LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1144 AM CDT Sun Aug 06 2023
Valid 061630Z - 071200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MIDDLE
MISSISSIPPI/LOWER OHIO VALLEYS AND MID-SOUTH/SOUTHEAST...
...SUMMARY...
A few tornadoes along with scattered damaging winds and large hail
will be possible from late afternoon into tonight from the
Mid-Mississippi to Lower Ohio Valleys. Scattered damaging winds will
also be possible, mainly this afternoon into early evening across
parts of the Mid-South and Southeast.
...Middle Mississippi/Lower Ohio Valleys...
Multiple eastward-moving/decaying MCVs are still evident across the
region ahead of the primary synoptic cyclone across Iowa. Ahead of
this cyclone, a moisture-rich warm sector will expand
north-northeastward across downstate portions of Illinois/Indiana
this afternoon into tonight in tandem with a warm front. An arc of
initially semi-discrete thunderstorms are expected to develop within
the somewhat narrow warm sector by mid/late-afternoon, initially
across southeast Iowa/far eastern Missouri and
west-central/southwest Illinois.
Seasonally strong winds through a deep-layer will support
supercellular development, with low-level shear/SRH expected to be
maximized particularly across southern Illinois 1) in vicinity of
the warm front and 2) toward/after sunset as winds within the lowest
1-3 km AGL increase. A few tornadoes are possible regionally,
including supercell-related potential for large hail mainly within
the first couple of hours of deep convective development.
Into late evening, upscale growth into one or two organized clusters
is plausible, with the potential for an MCS to evolve along the
northern extent of the surface-based instability plume. An elongated
swath or two of damaging winds with embedded severe gusts, along
with a couple brief tornadoes may be sustained into the early
overnight into the Lower Ohio Valley.
...Mid-South/Southeast States...
The boundary layer across the region continues to steadily
warm/destabilize. A decaying MCS/MCV across Arkansas at midday
appears to already being influencing subsequent thunderstorm
development downstream across northern Mississippi, while additional
storms continue near the southern Appalachians. 25-35 kt 700-mb
westerlies across the Tennessee Valley should be adequate to support
semi-organized multicell clusters amid an extensive plume of large
buoyancy across the Deep South. Scattered damaging wind swaths from
water-loaded downbursts will be possible through early evening.
Later tonight, strengthening low-level warm theta-e advection
focused along residual outflow/effective baroclinic zone over the
Mid-South could influence additional strong thunderstorm
development. This activity could pose an isolated threat for severe
hail initially before potentially clustering into a localized
damaging wind threat overnight.
...Central/southern Rockies and Front Range...
The presence of 50s F surface dew points will support potential for
isolated but regenerative thunderstorms to develop along the Front
Range during the late afternoon and evening. A rather confined
corridor for weak buoyancy with MLCAPE of only 500-1000 J/kg should
be maximized near the Front Range. Deep-layer wind profiles will be
quite favorable for supercells and large hail potential given
near-perfectly straight-line hodographs.
Downstream of a minor shortwave trough over the interior Northwest,
isolated to scattered afternoon thunderstorms are anticipated around
the UT/WY/CO border area within a weak buoyancy plume. Adequate
deep-layer shear will exist for a threat of marginally severe hail
and wind centered on the late afternoon.
...Central/southern Appalachians to Lake Erie...
Multiple MCVs are expected to aid scattered intensifying
thunderstorm development downstream of these features this
afternoon. Pockets of modestly stronger low to mid-level flow
attendant to these MCVs may support sporadic localized damaging
winds, and perhaps even some funnel/brief tornado potential in
vicinity of Lake Erie near a weak surface low/warm front.
..Guyer/Squitieri.. 08/06/2023
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