LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0747 AM CDT Sat Aug 05 2023
Valid 051300Z - 061200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHEAST CO TO
SOUTH KS/NORTH OK...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SEPARATELY OVER
THE WABASH VALLEY TO CENTRAL IN...
...SUMMARY...
The most concentrated area of severe thunderstorms with potential
for destructive wind and hail is expected across parts of the
south-central Great Plains from mid-afternoon through tonight.
Potential for a few tornadoes will exist separately over the
Mid-Missouri and Wabash Valleys during the late afternoon to early
evening.
...South-central Great Plains to the Mid-South...
A small MCS is ongoing along the southeast KS/northeast OK border
area and may persist east-southeast across portions of the Ozark
Plateau through midday. How it evolves into the afternoon across the
Mid-South is uncertain given variation among CAM guidance that has
adequately simulated the MCS so far (namely the 06/09Z RRFS and 00Z
NSSL-WRF/10Z HRRR), as it progresses away from the more strongly
sheared environment to its west-northwest but impinges on larger
buoyancy over MO/AR. Have expanded the cat 2-SLGT risk some to
account for potentially greater east-southeast progression and/or
redevelopment later this afternoon with the remnant MCV.
In the wake of this morning MCS, convective outflow arcs across
central OK through the central TX Panhandle. Hot and deeply mixed
thermodynamic profiles will develop to the south of this boundary
amid full insolation, while capping to the north inhibits
thunderstorm development until peak heating. Initial cells should
develop off the Raton Mesa and Palmer Divide towards mid-afternoon
within a low-level upslope flow regime and the left exit region of
an intense upper jet from CA to CO. Potential will exist for
regenerative supercells spreading east-southeast off the higher
terrain. A few of these may become long-lived and capable of
producing baseball to softball-sized hail centered on the southeast
CO vicinity given highly elongated mid to upper hodographs and large
buoyancy amid very steep mid-level lapse rates.
A strengthening low-level jet over west TX during the evening will
favor increasing convective development downstream and yield
multiple clusters spreading across western and southern KS, the
Panhandles, and western to northern OK during the evening. Severe
wind gusts will become more prolific as this occurs, which should
include potential for sporadic gusts from 70-90 mph. CAM guidance
struggles to indicate a more prominent MCS evolving out of the
clusters that should form, lowering confidence on where the most
concentrated swath of significant severe wind gusts is likely to
evolve tonight. But a broad region of at least scattered severe wind
potential supports maintaining a cat 3-ENH risk.
...Mid-MO Valley vicinity...
A mid-level low over central SD will drift east with stronger
destabilization confined downstream of it from southeast SD to
eastern NE and far western IA. Early afternoon convective
development will initially be most pronounced across southeast SD
and likely arc southward into at least northeast NE before spreading
into northwest IA later. Weaknesses in the mid-level wind profile
may yield a linear cluster type mode, but some enlargement to the
low-level hodograph, especially in the SD/NE/IA border area, should
foster low-level updraft rotation capable of producing a couple
tornadoes. Otherwise, slow-moving linear clusters will yield a
threat for isolated severe hail and wind persisting through the
evening.
...IL/IN vicinity...
An MCV over central IL will drift east into IN through tonight.
Enhanced wind fields attendant to this MCV were sampled by the 12Z
ILX sounding and will yield a spatially confined corridor of
favorable low-level SRH overlapping the northeast extent of the
surface-based instability plume in southern parts of IL/IN. This
should support a few supercells developing during the mid afternoon
to early evening, centered on the Wabash Valley into portions of
central/southern IN. Any supercell will be capable of a tornado, and
localized severe wind gusts will be the primary threat with
convection that arcs southwestward towards larger buoyancy across
the Lower OH Valley.
..Grams/Broyles.. 08/05/2023
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