
by early afternoon. With large buoyancy downstream within the
gradient of the strong low to mid-level flow, an extensive linear
MCS will likely develop and spread east-southeast across the
Carolinas and GA. Widespread damaging winds will be possible here as
well, with convection likely weakening towards/after sunset as it
approaches the south Atlantic coast.

...Central High Plains...
A 50-60 kt mid-level speed max should become centered near the
NE/CO/KS border area by late afternoon with approach of a
low-amplitude shortwave impulse currently over southeast ID. This
will overlap a confined north/south-oriented corridor of moderate
buoyancy with MLCAPE of 1500-2500 J/kg along a lee trough across the
similar tri-state area. Initial high-based thunderstorm development
is anticipated off the higher terrain of CO/WY and will intensify as
it impinges on the larger buoyancy during the early evening. A few
supercells with very large hail will be possible along with a
meso-beta scale corridor favorable for a tornadic supercell or two.
Clustering of supercells may yield a short-duration uptick in severe
wind gust potential across parts of western KS before convection
spreads away from the relatively narrow instability plume and
encounters increasing MLCIN after sunset.

..Grams/Broyles.. 08/07/2023

$$
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* Origin: Ilink: CCO - capitolcityonline.net (454:1/105)

ACUS01 KWNS 072001
SWODY1
SPC AC 072000

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Mon Aug 07 2023

Valid 072000Z - 081200Z

...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS SOUTHERN WEST
VIRGINIA INTO WESTERN AND NORTHERN VIRGINIA...MARYLAND...AND FAR
SOUTHERN PENNSYLVANIA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE CENTRAL AND SOUTHERN HIGH PLAINS...

...SUMMARY...
A severe weather outbreak is expected across parts of the eastern
U.S. this afternoon into the early evening with widespread and
locally destructive damaging winds and tornadoes as the greatest
threats, especially across the southern/central Appalachians and
Mid-Atlantic States.

...Discussion...
Only notable change this convective outlook update is to remove
severe probabilities in wake of thunderstorm bands and where
low-level flow has strongly veered to westerly over much of the OH
Valley into portions of the upper TN Valley. Elsewhere, little
change was made to the previously issued forecast.

..Smith.. 08/07/2023

.PREV DISCUSSION... /ISSUED 1140 AM CDT Mon Aug 07 2023/

...Southeast to the Upper Ohio Valley to the Mid-Atlantic States...
Owing to a very moist/unstable air mass and very strong winds aloft
for August, a widespread severe-weather risk is already unfolding at
late morning/midday across a broad region, initially west of the
Appalachians spine. Refer to ongoing Watches and Mesoscale
Discussions for the latest regional details.

A shortwave trough over the Lower Ohio Valley will continue to
advance toward the northern Appalachians by evening. A pair of
500-mb speed maxima from 55-65 kts are expected to be centered by
late afternoon across eastern KY/TN and southern WV into western
VA/NC, and separately over the Mid-South. Peak flow within an
expansive 700-mb jet should be centered between the 500-mb maxima
across the TN Valley. A plume of large potential buoyancy supported
by high PW and steep mid-level lapse rates, and centered over the
Mid-South/TN Valley will expand east-northeast towards the
central/southern Appalachians with an expansive swath of MLCAPE from
2000-3500 J/kg expected by peak heating.

Ongoing storms across eastern portions of TN/KY and WV/southern OH
will progress into an increasingly favorable thermodynamic and
kinematic environment downstream, yielding many supercells capable
of producing large hail, damaging winds, and tornadoes. Upscale
growth into several linear clusters with embedded supercells is
anticipated this afternoon as convective coverage becomes widespread
from PA/MD south-southwest across the southern Appalachian states.
Forecast soundings suggest the greatest tornado threat will probably
exist across eastern KY/TN northeast across southern/eastern WV,
western VA, central MD and into southeast PA. Given the supercell
wind profiles, significant severe wind gusts will also be possible
on a localized basis.

Across the Southeast, aided by a separate mid-level speed max,
linear clusters of storms will continue to develop and spread
generally eastward across parts of the TN Valley toward the southern Appalachians and Carolinas, with damaging winds as the most common
hazard.

...Central High Plains...
No changes warranted for this region. A 50-60 kt mid-level speed max
should become centered near the NE/CO/KS border vicinity by late
afternoon with approach of a low-amplitude shortwave impulse
currently over southeast ID. This will overlap a confined
north/south-oriented corridor of moderate buoyancy with MLCAPE of
1500-2500 J/kg along a lee trough across the similar tri-state area.
Initial high-based thunderstorm development is anticipated off the
higher terrain of CO/WY and will intensify as it impinges on the
larger buoyancy during the early evening. A few supercells with very
large hail will be possible along with a meso-beta scale corridor
favorable for a tornadic supercell or two. Clustering of supercells
may yield a short-duration uptick in severe wind gust potential
across parts of western KS before convection spreads away from the
relatively narrow instability plume and encounters increasing MLCIN
after sunset.

...Southern High Plains...
A wind-driven Slight Risk has been introduced for portions of
eastern New Mexico into the Texas South Plains for later this
afternoon and evening. Strong westerlies, particularly by August
standards, and a hot/well-mixed boundary layer should support at
least some severe storms capable of severe-caliber wind gusts.

$$
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