LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1229 AM CDT Wed Aug 09 2023
Valid 091200Z - 101200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE
OZARKS INTO THE MID-MISSISSIPPI RIVER VALLEY...
...SUMMARY...
Severe thunderstorms are expected today from eastern Oklahoma/Kansas
eastward to the Lower Ohio and Tennessee Valley vicinity.
...Synopsis...
Overnight surface analysis reveals a surface low slowly deepening
over the High Plains ahead of an approaching upper wave. Further
deepening of the low is expected as it migrates east into the Ozarks
by early evening. A broad warm advection regime ahead of the
synoptic wave will support scattered elevated convection across
portions of the Ozarks to the mid-MS River Valley by late afternoon.
A second round of storms is expected during the early evening hours
across the Ozarks along a trailing cold front, and should pose a
risk for all hazards before spreading east during the overnight
hours.
...Ozarks into the Mid-MS River Valley...
Thunderstorm clusters developing over northwest KS as of 05 UTC are
expected to propagate to the southeast in tandem with the deepening
surface low. While it remains unclear how much of this initial
activity will persist into MO, convective re-development appears
probable by mid-afternoon with additional development within a warm
advection regime across northern MS/AL and western TN. 40-50 knot
mid-level flow over the region will support adequate shear for
organized cells with an attendant large hail risk prior to gradual
upscale growth into clusters. Low-level shear is expected to
gradually improve through the day with the approach of the synoptic
wave with forecast soundings across the mid-MS Valley showing ESRH
values between 100-200 m2/s2. This should support a tornado threat
with initially discrete cells, though this may be conditional on the
degree of destabilization that can occur prior to convective
initiation (most forecast soundings suggest temperatures in the low
to mid-80s are required).
A second round storms will likely develop across southwest MO into
northwest AR/northeast OK along a trailing cold front closer to 00
UTC. Although a residual cold pool may be in place from prior
convection, southwesterly low-level flow should aid in air mass
recovery, and steep lapse-rate advection aloft will compensate for
any weakness in low-level thermodynamics. Deep-layer shear vectors
orthogonal to the front should support initially discrete cells. The
longevity of discrete storm modes is uncertain with spread noted in
latest CAM guidance, but more south/southwesterly flow in the
vicinity of the surface low should support effective SRH values on
the order of 150-250 m2/s2 at the time of initiation. Consequently,
a tornado or two is possible across northern AR into southwest MO.
Further southwest into OK, a hotter, more deeply mixed air mass may
limit the tornado potential, but will support severe downburst
winds. Storms along the front are expected to gradually spread east
overnight into TN and northern MS/AL as one or more organized lines.
The potential for severe/damaging winds may be modulated by cold
pools from prior convection and background nocturnal stabilization
to some degree.
...Dakotas into the Upper Peninsula of Michigan...
Thunderstorms developing along a diffuse cold front will mature in
an environment with only modest buoyancy (MLCAPE between 500-1000
J/kg), but effective shear values between 30-35 knots. Given storm
motions and deep-layer shear vectors largely off the front, discrete
to semi-discrete storms appear probable. A similar environment
Tuesday supported isolated severe storms, and this should be the
case again today from the eastern Dakotas into MN, WI, and the Upper
Peninsula of MI.
..Moore/Jewell.. 08/09/2023
Read more CHECK UPDATE ZOOM GRAPHIC
http://dlvr.it/StPFrp
