LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
1249 AM CDT Tue Aug 08 2023
Valid 081200Z - 091200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS CENTRAL HIGH
PLAINS...
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS CENTRAL PLAINS AND
ACROSS THE SOUTHEAST...
CORRECTED FOR ERRONEOUS THUNDER LINE DIRECTION
...SUMMARY...
Scattered severe thunderstorms are possible across portions of the
central High Plains this afternoon into tonight. Large to very
large hail, along with a risk for a tornado and widely scattered
severe gusts, will be the potential hazards. Scattered severe
thunderstorms are also expected through the day across portions of
the Southeast.
...Synopsis...
An unseasonably strong upper wave is noted in overnight water-vapor
imagery lifting to the northeast across the New England region. In
its wake, a broad northwesterly flow regime is in place from the
Pacific Northwest to the southeastern states. Several disturbances
are embedded within this mean flow regime from the High Plains into
the northern Great Basin. These disturbances are expected to
propagate to the southeast over the next 24 hours, and will be the
impetus for severe weather potential for the High Plains and
Southeast.
...Central Plains/High Plains...
The upper wave over the northern Great Basin is forecast to move
into the central Rockies by 00-06 UTC this evening. As this occurs,
modest lee troughing will support southeasterly return flow, which
should allow for air mass recovery in the wake of early morning
convection. The combination of southeasterly low-level flow under
40-50 knot zonal flow aloft will yield nearly-straight hodographs
featuring strong deep-layer shear (on the order of 50 knots). This
zonal flow will foster eastward advection of steep 700-500 mb lapse
rates sampled upstream by 00 UTC soundings, which when combined with
low-level moistening, will result in MLCAPE values near 2500-3000
J/kg by late afternoon.
Initially discrete cells are expected to develop within the upslope
flow regime across northeast CO to southeast WY and the NE
Panhandle. Given the aforementioned thermodynamic/kinematic
environment, splitting supercells appear likely. These will pose a
threat for very large hail (2+ inches in diameter) and a tornado or
two, as cells migrate into improving low-level moisture across
northwest KS. Consolidating outflow from storm interactions should
foster gradual upscale growth by late evening. Lift associated with
the ejection of the upper wave and a strengthening low-level jet
will aid in MCS organization overnight across KS with an attendant
severe wind risk.
...Southeast...
A convectively reinforced MCV is forecast to emanate from the
southern Plains into the lower MS River Valley and Southeast today.
One or more thunderstorm clusters associated with this feature will
likely be elevated at the start of the forecast period, posing a
severe hail risk across AR/northern LA. The convective threat will
transition to a damaging wind threat by late morning and early
afternoon across central MS/southern AL, where temperatures are
forecast to reach the low to mid 90s along and south of a residual
outflow boundary/cold front. Enhanced mid-level flow associated with
the MCV should provide adequate deep-layer shear for organized
convection. While a few semi-discrete cells are possible, one or
more organized clusters/lines appear probable as the system moves
into southern GA/north FL by late afternoon/early evening.
...New England...
A secondary surface low associated with the northeastern upper wave
is expected to meander northeast through the New England region
during peak daytime heating. Warming surface temperatures should be
adequate to support surface-based convection, and effective SRH on
the order of 100 m2/s2 in the vicinity of the low may allow for a
few transient mesocyclones with an attendant tornado threat.
However, this potential will be conditional on sufficient low-level
heating, which is uncertain given lingering precipitation and cloud
cover.
..Moore/Jewell.. 08/08/2023
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