ACUS01 KWNS 061247
SWODY1
SPC AC 061246

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0746 AM CDT Fri Sep 06 2024

Valid 061300Z - 071200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
OHIO TO THE OHIO VALLEY...

...SUMMARY...
Strong to locally severe storms are possible this afternoon from
Lake Erie across much of Ohio to the Ohio Valley.

...Synopsis...
A highly amplified mid/upper-level pattern will persist across the
CONUS, but with some weakening of the western mean ridge and
intensification of troughing over the Great Lakes/Ohio Valley
regions.  The latter will occur in relation to a synoptic-scale
trough with several accompanying vorticity maxima and broad cyclonic
flow -- apparent in moisture-channel imagery over much of northern
ON and the Lake Superior vicinity.  Phasing of accompanying
shortwaves/ vorticity lobes will contribute to both amplification
and wavelength shortening through the period.  A closed 500-mb low
should develop around 00Z near the eastern end of Upper MI, with
trough near an MKG-ORD-MVN line.  By 12Z, a fully developed cyclone
should cover much of ON from the southern end of James Bay to Lake
Erie, with 500-mb trough extending southwestward near a CVG-BNA
line.  Associated cyclonic flow at that time will cover most of the
CONUS over and east of the mid/upper Mississippi Valley.

At the surface, a cold front related to the ON trough was drawn at
11Z near a DTW-FDY-IND-ICT line.  This front should proceed
eastward/southeastward across the Ohio Valley, Lower Great Lakes and
into the central/northern Appalachians through the period, ahead of
the mid/upper trough.  By 00Z, the front should extend from Lake
Ontario across western parts of NY/PA to southeastern OH, northern
middle to western TN, and AR, becoming diffuse amidst northeast flow
on both sides over OK.  Northeasterlies over the southern Plains
south of the cold front will be largely in isallobaric response to a
deepening surface frontal-wave low over the northwestern Gulf,
initially drawn about 100 nm south of GLS, and forecast to drift
erratically eastward through tonight.  Strong/organized convection
related to the Gulf cyclone is expected to remain over water through
the period.

...OH, Ohio Valley...
Damaging to isolated, marginally severe gusts, as well as marginal
hail, will be possible with thunderstorms moving eastward across the
outlook area today.

A broken line of convection -- including widely scattered non-severe
thunderstorms -- is apparent this morning from northwestern OH to
western MO approximately along the low-level cold front.  This
activity, or succeeding/newer development after a short time gap
later this morning -- should become better organized between Lake
Erie and the Ohio Valley around midday as the foregoing boundary
layer (and prospective inflow) destabilizes.  This will occur in
response to a combination of warm advection and diurnal heating/
mixing, whose mixing-related moisture-reduction effects will be
counterbalanced to some extent by moist advection.  Activity should
move into a narrow corridor of 50s to mid 60s F surface dewpoints,
combining with diurnal heating to support patchy, highly variable
MLCAPE in the 500-1500 J/kg range.

Substantial westerly component to prefrontal near-surface flow will
limit both convergence and vertical shear, though weak MLCINH will
permit frontal development/maintenance of thunderstorms, regardless.
Around 30-35 kt effective-shear magnitudes will support mainly
multicells, though some intermittent/transient supercell character
will be possible for longer-lived, discrete cells.  Activity should
weaken this evening as it moves eastward out of the most favorable
moisture, and into a nocturnally cooling/stabilizing boundary layer.

..Edwards/Kerr.. 09/06/2024

$$
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